BEN MC GEE · Mantle dynamics have long been considered to influence the topography and mechanics...

Supercontinents and Glaciation: a perspective from western Gondwana

B E N M C G E E

Geology and GeophysicsEarth and Environmental Sciences

The University of Adelaideand

The University of São Paulo

July 2013

Thesis Author Statement

I, Ben McGee, certify that this work contains no material which has been accepted for the award of any other degree or diploma in any university or other tertiary institution, and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference has been made in the text.

I give consent to this copy of my thesis when deposited in the University Library, being made available for loan and photocopying, subject to the provisions of the Copyright Act 1968.

The author acknowledges that copyright of published works contained within this thesis (as listed in “Pub-lications Arising From This Thesis”) resides with the copyright holder(s) of those works.

I also give permission for the digital version of my thesis to be made available on the web, via the Uni-versity’s digital research repository, the Library catalogue, and also through web search engines, unless permission has been granted by the University to restrict access for a period of time.

Ben McGee Date

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Table of ContentsThesis Abstract v

Publications Arising From This Thesis vii

Thesis Outline

Author Contribution Statement

Chapter 1: Cryogenian rift-related magmatism and sedimentation: 3 South-western Congo Craton, Namibia.

Introduction 3 Regional Geology 4 Pre-Chuos sedimentation on the southern margin of the 4 Congo Craton The Toekems Sub-basin 6 Analytical Methods 7 U-Pb geochronology 7 Results 7 Stratigraphy and field relationships 7 Lonestones 9 Geochronology 10 Discussion 14 Timing and origin of the Toekems Sub-basin 15 Implications for the age of Chuos glaciation 16 Conclusion 17 References 17

Chapter 2: G’day Gondwana - the final accretion of a supercontinent: 21 U-Pb ages from the post-orogenic São Vicente Granite, northern Paraguay Belt, Brazil Introduction 21 Regional setting 22 Analytical methods 23 U-Pb geochronology 23 Age estimates 24 Discussion: crystallisation age of the São Vicente Granite 24 References 26

Chapter 3: A glacially incised canyon in Brazil: Further evidence for 31 mid-Ediacaran glaciation?

Introduction 31 Regional setting 31 Measured sections 33 Serra Azul 33 São Sebastião 33 Boa Sorte 33 Discussion and conclusions 33 References cited 38

Chapter 4: The tectonic and palaeoenvironmental significance of the 45 Ediacaran to Cambrian Alto Paraguay Group, Paraguay Belt, Brazil.

Introduction 45 Regional setting 46 Analytical methods 47

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Detrital muscovite 40Ar/39Ar isotopic analysis 47 Measured sections 47 Serra Azul section 47 Boa Sorte section 48 Nobres section 48 40Ar/39Ar isotopic results 51 Discussion 53 Facies variations and relative sea level change exhibited by the Alto 53 Paraguay Group Maximum depositional ages of the Alto Paraguay Group 54 Sources of the Alto Paraguay Group 55 Sedimentary-tectonic model for the formation of the Alto Paraguay 55 Group Conclusions 57 References 57

Chapter 5: Age and Provenance of the Cryogenian to Cambrian 67 passive margin to foreland basin sequence of the northern Paraguay Belt, Brazil.

Introduction 67 Regional setting 67 Analytical methods 69 Zircon U-Pb LA-ICPMS analysis 69 Zircon Hf isotopic analysis 69 Results 69 Zircon U-Pb LA-ICPMS isotopic results 69 Age estimates 69 Zircon Hf isotopic results 70 Discussion 71 U-Pb isotopic age constraints and maximum depositional ages 71 U-Pb and Hafnium isotopic results and correlation with potential 72 source regions Tectonic model and the Paraguay Belt within South America and 73 Gondwana Conclusions 76 References cited 76

Chapter 6: An inconvenient truth: Multiple geomagnetic reversals 115 in the Neoproterozoic–Cambrian Alto Paraguay Group, Amazonian Craton, Brazil. Introduction 115 Geological setting 116 Methods 118 Results 119 Demagnetisations 119 Magnetic mineralogy 120 Magnetic components 121 Discussion 122 Conclusions 126 References 126

Chapter 7: Key outcomes and future research 131

Chapter 8: Sedimentological and provenance response to Cambrian 135closure of the Clymene ocean: The upper Alto Paraguai Group,Paraguay Belt, Brazil

Introduction 135

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Geological setting 137 The upper Alto Paraguai Group 138 Facies associations 138 Tidal and wave influenced marine platform 140 Distal turbidite deposits 141 Prodelta lake 142 Delta front 142 U-Pb age provenance analysis 143 Methodology 143 Results 145 Palaeoflow determination 145 Petrography and tectonic environment 145 Palaeogeography and potential source regions 145 Tectonic-sedimentary model 147 Conclusions 147 References 148

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Thesis AbstractPrecise timing for the formation of the Palaeozoic supercontinent Gondwana has long eluded the

geological community. Early hypotheses postulated that amalgamation occurred in the mid-late Neopro-terozoic via a collision between East and West Gondwana. This idea developed with the identification of discrete collisional events between diverse, relatively small Neoproterozoic continents that amalgamated Gondwana in a piecemeal fashion over 150 million years, with a series of late Ediacaran–Cambrian orogens that represent the final phase of Gondwana amalgamation. A salient feature of the rocks preserving these events in the Neoproterozoic sedimentary record is the preservation of glacial sediments. Significant debate has centred around firstly whether these deposits are in fact glacial and secondly the spatial extent of these glaciations. This thesis addresses these deficits in our knowledge by presenting detailed sedimentology, geochronology, palaeomagnetic results from western Gondwana.

The Cryogenian-aged Toekems Sub-basin in the Damara Belt, Namibia comprises a wedge domi-nantly clastic, glacially influenced sediments. Our field observations and results imply a significant discon-formity beneath the Naauwpoort Volcanics and suggest multi-phase rifting during the breakup of south-western Congo Craton from Rodinia.

The northern Paraguay Belt in South America developed in response to the collision between the Amazonian Craton, the Rio Apa Block, the São Francisco Craton and the Paranapanema Block. The al-leged ‘Brasiliano’ age (~620 Ma) of orogenesis was recently questioned by palaeomagnetic and radioiso-topic ages that indicate the closing stages of orogenesis occurred well into the Cambrian that are believed to mark the suture zone of the Clymene Ocean—interpreted amongst the youngest of the Gondwana amalgamation orogens. The post-orogenic São Vicente Granite provides a long sort after minimum age of 518 ± 4 Ma for orogenesis within the belt, constraining the termination of deformation within the northern Paraguay Belt.

The Alto Paraguay Group, the youngest stratigraphic unit in the northern Paraguay Belt, contains unequivocal evidence for a glacial influence on sedimentation. 40Ar/39Ar detrital muscovite cooling ages from the upper part of the Alto Paraguay Group are as young as 544 ± 7 Ma. When considered with other data presented here, these ages suggest that this package of rocks developed in a mid-Ediacaran glaciation consistent with that expressed in the Gaskiers Formation of Newfoundland, Canada. U/Pb zircon maxi-mum depositional ages from the top of the Alto Paraguay Group indicate that final sedimentation began no earlier than 527 Ma. The εHf signature is consistent with a predominantly Amazonian source until the early-Neoproterozoic at which point the signal becomes significantly more evolved.

new palaeomagnetic data from Alto Paraguay Group represent a secondary magnetisation, likely acquired during regional emplacement of Jurassic basalt. This finding is at odds with recent results that have been used to suggest Amazonia was at low latitudes during the Ediacaran, which has implications for the snowball earth hypothesis and the tectonic evolution of the Paraguay Belt.

These data, when combined with other evidence discussed here, are consistent with an ocean to the east of the present-day Amazonian Craton that didn’t close until the Cambrian.

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McGee, B., Collins, A.S. and Trindade, R.I.F., 2012. G’day Gondwana - the final accretion of a su-percontinent: U-Pb ages from the post-orogenic Sao Vicente Granite, northern Paraguay Belt, Brazil. Gondwana Research 21, 316-322.

Bandeira, J., McGee, B., Nogueira, A.C.R., Collins, A.S. and Trindade, R.I.F., 2012. Closure of the Neo-proterozoic Clymene Ocean: sedimentary and detrital zircon geochronology evidence from the siliciclas-tic upper Alto Paraguai Group, northern Paraguay Belt, Brazil. Gondwana Research.

McGee, B., Halverson, G.P. and Collins, A.S., 2012. Cryogenian rift-related magmatism and sedimenta-tion: South-western Congo Craton, Namibia. Journal of African Earth Sciences 76, 34-49.

McGee, B., Collins, A.S. and Trindade, R.I.F., Accepted. A glacially incised canyon in Brazil: Further evidence for mid-Ediacaran glaciation? The Journal of Geology.

McGee, B., Collins, A.S., Trindade, R.I.F. and Jourdan, F. Under review. The tectonic and palaeoen-vironmental significance of the Ediacaran to Cambrian Alto Paraguay Group, Paraguay Belt, Brazil: Sedimentology and 40Ar/39Ar detrital muscovite provenance. Sedimentology.

McGee, B., Collins, A.S. and Trindade, R.I.F., Under Review. Age and Provenance of the Cyrogenian to Cambrian passive margin to foreland basin sequence of the northern Paraguay Belt, Brazil. Bulletin of the Geological Society of America.

McGee, B., Trindade, R.I.F., Rosaffa, M., Collins, A.S. and Tohver, E., Under review. An inconvenient truth: Multiple geomagnetic reversals in the Neoproterozoic–Cambrian Alto Paraguay Group, Amazo-nian Craton, Brazil. Precambrian Research.

Publications Arising From This Thesis

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Thesis OutlineThe latest Proterozoic and earliest Paleozoic eras beautifully illustrate the complexity and intercon-

nectedness of the interactions between Earth’s systems. Mantle dynamics have long been considered to influence the topography and mechanics of the overlying lithosphere (Mitrovica et al., 1989; Pysklywec and Mitrovica, 1997). The impact of ‘mantle avalanches’ have been suggested to play a causal role in the supercontinent cycle (Condie, 1998; Li et al., 2008) – by initiating superplume development – cited as one potential cause for the break-up of Rodinia (Frimmel et al., 2001; Li et al., 2008; Li et al., 1999). The frag-mentation of this supercontinent provided the building blocks for its successor Gondwana.

Undeniably, these deep processes began to effect surface processes, irrevocably changing the Earth to its current biologically rich/diverse state. Increased heat transfer, afforded by the superheated plume head (Campbell and Davies, 2006), enhanced hydrothermal activity in the oceans – indicated by Sr isotopes (Melezhiik et al., 2001) – resulting in increased leaching of metals, capturing large amounts of oxygen, stratifying the ocean and depositing vast banded iron formations (Kaufman et al., 1991) after a hiatus for some 1000 million years. Other important elements were also released initiating plankton hy-perproductivity (Gaucher et al., 2003) and 13C levels were enriched (Halverson et al., 2005). The changing oceans caused the atmosphere to evolve to its oxygenated state (Canfield et al., 2007; Canfield and Teske, 1996; Garrels et al., 1973) and the most intense periods of glaciation in Earth’s history (Hoffman et al., 1998; Kirschvink, 1992; Roberts, 1971). These extreme glacial events are suggested to be partly responsible for the birth of diverse animal life (Bowring and Erwing, 1998; Knoll, 1992; Narbonne and Gehling, 2003) and us such understanding them is crucial to our knowledge of the Earth system.

The central aim of this thesis is to investigate some examples of Neoproterozoic sedimentary basins that record evidence for these glacial events and the tectonic history of their cratonic roots in their journey from Rodinia to Gondwana. This is achieved through detailed sedimentary, geochronological and palaeomagnetic studies with a focus on western Gondwana.

The specific aims of this thesis are:1. Shed light on the relationship between Rodinian rifting and glaciation from the Damara Belt in

Namibia and to show that there is a glacial influence on sedimentation.2. Constrain the termination of deformation in the Paraguay Belt

3. Delineate a glacial incision surface along the Serra Azul in the northern Paraguay Belt and dis-cuss other global evidence for similar aged glacial deposits.

4. Provide a detailed sedimentary and stratigraphic analysis of the Serra Azul Formation comple-mented by Argon cooling ages to provide the first age constraints on the Serra Azul Formation and informa-tion on low temperature events within the northern Paraguay Belt

5. Provide a long-awaited and comprehensive detrital zircon study from the northern Paraguay Belt and discuss the now significant body of evidence that exists for a Cambrian age of orogenesis.

6. To show that new palaeomagnetic data from the Alto Paraguay Group suggest a significant remagnetisation event occurred in the northern Paraguay Belt, most likely in the Jurassic.

The location for the first aim was selected in Namibia based on the excellent exposure of Neopro-terozoic rift basins in the Damara Belt. The Toekems Sub-basin contains a unique exposure of rift-related sediments under a Sturtian aged cap-carbonate.

The remaining aims are addressed in the northern Paraguay Belt in central South America, which provides a place where the relationship between tectonics, oceans, atmosphere and the biosphere during the Neoproterozoic–Cambrian can be studied. The belt is comprised of a thick succession of passive mar-gin sediments on the southwestern edge of the Amazonian Craton. Mounting evidence suggests that the Paraguay Belt marks the suture zone of the Clymene Ocean, which separated Amazonia, Rio Apa, Pampia and proto-Gondwana (Bandeira et al., 2011; Tohver et al., 2011; Tohver et al., 2010; Trindade et al., 2006).

REFERENCES CITED

Bandeira, J., McGee, B., Nogueira, A.C.R., Collins, A.S., Trindade, R.I.F., 2011. Closure of the Neoproterozoic Clymene Ocean: sedimentary and detrital zircon geochronology evidence from the siliciclastic upper Alto Paraguai Group, northern Paraguay Belt, Brazil. Gondwana Research.

Bowring, S., Erwing, D.H., 1998. A new look at evolutionary rates in deep time: uniting paleontology and high-precision geochronol-ogy. GSA Today 8, 1-8.

Campbell, I.H., Davies, G.F., 2006. Do mantle plumes exist? Episodes 29, 162-168.Canfield, D.E., Poulton, S.W., Narbonne, G.M., 2007. Late-Neoproterozoic deep-ocean oxygenation and the rise of animal life. Sci-

ence 315, 92-95.Canfield, D.E., Teske, A., 1996. Late Proterozoic rise in atmospheric oxygen concentration inferred from phylogenetic and sulphur-

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isotope studies. Nature 382, 127-132.Condie, K.C., 1998. Episodic continental growth and supercontinents: a mantle avalanche connection? Earth Planet. Sci. Lett. 163,

97-108.Frimmel, H.E., Zartman, R.E., Spath, A., 2001. The Richtersveld Igneous Complex, South Africa: U-Pb Zircon and Geochemical Evi-

dence for the Beginning of Neoproterozoic Continental Breakup. Journal of Geology 109, 493-508.Garrels, R.M., Perry, E.A., Mackenzi.Ft, 1973. Genesis of Precambrian iron-formations and development of atmospheric oxygen.

Economic Geology 68, 1173-1179.Gaucher, C., Boggiani, P.C., Sprechmann, P., Sial, A.C., Fairchild, T.R., 2003. Integrated correlation of the Vendian to Cambrian Ar-

royo del Soldado and Corumba´ Groups (Uruguay and Brazil): palaeogeographic, palaeoclimatic and palaeobiologic implications. Precambrian Research 120, 241-278.

Halverson, G.P., Hoffman, P.F., Schrag, D.P., Maloof, A.C., Rice, A.H.N., 2005. Toward a Neoproterozoic composite carbon-isotope record. GSA Bulletin 117, 1181-1207.

Hoffman, P.F., Kaufman, A.J., Halverson, G.P., Schrag, D.P., 1998. A Neoproterozoic snowball earth. Science 281, 1342-1346.Kaufman, A.J., Hayes, J.M., Knoll, A.H., Germs, G.J.B., 1991. Isotopic compositions of carbonates and organic carbon from up-

per Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism. Precambrian Research 49, 301-327.

Kirschvink, J.L., 1992. Late Neoproterozoic low-latitude global glaciation: the Snowball Earth, in: Schopf, J.W., Klein, C. (Eds.), The Proterozoic Biosphere. Cambridge University Press, New York, pp. 51-52.

Knoll, A.H., 1992. Biological and biogeochemical preludes to the Ediacaran radiation, in: Lipps, J.H., Signor, P.W. (Eds.), Origin and Early Evolution of the Metazoa. Plenum Press, New York, pp. 53-84.

Li, Z.X., Bogdanova, S.V., Collins, A.S., Davidson, A., De Waele, B., Ernst, R.E., Fitzsimons, I.C.W., Fuck, R.A., Gladkochub, D.P., Jacobs, J., Karlstrom, K.E., Lu, S., Natapov, L.M., Pease, V., Pisarevsky, S.A., Thrane, K., Vernikovsky, V., 2008. Assembly, con-figuration, and break-up history of Rodinia: A synthesis. Precambrian Research 160, 179-210.

Li, Z.X., Li, X.H., Kinny, P.D., Wang, J., 1999. The breakup of Rodinia: did it start with a mantle plume beneath South China? Earth Planet. Sci. Lett. 173, 171-181.

Melezhiik, V.A., Gorokhov, I.M., Kuznetsov, A.B., Fallick, A.E., 2001. Chemostratigraphy of Neoproterozoic carbonates: implications for `blind dating’. Terra Nova 13, 1-11.

Mitrovica, J.X., Beaumont, C., Jarvis, G.T., 1989. Tilting of continental interiors by the dynamic effects of subduction. Tectonics 8, 1079-1094.

Narbonne, G.M., Gehling, J.G., 2003. Life after snowball: The oldest complex Ediacaran fossils. Geology 31, 27-30.Pysklywec, R.N., Mitrovica, J.X., 1997. Mantle avalanches and the dynamic topography of continents. Earth Planet. Sci. Lett. 148,

447-455.Roberts, J.D., 1971. Late Precambrian glaciation: an anti-greenhouse effect? Nature 234, 216-217.Tohver, E., Cawood, P.A., Rosello, E.A., Jourdan, F., 2011. Closure of the Clymene Ocean and formation of West Gondwana in the

Cambrian: evidence from the Sierras Australes of the southernmost Rio de la Plata craton, Argentina. Gondwana Research this volume.

Tohver, E., Trindade, R.I.F., Solum, J.G., Hall, C.M., Riccomini, C., Nogueira, A.C.R., 2010. Closing the Clymene ocean and bending a Brasiliano belt: Evidence for the Cambrian formation of Gondwana, southeast Amazon craton. Geology 38, 267-270.

Trindade, R.I.F., D’Agrella-Filho, M.S., Epof, I., Brito Neves, B.B., 2006. Paleomagnetism of Early Cambrian Itabaiana mafic dikes (NE Brazil) and the final assembly of Gondwana. Earth Planet. Sci. Lett. 244, 361-377.

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The research contained in this thesis has been published or submitted for publication in scientific journals. The bibliographic details of each journal article comprising a chapeter are listed at the beginning of the chapter, which includes the names of all authors involved in their production. The contribution of each author to the conceptualisation, realisation and documentation of these works is described below.

MCGEE, B. (Candidate)Chapters 1–6: Project conceptualisation and planning; fieldwork, including mapping and stratigraphic logging; sample selection and preparation; LA-ICPMS data collection; all calculations and data processing; data interpretation; manuscript design, writing and creation of all figures; article submission to journals.

I certify that the above statement is accurate

Signed Date

HALVERSON, G. P. (Supervisor)Chapter 1: Project conceptualisation and planning; fieldwork assistance; guidance with data interpretation; guidance with manuscript ouline; manuscript review.

I certify that the above statement is accurate and give permission for the relevant manuscripts to be included in this thesis

Signed Date 5/02/13

COLLINS, A. S. (Supervisor)Chapters 1–6: Project conceptualisation and planning; fieldwork assistance; guidance with data interpretation; guidance with manuscript ouline; manuscript review.


Signed Date 24/01/13

TRINDADE, R. I. F. (Supervisor)Chapters 2–6: Project conceptualisation and planning; fieldwork assistance; guidance with data interpretation; guidance with manuscript ouline; manuscript review.



Author Contribution Statement

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JOURDAN, F.Chapter 4: Argon isotope data collection; assistance with data preparation and interpretation; manuscript review.


Signed Date 5/02/13

ROSAFFA, M.Chapter 6: sample preparation and data collection.



TOHVER, E.Chapter 6: guidance with data interpretation; guidance with manuscript outline



Chapter 1: Cryogenian rift-related magmatism and sedimentation: South-western Congo Craton, Namibia.

This chapter is published as:McGee, B., Halverson, G.P. and Collins, A.S., 2012. Cryogenian rift-related magmatism and sedimentation: South-western Congo Craton, Namibia. Journal of African Earth Sciences 76, 34-49.

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Chapter 1 Cryogenian rift-related magmatism and sedimentationChapter 1 Cryogenian rift-related magmatism and sedimentation

A McGee, B., Halverson, G.P. & Collins, A.S. (2012) Cryogenian rift-related magmatism and sedimentation: South-western Congo Craton, Namibia. Journal of African Earth Sciences, v. 76, pp. 34-49

NOTE:

This publication is included on pages 3-18 in the print copy of the thesis held in the University of Adelaide Library.

It is also available online to authorised users at:

http://dx.doi.org/10.1016/j.jafrearsci.2012.09.003

Chapter 2: G’day Gondwana - the final accretion of a supercontinent: U-Pb ages from the post-orogenic São Vicente Granite, northern Paraguay Belt, Brazil

This chapter is published as:McGee, B., Collins, A.S., Trindade, R.I.F., 2012. G’day Gondwana - the final accretion of a supercontinent: U-Pb ages from the post-orogenic Sao Vicente Granite, northern Paraguay Belt, Brazil. Gondwana Research 21, 316-322.

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Chapter 2 Cryogenian rift-related magmatism and sedimentation

A McGee, B., Collins, A.S. & Trindade, R.I.F. (2012) G'day Gondwana - the final accretion of a supercontinent: U-Pb ages from the post-orogenic Sao Vicente Granite, northern Paraguay Belt, Brazil. Gondwana Research, v. 21(2-3), pp. 316-322

NOTE:



http://dx.doi.org/10.1016/j.gr.2011.04.011

Chapter 3: A glacially incised canyon in Brazil: Further evidence for mid-Ediacaran glaciation?

This chapter is published as:McGee, B., Collins, A.S. and Trindade, R.I.F., Accepted. A glacially incised canyon in Brazil: Further evidence for mid-Ediacaran glaciation? The Journal of Geology.

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Chapter 3 A glacially incised canyon in Brazil

A McGee, B., Collins, A.S. & Trindade, R.I.F. (2013) A glacially incised canyon in Brazil: further evidence for mid-Ediacaran glaciation. The Journal of Geology, v. 121(3), pp. 275-287

NOTE:



http://dx.doi.org/10.1086/669979

Chapter 4: The tectonic and palaeoenvironmental significance of the Ediacaran to Cambrian Alto Paraguay Group, Paraguay Belt, Brazil: Sedimentology and 40Ar/39Ar detrital muscovite provenance

This chapter is under review as:McGee, B., Collins, A.S., Trindade, R.I.F. and Jourdan, F. Under review. The tectonic and palaeoenvironmental significance of the Ediacaran to Cambrian Alto Paraguay Group, Paraguay Belt, Brazil: Sedimentology and 40Ar/39Ar detrital muscovite provenance. Sedimentology.

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Chapter 4 The tectonic and palaeoenvironmental significance of the Alto Paraguay Group

The tectonic and palaeoenvironmental significance of the Edia-caran to Cambrian Alto Paraguay Group, Paraguay Belt, Brazil: Sedimentology and 40Ar/39Ar detrital muscovite provenance

MCGEE, B.a, COLLINS, A.S.a, TRINDADE, R.I.F.b and JOURDAN, F.c

aCentre for Tectonics, Resources and eXploration (TRaX), School of Earth and Environmental Sciences, B09, Mawson Building, The University of Adelaide, SA 5005, Australia.bDepartamento de Geofísica, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, 05508-090, São Paulo, Brazil.cWestern Australian Argon Isotope Facility, Department of Applied Geology and John de Laeter Centre, Curtin University, GPO Box U1987, Perth, Western Australia, 6845, Australia

ABSTRACT

The Alto Paraguay Group in the northern Paraguay Belt, Brazil contains unequivocal evidence for a glacial influence on sedimentation. Within the Serra Azul Formation, multi-directional striations on sandstone clasts and striated, polished and bullet-shaped mudstone clasts have all been documented. However, a palaeodepositional model is not well established and due to a paucity of geochronological data its age is not well constrained. Given that the Serra Azul Formation is interpreted as being deposited during the Gaskiers glaciation, it is important to correctly understand its position within the Neoproterozoic tectono-stratigraphic framework. This contribution presents a detailed stratigraphy surrounding the Serra Azul Formation to show that it was deposited in a glacio-fluvial environment and on a lithostratigraphic basis the Serra Azul Formation is assigned to the basal part of the Alto Paraguay Group. A significant number of single grain 40Ar/39Ar detrital muscovite cooling ages (ca. 120) from the Alto Paraguay Group are also presented. The three youngest grains yield a weighted mean age providing a robust maximum depositional age of the Serra Azul Formation at 640 ± 15 Ma. This age, when considered with other data, suggest that the Serra Azul Formation developed in a mid-Ediacaran glaciation consistent with that expressed in the Gaskiers Formation of Newfoundland, Canada. 40Ar/39Ar ages from the upper part of the Alto Paraguay Group are as young as 544 ± 7 Ma, consistent with mounting evidence that indicate a Cambrian age for orogenesis within the Paraguay Belt at the final amalgamation of Gondwana.

INTRODUCTION

Identifying glacial deposits in the geological record is a longstanding and contentious issue. This is mostly due to the impact that the interpretations of these successions have on our understanding of Earth history. A recent contribution by Arnaud and Etienne (2011) concisely summarises key characteristics of Neoproterozoic glacial environments, pointing out that the presence of striations, faceting and bullet-shaped clasts confirms a glaciogenic influence on sedimentation. Global correlation of the fragmented Neoproterozoic glacial record is also another controversial issue. Existing evidence implies that there were at least three major glacial events during the Neoproterozoic; a middle Cryogenian event (~720 Ma ‘Sturtian’); an end-Cryogenian event (~635 Ma ‘Marinoan’) and a middle Ediacaran event (~582 Ma ‘Gaskiers’; Halverson et al., 2009). While reasonable evidence exists to suggest that the first two were global in extent (Hoffman et al., 1998), global correlation of younger Ediacaran glacial deposits has proven to be problematic. This may be due

to diachroneity, but available evidence is suggestive that the mid-Ediacaran event is at least visible in the global sedimentological record (McGee et al., Under review).

The timing of formation of the Palaeozoic supercontinent Gondwana is another issue that has received significant attention in the literature for many decades. Early interpretations of a collision between two large continents called East Gondwana and West Gondwana at ~650 Ma (Stern, 1994) have evolved to incorporate current evidence that identify a network of collisional events between relatively small Neoproterozoic continents that amalgamated to form Gondwana during the Ediacaran and Cambrian (e.g. Collins and Pisarevsky, 2005; Meert, 2003; Pisarevsky et al., 2008). The Paraguay Belt in Brazil is part of this network of Gondwana-forming orogens that for some time has been considered as ‘Brasiliano’ (ca. 940 – 630 Ma) in age (Cordani et al. 2009). More recent contributions (Bandeira et al., 2012; McGee et al., 2012; Tohver et al., 2011; Trindade et al., 2006) have demonstrated that the Paraguay Orogen is part of a larger

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orogenic belt that can be traced south to Argentina and north to the Amazon, and that is considerably younger than many Gondwana-amalgamation orogens—forming in the early Cambrian—therefore representing one of the final collisional belts in Gondwana.

This work addresses both the tectonic and palaeoenvironmental issues outlined above through presentation of detailed stratigraphic sections from the northern Paraguay Belt within the Alto Paraguay Group. The sedimentological work shows that the Serra Azul Formation was deposited in a glacio-fluvial environment. The new 40Ar/39Ar detrital muscovite ages show that the Serra Azul Formation clearly represents a glacial episode younger than ~640 Ma. The argon isotopic data also corroborates other radiometric ages that indicate orogenesis within the Paraguay belt is early Cambrian in age.

REGIONAL SETTING

The Paraguay Belt is located in central South America (Figure 1) and marks the boundary between the Amazon, São Francisco, Rio Apa and Rio de la Plata cratons. It comprises metamorphosed Neoproterozoic sedimentary strata that were deposited in a passive margin environment (Nogueira et al., 2007). These metasedimentary and sedimentary rocks are divided into the older pelites, diamictites and siliciclastics of the Cuiabá Group in the core of the orogen (Barros et al., 1982), diamictites of the Puga Formation, carbonates of the Araras Group and siliciclastics of

the upper Alto Paraguay Group. Whilst the nature of the contact between the Cuiabá Group and Puga Formation not well understood due to non-exposure, recent interpretations describe the Puga diamictite as the proximal ‘shelf’ facies of the extensive Cuiabá Group (Figure 1; Alvarenga et al., 2009). The age of the youngest detrital zircon in the Puga Formation is 706 ± 9 Ma (Babinski et al., 2012), which when coupled with the δ13C (5.0‰) and 87Sr/86Sr (0.7080) ratios from carbonates directly overlying the diamictites (Nogueira et al., 2003), suggest that these diamictites represent the ~635 Ma end-Cryogenian glaciation.

In the northern Paraguay Belt the stratigraphic framework of the Alto Paraguay Group—the focus of this study—was first described by Almeida (1964) who divided it into the ~1600 m sands, silts and shales of the Raizama Formation, overlain by ~900 m of shales, silts and sandstones of the Sepotuba Formation and ~600 m of Diamantino Formation siliciclastic rhythmites and sandstones. More recently Alvarenga et al. (2007) described a new unit, the Serra Azul Formation, in between carbonates of the Araras Group and the siliciclastics of the Alto Paraguay Group. The basal part of this formation is composed of a glaciogenic diamictite containing multiply striated sandstone clasts (Alvarenga et al., 2007) and striated, polished and bullet-shaped mudstone clasts (McGee et al., Under review), which is overlain by a transgressive package of interlayered silts and fine sands. The siltstone and sandstone of the upper Alto Paraguay Group are interpreted to be shed off rising topography—the evolving Paraguay orogen—

Fig. 1. Geological map showing lithostratigraphic relationships within the northern Paraguay Belt. Modified from CPRM Cuiabá 1:1000000 map sheet (Barros et al., 1982).

A NOTE:

This figure/table/image has been removed to comply with copyright regulations. It is included in the print copy of the thesis held by the University of Adelaide Library.

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in response to collision between the Amazon, the São Francisco and the Paraná cratons between ~540–520 Ma (Bandeira et al., 2012). The termination of orogenesis was marked by intrusion of post-orogenic granites into the base of these Neoproterozoic sediments at 518 ± 4 Ma (McGee et al., 2012).

ANALYTICAL METHODS

Detrital muscovite 40Ar-39Ar isotopic analysisFour fresh samples within the Alto Paraguay Group were selected from the northern Paraguay Belt for 40Ar/39Ar muscovite dating. Unaltered, optically transparent, 100–150 µm muscovite grains were separated and carefully handpicked under a binocular microscope and subsequently cleaned in a sonic bath of deionized water. Samples were loaded into aluminum discs with wells of 1.9 cm diameter and 0.3 cm depth, which were themselves bracketed by pits that included Fish Canyon sanidine (FCs) used as a neutron fluence monitor for which an age of 28.305 ± 0.036 Ma (1σ) was adopted (Renne et al., 2010) based on the calibration by (Jourdan and Renne, 2007). The disc was Cd-shielded to minimize undesirable nuclear interference reactions and irradiated in position 5C for 25 hours in the Hamilton McMaster University nuclear reactor in Canada. The mean J-value computed from standard grains within the small pits was 0.00954500 ± 0.00001145 determined as the average and standard deviation of J-values of the small wells for each irradiation disc. Mass discrimination was monitored using an automated air pipette and provided a mean value of 1.00543 ± 0.00004 per dalton (atomic mass unit) relative to an air ratio of 298.56 ± 0.31 (Lee et al., 2006). The correction factors for interfering isotopes were (39Ar/37Ar)Ca = 7.30x10-4 (± 11%), (36Ar/37Ar)Ca = 2.82x10-4 (± 1%) and (40Ar/39Ar)K = 6.76x10-4 (± 32%).

Ar isotopic analyses were performed at the Western Australian Argon Isotope Facility at Curtin University. Each muscovite grain was fused in one, two or in some rare cases three steps using a 110 W Spectron Laser Systems, with a continuous Nd-YAG (IR; 1064 nm) laser. The gas was purified in a stainless steel extraction line using one SAES AP10 getter and one SAES GP50 getter for the largest grains. Ar isotopes were measured in static mode using a MAP 215-50 mass spectrometer (resolution of ~400; sensitivity of 4x10-14 mol/V) with a Balzers SEV 217 electron multiplier mostly using 9 to 10 cycles of peak-hopping. The data acquisition was performed with the Argus program written by M.O. McWilliams and ran under a LabView environment. The raw data were processed using the ArArCALC software (Koppers, 2002) and the ages have been calculated using the decay constants recommended by Renne et al. (2010). Blanks were monitored every 3 to 4 steps and typical 40Ar blanks range from 1 x 10-16 to 2 x 10-16 mole. Ar isotopic data corrected for blank, mass discrimination and radioactive decay are given in Supplementary Table 1. Ages represent either the total fusion age or are calculated using the mean of

concordant heating steps, each weighted by the inverse variance of their individual analytical error.

MEASURED SECTIONS

In their first presentation of the Serra Azul Formation, Alvarenga et al. (2007) provided a cross section from the southern slopes of Serra Azul (Figures 1 and 2) dividing the formation up into two informal units; Unit A, a massive diamictite and Unit B, a mudstone-siltstone unit. In a subsequent contribution, Figueiredo et al. (2011) stated that the Serra Azul Formation is between 250 and 300 m thick in the region where it is completely exposed, however, the base of the Serra Azul Formation was not documented. McGee et al. (Under review), recently demonstrated the extreme thickness variations of the Serra Azul Formation, and interpreted that these were due to infilling of an incised topography.

4.1 Serra Azul sectionThe type locality for the Serra Azul Formation is located at the eponymous farm, on the southern limb of the large (15 km wide), tight, shallowly east-plunging Serra Azul syncline (Figure 1). The surface distance between outcrops of Araras Group carbonate and Serra Azul Formation diamictite is approximately 300 m (Figures 2a & b). This equates to ~170 m of unaccounted stratigraphy (using the average bedding inclination in the region). At this location the diamictite layer has a reddish/purple fine silty matrix (Figure 3a). Clast sizes are highly variable from a few millimetres to 10 cm and also vary in degrees of roundness from angular to well-rounded and they are predominantly composed of quartz, purple laminated siltstone, mudstone, chert, sandstone, feldspathic and micaceous granite, gneiss and blue/grey carbonate (Figure 3a). A significant number of the mudstone clasts are highly polished and striated and are bullet shaped (McGee et al., Under review).

The top of the diamictite represents a flooding surface, signified by the presence of fine, deep water siltstones (Figure 2c). The overlying package is a series of post-glacial progradational parasequences that coarsen-up on the scale of 10’s of metres. They begin with fine silts that show increasing levels of sandy input, both within the silt layers themselves and as discrete sandstone interlayers. The silts alternate between yellow and a deep purple colour and are often finely laminated on a millimetre scale. These parasequences are interpreted to represent prograding shelf sediment on the margin of the Amazon Craton.

There is a general shallowing-upward trend in the section from finely laminated deep water silts to the overlying storm and tidal dominated sandstones of the Raizama Formation as accommodation space was reduced. This is recognised by the gradual appearance of shallower-water facies including starved ripples, trough and planar cross-stratification, sinuous ripple crest casts (Figure 3b), tidal bundles and an increase in

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coarser material upward in the sequence concomitant with a progressive loss of the deeper water facies (finely laminated silts). Alvarenga et al. (2007) described the contact between the Serra Azul Formation and the Raizama Formation as ‘sharp’. However, the observations presented here indicate that there is a progressive increase in sand content in the Serra Azul Formation suggesting a gradational boundary is a more suitable description. It is therefore proposed that a logical placement for the base of the Raizama Formation is when the lower/upper shoreface facies begin to dominate over the more distal offshore facies or with the beginning of thick (>1 m) sandstone layers.

Heading north, stratigraphically above the measured section, outcrop is sporadic but the transition from the Raizama Formation to the Sepotuba Formation is inferred based on a colour change to lighter coloured outcrop, visible in the satellite image (Figure 2b). The estimated thickness of the Raizama Formation based on this division is 960 m, using the average bedding inclination in the area. Outcrops dispersed within the Sepotuba Formation here are predominantly yellow and pale grey/blue siltstones with interlayered fine and medium sandstone and minor coarse sands and pebble conglomerates (Figure 2a). The transition from the Sepotuba Formation to red and purple finely laminated silts and interlayered fine sands of the Diamantino Formation was observed in outcrop and is expressed in the satellite image with the appearance of finer, more planar form lines (Figure 2b & c). The estimated thickness of the Sepotuba Formation is 820 m, which compares well to the 900 m estimate of Almeida (1964).

4.2. Boa Sorte sectionThe Boa Sorte section, named after the eponymous farm it passes through, is located 66 km east of the type section along the same southern limb of the Serra Azul syncline (Figure 1). Such a detailed section was made possible by the recent construction of a new road through the range at this location. Geological mapping in the area shows that the Puga Formation diamictite is present south of the measured section (Figure 4a). At this location the Puga diamictite is massive and contains predominantly centimeter-scale clasts of granite and quartzite within a sandy matrix (Figure 3c). Lying above the Puga Formation are a sequence of vuggy and brecciated pink carbonate and chert (Figure 3d) that is interpreted to belong to the Serra do Quilombo Formation of the Araras Group. Using the inclination of beds overlying these carbonates and the surface distance to the first appearance of the Serra Azul Formation, an estimated stratigraphic thickness of 1730 m is obtained for these carbonates. The contact between the carbonates and the Serra Azul Formation was not observed at this locality.

The Serra Azul diamictite is estimated to be significantly thicker at this section (~480 m; Figure 4c), which has been interpreted to signify the presence of an incised valley (McGee et al., Under review). The Serra Azul diamictite consists of a dull green/grey diamictite

with a silty to sandy matrix. The clast population is similar to the diamictite at the Serra Azul section with foliated granite, gneiss, rounded quartzite, sub-rounded clasts of grey chert and clasts of the underlying pink dolostone. This observation suggests an erosive base for Serra Azul Formation that has completely removed the Nobres Formation at this locality and cut down into the dolomitic Serra do Quilombo Formation. The interlayered silts and sands documented at the type section were identified above the diamictite and have an estimated thickness of 210 m.

The measured section begins with the first appearance of massive sandstone beds, responsible for the Serra Azul topography (Figure 4c). This is interpreted as the base of the Raizama Formation, a conclusion that matches the calculated stratigraphic thicknesses of the Raizama and Sepotuba formations. At this locality the basal Raizama Formation is dominated by a greater amount of silt than at the Serra Azul section. This may be indicative of a more distal position on the margin relative to the Amazon Craton resulting in finer grained sediment deposition. The section does, however, exhibit the same shallowing-upward trend, with the appearance of swaley cross stratification in the mud and silt layers and subsequent introduction of increasing amounts of planar-stratified sandstone and coarser pebble conglomerate layers or lenses. The Raizama Formation becomes very coarse at its top, with the uppermost part expressing a ~40m massively bedded sandstone unit. A platform to fluvio-deltaic depositional setting is proposed.

The transition to the Sepotuba Formation is signified by a major decrease in sand content and a return to the predominance of siltstone. This most likely occurred as a result of basin subsidence and increased accommodation space. Here the Sepotuba Formation is expressed as flaser bedded and wavy, pinch-and-swell, planar-stratified fine sandstones interlayered with millimeter-laminated siltstones (Figure 3e). This heterogeneous bedding is suggestive of high-energy deposition on a storm and tidally influenced setting where individual sand layers were subsequently covered by silty or muddy material. The interpretation of a high-energy environment is also consistent with the presence of rip-up clasts of mudstone within the basal parts of some sandstone layers (Figure 3f). These rip-up clasts imply that the tidal currents were strong enough to have peeled off the underlying mudstone layers (e.g. Le Roux et al., 2004) and incorporated them into the more siliciclastic layers. This package crops out for around 120 m before the outcrop becomes discontinuous. The remaining Sepotuba Formation thickness was calculated to be ~810 m, indicating an overall thickness of ~930 m in this section. The Diamantino Formation is not exposed at this location but is most likely represented by the break in slope from the range to the plain (Figure 4a and b).

4.3. Nobres sectionTwo sections were measured in the area near the town

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Fig. 2. (a) Geological map at type locality of the Serra Azul Formation at the Serra Azul farm (b) Satellite image outlining major geological boundaries in white and location of measured sections (c) Serra Azul measured section.

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Fig. 3. (a) Purple silty matrix of the Serra Azul diamictite supporting sub-angular clasts of carbonate and gneiss (b) Sinuous ripple crests in the Raizama Formation (c) Puga Formation diamictite showing clasts of quartzite and weathered granite (d) Vuggy and brecciated dolomite of the Serra do Quilombo Formation (e) Flaser, pinch and swell bedding in the Sepotuba Formation showing planar stratification in the sand-stone lenses (below coin) indicating flow the right (west) (f) Mudstone rip up clasts (circled) in sandstone layers in the Sepotuba Formation (g) Swaley cross-stratification in the Nobres Formation (h) Asymmetric ripple casts in the Nobres Formation (i) Asymmetric gravel ripples composed surrounded by coarse sand (j) Desiccation crack casts in the Serra Azul Formation. Coin is 27 mm in diameter.

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of Nobres (Figure 5a & b), located in the NE-SW trending section of the northern Paraguay Belt (Figure 1). The area comprises a series of tight folds, plunging southwest and two similarly trending thrust faults (Figure 5a). Section A was measured on the southern limb of one of these folds at the Copacel quarry to document the uppermost part of the Nobres Formation and the transition to the basal part of the Serra Azul Formation. Section B, in conjunction with geological mapping, also captures this transition, on the northern limb of the same fold.

In section A of the Nobres Formation, it is possible to recognise the surfaces and sequences defined by Nogueira et al. (2007), with the lower section dominated by dark grey, laminated and silicified carbonate, contrasting with the significant siliciclastic input found in the upper section . The input of siliciclastic material occurs around 70 m into the section, where initial bed forms are wavy. Planar and swaley (Figure 3g) stratification are observed and evidence for unidirectional flow is inferred from the presence of asymmetric casts (Figure 3h) and asymmetric ripples (Figure 3i). These sedimentary structures are indicative of a shallow marine or lower shoreface/intertidal environment (e.g. Dalrymple, 1992; Walker and Plint, 1992). The parasequences are stacked progradational packages that commonly have a sandy base and fine upwards with interlayered silicified carbonates and mudstones on the scale of 10s of metres. Breccias were also observed but their pattern of cross-cutting bedding suggests they are not a primary depositional feature.

Siliciclastic material increases up-section until eventually at ~168 m a very coarse siliciclastic unit is reached. Nogueira et al. (2007) interpreted these siliciclastic deposits as belonging to the Raizama Formation. However, in light of the recent discovery of the Serra Azul Formation, this interpretation requires some discussion.

The Serra Azul diamictite is well documented along the Serra Azul above the Araras Group carbonates, despite the direct contact not being exposed there. Further west in the belt the Serra Azul diamictite has not been observed. Figueiredo et al. (2011) suggested that the diamictite is not observed in the west due to non-deposition or erosion after deposition. Erosion is not considered to be a likely possibility given that a flooding surface directly overlies the diamictite—such a transgressive systems tract is unlikely to result in erosion of the underlying sediments. Non-deposition is a possibility, if glaciation was a local feature, glacial rain-out would only be observed in the vicinity of glaciers.

A more accurate description than non-deposition is that the absence of the diamictite member is due to lateral facies changes within the Serra Azul Formation. Section B (Figure 5c), in conjunction with geological mapping (Figure 5d) also documents a transition from carbonate to overlying coarse-grained siliciclastics. This is interpreted to be correlative to the Serra Azul diamictite documented further east along the Serra

Azul.The parasequences in section B commonly fine

upwards on the scale of 5 m starting from a gravelly, or coarse sandy, base and fining upwards to fine or medium sands (Figure 5c). There are abundant grading sequences within these successions that also fine upwards. There are numerous lenses of pebbled material and swaley and planar stratification. Dessication cracks on the tops of some of the finer grained layers provide evidence for periods of sub aerial exposure (Figure 3j). These observations are indicative of a fluvially influenced tidal platform that was most likely exposed in response to glacioeustatic sea level fall associated with the Gaskiers glacial event (McGee et al., Under review).

40AR/39AR ISOTOPIC RESULTS

This study reports single grain ages for 121 muscovite grains (Figure 6 and Table 1). The broad age range of the muscovite populations within the samples indicates that large scale resetting has not occurred and that in-situ temperatures reached during orogenesis were below the closure temperature of Ar in muscovite, ~450 ± 50 °C (Harrison et al., 2009), which is supported by the un-metamorphosed nature of the rocks. The 32 muscovites analysed from the Serra Azul Formation yielded Palaeoproterozoic to Neoproterozoic ages (~2050 to ~613 Ma). The results are spread out over a near linear array in the Meso- and Neoproterozoic with a separate cluster in the Palaeoproterozoic. The 3 youngest ages define a small cluster with a weighted mean age of 640 ± 15 Ma (MSWD = 0.75; P= 0.47).

Thirty muscovites were analysed from the Raizama Formation giving Mesoproterozoic to Neoproterozoic ages (1520 to 899 Ma). One prominent age cluster is apparent in the Tonian with 11 grains defining a concordant set of ages, from which a weighted mean age of 924 ± 7 Ma (MSWD = 1.3, P = 0.24) was calculated. The youngest age (899 Ma) is not concordant with this group and it is not clear if it is affected by 40Ar loss or if it provides the true minimum of the age population. The remaining grains define a broad spread of older ages.

Two samples of the Diamantino Formation were analysed, the stratigraphically lower of the two (BDM-09), yields ages ranging from the Ediacaran to the early Mesoproterozoic (583 to 1074 Ma). The predominant age population in this sample contained 23 concordant earliest Ediacaran ages that yielded a weighted mean of 631 ± 9 Ma (MSWD = 1.10; P = 0.34), and a smaller population of four muscovites that yielded Mesoproterozoic concordant ages with a weighted mean of 1054 ± 24 Ma (MSWD = 0.55; P = 0.65). The second Diamantino Formation sample (BDM-12), the stratigraphically highest sample from the Alto Paraguay Group, gave Palaeoproterozoic to Cambrian (1749 to 524 Ma) ages. The youngest ages define a concordant population of 12 Cambrian ages, from which a weighted mean of 544 ± 7 Ma (MSWD = 0.71, P=0.73) was calculated. In addition, the largest proportion of the data

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Fig. 4. (a) Geological map at the Boa Sorte farm (b) Satellite image outlining major geological boundaries in white and location of measured sections (c) Boa Sorte measured section.

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Fig. 5. (a) Geological map surrounding the town of Nobres showing SW plunging folds (b) Satellite image outlining major geological boundar-ies in white and location of measured sections (c) Composite stratigraphic section compiled from the Nobres region.

lie in the Cyrogenian to Cambrian with only four grains older than this group.

DISCUSSION

6.1. Facies variations and relative sea level change exhibited by the Alto Paraguay GroupThe large variation in thickness of the Serra Azul diamictite, the presence of carbonate clasts and the complete removal of Araras Group carbonates in some locations indicate significant erosion at the base of this formation. As previously discussed, the Serra Azul Formation exhibits lateral facies variations across the northern Paraguay Belt from a glaciomarine environment

in the east to a fluvially influenced tidal platform in the west. This interpretation accounts for why the Serra Azul diamictite is absent in the sections measured in the north-western part of the belt. A significant marine transgression after diamictite deposition is signified by the overlying fine-grained, deep-water siltstones. A progressive facies change follows with a shallowing-upward trend including the increasing sand content and shallower water sedimentary features of the Raizama Formation. This deep-to-shallow facies trend is repeated above the Raizama Formation with the appearance of fine grained mudstone and siltstone of the Sepotuba Formation. The final shallowing and deposition is encapsulated in the Diamantino Formation from the

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basal turbidites, to a lake/prodelta setting followed by progradation of a delta front into the Diamantino Lake (Bandeira et al., 2012)

6.2. Maximum depositional ages of the Alto Paraguay GroupPrecise detrital zircon U-Pb age data in sedimentary rocks are widely used to provide first order constrains on palaeotectonic and palaeogeographic reconstructions owing to their capacity to fingerprint the provenance of sediments (Collins et al., 2012; Plavsa et al., Submitted). Detrital zircons are, however, limited in the information they record. The high closure temperature of Pb in zircon and the lack of new widespread zircon growth below upper amphibolite-facies conditions mean that low-temperature processes are largely invisible to zircon studies. The robust nature of the mineral also means that recycling of individual zircon crystals is a real consideration; the analysed detrital zircon may have passed through a number of previous sedimentary rocks before being deposited in the sample of interest. The application of 40Ar/39Ar single muscovite grain cooling or crystallisation ages to provenance analysis largely overcomes these problems as firstly, muscovite is considerably less robust than zircon. Muscovites are unlikely to survive more than one sedimentary cycle or even a very long waterborne transport (e.g. pancontinental river systems) and therefore the information encoded in detrital muscovite ages can be generally considered to offer constraints on proximal source areas where “primary” muscovite bearing rocks (namely peraluminous granites and medium to high-grade metamorphic rocks of pelitic-psammitic composition) were present. This means that muscovite ages preferentially provide information on the nearest source areas, therefore complementing and building on U-Pb zircon age data (e.g. Gutierrez-Alonso et al., 2005; Murphy and Collins, 2008). Secondly, since the closure temperature for Ar in muscovite is quite low (350–450˚C), detrital muscovite ages contain information on greenschist-facies events and the exhumation history of the source region – information that isn’t revealed by U-Pb zircon studies. Such muscovite ages are likely to be closer in age to the deposition of the sediment in question than U-Pb zircon ages, and therefore are likely to provide a tighter constrain the age of deposition. A caveat to the use of detrital 40Ar-39Ar muscovite ages is that the low closure temperature means that this technique is restricted to rocks that have not been metamorphosed above anchizone conditions after their deposition (i.e. post-depositional temperatures <350˚C).

The 40Ar/39Ar analyses of white mica reported here complement recent detrital zircon studies (McGee et al., Submitted) by providing constraints on source regions and recognising the age of lower temperature (<450 °C) events in the northern Paraguay Belt. The maximum depositional ages here are based on the ages of the youngest concordant cluster of detrital muscovite grains for each respective formation. Using

Fig. 6. Age distribution plots for 40Ar/39Ar cooling ages from single grain muscovites from the Alto Paraguay Group. Black vertical bars indicate the grains used in maximum depositional age calculations.

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a cluster of ages instead of the (single) youngest age provides the following advantages: (1) since this study deals with total fusion ages where it is impossible to test if the muscovite has been partially reset (which would result in a fickian diffusion profile if the grain were to be step-heated), this approach makes the minimum age calculation relatively insensitive to eventual 40Ar loss by the youngest grain(s); (2) as many grains are very small and thus analytically challenging to analyze, this approach prevents using analytical outliers as a geological minimum, (3) it provides an analytically more precise maximum depositional age compared to a single grain that could be plagued with uncertainties as large as 50 Ma due to the small size of the grains analyzed and (4) the reproducibility of ages observed for the youngest groups of grains gives support to the grains being derived from a single young and nearby source. A drawback is that the youngest possible limit might be missed, but this is largely compensated by a gain in accuracy and thus gives better confidence in the data and interpretation. Using this reasoning the Serra Azul Formation is interpreted to be deposited no earlier than 640 ± 15 Ma. The overlying Raizama Formation has a maximum depositional age of 924 ± 7 Ma. The uppermost unit of the Alto Paraguay Group, the Diamantino Formation, has the youngest maximum depositional age of the analyses presented here at 544 ± 7 Ma.

6.3. Sources of the Alto Paraguay GroupThe 40Ar/39Ar muscovite ages from the sedimentary units analysed here are displayed in Figure 6, spanning the early Cambrian to the Palaeoproterozoic. Neighbouring geological terranes with these same age populations are considered here as possible source regions.

Since the Paraguay Belt is considered to be a sequence of folded sedimentary rocks that formed on a passive margin on the Amazon Craton (Alvarenga and Trompette, 1992), this is the most obvious location to consider potential sources. This craton comprises two small Archaean cores—the Central Amazonian Province (>2600 Ma)—surrounded by predominantly accretionary Palaeoproterozoic belts; the Maroni-Itacaiunas Province (2250–2050 Ma); the Ventuari-Tapajós Province (1980–1810 Ma); the Rio Negro-Juruena Province (1780–1550 Ma); the Rondonian-San Ignácio Province (1550–1300 Ma) and the ca. 1250–950 Ma Sunsás Province (Cordani and Teixeira, 2007; Cordani et al., 2009; Tassinari et al., 2000). These source regions can account for all of the pre-Neoproterozoic and Tonian ages reported here. However, the formations analysed here in the Alto Paraguay Group also contains inheritance of Cryogenian-aged material— such ages are not reported from the Amazon Craton.

To the east of the Paraguay Belt a number of Neoproterozoic ages have been reported in the Goiás Massif and the Brasília Belt and could represent potential sources for the Alto Paraguay Group sedimentary rocks. From the Brasília Belt these ages include the foreland sequences of the Bambuí Group, the Vazante

Group and their correlatives (790 – 600 Ma) and the Macaúbas Group (950 – 650 Ma; Coelho et al., 2008 and references therein). A Cryogenian Pb/Pb age (740 ± 22 Ma) for sedimentary cover on the São Francisco Craton was reported by Babinski and Kaufman (2003). Ages from the Goiás Massif include a Rb/Sr age of 643 ± 19 Ma from granites and greenstones (Nilson et al., 1997; Pimentel and Fuck, 1994) and Sm/Nd age of 612 ± 66 Ma from mafic to ultramafic rocks (Nilson et al., 1997). A Nd provenance study in the northern Paraguay Belt by Dantas et al. (2009), did not include the Serra Azul Formation in the stratigraphic framework, but did come to the conclusion that material from the upper Alto Paraguay Group was sourced from the Goiás Massif or Brasília Belt to the east. A recent study by Bandeira et al. (2012) also drew the same conclusion based on analysis of palaeocurrent indicators in the upper Alto Paraguay Group. These regions are therefore considered to be the best candidates for sources of the mid- to late-Neoproterozoic ages in the Alto Paraguay Group sediments.

A significant number of the 40Ar/39Ar muscovite analyses are, however, much younger than the reported ages in the Goías Massif and the Brasília Belt. Late Cryogenian–Ediacaran intrusive plutons are found in the present-day core of the Paraguay Belt (Ferreira, 2009; McGee et al., 2012). Erosion of these plutons concomitant with the rising topography of the Paraguay Orogen was suggested as a source for the younger Ediacaran ages by Bandeira et al. (2012). Another possible source for these younger muscovite grains is that they represent grains formed during metamorphism within the belt. The lack of a strong metamorphic overprint or the presence of metamorphic minerals suggests that the presently exposed section of the Paraguay Belt did not reach high temperatures. However, if temperatures did rise above ca. 350˚C in the orogenic hinterland, it is conceivable that some of these grains record exhumation and cooling through the muscovite cooling temperature. If this is the case, a circa 544 ± 7 Ma age for exhumation corroborates well with the end of orogenesis at 518 Ma proposed by (McGee et al., 2012).

6.4. Sedimentary-tectonic model for the formation of the Alto Paraguay GroupThe interpretation of source regions for the Paraguay Belt has important implications for its evolution and tectonic models of Gondwana formation. The Paraguay Belt has for some time has been considered as ‘Brasiliano’ (ca. 940 – 630 Ma) in age (Cordani et al. 2009). However, mounting evidence indicates that it is considerably younger than other orogens involved in suturing Gondwana. To date, no post-Tonian ages have been reported from the Amazon Craton, leading to hypotheses that invoke an easterly source for the late Cryogenian to Ediacaran aged sediments reported here. If this hypothesis is correct and the younger material did come from the east, tectonic inversion of the passive margin, responsible for deposition of the

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Fig. 7. Tectonic model for the evolution of the Paraguay Belt. (a) Serra Azul glaciation at ca. 582 Ma. (b) Initiation of compression resulting in flexural warping of the lithosphere and deposition of the Raizama Formation into the proto-foredeep basin; (c) Continued lithospheric flexure and deepening of the foredeep basin; (d) Termination of orogenesis and deposition of the Diamantino Formation into the Diamantino Lake.

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Puga Formation, Cuiabá Group and Araras Group, to a compressional collisional event is implied by the data presented here. A tectonic model is presented in Figure 7 that fits the currently available geological and radioisotopic data set.

Figure 7a shows the deposition of the Serra Azul Formation diamictite in a passive margin setting on the edge of the Amazon Craton. This formation, at the base of the Alto Paraguay Group, contains inheritance of Cryogenian-aged material. Basin inversion by the time the Serra Azul Formation was deposited is possible, however, the absence of Cryogenian and Ediacaran ages in the overlying Raizama Formation suggests that it occurred at some later stage. If this is the case, given that a glacial influence is recognised for the Serra Azul Formation (Alvarenga et al., 2007; McGee et al., Under review), the Cryogenian detritus in the Serra Azul Formation samples may have been transported from the present-day east by floating ice.

Deposition of the Raizama Formation is interpreted to be tectonically controlled by the initiation of topography, the ‘proto-Paraguay Orogeny’, in the form of a peripheral bulge (Figure 7b). Foreland basin systems form by flexural warping of the lithosphere that generate a downwarp proximal to the orogen, the foreland basin, and a low amplitude, long-wavelength upwarp, the peripheral bulge (Catuneanu et al., 1997). As indicated in Figure 7b, we suggest that the proto-Paraguay Belt was created by such a peripheral bulge—signifying the incipient stages of basin inversion had begun as oceanic crust connected to the Amazon Craton began to be underthrust beneath the Paranapanema Block and the Goiás Massif. A minor influence from volcanic arcs is interpreted in the Raizama Formation based on U-Pb ages reported by (McGee et al., Submitted). These arcs are now buried under the Paraná Basin, to the south east of the Paraguay Belt (Figure 1), and their presence and morphology has been interpreted based on petroleum wells and geophysical techniques (Mantovani and Brito Neves, 2009). Based on currently available ages the Raizama Formation was deposited after middle Ediacaran times (~582 Ma). The Raizama Formation also does not contain the prominent ~544 Ma detritus seen in the overlying Diamantino Formation suggesting that it probably predates this time.

After deposition of the Raizama Formation, a major decrease in sand content and the predominance of siltstone indicates deepening of the foreland basin (Figure 7c). This most likely occurred in response to increased lithospheric flexure as the collision advanced on the Amazonian margin. At this time the interlayered sandstones and siltstones of the Sepotuba Formation were deposited into the foreland basin. The heterogeneous nature of the material deposited in this formation and the presence of rip-up clasts indicates that this was a high-energy environment, influenced by strong currents and storms.

The stacking of progradational parasequences indicates that the basin was progressively filled with coarser sediment of the Diamantino Formation

(Figure 7d). Bandeira et al. (2012) interpreted the Diamantino Formation to record the final exhumation and erosion of the orogen that was deposited into the foreland basin—which they interpreted to be a closed system by this stage—the ‘Diamantino Lake’. Another indicator that the Diamantino Formation is likely to be lacustrine is that the majority of correlative marine Cambrian sequences contain fossils (e.g. Aceñolaza et al., 2009), whilst none have been reported for the Diamantino Formation. The predominance of much younger muscovite ages in the Diamantino Formation most likely represents the increased input from the upper plate of the colliding blocks (the Paranapanema block and Goiás Massif; Figure 7d) and, as previously discussed, the cannibalisation of igneous plutons from within the belt and metamorphic ages as the rocks were exhumed and cooled through the muscovite closure temperature. These ages for final sedimentation and exhumation at circa 544 Ma are in agreement with the observed intrusion of post-orogenic granites at 518 Ma (McGee et al., 2012) and indicate that detachment of the down-going oceanic slab and subsequent removal of the slab-pull force, resulting in the cessation of compressional tectonics, occurred around this time (Figure d).

CONCLUSIONSThe sedimentological work presented here indicates that the Serra Azul Formation was deposited in a glacio-fluvial environment. The three youngest muscovite grains analysed yield a weighted mean age providing a robust maximum depositional age for the Serra Azul Formation at 640 ± 15 Ma. This age, when considered with other data, suggest that the Serra Azul Formation developed in a mid-Ediacaran glaciation consistent with that expressed in the Gaskiers Formation of Newfoundland, Canada. 40Ar/39Ar ages from the upper part of the Alto Paraguay Group are as young as 544 ± 7 Ma, consistent with mounting evidence that indicate a Cambrian age for orogenesis within the Paraguay Belt at the final amalgamation of Gondwana. The tectonic model presented here, based on our sedimentary and stratigraphic analysis and these new ages, shows the transition from a marine passive margin environment to a compressional setting where the Paraguay Orogen formed as a peripheral bulge in the lithosphere of the Amazonian Craton.

ACKNOWLEDGEMENTSThe authors would like to thank Marly Babinski for her assistance in São Paulo, for access to laboratories and facilities required to write this manuscript. Ben McGee would like to thank Vasco for his assistance in the laboratory. C. Mayer and A. Frew are acknowledged for their help during the 40Ar/39Ar analyses of muscovite. ASC thanks FAPESP and the Australian Research Council (FT120100340) for funding. This paper forms TRaX Record #xxx. REFERENCES

58


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60

Chapter 4 The tectonic and palaeoenvironmental significance of the Alto Paraguay GroupTa

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610.

0244

0.05

132A

1973

9D9.

4702

E-0

680

1.93

18E

-03

275

2.04

12E

-05

191.

8210

E-0

32

2.46

44E

-01

014

8140

98.7

93.

630.

4056

2.22

782A

1974

0D1.

1193

E-0

565

1.12

53E

-03

531

4.30

02E

-06

714.

1017

E-0

42

2.70

51E

-02

179

612

388

.00

0.81

0.15

641.

6600

2A19

741D

2.64

93E

-08

3028

45.

9058

E-0

389

1.73

49E

-05

201.

0873

E-0

32

9.72

48E

-02

011

0549

99.5

02.

170.

0795

0.14

172A

1974

3D1.

2488

E-0

584

9.03

92E

-03

595.

5682

E-0

59

4.24

77E

-03

11.

9505

E-0

10

641

1997

.70

8.47

0.20

240.

2375

2A19

744D

5.83

03E

-06

134

6.26

85E

-04

855

1.32

82E

-06

273

4.00

16E

-04

43.

4463

E-0

20

1037

129

94.8

00.

800.

2748

4.70

11

BS

A 08

61


Tabl

e 1.

(con

tinue

d)

Ana

lysi

s N

ame

36A

r%

1σ37

Ar

%1σ

38A

r%

1σ39

Ar

%1σ

40A

r%

1σA

ge (M

a)±

2σ40

Ar(

r)(%

)39

Ar(

k)(%

)K

/Ca

± 2σ

2A19

555D

1.40

93E

-06

312

2.59

77E

-03

129

4.21

25E

-05

163.

1035

E-0

31

2.23

14E

-01

093

919

99.7

13.

300.

5140

1.33

062A

1955

6D4.

4722

E-0

611

99.

6953

E-0

424

81.

2736

E-0

544

1.20

48E

-03

18.

3204

E-0

20

925

3110

1.70

1.28

0.53

402.

6460

2A19

557D

7.21

94E

-06

658.

4430

E-0

433

73.

6637

E-0

514

2.26

10E

-03

11.

5765

E-0

10

909

1898

.59

2.40

1.15

197.

7734

2A19

559D

4.93

40E

-06

985.

3895

E-0

445

29.

4169

E-0

58

7.46

51E

-03

15.

2335

E-0

10

921

1299

.71

7.93

5.95

6353

.824

22A

1956

0D6.

3775

E-0

654

4.95

99E

-05

6689

2.45

33E

-05

241.

3663

E-0

32

1.15

03E

-01

010

4932

98.3

41.

4511

.845

815

84.7

231

2A19

561D

7.69

65E

-06

816.

2964

E-0

438

05.

8248

E-0

57

4.65

06E

-03

14.

0955

E-0

10

1095

1499

.45

4.94

3.17

5724

.142

62A

1956

2D1.

7391

E-0

630

71.

4326

E-0

320

45.

6776

E-0

514

3.93

93E

-03

12.

7298

E-0

10

914

1299

.85

4.18

1.18

214.

8347

2A19

564D

5.62

07E

-07

715

3.39

73E

-03

763.

4650

E-0

514

1.81

83E

-03

11.

2775

E-0

10

923

2299

.91

1.93

0.23

050.

3519

2A19

565D

9.39

99E

-06

492.

0284

E-0

312

81.

2309

E-0

557

1.73

62E

-03

11.

2751

E-0

10

939

2197

.66

1.85

0.36

840.

9447

2A19

566D

1.03

49E

-05

431.

4718

E-0

328

61.

3751

E-0

532

1.29

65E

-03

11.

4213

E-0

10

1272

2797

.91

1.38

0.37

852.

1680

2A19

569D

2.33

18E

-06

304

2.18

38E

-03

163

1.54

86E

-05

441.

0532

E-0

31

1.33

41E

-01

014

2040

99.3

41.

120.

2077

0.67

772A

1957

0D8.

6296

E-0

764

92.

4875

E-0

315

71.

5092

E-0

571

2.86

70E

-03

13.

9848

E-0

10

1520

1599

.88

3.05

0.49

591.

5527

2A19

571D

7.06

41E

-07

839

1.74

27E

-03

227

1.90

23E

-05

392.

0781

E-0

31

2.13

19E

-01

012

3124

99.9

72.

210.

5124

2.33

092A

1957

2D2.

0279

E-0

628

52.

5881

E-0

313

73.

9044

E-0

525

3.24

75E

-03

03.

7343

E-0

10

1332

1399

.78

3.45

0.53

991.

4846

2A19

574D

6.52

12E

-06

742.

0873

E-0

319

61.

3861

E-0

554

2.26

49E

-03

02.

5416

E-0

10

1318

1410

0.70

2.41

0.46

691.

8316

2A19

575D

5.74

63E

-06

113

1.10

92E

-03

342

1.53

43E

-05

512.

0351

E-0

32

1.44

57E

-01

094

230

101.

252.

160.

7886

5.39

842A

1957

6D1.

6911

E-0

634

74.

2353

E-0

310

83.

7864

E-0

525

3.44

49E

-03

13.

8632

E-0

10

1308

1799

.78

3.66

0.35

010.

7581

2A19

579D

1.61

54E

-07

3285

7.85

13E

-04

470

3.15

37E

-05

211.

8193

E-0

31

1.28

83E

-01

093

124

100.

011.

930.

9961

9.36

432A

1958

0D1.

2287

E-0

646

07.

8572

E-0

442

63.

1960

E-0

529

2.44

63E

-03

12.

2350

E-0

10

1128

2799

.81

2.60

1.33

9111

.415

32A

1958

1D8.

8558

E-0

772

71.

3051

E-0

326

93.

9001

E-0

517

2.90

13E

-03

12.

6120

E-0

10

1116

2299

.86

3.08

0.95

625.

1470

2A19

582D

6.93

42E

-06

724.

7081

E-0

382

5.86

55E

-05

134.

7158

E-0

31

3.53

25E

-01

096

915

99.5

35.

000.

4304

0.70

952A

1958

4D4.

2432

E-0

615

61.

0214

E-0

334

31.

6644

E-0

47

1.31

88E

-02

18.

9294

E-0

10

899

1010

0.15

14.0

05.

5514

38.0

856

2A19

746D

5.75

61E

-06

841.

6905

E-0

325

62.

8895

E-0

517

2.77

75E

-03

12.

7995

E-0

10

1219

1510

0.56

2.95

0.70

683.

6141

2A19

747D

6.09

69E

-08

1256

13.

8434

E-0

372

2.73

93E

-05

121.

8059

E-0

31

2.10

65E

-01

013

5131

100.

141.

910.

2017

0.29

082A

1974

8D9.

5870

E-0

752

71.

2318

E-0

333

55.

3235

E-0

513

5.05

53E

-03

13.

5651

E-0

10

927

1599

.89

5.37

1.76

5111

.838

42A

1974

9D1.

6229

E-0

633

53.

7369

E-0

394

1.66

86E

-05

341.

8328

E-0

31

1.29

85E

-01

093

125

100.

131.

950.

2112

0.39

652A

1975

2D2.

5391

E-0

622

89.

4659

E-0

382

2.37

43E

-05

342.

9119

E-0

31

3.42

77E

-01

013

5516

99.9

93.

100.

1326

0.21

762A

1975

3D7.

2381

E-0

690

1.56

54E

-04

4552

3.18

01E

-05

242.

6361

E-0

31

2.99

69E

-01

013

1728

99.2

72.

807.

2415

659.

2694

2A19

754D

1.86

53E

-07

3800

5.46

02E

-03

135

2.83

85E

-05

233.

6613

E-0

30

4.93

67E

-01

014

8912

99.9

03.

890.

2886

0.77

972A

1975

5D5.

2625

E-0

611

78.

4628

E-0

391

2.57

85E

-05

322.

5514

E-0

31

1.94

09E

-01

097

325

98.8

22.

720.

1300

0.23

72

1A18

396/

97D

1.02

65E

-05

148

2.46

28E

-03

212.

7281

E-0

536

1.62

12E

-03

27.

2418

E-0

20

667

68-

-0.

2275

0.14

341A

1841

8/19

D2.

6072

E-0

555

7.79

34E

-04

743.

7576

E-0

533

2.88

36E

-03

12.

0632

E-0

10

1027

72-

-0.

9724

2.93

91

BR

Z 09

BD

M 0

9

62

Chapter 4 The tectonic and palaeoenvironmental significance of the Alto Paraguay GroupTa

ble

1. (c

ontin

ued)

Ana

lysi

s N

ame

36A

r%

1σ37

Ar

%1σ

38A

r%

1σ39

Ar

%1σ

40A

r%

1σA

ge (M

a)±

2σ40

Ar(

r)(%

)39

Ar(

k)(%

)K

/Ca

± 2σ

1A18

420D

8.15

20E

-06

947.

7481

E-0

540

31.

8458

E-0

545

2.01

35E

-03

11.

6337

E-0

10

1045

3110

1.48

100.

0011

.174

590

.059

31A

1847

7/79

D1.

3534

E-0

582

1.40

89E

-03

391.

8820

E-0

564

2.83

10E

-03

11.

2658

E-0

10

625

51-

-0.

7321

0.50

341A

1845

8D2.

4518

E-0

660

61.

3264

E-0

442

81.

9831

E-0

554

1.69

04E

-03

11.

4355

E-0

10

1074

5510

0.52

100.

005.

4797

46.8

613

1A18

460/

61D

4.08

47E

-06

584

1.96

14E

-04

437

9.32

49E

-07

2335

1.43

38E

-03

26.

3809

E-0

21

612

107

--

1.36

0012

.890

01A

1845

7D2.

4794

E-0

660

13.

6587

E-0

416

02.

2963

E-0

545

1.27

21E

-03

25.

8551

E-0

20

664

8610

1.32

100.

001.

4948

4.78

821A

1845

5/56

D1.

7667

E-0

512

22.

8479

E-0

428

91.

3454

E-0

510

56.

5130

E-0

43

5.36

45E

-02

111

0116

3-

-0.

1800

0.78

001A

1843

8/39

D7.

6303

E-0

618

51.

9246

E-0

436

13.

5329

E-0

624

92.

1228

E-0

31

8.48

53E

-02

058

338

--

0.16

000.

8000

1A18

436/

37D

5.62

86E

-07

2429

7.16

99E

-04

92-7

.570

8E-0

613

71.

6994

E-0

32

7.66

14E

-02

064

760

--

0.81

001.

5200

1A18

527/

28D

3.18

11E

-06

351

1.12

03E

-03

584.

8708

E-0

634

61.

1092

E-0

32

5.03

93E

-02

063

170

--

0.42

920.

4827

1A18

529/

30D

1.71

72E

-06

686

8.73

32E

-04

831.

9777

E-0

585

1.55

30E

-03

26.

7182

E-0

20

608

55-

-0.

7100

1.07

041A

1853

2/3D

1.82

79E

-05

781.

1535

E-0

470

73.

4593

E-0

554

2.28

66E

-03

21.

0446

E-0

10

632

40-

-0.

7000

5.60

002A

1950

7D3.

5572

E-0

615

41.

7213

E-0

316

82.

1178

E-0

523

1.29

90E

-03

25.

6111

E-0

20

630

3910

1.63

100.

000.

3248

1.09

152A

1950

8D1.

0401

E-0

575

5.37

00E

-03

751.

4434

E-0

540

1.00

34E

-03

24.

5683

E-0

20

605

6092

.21

100.

000.

0807

0.12

152A

1950

9D1.

8908

E-0

524

2.84

64E

-03

116

2.24

03E

-05

302.

0199

E-0

31

1.41

61E

-01

089

218

95.8

410

0.00

0.30

550.

7107

2A19

511D

1.32

52E

-07

3056

2.48

50E

-03

110

1.76

22E

-05

458.

6178

E-0

41

3.79

17E

-02

163

638

100.

6610

0.00

0.14

880.

3259

2A19

512D

4.25

55E

-06

218

8.42

28E

-03

312.

3550

E-0

532

1.40

17E

-03

17.

5520

E-0

20

729

4897

.38

100.

000.

0719

0.04

392A

1951

3D2.

9074

E-0

627

81.

2509

E-0

318

44.

4034

E-0

514

1.93

20E

-03

18.

5565

E-0

20

629

3498

.86

100.

000.

6645

2.44

062A

1951

5D2.

8972

E-0

614

25.

1148

E-0

366

2.92

86E

-05

161.

8325

E-0

31

8.19

67E

-02

063

918

99.4

710

0.00

0.15

370.

2033

2A19

516D

5.12

49E

-06

415.

8344

E-0

340

5.87

80E

-06

413.

1128

E-0

43

1.32

79E

-02

170

159

115.

2210

0.00

0.02

260.

0182

2A19

720D

4.18

67E

-06

191

2.39

90E

-03

352

1.51

87E

-05

361.

0652

E-0

31

4.47

80E

-02

059

759

97.6

611

.39

0.19

061.

3424

2A19

721D

2.63

92E

-06

276

8.62

38E

-04

986

2.33

39E

-05

352.

0426

E-0

31

9.35

84E

-02

064

931

99.0

821

.88

1.01

8820

.080

92A

1972

2D1.

4060

E-0

556

3.43

88E

-04

2636

1.17

50E

-05

521.

0810

E-0

31

4.88

94E

-02

059

959

91.3

511

.58

1.35

2171

.274

72A

1972

3D3.

6262

E-0

622

63.

8916

E-0

321

91.

8163

E-0

528

1.43

94E

-03

16.

4512

E-0

20

636

4698

.83

15.3

80.

1587

0.69

532A

1972

5D5.

1578

E-0

614

71.

0082

E-0

287

1.06

14E

-05

461.

1901

E-0

31

5.43

68E

-02

062

551

95.6

012

.82

0.05

1 10.

0889

2A19

726D

2.99

46E

-06

318

1.22

90E

-03

714

1.18

05E

-05

571.

5073

E-0

31

6.33

31E

-02

061

650

101.

5716

.13

0.52

717.

5318

2A19

727D

1.75

26E

-06

512

1.53

90E

-03

565

9.62

48E

-06

641.

0114

E-0

32

4.72

11E

-02

067

269

101.

3810

.82

0.28

233.

1877

2A19

677D

5.10

45E

-06

976.

7497

E-0

477

44.

8231

E-0

511

4.36

68E

-03

11.

8051

E-0

10

595

1699

.12

8.59

2.78

2243

.092

72A

1967

8D2.

1549

E-0

626

58.

4614

E-0

372

3.67

43E

-05

272.

8051

E-0

31

2.03

05E

-01

094

017

99.3

35.

530.

1429

0.20

682A

1967

9D4.

3849

E-0

796

22.

5035

E-0

321

43.

1426

E-0

517

2.73

68E

-03

19.

9504

E-0

20

539

1810

0.34

5.38

0.46

982.

0129

2A19

681D

3.54

28E

-07

1457

3.21

02E

-03

169

2.23

18E

-05

221.

3776

E-0

31

5.57

51E

-02

059

333

100.

672.

700.

1842

0.62

222A

1968

2D2.

1390

E-0

621

41.

9098

E-0

328

41.

0380

E-0

557

5.49

97E

-04

36.

1160

E-0

20

1289

7098

.69

1.08

0.12

410.

7041

2A19

683D

5.73

45E

-06

925.

2729

E-0

310

01.

8401

E-0

528

1.30

18E

-03

14.

9995

E-0

20

574

3310

2.54

2.57

0.10

650.

2122

2A19

686D

2.46

23E

-06

122

6.74

60E

-03

811.

4119

E-0

538

1.20

26E

-03

15.

4511

E-0

20

647

2310

0.31

2.37

0.07

700.

1250

BD

M 1

2

63


Tabl

e 1.

(con

tinue

d)

Ana

lysi

s N

ame

36A

r%

1σ37

Ar

%1σ

38A

r%

1σ39

Ar

%1σ

40A

r%

1σA

ge (M

a)±

2σ40

Ar(

r)(%

)39

Ar(

k)(%

)K

/Ca

± 2σ

2A19

687D

2.03

17E

-06

361

3.29

69E

-03

197

4.89

12E

-05

113.

1165

E-0

31

1.16

42E

-01

054

922

99.7

26.

120.

4062

1.59

982A

1968

8D1.

1804

E-0

635

92.

2312

E-0

324

32.

6218

E-0

529

2.30

46E

-03

19.

9214

E-0

20

620

1799

.83

4.53

0.44

382.

1598

2A19

689D

5.54

87E

-06

831.

0185

E-0

356

33.

1660

E-0

520

2.28

34E

-03

18.

6950

E-0

20

549

2097

.99

4.49

0.96

4310

.865

32A

1969

1D8.

3641

E-0

749

37.

0643

E-0

384

2.58

34E

-05

231.

5079

E-0

31

5.51

06E

-02

053

124

98.4

72.

980.

0921

0.15

452A

1969

2D2.

0038

E-0

626

01.

1045

E-0

359

41.

8938

E-0

533

1.39

01E

-03

16.

6742

E-0

20

676

3099

.24

2.73

0.54

096.

4278

2A19

693D

4.29

08E

-08

8214

1.72

13E

-03

388

2.62

93E

-05

181.

7534

E-0

32

7.40

68E

-02

061

224

100.

183.

450.

4377

3.39

242A

1969

4D3.

5627

E-0

611

01.

2378

E-0

354

72.

2316

E-0

516

1.15

65E

-03

14.

2935

E-0

20

560

3210

2.72

2.27

0.40

144.

3879

2A19

696D

2.83

60E

-07

2009

5.01

30E

-03

120

2.18

79E

-05

231.

6515

E-0

32

6.22

85E

-02

054

933

99.1

83.

250.

1420

0.34

182A

1969

7D5.

5570

E-0

677

1.01

62E

-03

573

5.58

22E

-06

946.

5428

E-0

42

2.48

86E

-02

052

458

92.9

91.

290.

2772

3.17

482A

1969

8D4.

5284

E-0

611

43.

2457

E-0

417

275.

7442

E-0

512

4.06

42E

-03

11.

4718

E-0

10

539

1310

0.90

7.99

5.38

4818

5.98

352A

1969

9D1.

1435

E-0

638

69.

1827

E-0

459

63.

3085

E-0

520

1.83

90E

-03

19.

0201

E-0

20

695

2110

0.46

3.61

0.86

0810

.261

42A

1970

1D3.

3514

E-0

913

7429

7.65

38E

-04

836

2.02

33E

-05

242.

3088

E-0

31

3.96

54E

-01

017

4934

100.

024.

541.

2968

21.6

697

2A19

702D

4.89

10E

-06

923.

8461

E-0

315

49.

3168

E-0

649

6.29

95E

-04

22.

6764

E-0

20

650

6010

6.67

1.23

0.07

010.

2163

2A19

703D

7.79

49E

-06

492.

9005

E-0

420

493.

5431

E-0

616

76.

5122

E-0

43

2.92

43E

-02

168

655

108.

041.

280.

9651

39.5

409

2A19

704D

2.01

61E

-07

2021

6.96

15E

-04

849

7.93

96E

-06

547.

9657

E-0

41

2.96

62E

-02

054

843

100.

001.

570.

4923

8.35

722A

1970

6D6.

5561

E-0

749

13.

6087

E-0

416

041.

7538

E-0

523

1.13

40E

-03

15.

1410

E-0

20

650

2610

0.44

2.23

1.35

1043

.342

52A

1993

1D2.

5669

E-0

636

41.

3783

E-0

361

32.

3148

E-0

529

1.92

27E

-03

17.

2968

E-0

20

551

3998

.79

3.78

0.60

017.

3573

2A19

932D

5.95

58E

-06

142

1.53

62E

-03

507

9.04

01E

-06

729.

3056

E-0

41

3.78

80E

-02

056

572

94.9

61.

830.

2608

2.64

602A

1993

3D2.

7582

E-0

633

86.

2082

E-0

313

61.

1323

E-0

552

1.10

72E

-03

25.

0140

E-0

20

648

6510

0.60

2.19

0.07

700.

2090

2A19

934D

4.05

65E

-06

212

2.78

82E

-03

285

2.44

43E

-05

361.

8348

E-0

32

8.51

44E

-02

065

539

98.8

53.

600.

2827

1.61

182A

1993

6D3.

2488

E-0

726

971.

5828

E-0

349

91.

5979

E-0

539

1.28

87E

-03

16.

0945

E-0

20

674

5210

0.38

2.53

0.34

983.

4942

2A19

937D

3.49

17E

-06

270

6.08

39E

-04

1285

8.94

15E

-06

511.

2033

E-0

31

5.13

31E

-02

060

661

98.0

72.

370.

8502

21.8

525

2A19

938D

2.76

33E

-06

354

2.83

60E

-03

304

5.76

35E

-06

779.

6808

E-0

42

6.87

13E

-02

091

972

98.4

51.

910.

1471

0.89

34

Chapter 5: Age and Provenance of the Cryogenian to Cambrian passive margin to foreland basin sequence of the northern Paraguay Belt, Brazil.

This chapter is under review as:McGee, B., Collins, A.S. and Trindade, R.I.F., Under Review. Age and Provenance of the Cyrogenian to Cambrian passive margin to foreland basin sequence of the northern Paraguay Belt, Brazil. Bulletin of the Geological Society of America.

67

Chapter 5 Age and provenance of the northern Paraguay Belt

Age and Provenance of the Cryogenian to Cambrian passive margin to foreland basin sequence of the northern Paraguay Belt, Brazil

Ben McGee1, Alan S. Collins1 and Ricardo I.F. Trindade2

1Centre for Tectonics, Resources and eXploration (TRaX), School of Earth and Environmental Sciences, B09, Mawson Building, The University of Adelaide, SA 5005, Australia.2Departamento de Geofísica, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, 05508-090, São Paulo, Brazil.

ABSTRACT

The Paraguay Belt in central South America developed in response to the collision between the Amazonian Craton, the Rio Apa Block, the São Francisco Craton and the Paranapanema Block. The alleged ‘Brasiliano’ age (~620 Ma) of orogenesis has recently been questioned by palaeomagnetic and radioisotopic ages that indicate the closing stages of orogenesis occurred well into the Cambrian. The timing of deposition and source areas for these sedimentary rocks overlying the Amazonian Craton are investigated here using integrated U-Pb and Hf isotope data of detrital zircons from within this sequence. 742 detrital zircon LA-ICPMS U-Pb ages were analysed from samples taken from the base to the top of this sedimentary succession. Maximum depositional ages from the uppermost part of this sequence of rocks, the Diamantino Formation, indicate that final sedimentation began no earlier than 527 Ma. Given that zircon inheritance in these rocks continues up until this age and that known Amazonian Craton ages are older than ~950 Ma we consider other potential sources for these sediments. This is achieved by integrating the U-Pb detrital zircon data with Hf isotopic data from these zircons that have εHf values ranging from -18 to 12. The εHf signature is consistent with a predominantly Amazonian source until the early-Neoproterozoic at which point the signal becomes significantly more evolved. These data, when combined with other evidence

discussed here, are consistent with an ocean to the east of the present-day Amazonian Craton that didn’t close until the Cambrian.

INTRODUCTION

Reconstructing the palaeogeography and the timing of formation of the Palaeozoic supercontinent Gondwana has received significant attention in the literature for many decades (e.g. Collins and Pisarevsky, 2005; Stern, 1994). A fundamental requirement of these reconstructions is that they fulfill available geological constraints, including correlations based on ages of events in neighbouring orogenic belts, palaeomagnetic constraints and relationships between sedimentary, geochemical and temporal provenance patterns. Early Gondwana reconstruction models of a collision between large fragments of east and west Gondwana at ~650 Ma (Stern, 1994) have evolved to incorporate current evidence that identify a network of suturing events between relatively small Neoproterozoic continents that amalgamated to form Gondwana during the Ediacaran and Cambrian (e.g. Collins and Pisarevsky, 2005; Meert, 2003; Pisarevsky et al., 2008). The Paraguay Belt in Brazil is part of this network of Gondwana-forming orogens that for some time has been considered as ‘Brasiliano’ (ca. 940 – 620 Ma) in age (Cordani et al. 2009). This interpretation is based upon ages from the western border of the São Francisco Craton and implies that amalgamation of western Gondwana occurred at around 620 Ma.

This hypothesis was brought

into question by the presentation of a palaeomagnetic pole from carbonates of the Araras Group, from the northern Paraguay Belt, that indicated Amazonia was at low latitudes at the beginning of the Ediacaran (Trindade et al., 2003). This finding suggested that Amazonia was separated from proto-Gondwana by a large ocean—the Clymene Ocean—up until the Cambrian (Trindade et al., 2006). In this model a major orogenic belt encompassing the Araguaia, Paraguay and Pampean belts represented the suture zone of this ocean and the final amalgamation of Gondwana. This proposition promoted interest in these regions and several studies incorporating palaeomagnetic, Sm-Nd, geochronological, sedimentary and stratigraphic methodologies have since followed.

In this study we present a large U-Pb data set to complement these previous works in order to better understand the provenance of these sediments. In addition to these temporal constraints we present accompanying Lu-Hf isotope data that provide information about the crustal evolution of the source region and allow for comparisons between sedimentary packages. We go on to discuss the implications of these finding on the tectonic and palaeogeographic reconstructions for Amazonia in the context of Gondwana amalgamation.

REGIONAL SETTING

The Paraguay Belt is located in central South America (Figure 1) and marks the boundary between the Amazon, São Francisco, Paranapanema, Rio Apa and Rio de la Plata cratons. It comprises

68


metamorphosed Neoproterozoic and Cambrian sedimentary strata that were deposited in a passive margin environment (Alvarenga and Trompette, 1992). These metasedimentary and sedimenatary rocks are divided into the older pelites, diamictites and siliciclastics of the Cuiabá Group in the core of the orogen (Barros et al., 1982), diamictites of the Puga Formation, carbonates of the Araras Group and siliciclastics of the upper Alto Paraguay Group. While the nature of the contact between the Cuiabá Group and Puga Formation not well understood do to non-exposure, recent interpretations describe the Puga diamictite as the proximal ‘shelf’ facies of the Cuiabá Group

(Alvarenga et al., 2009). The age of the youngest detrital zircon in the Puga Formation (706 ± 9 Ma; Babinski et al., In press). The δ13C (5.0‰) and the 87Sr/86Sr (0.7080) ratios from carbonates directly overlying the diamictites (Nogueira et al., 2003), suggest that these represent the ~635 Ma end-Cryogenian glaciation.

In the northern Paraguay Belt the stratigraphic framework of the Alto Paraguay Group was first described by Almeida (1964) who divided it into the ~1600 m sands, silts and shale of the Raizama Formation, ~900 m of shale, silts and sandstones of the Sepotuba Formation and ~600 m of Diamantino Formation rhythmites

and sandstones. More recently Alvarenga et al. (2007) described a new unit, the Serra Azul Formation, in between carbonates of the Araras Group and the siliclastics of the Alto Paraguay Group. The basal part of this formation is composed of a glaciogenic diamictite containing multiply striated sandstone clasts (Alvarenga et al., 2007) and striated, polished and bullet-shaped mudstone clasts (McGee et al., Under Review), which is overlain by a transgressive package of interlayered silts and fine sands. The siltstone and sandstone of the upper Alto Paraguay Group were shed off rising topography—the Paraguay orogen—in response to collision between the Amazonian

Figure 1 - Author: Ben McGee , Extension: .pdf

Figure 1. Geological map showing lithostratigraphic relationships within the northern Paraguay Belt. Modified from CPRM Cuiabá 1:1000000 map sheet (Barros et al., 1982). Stars indicate the location of samples for geochronological analysis; 1: BDM-01 and BRZ-02; 2: BRZ-02; 3: BSA-07, BRZ-15; 4: BPUG-02, BSA-20, BST-24.

A NOTE:


69


Craton, the São Francisco Craton and the Paranapanema Block between ~540–520 Ma (Bandeira et al., 2011). The termination of orogenesis was marked by intrusion of post-orogenic granites into the base of these sediments at ~518 Ma (McGee et al., 2012).

ANALYTICAL METHODS

Zircon U-Pb LA-ICPMS analysis

The location of samples collected for geochronological analysis are shown in Figure 1. These samples were prepared using the methods described in McGee et al. (2012). U–Pb fractionation was corrected using the GEMOC GJ-1 zircon standard (TIMS normalisation data 207Pb/206Pb = 608.3 Ma, 206Pb/238U = 600.7 Ma and 207Pb/235U = 602.2 Ma, (Jackson et al., 2004)) and accuracy was checked using the recognised zircon standard ‘Plesovice’ with a 206Pb/238U = 337.13 ± 0.37 Ma (Slama et al., 2008). Data reduction was performed using GLITTER (Van Achterbergh et al., 2001). The average normalised ages for GJ-1 during the course of this study were 608.6 Ma ± 9.2 (2s) Ma (MSWD = 0.030), 601.4 ± 2.4 (2s) Ma (MSWD = 0.094) and 602.7 ± 2.3 (2s) Ma (MSWD = 0.058) for the 207Pb/206Pb, 206Pb/238U and 207Pb/235U ratios respectively (n = 362). The average normalised 206Pb/238U age for Plesovice is 337.9 ± 1.3 (2s) Ma (MSWD = 0.057; n = 139). Probability density plots were constructed using Isoplot version 3.0 (Ludwig, 2003).

Zircon Hf isotopic analysis

The same zircon mount discs prepared for U-Pb isotopic analysis were used for Hf. Hafnium analyses were conducted via Laser Ablation Multicollector Inductively Coupled Plasma Mass Spectrometry (LA-MC-ICPMS) at the University of Adelaide and CSIRO’s joint facility at the Waite campus in South Australia. Ablation was achieved using a New Wave UP-193 Excimer laser (193 nm) using a spot size of 50 μm; frequency of 4 Hz; 4 ns pulse

length and an intensity of ∼8–10 J/cm2. Hafnium ablation pits targeted the same textural CL zone as the corresponding U-Pb ablation pit and were made in a helium atmosphere and subsequently mixed with argon upstream of the ablation cell. The attached Thermo-Scientific Neptune Multi Collector ICP-MS measured 171Yb, 173Yb, 175Lu, 176Hf, 177Hf, 178Hf, 179Hf and 180Hf on Faraday detectors with 1011 Ω amplifiers. 500 sweeps of this isotope array were made, each of 0.262 seconds length, for a total analysis time of 131 seconds, including a 30 second Helium gas background measurement. Hf Mass bias was corrected using an exponential fractionation law with a stable 179Hf/177Hf ratio of 0.7325. Yb and Lu isobaric interferences on 176Hf were corrected using the methods of (Woodhead et al., 2004). 176Yb interference on 176HF was corrected through direct measurement of Yb fractionation using measured 171Yb/173Yb with the Yb isotopic values of (Segal et al., 2003). The applicability of these values were verified by analysing JMC 475 Hf solutions doped with varying levels of Yb with interferences up to 176Yb/177Hf = ∼0.5. Lu isobaric interference on 176Hf was corrected using a 176Lu/175Lu ratio of 0.02655 (Vervoort et al., 2004) assuming the same mass bias behaviour of as Yb.

Set-up of the system prior to ablation sessions was conducted using analysis of JMC475 Hf solution and an AMES Hf solution. Confirmation of accuracy of the technique for zircon analysis was monitored using a combination of the Plesovice, Mudtank and QGNG standards. The average value for Plesovice for the analytical session was 0.282471 ± 0.000017 (2σ; n = 24), which statistically overlaps the published value of 0.282482 ± 0.000013 (2σ; Slama et al., 2008). TDM and TDM crustal were calculated using 176Lu decay constant after (Scherer et al., 2001). TDM crustal was calculated using the methods of (Griffin et al., 2000) with an average crustal composition of 176Lu/177Hf = 0.015.

RESULTS

Zircon U-Pb LA-ICPMS isotopic results

Eight samples were selected for geochronological analysis that gave the broadest temporal range, from the base of the Puga Formation to the top of the Alto Parauay Group (Figure 1). Sample BPUG-02 is a green/grey diamictite with a coarse matrix from the Puga Formation. Samples BSA-07 and BSA-20 are from the Serra Azul Formation and are a brown/maroon diamictite with a fine silty matrix and a pale green diamictite with a fine sandy matrix respectively. Samples BRZ-01, BRZ-02 & BRZ-15 are medium and coarse arenites with lenses of matrix supported pebble conglomerate from the Raizama Formation. Sample BST-24 is from the Sepotuba Formation and is a deep red/purple coarse-grained arenite. BDM-01 is from the top of the sequence—the Diamantino Formation—and is a mature, white coarse sandstone.

Geochronological data are presented in Figures 2 and 3 and analytical data are provided in supplemental Table 1. Ages are reported using the 206Pb/238U ratio, all errors are quoted at the 2 sigma (2σ) level and weighted averages are at 95 % confidence. Laser-ablation spots targeted oscillatory-zoned magmatic cores where possible (Figure 4).

Age Estimates

BDM-01 (Mature pale arenite)98 LA-ICPMS analyses of 96

zircon grains were collected from sample BDM-01 (Table 1), targeting moderately luminescent cores and rims, in some cases with oscillatory zoning (Figure 4a). BDM-01 is the only sample that shows Cambrian zircon inheritance (Figure 3), with the youngest grain at 527 Ma (Figure 2). The majority of other grains are Mesoproterozoic and another peak in the Palaeoproterozoic (Figure 3).

BST-24 (Deep purple coarse grained arenite)

70


99 LA-ICPMS analyses of an equal number of zircon grains were collected from sample BRZ-24 (Table 1), targeting moderately luminescent, oscillatory-zoned magmatic growth regions (Figure 4b). All analyses are highly concordant (Figure 2) and lie between 615 Ma and 1950 Ma (Figure 3).

BRZ-15 (Coarse grained arenite)81 LA-ICPMS analyses of an

equal number of zircon grains were collected from sample BRZ-15 (Table 1), targeting moderate- to highly-luminescent oscillatory-zoned magmatic regions (Figure 4c). The analyses are predominantly concordant (Figure 2) and lie between 950 Ma and 1800 Ma (Figure 3) with one large peak at 1550 Ma.

BRZ-01 (Medium grained arenite)82 LA-ICPMS analyses of

an equal number of zircon grains were collected from sample BRZ-01 (Table 1), targeting moderately luminescent, oscillatory-zoned magmatic growth regions (Figure 4d). The analyses are generally concordant (Figure 2) and mainly

spread between 900 Ma and 1560 Ma with two outliers, one at 635 Ma and the other at 1984 Ma (Figure 3).

BRZ-02 (Coarse grained arenite)86 LA-ICPMS analyses of

85 zircon grains were collected from sample BRZ-02 (Table 1), targeting moderately luminescent, oscillatory-zoned magmatic growth regions (Figure 4e). The majority of analyses are highly concordant (Figure 2) and lie between 900 Ma and 1850 Ma (Figure 3).

BSA-07 (Green/grey diamictite)105 LA-ICPMS analyses of 103

zircon grains were collected from sample BSA-07 (Table 1), targeting moderate- to highly-luminescent oscillatory-zoned magmatic growth zones (Figure 4f). The majority of grains are concordant with a small number of discordant grains with no obvious common-Pb or Pb-loss trend (Figure 2). The three youngest analyses are grouped around 650 Ma, the youngest at 646 Ma, with the majority of grains spread between 900 and 1700 Ma (Figure 3). Three prominent peaks occur at 1860 Ma, 1975 Ma and 2090 Ma respectively.

BSA-20 (Green/grey diamictite)98 LA-ICPMS analyses of

97 zircon grains were collected from sample BSA-20 (Table 1), targeting moderately luminescent, oscillatory-zoned magmatic growth regions (Figure 4g). The majority of samples lie along concordia (Figure 2) from 665 Ma to 2050 Ma (Figure 3).

BPUG-02 (Red/brown to purple Diamictite)

93 LA-ICPMS analyses of an equal number of zircon grains were collected from sample BPUG-02 (Table 1), targeting dark to moderately luminescent oscillatory-zoned magmatic growth regions (Figure 4h). The analyses are highly to moderately concordant, with a slight spread of data below concordia (Figure 2). Two main clusters of data are apparent; at 1050 Ma and spread between 1400 Ma and 1800 Ma (Figure 3).

Zircon Hf isotopic results

Hf istopic results are presented in an εHf vs. time plot in Figure 5 and the corresponding data are

200

BDM-01Areniten = 98

206Pb/238U

2200

1800

1400

1000

600

200

BST-24Areniten = 99

2200

1800

1400

1000

600

200

BRZ-15Areniten = 81

2200

1800

1400

1000

600

200

BRZ-01Areniten = 82

2200

1800

1400

1000

600

200

BRZ-02Areniten = 86

2200

1800

1400

1000

600

200

BSA-07Diamictiten = 105

2200

1800

1400

1000

600

200

BSA-20Diamictiten = 98

0.0

0.1

0.2

0.3

0.4

0 2 4 6 8207Pb/235U

U20

6 Pb/23

8

2200

1800

1400

1000

600

200

BPUG-02Diamictiten = 93

Cam

bria

nEd

iaca

ran

Cryo

geni

anTo

nian

Figure 2 - Colour for web only. Author: Ben McGee, Extension: .pdf

Figure 2. Concordia plots for U-Pb detrital zircon LA-ICPMS data from the northern Paraguay Belt.

71


BPUG-02Diamictite

n = 93

BSA-20Arenite

n = 99

BSA-07Diamictite

n = 105

0.000

0.001

0.002

0.003

Pro

bab

ility

Den

sity

0.000

0.001

0.002

0.003

0.000

0.001

0.002

0.003

0.000

0.001

0.002

0.003

0.004

0.000

0.001

0.002

0.003

0.004

0.000

0.001

0.002

0.003

0.000

0.001

0.002

0.003

0.004

0.005

0.000

0.001

0.002

0.003

0.004

BDM-01Arenite

n = 99

BRZ-02Arenite

n = 86

BRZ-15Arenite

n = 81

Age (Ma)

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

BRZ-01Arenite

n = 82

BST-24Arenite

n = 99

Figure 3 - Probability Density Plots. Author: Ben McGee, Extension: .pdfformations and of the total 255 zircons that were analysed, 240 analyses are plotted, limited to <10% age discordancy. By sample, 42 grains were analysed and 33 are plotted for BDM-01; 35 grains were analysed and 34 are plotted for BPUG-02; all grains analysed (32) are plotted for BRZ-01; all grains analysed (10) are plotted for BRZ-02; all grains analysed (35) are plotted for BRZ-15; all grains analysed (38) are plotted for BST-24; 23 grains were analysed and 22 are plotted for BSA-07 and 40 grains were analysed and 36 are plotted for BSA-20.

The zircons from sample BRZ-01 with ages between 1984 and 636 Ma have εHf values between -4 and +7. The zircons from sample BRZ-02 with ages between 1556 and 937 Ma have εHf values between -2 and +5. The zircons from sample BRZ-15 with ages between 1818 and 929 Ma have εHf values between -6 and +11. The zircons from sample BST-24 with ages between 1916 and 6115 Ma have εHf values between -8 and +6. The zircons from sample BSA-20 with ages between 1863 and 653 Ma have εHf values between -22 and +7. The zircons from sample BSA-07 with ages between 1542 and 651 Ma have εHf values between -8 and +6. The zircons from sample BDM-01 with ages between 1950 and 528 Ma have εHf values between -24 and +27. The zircons from sample BPUG-02 with ages between 1975 and 968 Ma have εHf values between -14 and +5.

Crustal model ages were calculated for each zircon assuming average continental crust with 176Lu/177Hf of 0.0015 as the zircon grain growth reservoir. Based on this crustal model, an age range of 1.4 Ga to 2.9 Ga is obtained for this package of sediments, represented by the envelope drawn on Figure 5. Overall the compilation of εHf(t) data for all formations are widely dispersed. The data begin with a more evolved signal in the late-Palaeoproterozoic, which gradually becomes more juvenile through most of the Mesoproterozoic after which point in time the signal

becomes much more evolved until 527 Ma.

DISCUSSION

U-Pb isotopic age constraints and maximum depositional ages

The U-Pb data reported here complement recent detrital muscovite 40Ar–39Ar analyses (McGee et al., submitted) by providing constraints on source regions and recognising the age of higher temperature events in the northern Paraguay Belt. The maximum depositional ages presented here are based on the ages of the youngest detrital zircon grain for each respective formation.

The U-Pb data presented here for the Puga Formation show only post-Cryogenian inheritance (>918 Ma) and do not improve the maximum depositional age of 706 Ma provided by Babinski et al. (In press). Analyses of the glaciogenic Serra Azul Formation give a maximum depositional age of 646 Ma. This age constraint means that the Serra Azul Formation is permissibly Marinoan (~635 Ma) or Gaskiers (~582 Ma) in age. Given that the Serra Azul Formation diamictite lies stratigraphically above a supposed Marinoan cap carbonate (Babinski et al., 2006; Nogueira et al., 2003) several authors have correlated the Serra Azul diamictite with the ~582 Ma Gaskiers glaciation (Alvarenga et al., 2007; McGee et al., Under Review). The maximum depositional ages of the Raizama and Sepotuba formations are constrained by the youngest analysed grains at 635 and 615 Ma respectively. The youngest analysed zircon from the Diamantino Formation is 527 Ma, which we interpret as the maximum depositional age for this formation. This age is some 15 million years younger than the 541 Ma age reported for the Diamantino Formation by (Bandeira et al., 2011) indicating that deposition in the foreland of the Paraguay orogen continued well into the Cambrian.

Figure 3. Relative probability plots for U-Pb detrital zircon analyses. Light grey shading represents all detrital grains analysed, dark grey represents detrital grains between 90 and 110% concordant. Black line represents the Cambrian/Ediacaran boundary.

in supplemental Table 2. Hf data was collected for each of the eight samples that were analysed for U-Pb isotopes in order to determine the provenance of the protoliths for the Alto Paraguay Group sediments. The analyses are plotted in their respective

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U-Pb and Hafnium isotopic results and correlation with potential source regions

Integrated U-Pb and Hf isotope composition data of detrital zircons from the sedimentary rocks of the northern Paraguay Belt provides insight into the tectonomagmatic evolution of their source areas. The age spectra represented by the samples are characterised by polymodal zircon age spectra

(Figure 3). Suitable source regions would need to contain the same zircon populations to be considered viable. The series of ages can be considered as a diagnostic pattern for the source of the strata in the northern Paraguay Belt. Coupling this with the εHf(t) values, which provide the petrological signature of the melt in which the zircons crystallised it is possible to gain some insight about the source regions for these rocks.

The data presented in the εHf versus time plot in Figure 5 begin with a more evolved signal in the late-Palaeoproterozoic, which gradually becomes more juvenile through most of the Mesoproterozoic. This trend is consistent with the the global data set (Belousova et al., 2010) and also matches the signal for modern day εHf from detrital zircons from the Amazon River represented by the grey envelope (Figure 5). Since

Figure 4 - Zircon morphology. Author: Ben McGee, Extension: .pdf

BDM-01 100 μm

Spot 156527 ± 6 Ma90 % conc.

Spot 188547 ± 8 Ma112 % conc.

Spot 1431265 ± 37 Ma105 % conc.

Spot 188554 ± 10 Ma100 % conc.

Spot 581905 ± 19 Ma96 % conc.

BPUG-02 100 μm

Spot 1071764 ± 22 Ma98 % conc. Spot 49

1737 ± 20 Ma95 % conc.

Spot 621032 ± 27 Ma98 % conc.

Spot 821270 ± 29 Ma92 % conc.

BRZ-02 100 μm

Spot 2936 ± 11 Ma98 % conc.

Spot 18924 ± 11 Ma96 % conc.

Spot 171352 ± 24 Ma100 % conc.

Spot 141048 ± 25 Ma100 % conc.

BRZ-01 100 μm

Spot 19929 ± 12 Ma99 % conc.

Spot 24903 ± 11 Ma97 % conc.

Spot 1091391 ± 23 Ma101 % conc.

Spot 71635 ± 9 Ma93 % conc.

TA01

100 μm

Spot 4988 ± 11 Ma97 % conc.

Spot 171338 ± 24 Ma97 % conc.

Spot 93665 ± 9 Ma92 % conc.

Spot 35665 ± 9 Ma92 % conc.

BST-24100 μm

Spot 151555 ± 20 Ma100 % conc.

Spot 22615 ± 64 Ma99 % conc.

BSA-20

Spot 28934 ± 12 Ma99 % conc.

Spot 34737 ± 9 Ma105 % conc.

BRZ-15100 μm

Spot 81561 ± 28 Ma100 % conc.

Spot 381184 ± 32 Ma99 % conc.

Spot 1201308 ± 27 Ma96 % conc.

Spot 1391203 ± 26 Ma103 % conc.

Spot 60a651 ± 9 Ma93 % conc.

Spot 60b647 ± 9 Ma100 % conc.

Spot 641051 ± 37 Ma99 % conc.

Spot 107b1048 ± 26 Ma102 % conc.

Spot 107a1072 ± 42 Ma102 % conc.

Spot 1551072 ± 42 Ma

102 % conc.

(f )

(c)

BSA-07 100 μm

(b)

(g)

(d)

(e)

(a)

(h)

Figure 4. Cathodoluminescence images of representative zircon grains from sample (a) BDM-01; (b) BST-24; (c) BRZ-15; (d) BRZ-01; (e) BRZ-02; (f) BSA-07; (g) BSA-20 and (h) BPUG-02. Displayed spot ages <1000 Ma and >1000 Ma are 206Pb/238U and 207Pb/206Pb ages respectively. Small circles (30 μm) and large circles (50 μm) represent the location of U-Pb and Lu-Hf analyses respectively.

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the Paraguay Belt is considered to be a sequence of folded sediments that formed on a passive margin on the south-eastern margin of the Amazonian Craton, this is a logical source area for these sediments. This craton comprises two small Archean cores—the Central Amazonian Province (>2600 Ma)—surrounded by predominantly accretionary Paleoproterozoic belts; the Maroni-Itacaiunas Province (2250–2050 Ma); the Ventuari-Tapajós Province (1980–1810 Ma); the Rio Negro-Juruena Province (1780–1550 Ma); the Rondonian-San Ignácio Province (1550–1300 Ma) and the ca. 1250–950 Ma Sunsás Province (Cordani and Teixeira, 2007; Cordani et al., 2009; Tassinari et al., 2000). The similarities in age and the εH signature with modern day Amazon River detrital zircons indicate that the Amazon Craton was a major contributor to the Paraguay Belt sediments. However, the vertical line in Figure 5 represents the minimum age of currently known sources on the Amazonian Craton (950 Ma). If this is taken as the minimum age limit for rocks on this craton, alternative regions must be considered as sources.

Another potential source region to consider are the blocks underneath the Paraná Basin. While

some authors have suggested the existence of several blocks under the Paraná Basin (e.g. Cordani et al., 2003; Milani, 1997), a recent review by Mantovani and Brito Neves (2009) suggested that a simpler interpretation—the existence of one body, the Paranapanema Block—was more favourable. Based on deep oil exploration wells that intersected basement, the Paranapanema Block is described by Mantovani and Brito Neves (2009) as “pre-Brasiliano in general”. This block is likely to have contributed sediment to the Paraguay Belt but due to it’s burial beneath the Paraná Basin it is difficult to assess to what degree.

Bandeira et al. (2011) used palaeocurrent indicators from the upper Diamantino Formation to show that the prevailing source regions are to the east of the present day Paraguay Belt. Potential source regions they identified include the 790–600 Ma Brasilia Belt and the Neoproterozoic Goiás Massif. In Figure 5 we have represented Hf data after Matteini et al. (2010) from the Goiás Massif as closed polygons. These polygons show that the Goiás contains highly juvenile material, but also more evolved material that could have been a potential source for the Paraguay Belt sediments. Bandeira

et al. (2011) interpreted the rest of the sediments to be cannibalised from the rising topography of the Paraguay Belt. The proven presence of zircons with a similar age from within the core of the Paraguay Belt (today to the southeast of the sample site), strongly suggests that the Diamantino Formation was sourced from elevated topography developed during Paraguay Belt orogenesis. This interpretation is supported by the Sm/Nd data of Dantas et al. (2009).

Tectonic model and the Paraguay Belt within South America and Gondwana

Owing to the scarcity of reliable Neoproterozoic palaeomagnetic poles, the location of the Amazonian Craton and its role in Gondwana amalgamation has been the subject of debate for some time (e.g. Cordani et al., 2009; Pisarevsky et al., 2008). The Paraguay Belt on the southern margin of the Amazonian Craton is at the centre of this debate. Currently there are two competing models for the tectonic evolution of the Paraguay Belt and surrounding orogens. The first model considers the ages of juvenile arcs (940–620 Ma) at the western border of the São Francisco

ɛ H

f

Age (Ma)

DM

CHUR

Raizama Formation Serra Azul Formation Diamatino Formation Puga Formation

0 500 1000 1500 2000 2500 3000 3500 -20

-15

-10

-5

0

5

10

15

20

Figure 5 - Epsilon Hf. Author: Ben McGee, Extension: .pdf

Known Amazon Craton Sources

Figure 5. εHf values plotted against…Grains with more than 10% discordancy have been omitted. The grey envelope represents the first to third quartile of modern day zircons collected from the Amazon River (Iizuka et al., 2010). White polygons represent εHf data from the Goiás Massif after Matteini et al. (2010).

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(a) Incipient stages of basin inversion

Peripheral bulge(Proto-Paraguay Belt)

Raizama deposition

Proto-foredeepbasin

Brasiliano ArcAccretionary wedge

Amazon CratonAmazon Craton Paranapanema/Goias Massif

(b) Deepening of the foreland basin

ParaguayOrogen

ForedeepBasin

Amazon CratonAmazon Craton

Paranapanema/Goias Massif

SepotubaFormationDeposition

Brasiliano Arc

(c) Final stages of orogenesis and sediment deposition in Alto Paraguay Group

ParaguayOrogen

Diamantino deposition

Juvenilesediment

input

Amazon CratonAmazon Craton

Paranapanema/Goias Massif

Diamantino Lake

Detachment of oceanic crust

Figure 6 - Tectonic Model. Author: Ben McGee, Extension: .pdf

Figure 6. Tectonic model for the evolution of the Paraguay Belt. (a) Initiation of compression resulting in flexural warping of the litho-sphere and deposition of the Raizama Formation into the proto-foredeep basin; (b) Continued lithospheric flexure and deepening of the foredeep basin; (c) Termination of orogenesis and deposition of the Diamantino Formation into the Diamantino Lake.

Craton to represent the age of collision of the Amazonian Craton with proto-Gondwana, implying suturing at ~620 Ma (Cordani et al., 2009). In this scenario the Paraguay Belt sediments would presumably represent a rift basin that was subsequently inverted. However, little evidence for ca. 620 Ma orogenesis exists, with ages of metamorphism and intrusive plutons much younger in age.

The second model, proposed by Trindade et al. (2006), used a palaeomagnetic pole (Trindade

et al. 2003) that suggested that the Amazonian Craton was at low latitudes and not joined to Gondwana until Cambrian times. The hypothesis infers that the Amazonian Craton and other minor adjoining blocks were separated from proto-Gondwana by the Clymene Ocean and collided in the Cambrian forming a major orogenic belt, comprising the Araguaia, Paraguay and Pampean belts. Several other contributions have since provided evidence that corroborate such an evolution for

the Paraguay Belt based on a range of different evidence.

Sedimentation and provenance studies have helped to constrain the depositional environments and sources for the Paraguay Belt sediments. Geochemical provenance patterns of the northern Paraguay Belt were investigated by Dantas et al. (2009), where they studied the Nd isotopic signature of rocks in the sequence. They found that the lower part of the succession was dominated by Nd isotopic ratios that and TDM model ages that

75


suggest a continental source from the Amazonian Craton, whilst the upper siliciclastic succession shows lower Nd isotopic ratios that is consistent with a source from the Paraguay Belt itself, or another Neoproterozoic continental source. More recently, detrital zircon ages from the Diamantino Formation of 541 Ma (Bandeira et al., 2011) and 40Ar/39Ar muscovite ages from the upper part of the Alto Paraguay Group of 544 Ma (McGee et al. submitted) indicate that final sedimentation within the Paraguay Belt occurred up to the Cambrian. The U-Pb data presented here add to this database of maximum depositional ages for the sediments of the Paraguay Belt.

Several authors have also investigated the timing of deformation and metamorphism within the orogen. Regional metamorphism of the Cuiabá Group was estimated between 541 and 531 Ma based on 40Ar/39Ar cooling ages of biotite flakes (Geraldes et al., 2008). The incipient stages of deformation in the form of early thrusting was inferred to be associated with clay mineral transformations and chemical remagnetisation of carbonates in the Araras Group at ca. 528 Ma (Tohver et al., 2010). In this contribution Tohver et al. (2010) showed that oroclinal bending of the Paraguay Belt was caused by a 90° clockwise rotation of the east-limb some time after 528 Ma. Tohver et al. (2010) also pointed out that the age of the Paraguay Belt overlaps with that of the Pampean Belt further south suggesting that a coeval closure for the Clymene Ocean separating the Amazonian Craton from the São Francisco and Rio de la Plata cratons. Tohver et al. (2011) elaborated on the theory of a Cambrian formation for Gondwana with evidence from the Sierra Australis, including late Ediacaran to late Cambrian magmatism and showing a close overlap of geochronological data with Clymene collision belts to the north—the Paraguay and Araguaia belts.

A geophysical study that combined magnetotelluric and

gravimetric data proposed that a plate interaction zone exists at the western border of the Paraná Basin, proposing a collision between the Rio Apa Craton to the west and the Paranapanema Block to the east (Woldemichael, 2003). Woldemichael (2003) modeled this interaction as a subduction zone from 550–520 Ma of the Rio Apa oceanic crust under the Paranapanema with the development of an Andean type magmatic arc. A subsequent investigation of the geochemistry of the granitic bodies that outcrop at the western margin of the Paraná Basin showed that these rocks are potassic to high K, calc-alkaline, peraluminous to metaluminous, type-I granitoids that plot in the syn-collisional field of the tectonic classification diagrams (Godoy et al., 2007). Early work constraining the ages of these intrusives include a 503 Ma K/Ar age (Almeida, 1968) and 483 Ma Rb/Sr age (Almeida and Mantovani, 1975) for the post-orogenic São Vicente granite (Figure 1). These ages have been supported by more recent U-Pb zircon analyses of the same intrusive batholith of 521 Ma (Ferreira, 2009) and 518 Ma (McGee et al., 2012). Other granitic intrusions from the interior of the belt have similar ages including a U-Pb SHRIMP zircon age of 510 ± 12 Ma for the Araguainha Granite (Tohver et al., 2012) and the Lajinha Granite which yielded a U-Pb zircon age of 505.4 ± 4.1 Ma (Manzano, 2009).

The palaeomagnetic result of Trindade et al. (2003) that suggested the Amazon was not connected to proto-Gondwana until the Cambrian has recently been questioned, after McGee et al. (Submitted) reproduced similar geomagnetic reversals of an orientation very similar to those of Trindade et al (2003) much higher in the stratigraphy, from the Alto Paraguay Group. McGee et al. (Submitted) suggested that this result is indicative of a remagnetisation, potentially associated with Jurassic tholeittic basalts that intrude into the western part of the northern Paraguay Belt. If this is the case, the palaeomagnetic database no longer

provides information about the location of the Amazonian Craton for much of the Neoproterozoic, leaving the tectonic evolution of the belt open to debate. Despite this uncertainty in the palaeomagnetic database, the amount of other supporting evidence for a late (Cambrian) collision of Amazonia is difficult to ignore.

Based on this amalgam of evidence and our new U-Pb and Hf data we propose a tectonic model (Figure 6) that incorporates all of this information. The first sediments found on the Amazonian Craton are the glacial diamictites of the Puga Formation and the more distal turbidites of the Cuiaba Group. The thickness (4–6 km) and aerial extent (~700 km) of these units is suggestive of a large marine basin, which has previously been proposed by numerous authors (e.g. Alvarenga and Trompette, 1992; Alvarenga et al., 2009; Nogueira et al., 2007). The depositional model proposed for these units is in a passive margin environment from platformal to outer slope from west to east respectively (Alvarenga and Trompette, 1992). This period of deposition was followed by a period of glaciation responsible for depositing the Serra Azul Formation in a glaciomarine environment inferred to be related to the Gaskiers glaciation (Alvarenga et al., 2007; McGee et al., Under Review).

The conformable nature of the Raizama Formation with the upper Serra Azul Formation implies the gradual initiation of topography and that the deposition of the Raizama Formation was tectonically controlled by this rising topography. We propose that the incipient stages of deformation—the ‘proto-Paraguay Orogeny’—formed as a peripheral bulge (Figure 6a) in response to the flexural warping of the lithosphere. This lithospheric deformation and associated basin inversion begun as oceanic crust connected to the Amazonian Craton was thrust under the Paranapanema Block and the Goiás Massif. In such a system a downwarp is generated proximal to the orogen, the foreland

76


basin, and a low amplitude, long-wavelength upwarp, the peripheral bulge developes proximal to subduction (Catuneanu et al., 1997). A minor influence from volcanic arcs is interpreted in the Raizama Formation based on the U-Pb ages reported in this study. These arcs are probably now buried under the Paraná Basin, to the south east of the Paraguay Belt (Figure 1), and their presence and morphology has been interpreted based on petroleum wells and geophysical techniques (Mantovani and Brito Neves, 2009). Based on currently available ages the Raizama Formation was deposited after middle Ediacaran times (~582 Ma). The Raizama Formation also does not contain the prominent ~544 Ma detritus seen in the overlying Diamantino Formation suggesting that it probably predates this time.

After deposition of the Raizama Formation, a major decrease in sand content and the predominance of siltstone (McGee et al., Submitted) indicates deepening of the foreland basin (Figure 6b). This most likely occurred in response to increased lithospheric flexure as the collision advanced on the Amazonian margin. At this time the interlayered sandstones and siltstones of the Sepotuba Formation were deposited into the foreland basin.

The stacking of progradational parasequences indicates that the basin was progressively filled with coarser sediment of the Diamantino Formation (Figure 6c). Bandeira et al. (2011) interpreted the Diamantino Formation to record the final exhumation and erosion of the orogen that was deposited into the foreland basin—which they interpreted to be a closed system by this stage—the ‘Diamantino Lake’. Another indicator that the Diamantino Formation is likely to be lacustrine is that the majority of correlative marine Cambrian sequences contain fossils (Aceñolaza et al., 2009), whilst none have been reported for the Diamantino Formation. The predominance of much younger muscovite ages in the Diamantino Formation most likely represents

the increased input from the upper plate of the colliding blocks (the Paranapanema block and Goiás Massif; Figure 7d) and, as previously discussed, the cannibalisation of igneous plutons from within the belt and metamorphic ages as the rocks were exhumed and cooled through the muscovite closure temperature. These ages for final sedimentation and exhumation at circa 544 Ma are in agreement with the observed intrusion of post-orogenic granites at 518 Ma (McGee et al., 2012) and indicate that detachment of the down-going oceanic slab and subsequent removal of the slab-pull force, resulting in the cessation of compressional tectonics, occurred around this time (Figure d). All these data are consistent with an ocean to the east of the Amazonian Craton that didn’t close until the Cambrian.

CONCLUSIONS

The maximum depositional ages provided by the U-Pb zircon analyses from the uppermost part of this sequence of rocks, the Diamantino Formation, indicate final sedimentation in the Paraguay Belt began no earlier than 527 Ma. Based on the integrated U-Pb and Hf isotope data of detrital zircons presented here, potential sources for these sediments are consistent with a predominantly Amazonian source until the early-Neoproterozoic at which point the signal becomes significantly more evolved and influence from the Paranapanema, and Goiás Massif to the east are inferred. Based on the combination of magnetotelluric, gravimetric, geochemical, geochronological and sedimentological evidence discussed here we propose that the Paraguay Belt inititated as a peripheral bulge in response to subduction of Amazonian oceanic crust underneath the Paranapanema Block. Available evidence suggests that final sedimentation, deformation and metamorphism in the Paraguay Belt occurred between 540 and 510 Ma.

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Dantas, E. L., Pimentel, M. M., and Buhn, B., 2010, In situ zircon U-Pb and Lu-Hf isotope systematic on magmatic rocks: Insights on the crustal evolution of the Neoproterozoic Goias Magmatic Arc, Brasilia belt, Central Brazil: Gondwana Research, v. 17, no. 1, p. 1-12.

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80

Chapter 5 Age and provenance of the northern Paraguay BeltTa

ble

1. L

A-IC

PM

S Z

ircon

U-T

h-P

b A

ge D

ata

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 10.

320.

0721

0.00

130.

1559

0.00

211.

5481

0.02

970.

0479

0.00

110.

699

988

3793

412

950

1294

521

9593

4

Spo

t 20.

260.

0799

0.00

100.

2019

0.00

282.

2249

0.03

390.

0601

0.00

090.

910

1196

2511

8515

1189

1111

8118

9911

96

Spo

t 30.

330.

0751

0.00

130.

1768

0.00

241.

8300

0.03

350.

0574

0.00

120.

726

1071

3510

4913

1056

1211

2823

9810

71

Spo

t 40.

360.

0731

0.00

100.

1658

0.00

221.

6700

0.02

600.

0497

0.00

080.

833

1017

2898

912

997

1098

016

9798

9

Spo

t 51.

670.

0794

0.00

270.

1509

0.00

231.

6515

0.05

570.

0474

0.00

090.

460

1182

6690

613

990

2193

517

7790

6

Spo

t 61.

020.

1082

0.00

170.

3084

0.00

414.

6005

0.07

600.

0890

0.00

140.

811

1770

2817

3320

1749

1417

2325

9817

70

Spo

t 70.

730.

1095

0.00

130.

3141

0.00

404.

7419

0.06

430.

0896

0.00

120.

946

1791

2117

6120

1775

1117

3522

9817

91

Spo

t 80.

410.

0798

0.00

110.

2015

0.00

292.

2181

0.03

650.

0581

0.00

090.

866

1193

2711

8415

1187

1211

4218

9911

93

Spo

t 90.

360.

0797

0.00

100.

2018

0.00

282.

2170

0.03

410.

0579

0.00

090.

897

1190

2511

8515

1186

1111

3817

100

1190

Spo

t 10

1.33

0.10

820.

0015

0.30

890.

0041

4.60

540.

0702

0.08

720.

0012

0.86

317

6825

1735

2017

5013

1690

2298

1768

Spo

t 12

0.82

0.09

260.

0014

0.25

830.

0034

3.29

680.

0528

0.07

570.

0011

0.82

714

7928

1481

1814

8012

1475

2110

014

79

Spo

t 13

0.31

0.07

160.

0012

0.15

510.

0021

1.53

210.

0280

0.04

620.

0010

0.73

097

635

930

1294

311

914

1995

930

Spo

t 14

0.42

0.09

770.

0014

0.28

460.

0040

3.83

560.

0610

0.08

000.

0015

0.87

315

8126

1615

2016

0013

1556

2810

215

81

Spo

t 16

1.31

0.11

390.

0012

0.31

970.

0044

5.02

120.

0686

0.08

620.

0009

0.99

918

6319

1788

2118

2312

1671

1796

1863

Spo

t 17

0.28

0.08

600.

0011

0.22

200.

0029

2.63

310.

0383

0.06

430.

0011

0.89

213

3925

1293

1513

1011

1260

2197

1339

Spo

t 18

0.24

0.07

370.

0014

0.16

270.

0022

1.65

240.

0320

0.04

820.

0013

0.70

110

3237

972

1299

112

952

2594

1032

Spo

t 19

2.54

0.07

840.

0036

0.15

090.

0026

1.63

020.

0727

0.04

560.

0009

0.39

111

5787

906

1598

228

902

1878

906

Spo

t 20

0.51

0.08

670.

0013

0.22

820.

0030

2.72

690.

0434

0.06

660.

0012

0.83

413

5328

1325

1613

3612

1304

2298

1353

Spo

t 21

0.32

0.07

870.

0017

0.20

130.

0031

2.18

350.

0479

0.05

380.

0018

0.70

211

6341

1182

1711

7615

1059

3510

211

63

Spo

t 22

0.45

0.13

400.

0016

0.34

720.

0054

6.41

310.

1008

0.05

420.

0009

0.98

421

5120

1921

2620

3414

1067

1789

2151

Spo

t 23

3.44

0.07

390.

0018

0.15

560.

0023

1.58

520.

0404

0.04

320.

0006

0.58

010

3849

932

1396

416

855

1190

932

Spo

t 24

0.87

0.09

270.

0012

0.25

710.

0036

3.28

680.

0500

0.06

770.

0009

0.91

214

8224

1475

1814

7812

1324

1699

1482

Spo

t 25

0.37

0.07

120.

0015

0.15

860.

0022

1.55

780.

0330

0.05

110.

0012

0.65

496

441

949

1295

413

1008

2498

949

Spo

t 26

0.39

0.09

440.

0011

0.27

850.

0036

3.62

530.

0503

0.07

990.

0013

0.93

315

1622

1584

1815

5511

1554

2410

415

16

Spo

t 28

0.34

0.08

230.

0009

0.21

180.

0029

2.40

180.

0342

0.05

900.

0008

0.96

712

5222

1238

1612

4310

1158

1499

1252

Spo

t 29

1.66

0.07

190.

0020

0.15

720.

0023

1.55

830.

0442

0.04

820.

0009

0.52

198

356

941

1395

418

951

1696

941

Spo

t 30

0.28

0.07

010.

0010

0.16

060.

0021

1.55

240.

0247

0.04

840.

0009

0.83

093

229

960

1295

110

955

1810

396

0

Spo

t 31

0.31

0.08

620.

0011

0.23

280.

0032

2.76

750.

0412

0.07

400.

0014

0.91

313

4324

1349

1713

4711

1443

2610

013

43

Spo

t 32

0.21

0.07

300.

0011

0.16

490.

0022

1.65

940.

0282

0.05

670.

0013

0.78

810

1431

984

1299

311

1114

2597

984

Spo

t 33

0.60

0.08

440.

0027

0.21

460.

0034

2.49

860.

0782

0.06

290.

0019

0.50

013

0360

1253

1812

7223

1233

3696

1303

Spo

t 34

0.50

0.07

370.

0013

0.17

050.

0024

1.73

230.

0335

0.05

220.

0010

0.72

810

3336

1015

1310

2112

1029

1898

1033

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BS

A-2

0

81


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 35

0.30

0.07

590.

0011

0.17

620.

0024

1.84

240.

0305

0.05

420.

0011

0.80

710

9130

1046

1310

6111

1066

2196

1091

Spo

t 36

0.42

0.07

580.

0018

0.15

700.

0024

1.63

990.

0400

0.04

900.

0012

0.61

910

8946

940

1398

615

966

2486

940

Spo

t 37

0.73

0.06

500.

0014

0.11

800.

0017

1.05

810.

0234

0.03

730.

0008

0.64

877

544

719

1073

312

739

1593

719

Spo

t 38

1.18

0.10

770.

0015

0.31

930.

0043

4.74

100.

0739

0.09

110.

0015

0.86

217

6125

1786

2117

7513

1762

2810

117

61

Spo

t 39

0.39

0.08

800.

0017

0.19

260.

0028

2.33

620.

0468

0.05

030.

0014

0.71

213

8236

1136

1512

2314

991

2682

1382

Spo

t 40

0.50

0.07

520.

0015

0.17

080.

0024

1.77

080.

0365

0.05

030.

0011

0.67

710

7439

1017

1310

3513

992

2295

1074

Spo

t 41

0.57

0.08

700.

0011

0.23

530.

0032

2.82

000.

0416

0.07

030.

0009

0.92

813

5923

1362

1713

6111

1372

1810

013

59

Spo

t 42

0.32

0.08

030.

0014

0.20

580.

0029

2.27

880.

0428

0.06

020.

0016

0.75

412

0534

1206

1612

0613

1182

3010

012

05

Spo

t 44

0.67

0.12

470.

0014

0.32

080.

0046

5.51

870.

0811

0.09

230.

0031

0.97

420

2520

1794

2219

0413

1785

5889

2025

Spo

t 45

0.50

0.07

360.

0010

0.15

990.

0021

1.62

170.

0249

0.04

720.

0008

0.86

410

2927

956

1297

910

933

1693

956

Spo

t 46

0.48

0.08

690.

0013

0.21

110.

0028

2.52

970.

0417

0.05

910.

0012

0.80

713

5829

1235

1512

8112

1160

2391

1358

Spo

t 47

0.30

0.07

160.

0021

0.16

240.

0024

1.60

380.

0473

0.05

110.

0018

0.49

997

559

970

1397

218

1007

3599

970

Spo

t 49

0.26

0.07

400.

0013

0.15

950.

0022

1.62

640.

0303

0.04

600.

0012

0.73

810

4135

954

1298

112

908

2392

954

Spo

t 50

0.34

0.08

450.

0016

0.20

140.

0028

2.34

680.

0464

0.05

950.

0015

0.71

113

0536

1183

1512

2714

1169

2991

1305

Spo

t 53

0.48

0.09

770.

0012

0.27

240.

0039

3.66

740.

0565

0.07

960.

0011

0.93

715

8023

1553

2015

6412

1549

2198

1580

Spo

t 54

0.32

0.07

240.

0013

0.16

520.

0023

1.64

860.

0311

0.04

910.

0012

0.72

899

836

985

1398

912

969

2399

985

Spo

t 55

0.57

0.08

960.

0022

0.20

040.

0031

2.47

430.

0610

0.05

900.

0018

0.62

914

1745

1177

1712

6518

1159

3483

1417

Spo

t 56

0.29

0.07

620.

0011

0.17

640.

0025

1.85

310.

0313

0.05

380.

0010

0.82

111

0030

1048

1310

6511

1058

2095

1100

Spo

t 57

0.40

0.07

920.

0022

0.17

840.

0028

1.94

690.

0537

0.06

050.

0025

0.56

311

7754

1058

1510

9719

1186

4890

1177

Spo

t 58

0.40

0.12

470.

0014

0.35

620.

0049

6.12

510.

0859

0.10

400.

0026

0.97

320

2520

1964

2319

9412

2000

4797

2025

Spo

t 60

0.38

0.07

320.

0008

0.17

430.

0023

1.75

960.

0239

0.05

220.

0010

0.95

810

2022

1036

1210

319

1029

1910

210

20

Spo

t 64

0.55

0.08

400.

0016

0.23

100.

0032

2.67

330.

0523

0.06

900.

0017

0.71

812

9136

1340

1713

2114

1349

3110

412

91

Spo

t 66

0.32

0.07

730.

0021

0.15

640.

0025

1.66

690.

0465

0.05

280.

0025

0.58

21 1

2954

937

1499

618

1039

4783

937

Spo

t 68

0.29

0.08

360.

0019

0.21

580.

0031

2.48

770.

0579

0.06

850.

0024

0.62

612

8344

1260

1712

6917

1339

4598

1283

Spo

t 70

0.34

0.08

060.

0013

0.19

170.

0026

2.13

040.

0369

0.05

640.

0014

0.78

612

1231

1130

1411

5912

1109

2693

1212

Spo

t 72

0.51

0.07

450.

0015

0.17

150.

0024

1.76

140.

0360

0.05

090.

0012

0.68

510

5539

1020

1310

3113

1004

2497

1055

Spo

t 73

0.28

0.07

230.

0019

0.15

680.

0024

1.56

310.

0421

0.04

470.

0017

0.56

199

453

939

1395

617

884

3494

939

Spo

t 74

0.27

0.07

840.

0011

0.19

820.

0029

2.14

150.

0368

0.05

360.

0010

0.86

011

5729

1166

1611

6212

1056

2010

111

57

Spo

t 76

0.57

0.06

930.

0028

0.10

660.

0018

1.01

820.

0401

0.02

960.

0011

0.42

490

780

653

1071

320

590

2272

653

Spo

t 76r

10.

590.

0693

0.00

860.

1086

0.00

321.

0371

0.12

560.

0344

0.00

300.

246

907

236

665

1972

363

683

5873

665

Spo

t 76r

21.

170.

2114

0.00

950.

0842

0.00

222.

4548

0.09

900.

0351

0.00

180.

639

2916

7152

113

1259

2969

834

1852

1

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

82


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 77

0.63

0.11

050.

0018

0.32

260.

0047

4.91

600.

0866

0.08

630.

0028

0.82

218

0829

1802

2318

0515

1673

5110

018

08

Spo

t 78

0.26

0.08

000.

0010

0.20

340.

0027

2.24

190.

0328

0.05

550.

0013

0.90

311

9624

1193

1411

9410

1092

2510

011

96

Spo

t 79

0.32

0.08

310.

0020

0.20

270.

0032

2.32

380.

0576

0.05

670.

0028

0.63

712

7246

1190

1712

2018

1115

5494

1272

Spo

t 84

0.27

0.07

960.

0012

0.20

110.

0027

2.20

740.

0360

0.05

800.

0015

0.83

011

8728

1181

1511

8311

1140

2999

1187

Spo

t 85

0.33

0.08

180.

0013

0.19

930.

0027

2.24

680.

0388

0.05

790.

0015

0.79

412

4131

1171

1511

9612

1137

2994

1241

Spo

t 88

0.24

0.08

300.

0011

0.21

690.

0031

2.48

110.

0389

0.05

750.

0027

0.90

912

6925

1265

1612

6711

1130

5110

012

69

Spo

t 89

0.54

0.08

310.

0017

0.20

530.

0030

2.35

190.

0509

0.06

010.

0016

0.66

412

7140

1204

1612

2815

1179

3195

1271

Spo

t 90

0.27

0.07

040.

0012

0.15

980.

0022

1.55

070.

0291

0.04

520.

0013

0.73

893

935

956

1295

112

893

2510

295

6

Spo

t 91

0.30

0.08

750.

0010

0.21

390.

0028

2.57

930.

0367

0.06

510.

0015

0.93

313

7123

1250

1512

9510

1275

2891

1371

Spo

t 93

0.41

0.06

350.

0017

0.10

870.

0016

0.95

120.

0263

0.03

190.

0010

0.53

272

457

665

967

914

635

2092

665

Spo

t 95

0.27

0.08

760.

0011

0.24

720.

0033

2.98

430.

0426

0.06

970.

0016

0.93

213

7423

1424

1714

0411

1361

3110

413

74

Spo

t 101

0.31

0.07

850.

0040

0.16

080.

0031

1.74

090.

0877

0.05

200.

0035

0.38

811

6099

961

1710

2432

1024

6783

961

Spo

t 103

0.37

0.08

040.

0012

0.23

880.

0034

2.64

680.

0453

0.06

830.

0023

0.82

512

0730

1381

1813

1413

1335

4311

412

07

Spo

t 107

0.10

0.07

130.

0010

0.15

830.

0023

1.55

590.

0260

0.04

570.

0022

0.85

396

629

947

1395

310

904

4398

947

Spo

t 108

0.35

0.09

910.

0016

0.29

050.

0042

3.96

810.

0721

0.08

820.

0033

0.80

316

0730

1644

2116

2815

1708

6210

216

07

Spo

t 110

0.44

0.09

800.

0014

0.28

250.

0039

3.81

650.

0598

0.08

060.

0022

0.87

315

8725

1604

1915

9613

1567

4110

115

87

Spo

t 111

0.71

0.11

000.

0014

0.32

520.

0047

4.92

990.

0776

0.08

770.

0049

0.92

017

9923

1815

2318

0713

1699

9110

117

99

Spo

t 112

0.23

0.06

980.

0009

0.15

940.

0021

1.53

260.

0224

0.04

730.

0013

0.91

492

125

953

1294

49

934

2410

395

3

Spo

t 114

0.39

0.09

480.

0011

0.26

260.

0035

3.43

060.

0489

0.07

290.

0019

0.93

815

2422

1503

1815

1111

1422

3699

1524

Spo

t 117

0.29

0.07

160.

0010

0.15

690.

0021

1.54

860.

0254

0.04

630.

0013

0.82

997

529

939

1295

010

915

2696

939

Spo

t 118

0.24

0.17

520.

0018

0.10

730.

0014

2.59

140.

0338

0.13

200.

0033

0.99

926

0817

657

812

9810

2506

5825

657

Spo

t 120

0.24

0.07

120.

0019

0.15

390.

0023

1.51

080.

0414

0.04

680.

0021

0.54

396

354

923

1393

517

925

4096

923

Spo

t 121

0.29

0.08

430.

0012

0.21

380.

0030

2.48

610.

0407

0.06

090.

0020

0.84

813

0028

1249

1612

6812

1195

3896

1300

Spo

t 125

0.30

0.07

940.

0021

0.19

270.

0030

2.10

950.

0575

0.06

190.

0027

0.56

911

8352

1136

1611

5219

1214

5196

1183

Spo

t 127

0.26

0.10

170.

0019

0.28

120.

0044

3.93

900.

0790

0.06

780.

0064

0.77

316

5534

1598

2216

2216

1326

121

9716

55

Spo

t 130

0.82

0.11

110.

0014

0.32

570.

0046

4.98

960.

0751

0.08

110.

0040

0.93

718

1822

1818

2218

1813

1577

7510

018

18

Spo

t 131

0.29

0.07

100.

0014

0.15

890.

0022

1.55

530.

0313

0.04

270.

0015

0.70

095

838

950

1295

312

845

2999

950

Spo

t 132

0.38

0.07

100.

0024

0.16

680.

0028

1.63

310.

0557

0.04

980.

0026

0.48

995

868

995

1598

321

981

5010

499

5

Spo

t 139

0.32

0.07

450.

0011

0.18

140.

0025

1.86

160.

0311

0.05

350.

0017

0.81

510

5430

1074

1310

6811

1054

3210

210

54

Spo

t 141

1.83

0.07

880.

0024

0.16

500.

0026

1.79

350.

0541

0.04

760.

0014

0.51

611

6859

985

1410

4320

940

2784

985

Spo

t 145

0.35

0.09

680.

0013

0.27

200.

0037

3.63

000.

0544

0.07

540.

0022

0.89

815

6424

1551

1915

5612

1469

4099

1564

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

83


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 147

0.32

0.09

670.

0012

0.29

010.

0039

3.86

600.

0562

0.08

100.

0023

0.91

815

6123

1642

1916

0712

1574

4310

515

61

Spo

t 148

0.29

0.07

630.

0019

0.17

400.

0026

1.83

020.

0454

0.05

110.

0022

0.61

211

0348

1034

1410

5616

1007

4394

1103

Spo

t 149

0.32

0.08

450.

0011

0.23

800.

0032

2.77

350.

0410

0.06

590.

0019

0.90

413

0424

1376

1713

4811

1289

3510

613

04

Spo

t 151

0.53

0.08

180.

0021

0.21

220.

0034

2.39

030.

0634

0.05

840.

0032

0.60

412

4050

1240

1812

4019

1148

6110

012

40

Spo

t 154

0.39

0.07

080.

0012

0.15

800.

0022

1.54

210.

0285

0.04

400.

0014

0.74

695

135

946

1294

711

871

2699

946

Spo

t 20.

350.

1160

0.00

120.

3112

0.00

414.

9768

0.06

570.

0902

0.00

110.

986

1896

1917

4720

1815

1117

4621

9218

96

Spo

t 30.

330.

0984

0.00

170.

2693

0.00

433.

6537

0.07

180.

0905

0.00

250.

803

1594

3215

3722

1561

1617

5146

9615

94

Spo

t 70.

630.

0917

0.00

140.

2443

0.00

343.

0888

0.05

250.

0701

0.00

110.

821

1462

2914

0918

1430

1313

6921

9614

62

Spo

t 80.

130.

0763

0.00

110.

1703

0.00

231.

7914

0.02

930.

0578

0.00

150.

832

1103

2910

1413

1042

1111

3628

9211

03

Spo

t 12

0.76

0.09

940.

0026

0.25

940.

0049

3.55

530.

0958

0.08

250.

0024

0.70

116

1347

1487

2515

4021

1603

4692

1613

Spo

t 13

0.54

0.07

920.

0019

0.17

050.

0030

1.86

200.

0480

0.05

520.

0016

0.67

511

7848

1015

1610

6817

1087

3186

1178

Spo

t 14

0.33

0.07

470.

0011

0.16

430.

0023

1.69

110.

0289

0.04

830.

0009

0.81

710

6030

981

1310

0511

952

1793

981

Spo

t 15

0.61

0.10

890.

0014

0.30

590.

0042

4.59

190.

0699

0.08

440.

0012

0.90

717

8123

1720

2117

4813

1637

2397

1781

Spo

t 19

0.12

0.10

630.

0015

0.24

450.

0037

3.58

320.

0613

0.16

990.

0040

0.88

817

3725

1410

1915

4614

3172

6981

1737

Spo

t 20

0.28

0.08

200.

0016

0.17

770.

0028

2.00

770.

0425

0.06

980.

0019

0.73

612

4637

1054

1511

1814

1364

3585

1246

Spo

t 22

0.35

0.10

280.

0014

0.27

200.

0038

3.85

650.

0601

0.07

830.

0014

0.88

716

7625

1551

1916

0513

1523

2693

1676

Spo

t 23

0.37

0.09

720.

0011

0.27

420.

0039

3.67

280.

0541

0.08

470.

0014

0.95

315

7121

1562

1915

6612

1644

2599

1571

Spo

t 24

0.22

0.12

490.

0016

0.19

940.

0030

3.43

340.

0560

0.12

110.

0023

0.93

420

2722

1172

1615

1213

2310

4158

2027

Spo

t 25

0.70

0.09

690.

0018

0.23

850.

0036

3.18

270.

0637

0.07

630.

0016

0.76

015

6434

1379

1914

5315

1486

2988

1564

Spo

t 26

0.34

0.07

360.

0009

0.17

1 10.

0023

1.73

600.

0250

0.04

890.

0007

0.92

310

3124

1018

1310

229

965

1399

1031

Spo

t 27

0.15

0.08

130.

0015

0.16

960.

0027

1.89

960.

0394

0.07

730.

0024

0.76

712

2836

1010

1510

8114

1506

4582

1228

Spo

t 28

0.38

0.09

660.

0012

0.26

370.

0035

3.51

440.

0504

0.07

510.

0012

0.92

915

6022

1509

1815

3011

1464

2297

1560

Spo

t 31

0.45

0.09

680.

0014

0.25

330.

0035

3.38

230.

0550

0.07

590.

0014

0.84

015

6427

1455

1815

0013

1479

2793

1564

Spo

t 32

0.67

0.07

310.

0010

0.16

310.

0022

1.64

380.

0250

0.04

820.

0006

0.87

910

1726

974

1298

710

952

1296

974

Spo

t 33

0.45

0.11

000.

0015

0.31

490.

0046

4.77

450.

0778

0.08

580.

0017

0.90

417

9924

1765

2317

8014

1664

3198

1799

Spo

t 34

0.34

0.10

010.

0012

0.27

370.

0038

3.77

800.

0553

0.07

120.

0012

0.95

616

2721

1559

1915

8812

1391

2296

1627

Spo

t 35

1.22

0.07

350.

0015

0.16

190.

0023

1.64

000.

0354

0.05

060.

0009

0.65

310

2642

967

1398

614

998

1794

1026

Spo

t 37

0.37

0.07

490.

0008

0.17

400.

0023

1.79

570.

0242

0.05

020.

0006

0.99

010

6521

1034

1310

449

990

1197

1065

Spo

t 40

0.56

0.09

030.

0016

0.24

980.

0035

3.11

070.

0591

0.06

740.

0013

0.74

014

3334

1437

1814

3515

1319

2510

014

33

Spo

t 41

0.30

0.09

660.

0012

0.27

060.

0036

3.60

300.

0516

0.07

970.

0014

0.91

615

5923

1544

1815

5011

1550

2699

1559

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BP

UG

-02

84


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 42

0.47

0.07

550.

0014

0.16

930.

0023

1.76

330.

0340

0.05

050.

0011

0.71

710

8236

1008

1310

3212

995

2093

1082

Spo

t 44

0.60

0.09

350.

0013

0.22

780.

0031

2.93

570.

0469

0.06

900.

0012

0.84

014

9827

1323

1613

9112

1349

2288

1498

Spo

t 45

0.65

0.07

580.

0009

0.16

980.

0022

1.77

510.

0254

0.05

120.

0007

0.91

210

9024

1011

1210

369

1009

1493

1090

Spo

t 46

0.66

0.10

480.

0014

0.26

930.

0037

3.89

000.

0611

0.07

580.

0013

0.87

817

1125

1537

1916

1213

1478

2390

1711

Spo

t 47

0.34

0.08

960.

0013

0.23

390.

0032

2.88

880.

0462

0.06

570.

0013

0.85

514

1727

1355

1713

7912

1287

2496

1417

Spo

t 48

0.38

0.09

120.

0012

0.23

440.

0033

2.94

680.

0470

0.06

570.

0011

0.89

314

5025

1358

1713

9412

1286

2094

1450

Spo

t 49

0.53

0.10

640.

0012

0.29

340.

0037

4.30

290.

0569

0.08

050.

0016

0.94

917

3821

1659

1816

9411

1566

3095

1738

Spo

t 50

0.36

0.09

980.

0015

0.24

920.

0035

3.42

740.

0561

0.07

540.

0023

0.84

816

2027

1434

1815

1113

1470

4489

1620

Spo

t 51

0.55

0.08

930.

0013

0.24

190.

0033

2.98

110.

0498

0.07

010.

0013

0.82

114

1128

1397

1714

0313

1369

2499

1411

Spo

t 52

0.30

0.10

060.

0015

0.18

180.

0025

2.52

240.

0421

0.09

010.

0017

0.81

516

3628

1077

1312

7912

1744

3266

1636

Spo

t 53

0.09

0.07

130.

0012

0.16

570.

0021

1.62

820.

0278

0.05

450.

0020

0.74

796

533

988

1298

111

1072

3910

298

8

Spo

t 54

0.23

0.09

690.

0012

0.27

280.

0036

3.64

460.

0526

0.08

300.

0015

0.91

915

6522

1555

1815

5912

1612

2899

1565

Spo

t 55

0.52

0.07

510.

0013

0.16

830.

0023

1.74

250.

0317

0.05

060.

0010

0.75

710

7033

1003

1310

2412

997

1994

1070

Spo

t 56

0.44

0.09

690.

0011

0.26

370.

0033

3.52

420.

0469

0.07

890.

0011

0.93

115

6621

1509

1715

3311

1535

2196

1566

Spo

t 57

0.66

0.09

770.

0016

0.26

970.

0036

3.63

160.

0634

0.08

230.

0015

0.75

415

8031

1539

1815

5714

1599

2997

1580

Spo

t 59

0.29

0.07

390.

0012

0.16

980.

0022

1.72

960.

0298

0.05

080.

0012

0.75

610

3832

1011

1210

2011

1001

2297

1038

Spo

t 62

0.51

0.07

370.

0010

0.16

930.

0024

1.71

940.

0278

0.04

950.

0007

0.85

910

3228

1008

1310

1610

977

1498

1032

Spo

t 63

0.06

0.09

610.

0011

0.26

980.

0035

3.57

430.

0484

0.08

230.

0017

0.95

315

4921

1540

1815

4411

1599

3299

1549

Spo

t 64

0.66

0.10

100.

0016

0.27

160.

0037

3.78

250.

0648

0.08

200.

0016

0.80

216

4329

1549

1915

8914

1593

2994

1643

Spo

t 65

0.22

0.09

370.

001 1

0.22

010.

0027

2.84

200.

0378

0.06

270.

0011

0.90

915

0122

1282

1413

6710

1229

2185

1501

Spo

t 66

0.43

0.09

690.

0021

0.24

330.

0035

3.25

040.

0701

0.07

450.

0021

0.66

915

6639

1404

1814

6917

1452

4090

1566

Spo

t 67

0.36

0.09

660.

0015

0.27

250.

0038

3.62

740.

0610

0.07

920.

0021

0.81

915

5928

1553

1915

5613

1541

3910

015

59

Spo

t 68

0.32

0.08

180.

0021

0.17

120.

0027

1.93

130.

0501

0.06

400.

0025

0.60

112

4150

1019

1510

9217

1255

4882

1241

Spo

t 69

0.26

0.07

620.

0014

0.16

540.

0023

1.73

830.

0338

0.05

600.

0013

0.72

411

0136

987

1310

2313

1100

2490

987

Spo

t 70

0.42

0.09

610.

0012

0.24

790.

0030

3.28

240.

0443

0.07

180.

0012

0.90

615

4922

1428

1614

7711

1401

2292

1549

Spo

t 71

1.17

0.07

660.

0023

0.14

800.

0022

1.56

300.

0464

0.04

210.

0011

0.51

011

1159

890

1395

618

833

2180

890

Spo

t 72

0.45

0.09

750.

0026

0.24

620.

0041

3.31

010.

0873

0.08

260.

0034

0.62

715

7848

1419

2114

8321

1604

6390

1578

Spo

t 73

0.86

0.09

360.

0045

0.16

630.

0029

2.14

490.

1013

0.05

580.

0019

0.37

315

0088

991

1611

6333

1097

3766

991

Spo

t 74

0.36

0.07

860.

0013

0.16

140.

0021

1.74

840.

0312

0.04

800.

0012

0.74

111

6133

965

1210

2712

949

2283

965

Spo

t 75

0.43

0.09

520.

0021

0.22

910.

0032

3.00

610.

0661

0.06

610.

0020

0.62

515

3241

1330

1714

0917

1294

3787

1532

Spo

t 77

0.64

0.10

320.

0013

0.28

500.

0041

4.05

390.

0633

0.07

530.

0011

0.91

616

8223

1617

2016

4513

1468

2096

1682

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

85


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 78

0.42

0.08

140.

0012

0.17

430.

0024

1.95

650.

0328

0.05

680.

0009

0.82

412

3229

1036

1311

0111

1117

1884

1232

Spo

t 80

0.32

0.07

450.

0020

0.15

970.

0024

1.64

110.

0443

0.05

020.

0019

0.55

010

5654

955

1398

617

990

3690

955

Spo

t 81

0.40

0.07

600.

0017

0.15

310.

0020

1.60

300.

0355

0.04

660.

0012

0.59

910

9443

918

1197

114

921

2484

918

Spo

t 82

0.43

0.08

310.

0013

0.19

920.

0026

2.28

100.

0373

0.05

830.

0012

0.78

312

7130

1171

1412

0612

1146

2492

1171

Spo

t 83

0.37

0.07

190.

0019

0.16

200.

0023

1.60

650.

0424

0.04

570.

0016

0.53

198

453

968

1397

317

904

3198

968

Spo

t 84

0.61

0.09

750.

0016

0.23

540.

0031

3.16

500.

0561

0.07

500.

0016

0.75

215

7731

1363

1614

4914

1462

2986

1577

Spo

t 86

0.36

0.07

780.

0020

0.16

440.

0023

1.76

400.

0454

0.05

340.

0018

0.55

311

4250

981

1310

3217

1051

3486

981

Spo

t 87

0.16

0.09

170.

0011

0.24

080.

0030

3.04

390.

0426

0.06

770.

0016

0.90

314

6123

1391

1614

1911

1324

2995

1461

Spo

t 89

0.09

0.09

500.

0012

0.24

700.

0031

3.23

580.

0457

0.10

720.

0027

0.89

515

2923

1423

1614

6611

2057

4993

1529

Spo

t 90

0.22

0.12

080.

0013

0.31

250.

0040

5.20

670.

0696

0.06

550.

0014

0.95

819

6920

1753

2018

5411

1283

2689

1969

Spo

t 93

0.40

0.10

350.

0014

0.27

650.

0037

3.94

640.

0610

0.08

160.

0018

0.85

416

8826

1574

1816

2313

1586

3393

1688

Spo

t 95

0.40

0.09

450.

0012

0.26

610.

0034

3.46

630.

0505

0.07

780.

0016

0.87

315

1825

1521

1715

2011

1514

2910

015

18

Spo

t 96

0.61

0.09

600.

0013

0.25

690.

0037

3.40

120.

0546

0.06

070.

0025

0.90

415

4925

1474

1915

0513

1191

4795

1549

Spo

t 98

0.30

0.11

860.

0015

0.24

350.

0033

3.98

160.

0578

0.09

570.

0021

0.92

219

3622

1405

1716

3012

1848

3973

1936

Spo

t 99

0.41

0.08

070.

0010

0.17

780.

0022

1.97

800.

0274

0.04

260.

0008

0.91

112

1524

1055

1211

089

843

1587

1215

Spo

t 100

0.77

0.09

560.

0012

0.26

540.

0034

3.49

660.

0501

0.07

740.

0015

0.88

615

4024

1518

1715

2711

1506

2899

1540

Spo

t 101

0.30

0.09

420.

0011

0.26

560.

0033

3.44

740.

0467

0.07

430.

0015

0.92

515

1122

1518

1715

1511

1449

2810

015

11

Spo

t 102

0.36

0.07

590.

0026

0.17

490.

0032

1.83

210.

0618

0.05

790.

0059

0.54

210

9268

1039

1810

5722

1138

112

9510

92

Spo

t 103

0.44

0.08

660.

0011

0.23

330.

0029

2.78

390.

0391

0.06

690.

0014

0.89

713

5124

1352

1513

5110

1308

2610

013

51

Spo

t 104

0.33

0.09

590.

001 1

0.26

770.

0034

3.53

920.

0478

0.08

040.

0015

0.93

515

4622

1529

1715

3611

1562

2999

1546

Spo

t 106

0.42

0.10

640.

0014

0.29

280.

0039

4.29

530.

0637

0.08

890.

0022

0.89

917

3923

1656

1916

9312

1721

4195

1739

Spo

t 107

0.50

0.10

790.

0014

0.30

610.

0040

4.55

380.

0652

0.08

640.

0021

0.90

317

6523

1721

2017

4112

1674

3998

1765

Spo

t 112

0.42

0.07

460.

0011

0.16

870.

0021

1.73

400.

0277

0.04

910.

0012

0.79

110

5730

1005

1210

2110

970

2495

1057

Spo

t 113

0.36

0.07

580.

0019

0.16

940.

0024

1.77

010.

0443

0.05

190.

0020

0.57

310

9049

1009

1310

3516

1022

3893

1090

Spo

t 114

0.39

0.08

440.

0018

0.19

400.

0027

2.25

710.

0486

0.06

090.

0019

0.64

613

0241

1143

1511

9915

1195

3688

1302

Spo

t 116

0.20

0.10

240.

0011

0.28

310.

0035

3.99

460.

0515

0.09

060.

0021

0.94

516

6821

1607

1716

3310

1754

4096

1668

Spo

t 119

0.34

0.09

200.

0013

0.24

880.

0033

3.15

480.

0489

0.07

400.

0020

0.84

314

6727

1432

1714

4612

1442

3798

1467

Spo

t 120

0.24

0.09

580.

0011

0.27

180.

0034

3.59

040.

0480

0.07

330.

0016

0.94

715

4521

1550

1715

4711

1431

3010

015

45

Spo

t 121

0.66

0.07

640.

0010

0.17

020.

0023

1.79

320.

0280

0.05

020.

0013

0.86

611

0727

1013

1310

4310

990

2592

1107

Spo

t 122

0.81

0.12

120.

0014

0.34

840.

0044

5.82

280.

0765

0.09

710.

0021

0.95

219

7520

1927

2119

5011

1874

3998

1975

Spo

t 123

0.41

0.07

860.

0014

0.17

090.

0025

1.85

040.

0346

0.04

960.

0019

0.76

711

6234

1017

1310

6412

979

3788

1162

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

86


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 124

0.96

0.10

340.

0012

0.24

850.

0032

3.54

110.

0471

0.07

110.

0014

0.95

316

8620

1431

1615

3611

1389

2785

1686

Spo

t 125

0.10

0.09

560.

0011

0.25

080.

0034

3.30

440.

0473

0.08

450.

0031

0.94

815

4021

1443

1814

8211

1639

5894

1540

Spo

t 127

0.43

0.09

300.

0013

0.27

050.

0034

3.46

680.

0515

0.07

690.

0022

0.85

414

8725

1543

1715

2012

1498

4110

414

87

Spo

t 128

0.42

0.07

310.

0011

0.16

850.

0022

1.69

650.

0272

0.05

230.

0013

0.80

710

1529

1004

1210

0710

1030

2499

1015

Spo

t 129

0.48

0.09

750.

0012

0.27

210.

0035

3.65

620.

0512

0.07

990.

0018

0.90

815

7623

1551

1815

6211

1554

3498

1576

Spo

t 130

1.59

0.08

780.

0014

0.22

770.

0030

2.75

670.

0468

0.06

680.

0015

0.77

913

7830

1323

1613

4413

1306

2896

1378

Spo

t 20.

230.

0826

0.00

140.

2070

0.00

302.

3571

0.04

270.

0671

0.00

150.

7994

2271

912

6032

1213

1612

3013

1313

2896

1260

Spo

t 30.

710.

1099

0.00

140.

3214

0.00

444.

8705

0.07

180.

0812

0.00

110.

9355

7563

917

9823

1797

2217

9712

1578

2110

017

98

Spo

t 50.

250.

1071

0.00

130.

2985

0.00

424.

4052

0.06

580.

0706

0.00

120.

9469

9692

417

5122

1684

2117

1312

1379

2296

1751

Spo

t 71.

260.

0911

0.00

200.

2519

0.00

393.

1630

0.07

120.

0737

0.00

120.

6841

4752

514

4842

1448

2014

4817

1437

2310

014

48

Spo

t 90.

470.

0798

0.00

100.

1902

0.00

272.

0921

0.03

210.

0538

0.00

070.

9295

9580

411

9225

1122

1511

4611

1059

1394

1192

Spo

t 12

0.11

0.09

070.

0012

0.24

160.

0033

3.02

150.

0472

0.07

530.

0018

0.88

4453

573

1441

2613

9517

1413

1214

6833

9714

41

Spo

t 17

0.29

0.09

560.

0010

0.27

820.

0036

3.66

430.

0484

0.07

820.

0009

0.97

4591

376

1539

2015

8218

1564

1115

2117

103

1539

Spo

t 20

0.37

0.08

690.

0011

0.23

000.

0030

2.75

620.

0396

0.06

640.

0009

0.90

4021

296

1359

2413

3416

1344

1112

9917

9813

59

Spo

t 21

0.27

0.08

990.

0011

0.24

830.

0032

3.07

550.

0427

0.07

450.

0010

0.93

7031

715

1423

2214

3017

1427

1114

5219

100

1423

Spo

t 22

0.13

0.09

640.

0012

0.24

780.

0033

3.29

230.

0477

0.08

430.

0016

0.92

1986

826

1555

2314

2717

1479

1116

3629

9215

55

Spo

t 23

1.52

0.09

050.

0011

0.24

800.

0033

3.09

410.

0450

0.06

320.

0008

0.92

0367

5914

3624

1428

1714

3111

1239

1599

1436

Spo

t 24

0.32

0.09

430.

0012

0.25

970.

0038

3.37

580.

0530

0.04

840.

0012

0.93

6804

377

1515

2414

8820

1499

1295

522

9815

15

Spo

t 26

0.28

0.08

130.

0011

0.15

930.

0023

1.78

610.

0286

0.03

940.

0007

0.91

0422

346

1230

2695

313

1040

1078

114

7795

3

Spo

t 29

0.43

0.09

630.

0014

0.26

910.

0037

3.57

230.

0576

0.07

250.

0013

0.85

4794

751

1553

2715

3619

1543

1314

1424

9915

53

Spo

t 31

0.65

0.10

220.

0018

0.27

460.

0041

3.86

700.

0727

0.07

510.

0016

0.79

4575

125

1664

3215

6421

1607

1514

6331

9416

64

Spo

t 32

0.77

0.08

950.

001 1

0.24

230.

0032

2.98

890.

0426

0.06

490.

0007

0.93

5442

305

1414

2313

9917

1405

1112

7214

9914

14

Spo

t 33

0.49

0.09

820.

0014

0.27

050.

0037

3.66

040.

0583

0.07

440.

0012

0.86

7882

956

1590

2615

4319

1563

1314

5022

9715

90

Spo

t 34

0.58

0.09

450.

0011

0.25

690.

0034

3.34

670.

0455

0.06

980.

0008

0.96

2095

681

1518

2114

7417

1492

1113

6314

9715

18

Spo

t 35

0.39

0.08

760.

0012

0.22

410.

0030

2.70

640.

0422

0.06

180.

0010

0.84

7547

284

1373

2713

0416

1330

1212

1218

9513

73

Spo

t 36

0.11

0.13

340.

0014

0.27

540.

0039

5.06

350.

0715

0.09

230.

0018

0.98

6402

358

2143

1815

6820

1830

1217

8432

7321

43

Spo

t 37

0.30

0.08

430.

0013

0.19

960.

0028

2.31

840.

0399

0.06

270.

0012

0.80

1720

498

1299

3111

7315

1218

1212

3023

9012

99

Spo

t 39

0.30

0.08

570.

0013

0.22

620.

0031

2.67

330.

0447

0.05

940.

0011

0.82

7172

364

1332

2913

1516

1321

1211

6622

9913

32

Spo

t 40

0.32

0.11

180.

0014

0.31

410.

0042

4.84

200.

0711

0.08

280.

0013

0.91

4664

727

1829

2317

6121

1792

1216

0824

9618

29

Spo

t 43

0.58

0.06

690.

0013

0.08

580.

0012

0.79

130.

0164

0.02

370.

0005

0.69

8815

125

835

4153

17

592

947

410

6453

1

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BD

M-0

1

87


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 44

0.66

0.09

430.

0013

0.26

360.

0036

3.42

770.

0532

0.06

750.

0010

0.88

3333

507

1515

2515

0818

1511

1213

2118

100

1515

Spo

t 45

0.85

0.37

220.

0037

0.09

460.

0012

4.85

260.

0614

0.08

160.

0010

0.97

2895

238

0115

583

717

9411

1585

1815

583

Spo

t 49

0.85

0.11

330.

0018

0.32

170.

0045

5.02

220.

0857

0.08

500.

0013

0.82

7042

857

1852

2817

9822

1823

1416

4924

9718

52

Spo

t 50

0.34

0.08

690.

0013

0.22

340.

0033

2.67

930.

0467

0.05

620.

0013

0.85

7342

323

1359

2913

0018

1323

1311

0524

9613

59

Spo

t 51

0.56

0.13

120.

0017

0.33

250.

0048

6.01

470.

0919

0.09

530.

0015

0.94

2417

109

2114

2218

5123

1978

1318

4128

8821

14

Spo

t 53

0.67

0.08

030.

0011

0.19

640.

0027

2.17

490.

0335

0.05

260.

0010

0.88

0434

149

1204

2611

5614

1173

1110

3719

9612

04

Spo

t 54

0.44

0.06

160.

0009

0.10

490.

0014

0.89

110.

0145

0.02

880.

0005

0.82

4746

836

661

3164

38

647

857

310

9764

3

Spo

t 55

0.60

0.06

150.

0029

0.08

630.

0016

0.73

090.

0332

0.02

530.

0014

0.41

8058

717

656

9853

310

557

2050

527

8153

3

Spo

t 56

0.34

0.23

940.

0024

0.10

380.

0014

3.42

610.

0440

0.12

510.

0013

0.98

1085

796

3116

1663

78

1510

1023

8324

2063

7

Spo

t 57

0.60

0.11

200.

0017

0.30

740.

0043

4.74

430.

0793

0.07

940.

0014

0.83

8482

3218

3128

1728

2117

7514

1545

2794

1831

Spo

t 58

0.47

0.11

660.

0013

0.32

920.

0044

5.29

280.

0709

0.08

650.

0010

0.98

6689

427

1905

1918

3521

1868

1116

7719

9619

05

Spo

t 59

0.52

0.10

830.

0012

0.30

890.

0040

4.61

150.

0599

0.07

880.

0010

0.98

5429

739

1771

2017

3519

1751

1115

3419

9817

71

Spo

t 62

0.51

0.10

860.

0014

0.30

580.

0040

4.57

680.

0655

0.07

930.

0012

0.91

8419

317

1775

2317

2020

1745

1215

4323

9717

75

Spo

t 65

0.40

0.06

610.

0015

0.08

490.

0012

0.77

320.

0168

0.02

760.

0016

0.62

2240

052

810

4552

57

582

1054

931

6552

5

Spo

t 65b

0.29

0.09

790.

0016

0.07

710.

0012

1.03

890.

0189

0.03

090.

0010

0.86

2313

8115

8430

479

772

39

615

2030

479

Spo

t 69

0.44

0.11

270.

0014

0.31

040.

0046

4.81

410.

0757

0.08

450.

0021

0.94

4841

111

1843

2317

4323

1787

1316

3939

9518

43

Spo

t 70

0.38

0.10

050.

0013

0.26

710.

0041

3.69

270.

0605

0.06

720.

0022

0.93

1615

609

1633

2415

2621

1570

1313

1542

9316

33

Spo

t 71

0.40

0.06

350.

0013

0.08

730.

0013

0.76

380.

0163

0.02

910.

0008

0.68

8633

325

725

4254

08

576

958

015

7454

0

Spo

t 76

0.11

0.20

520.

0022

0.10

430.

0013

2.94

960.

0377

0.26

800.

0042

0.98

2779

9628

6818

640

813

9510

4799

6722

640

Spo

t 77

0.38

0.08

150.

001 1

0.20

760.

0028

2.33

110.

0357

0.06

120.

0010

0.88

3712

353

1233

2612

1615

1222

1112

0119

9912

33

Spo

t 78

0.33

0.08

170.

0011

0.20

840.

0028

2.34

670.

0364

0.06

110.

0011

0.86

2922

167

1238

2712

2015

1227

1111

9920

9912

38

Spo

t 81

0.41

0.10

970.

0014

0.32

680.

0044

4.94

030.

0716

0.09

320.

0015

0.91

8728

123

1794

2318

2321

1809

1218

0028

102

1794

Spo

t 83

0.47

0.10

930.

0013

0.32

310.

0043

4.86

770.

0690

0.09

300.

0014

0.93

4851

4717

8822

1805

2117

9712

1797

2610

117

88

Spo

t 85

0.31

0.09

650.

0011

0.27

480.

0036

3.65

410.

0493

0.07

750.

0011

0.96

3031

078

1557

2115

6518

1561

1115

0921

101

1557

Spo

t 86

0.21

0.07

570.

0010

0.17

650.

0024

1.84

000.

0275

0.05

370.

0011

0.91

6616

738

1086

2510

4813

1060

1010

5720

9610

86

Spo

t 89

0.82

0.09

830.

0014

0.27

630.

0038

3.74

460.

0612

0.08

050.

0013

0.85

0841

627

1593

2715

7319

1581

1315

6525

9915

93

Spo

t 91

0.31

0.08

260.

0010

0.19

900.

0027

2.26

840.

0322

0.05

880.

0008

0.94

2340

674

1261

2311

7014

1203

1011

5415

9312

61

Spo

t 94

0.80

0.06

130.

0009

0.10

290.

0014

0.86

920.

0140

0.03

000.

0004

0.83

1207

785

649

3063

18

635

859

88

9763

1

Spo

t 98

0.37

0.26

130.

0027

0.08

870.

0013

3.19

610.

0453

0.11

460.

0013

0.98

2183

993

3255

1654

88

1456

1121

9223

1754

8

Spo

t 104

0.66

0.05

980.

0014

0.09

140.

0014

0.75

320.

0182

0.02

430.

0008

0.64

3245

776

597

5056

48

570

1148

616

9456

4

Spo

t 105

0.45

0.11

210.

0013

0.18

900.

0026

2.92

100.

0413

0.06

080.

0008

0.97

6371

418

1833

2011

1614

1387

1111

9415

6118

33

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

88


Tabl

e 1.

(con

tinue

d)

Anal

ysis

Th/U

207 Pb

/206 Pb

± 1σ

206 Pb

/238 U

± 1σ

207 Pb

/235 U

± 1σ

208 Pb

/232 Th

± 1σ

Rho

b20

7 Pb/20

6 Pb±

1σ20

6 Pb/23

8 U±

1σ20

7 Pb/23

5 U±

1σ20

8 Pb/23

2 Th±

1σC

onc.

c

Spot

114

0.64

0.09

140.

0011

0.08

800.

0011

1.10

890.

0155

0.03

800.

0005

0.91

3113

559

1455

2354

47

758

775

59

3754

4

Spot

115

0.11

0.32

370.

0032

0.08

160.

0011

3.64

310.

0479

0.45

210.

0050

0.97

5100

651

3587

1550

67

1559

1075

3969

1450

6

Spot

117

0.41

0.09

870.

0011

0.24

070.

0034

3.27

550.

0477

0.07

710.

0010

0.97

0884

075

1599

2113

9118

1475

1115

0119

8715

99

Spot

118

0.08

0.32

090.

0032

0.08

470.

0012

3.74

880.

0528

0.50

440.

0057

0.97

0626

875

3574

1552

47

1582

1182

5577

1552

4

Spot

121

1.07

0.06

240.

0008

0.10

620.

0015

0.91

310.

0139

0.02

980.

0004

0.90

5823

059

688

2665

19

659

759

47

9565

1

Spot

124

0.09

0.24

230.

0025

0.06

590.

0009

2.19

910.

0292

0.26

820.

0030

0.99

2595

855

3135

1641

15

1181

948

0348

1341

1

Spot

130

0.19

0.09

490.

0011

0.18

090.

0026

2.36

620.

0345

0.08

240.

0011

0.96

9292

446

1526

2110

7214

1233

1016

0021

7015

26

Spot

131

0.42

0.11

180.

0012

0.32

440.

0044

5.00

040.

0681

0.08

850.

0011

0.98

4224

145

1829

1918

1121

1819

1217

1420

9918

29

Spot

133

0.72

0.09

890.

0014

0.21

770.

0031

2.96

680.

0500

0.06

970.

0009

0.83

4289

126

1603

2712

7016

1399

1313

6316

7916

03

Spot

137

0.13

0.35

150.

0035

0.05

970.

0008

2.89

360.

0382

0.26

440.

0028

0.98

5230

784

3713

1537

45

1380

1047

4245

1037

4

Spot

140

0.30

0.24

580.

0025

0.08

990.

0012

3.04

580.

0402

0.11

720.

0013

0.98

8454

631

3158

1655

57

1419

1022

3923

1855

5

Spot

141

0.57

0.08

640.

0017

0.21

040.

0032

2.50

530.

0523

0.05

510.

0011

0.73

8332

656

1347

3712

3117

1274

1510

8422

9113

47

Spot

142

1.36

0.11

470.

0014

0.33

690.

0046

5.32

750.

0763

0.08

430.

0010

0.95

1131

9918

7521

1872

2218

7312

1636

1810

018

75

Spot

143

0.41

0.08

280.

0016

0.22

940.

0033

2.61

930.

0541

0.06

250.

0014

0.70

2676

1512

6538

1331

1713

0615

1225

2710

512

65

Spot

150

0.08

0.13

570.

0015

0.11

320.

0015

2.11

780.

0287

0.16

250.

0018

0.98

9453

391

2173

1969

19

1155

930

4332

3269

1

Spot

151

0.35

0.09

930.

0011

0.25

940.

0034

3.55

100.

0473

0.06

840.

0008

0.98

6151

0916

1120

1487

1715

3911

1338

1492

1611

Spot

154

0.62

0.11

890.

0029

0.11

160.

0017

1.82

830.

0423

0.03

180.

0009

0.65

4231

327

1940

4268

210

1056

1563

317

3568

2

Spot

156

0.53

0.05

950.

0013

0.08

530.

0012

0.69

940.

0153

0.02

240.

0004

0.62

8328

497

585

4552

87

538

944

99

9052

8

Spot

159

0.30

0.08

410.

0012

0.21

180.

0028

2.45

430.

0388

0.05

760.

0011

0.83

0971

283

1294

2812

3915

1259

1111

3220

9612

94

Spot

161

0.49

0.07

310.

0010

0.16

020.

0022

1.61

520.

0253

0.04

150.

0006

0.87

2427

668

1018

2795

812

976

1082

111

9495

8

Spot

163

0.20

0.19

600.

0020

0.09

730.

0012

2.62

790.

0333

0.15

680.

0016

0.99

6806

314

2793

1759

87

1309

929

4528

2159

8

Spot

164

0.46

0.11

150.

0017

0.30

000.

0043

4.61

220.

0779

0.07

750.

0014

0.85

6625

263

1824

2716

9222

1752

1415

0826

9318

24

Spot

165

0.48

0.11

750.

0013

0.32

800.

0042

5.31

200.

0697

0.08

400.

0009

0.97

8218

773

1918

1918

2920

1871

1116

3117

9519

18

Spot

166

0.48

0.10

090.

0011

0.27

060.

0035

3.76

280.

0488

0.06

890.

0007

0.98

6446

269

1640

1915

4418

1585

1013

4613

9416

40

Spot

170

0.39

0.13

450.

0017

0.15

840.

0023

2.93

750.

0450

0.05

650.

0009

0.94

7032

457

2158

2294

813

1392

1211

1118

4494

8

Spot

172

0.50

0.09

670.

0011

0.25

740.

0033

3.43

030.

0456

0.07

010.

0008

0.96

5530

488

1561

2114

7717

1511

1013

6915

9515

61

Spot

173

0.21

0.07

860.

0009

0.20

040.

0025

2.17

180.

0285

0.05

690.

0007

0.96

3068

471

1163

2211

7814

1172

911

1814

101

1163

Spot

174

0.57

0.14

480.

0019

0.19

060.

0027

3.80

260.

0581

0.09

230.

0016

0.93

3419

124

2285

2211

2515

1593

1217

8429

4922

85

Spot

175

0.48

0.07

550.

0008

0.14

130.

0018

1.47

080.

0193

0.03

860.

0004

0.96

1776

416

1082

2285

210

918

876

69

7985

2

Spot

176

0.27

0.08

790.

0012

0.22

970.

0028

2.78

210.

0394

0.06

310.

0012

0.86

3416

509

1379

2513

3315

1351

1112

3623

9713

79

Spot

177

0.40

0.08

570.

0009

0.22

040.

0028

2.60

410.

0342

0.05

640.

0006

0.97

7062

784

1332

2112

8415

1302

1011

0812

9613

32

Isot

opic

Rat

iosa

Age

Estim

ates

a (Ma)

Eff.

Aged

89


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 180

0.37

0.09

020.

0015

0.25

080.

0034

3.11

750.

0538

0.07

370.

0016

0.79

5288

6314

2930

1443

1814

3713

1437

3010

114

29

Spo

t 182

0.20

0.42

750.

0043

0.05

670.

0007

3.33

860.

0417

0.23

870.

0027

0.98

2746

906

4009

1535

54

1490

1043

2744

935

5

Spo

t 183

0.19

0.07

300.

0010

0.17

390.

0023

1.75

060.

0273

0.05

110.

0010

0.82

9383

904

1015

2910

3412

1027

1010

0720

102

1015

Spo

t 184

0.23

0.07

400.

0009

0.17

080.

0023

1.74

250.

0252

0.04

310.

0006

0.93

2178

603

1042

2410

1713

1024

985

312

9810

42

Spo

t 185

0.21

0.11

960.

0012

0.36

250.

0047

5.97

430.

0769

0.09

050.

0011

0.99

8954

953

1950

1819

9422

1972

1117

5021

102

1950

Spo

t 187

0.53

0.06

300.

0015

0.09

890.

0014

0.85

910.

0208

0.02

810.

0006

0.57

5154

986

708

5060

88

630

1155

912

8660

8

Spo

t 188

0.80

0.05

690.

0023

0.08

870.

0015

0.69

610.

0280

0.02

520.

0007

0.41

1690

1248

988

548

953

617

502

1411

254

8

Spo

t 188

b1.

100.

0587

0.00

390.

0897

0.00

180.

7258

0.04

700.

0276

0.00

090.

3046

9632

655

413

855

410

554

2855

118

100

554

Spo

t 189

0.52

0.08

760.

0012

0.24

940.

0037

3.01

270.

0497

0.05

190.

0011

0.88

9107

519

1374

2714

3619

1411

1310

2221

104

1374

Spo

t 194

0.27

0.09

350.

0010

0.26

830.

0036

3.45

870.

0469

0.06

870.

0010

0.98

4987

613

1498

2015

3218

1518

1113

4318

102

1498

Spo

t 195

0.56

0.11

030.

0013

0.32

270.

0042

4.90

800.

0670

0.08

480.

0011

0.95

3791

948

1805

2118

0320

1804

1216

4520

100

1805

Spo

t 198

0.38

0.07

470.

0011

0.17

500.

0023

1.80

170.

0287

0.04

880.

0008

0.81

7529

974

1060

2910

4012

1046

1096

315

9810

60

Spo

t 10.

430.

0822

0.00

160.

2130

0.00

292.

4128

0.04

740.

0639

0.00

150.

6936

1249

3712

4515

1246

1412

5328

100

1249

Spo

t 30.

300.

0746

0.00

210.

1657

0.00

251.

7032

0.04

650.

0548

0.00

200.

5571

1057

5598

814

1010

1710

7938

9398

8

Spo

t 4b

0.69

0.09

300.

0016

0.26

110.

0035

3.34

760.

0598

0.08

120.

0015

0.75

7414

8832

1496

1814

9214

1577

2810

114

88

Spo

t 50.

310.

0709

0.00

180.

1556

0.00

231.

5187

0.03

780.

0505

0.00

160.

5994

954

5093

213

938

1599

531

9893

2

Spo

t 90.

370.

2559

0.00

420.

2105

0.00

317.

4260

0.12

180.

2712

0.00

510.

8889

3222

2612

3116

2164

1548

5181

3832

22

Spo

t 10

0.68

0.18

750.

0032

0.22

280.

0032

5.75

760.

0980

0.12

740.

0025

0.84

4127

2128

1296

1719

4015

2424

4548

2721

Spo

t 11

0.26

0.13

860.

0021

0.18

630.

0025

3.56

000.

0579

0.14

610.

0028

0.83

2522

1026

1101

1415

4113

2756

5050

2210

Spo

t 12

0.44

0.21

950.

0056

0.23

130.

0041

6.99

870.

1688

0.20

260.

0058

0.73

1329

7740

1341

212 1

1121

3728

9745

2977

Spo

t 13

0.51

0.09

910.

0028

0.20

460.

0032

2.79

440.

0767

0.07

760.

0024

0.56

8216

0751

1200

1713

5421

1511

4575

1607

Spo

t 15

0.48

0.07

870.

0013

0.20

660.

0030

2.24

080.

0420

0.06

270.

0011

0.78

6111

6433

1211

1611

9413

1230

2110

411

64

Spo

t 16

0.45

0.10

280.

0017

0.23

670.

0032

3.35

560.

0574

0.08

600.

0018

0.78

3516

7630

1370

1714

9413

1668

3482

1676

Spo

t 17

0.25

0.10

140.

0012

0.25

590.

0032

3.57

480.

0491

0.08

870.

0017

0.91

1316

4922

1469

1615

4411

1717

3189

1649

Spo

t 18

0.30

0.08

730.

0016

0.19

980.

0027

2.40

400.

0447

0.06

750.

0018

0.71

9613

6734

1174

1412

4413

1321

3486

1367

Spo

t 20

0.34

0.07

790.

0016

0.21

220.

0029

2.27

810.

0480

0.06

950.

0019

0.65

1211

4341

1241

1512

0615

1358

3710

911

43

Spo

t 21

0.56

0.13

780.

0021

0.18

320.

0026

3.47

950.

0575

0.10

210.

0024

0.86

5722

0026

1085

1415

2313

1965

4449

2200

Spo

t 23

0.41

0.08

430.

0014

0.22

800.

0031

2.65

070.

0466

0.06

940.

0015

0.76

0313

0032

1324

1613

1513

1356

2910

213

00

Spo

t 24

0.52

0.07

380.

0029

0.15

630.

0027

1.59

070.

0616

0.04

580.

0020

0.45

0910

3678

936

1596

724

904

3890

1036

Spo

t 26

0.25

0.07

660.

0014

0.18

260.

0025

1.92

710.

0367

0.05

730.

0016

0.70

3711

0936

1081

1310

9113

1127

3197

1109

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BS

A-0

7

90


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 26b

0.23

0.08

080.

0025

0.18

270.

0028

2.03

440.

0613

0.06

430.

0032

0.50

7212

1758

1082

1511

2721

1260

6089

1217

Spo

t 27

0.54

0.07

220.

0014

0.17

450.

0023

1.73

590.

0342

0.05

710.

0014

0.66

8499

139

1037

1310

2213

1123

2610

599

1

Spo

t 28

0.74

0.09

180.

0012

0.25

670.

0033

3.24

980.

0461

0.07

380.

0015

0.89

7814

6424

1473

1714

6911

1439

2810

114

64

Spo

t 30

0.24

0.07

420.

0011

0.16

940.

0022

1.73

240.

0277

0.05

230.

0013

0.81

2610

4629

1009

1210

2110

1030

2696

1046

Spo

t 31

0.33

0.09

060.

0016

0.25

560.

0036

3.19

240.

0596

0.08

070.

0024

0.74

7814

3933

1467

1814

5514

1568

4510

214

39

Spo

t 34

0.32

0.07

130.

0017

0.14

950.

0021

1.47

010.

0345

0.04

970.

0016

0.59

5296

646

898

1291

814

980

3093

966

Spo

t 36

0.24

0.07

940.

0013

0.19

560.

0025

2.14

040.

0362

0.06

230.

0022

0.75

3311

8132

1152

1311

6212

1221

4297

1181

Spo

t 37

0.41

0.08

670.

0021

0.22

380.

0032

2.67

340.

0633

0.06

980.

0026

0.60

5913

5345

1302

1713

2118

1364

4996

1353

Spo

t 39

0.26

0.07

860.

0010

0.20

020.

0026

2.16

960.

0308

0.06

240.

0014

0.89

6911

6325

1176

1411

7110

1223

2710

111

63

Spo

t 40

0.49

0.08

860.

0016

0.22

960.

0031

2.80

500.

0531

0.07

020.

0019

0.72

2613

9634

1332

1613

5714

1371

3695

1396

Spo

t 41

0.23

0.08

540.

0012

0.22

550.

0029

2.65

360.

0399

0.06

970.

0018

0.86

1613

2426

1311

1513

1611

1361

3599

1324

Spo

t 44

0.47

0.07

790.

0012

0.17

110.

0023

1.83

790.

0310

0.04

500.

0011

0.78

7711

4431

1018

1310

5911

889

2289

1144

Spo

t 45

0.33

0.07

190.

0021

0.15

280.

0023

1.51

470.

0447

0.05

390.

0021

0.50

1898

459

917

1393

618

1062

4093

984

Spo

t 46

0.43

0.08

240.

0014

0.20

570.

0027

2.33

600.

0413

0.06

460.

0018

0.75

0912

5532

1206

1512

2313

1265

3396

1255

Spo

t 47

0.31

0.08

060.

0012

0.21

160.

0027

2.34

990.

0380

0.06

460.

0018

0.80

1612

1129

1237

1512

2812

1266

3410

212

11

Spo

t 48

0.38

0.07

270.

0010

0.16

810.

0021

1.68

550.

0249

0.05

130.

0012

0.85

7310

0627

1002

1210

039

1012

2410

010

06

Spo

t 49

0.36

0.07

540.

0014

0.17

800.

0024

1.84

980.

0351

0.05

850.

0018

0.71

6210

7836

1056

1310

6313

1149

3498

1078

Spo

t 50

0.65

0.08

350.

0022

0.20

280.

0030

2.33

510.

0626

0.06

870.

0022

0.55

5812

8152

1190

1612

2319

1344

4193

1281

Spo

t 51

0.50

0.07

240.

0022

0.15

170.

0023

1.51

490.

0451

0.05

060.

0018

0.50

0099

859

911

1393

618

997

3491

911

Spo

t 52

0.40

0.09

030.

0037

0.20

400.

0040

2.54

150.

1024

0.07

090.

0042

0.48

4114

3277

1 197

2112

8429

1384

8084

1432

Spo

t 53

0.21

0.08

150.

0009

0.21

480.

0031

2.41

440.

0367

0.06

180.

0009

0.96

1312

3423

1254

1712

4711

1211

1710

212

34

Spo

t 54

0.63

0.09

710.

0016

0.26

770.

0046

3.57

990.

0699

0.05

790.

0012

0.88

7515

6830

1529

2415

4516

1137

2397

1568

Spo

t 55

0.40

0.07

810.

0011

0.20

960.

0027

2.25

760.

0335

0.06

710.

0017

0.85

4811

5026

1227

1411

9910

1313

3210

711

50

Spo

t 56

0.98

0.07

320.

0017

0.17

860.

0025

1.80

300.

0424

0.05

730.

0015

0.59

5310

2046

1059

1410

4715

1127

2910

410

20

Spo

t 58

0.62

0.07

770.

0015

0.17

370.

0024

1.86

020.

0377

0.05

830.

0016

0.67

2811

3939

1032

1310

6713

1146

3191

1139

Spo

t 59

0.29

0.08

890.

0010

0.24

270.

0036

2.97

280.

0457

0.07

410.

0010

0.95

9314

0122

1401

1914

0112

1444

2010

014

01

Spo

t 60

0.54

0.06

270.

0021

0.10

630.

0016

0.91

880.

0306

0.03

720.

0014

0.44

8769

870

651

966

216

738

2793

651

Spo

t 60b

0.47

0.06

120.

0022

0.10

560.

0016

0.89

090.

0314

0.03

490.

0012

0.42

4164

675

647

964

717

693

2410

064

7

Spo

t 60b

0.46

0.07

930.

0014

0.19

210.

0026

2.09

920.

0381

0.05

840.

0016

0.73

1711

7934

1133

1411

4912

1146

3196

1179

Spo

t 60b

0.29

0.07

980.

0013

0.17

720.

0027

1.94

830.

0363

0.05

600.

0011

0.82

0011

9132

1052

1510

9813

1100

2288

1191

Spo

t 64

0.50

0.07

440.

0014

0.17

440.

0023

1.78

790.

0342

0.05

270.

0014

0.69

1510

5137

1037

1310

4112

1038

2799

1051

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

91


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 67

0.57

0.09

140.

0011

0.24

470.

0036

3.08

140.

0476

0.06

900.

0009

0.95

5614

5422

1411

1914

2812

1349

1797

1454

Spo

t 70

0.46

0.08

590.

0014

0.22

160.

0037

2.62

340.

0515

0.05

680.

0011

0.85

9213

3631

1290

2013

0714

1117

2197

1336

Spo

t 73

0.50

0.09

600.

0011

0.26

720.

0041

3.53

590.

0553

0.07

880.

0010

0.97

5715

4721

1527

2115

3512

1534

2099

1547

Spo

t 74

0.30

0.08

690.

0013

0.22

620.

0029

2.71

000.

0429

0.06

890.

0020

0.80

4313

5928

1314

1513

3112

1347

3897

1359

Spo

t 75

0.42

0.08

210.

0020

0.19

940.

0029

2.25

690.

0552

0.05

780.

0022

0.58

6412

4947

1172

1511

9917

1136

4294

1249

Spo

t 76

0.32

0.07

900.

0025

0.19

640.

0031

2.13

860.

0663

0.06

480.

0028

0.50

0911

7260

1156

1611

6121

1269

5499

1172

Spo

t 77

0.43

0.09

180.

0015

0.24

220.

0032

3.06

600.

0520

0.07

060.

0019

0.77

9714

6430

1398

1714

2413

1379

3596

1464

Spo

t 78

0.63

0.09

590.

0013

0.26

600.

0035

3.51

570.

0535

0.07

340.

0020

0.87

2015

4525

1520

1815

3112

1432

3798

1545

Spo

t 79

0.47

0.08

150.

0013

0.19

880.

0028

2.23

400.

0380

0.05

210.

0026

0.82

5812

3530

1169

1511

9212

1027

5195

1235

Spo

t 80

0.47

0.07

780.

0022

0.15

120.

0022

1.62

260.

0464

0.05

050.

0017

0.51

7911

4256

908

1397

918

995

3379

908

Spo

t 81

0.47

0.09

320.

0013

0.24

430.

0036

3.14

100.

0508

0.07

400.

0011

0.90

0614

9325

1409

1814

4312

1443

2194

1493

Spo

t 84

0.36

0.07

310.

0021

0.14

880.

0026

1.49

950.

0434

0.04

920.

0016

0.59

2710

1657

894

1493

018

970

3188

1016

Spo

t 86

0.34

0.08

160.

0010

0.21

490.

0032

2.41

840.

0383

0.06

560.

0009

0.93

2312

3724

1255

1712

4811

1285

1810

112

37

Spo

t 88

0.38

0.07

330.

0012

0.15

500.

0024

1.56

740.

0291

0.04

920.

0009

0.84

0010

2331

929

1495

712

971

1791

929

Spo

t 89

0.23

0.09

520.

0012

0.20

450.

0032

2.68

270.

0449

0.08

110.

0014

0.93

4615

3124

1199

1713

2412

1577

2578

1531

Spo

t 91

0.26

0.07

490.

0013

0.17

310.

0027

1.78

700.

0345

0.05

810.

0013

0.80

1310

6534

1029

1510

4113

1141

2497

1065

Spo

t 94

0.53

0.09

600.

0012

0.26

050.

0039

3.44

730.

0553

0.07

850.

0011

0.93

8815

4723

1493

2015

1513

1527

2096

1547

Spo

t 95

0.55

0.11

140.

0028

0.15

980.

0024

2.45

510.

0610

0.06

320.

0020

0.60

7218

2345

956

1312

5918

1238

3852

956

Spo

t 98

0.56

0.06

240.

0007

0.10

810.

0016

0.92

980.

0143

0.03

490.

0004

0.96

4468

724

662

966

88

694

896

662

Spo

t 101

0.31

0.07

960.

0009

0.19

050.

0028

2.08

940.

0321

0.06

120.

0008

0.97

021 1

8622

1124

1511

4511

1200

1595

1186

Spo

t 103

0.54

0.11

130.

0013

0.27

030.

0034

4.14

870.

0547

0.08

120.

0019

0.94

2418

2121

1542

1716

6411

1577

3685

1821

Spo

t 104

1.18

0.10

310.

0016

0.25

000.

0036

3.54

970.

0615

0.06

970.

0044

0.82

6216

8029

1438

1815

3814

1361

8386

1680

Spo

t 105

0.47

0.07

810.

0011

0.18

130.

0028

1.95

310.

0333

0.05

590.

0008

0.89

2111

5027

1074

1511

0011

1099

1693

1150

Spo

t 106

0.41

0.07

270.

0023

0.16

610.

0026

1.66

500.

0515

0.05

190.

0023

0.50

0310

0662

991

1499

520

1023

4498

991

Spo

t 107

0.89

0.07

520.

0016

0.18

410.

0025

1.90

680.

0409

0.05

660.

0017

0.63

8010

7242

1089

1410

8414

1113

3310

210

72

Spo

t 107

b0.

540.

0742

0.00

100.

1803

0.00

231.

8450

0.02

670.

0552

0.00

160.

8629

1048

2610

6812

1062

1010

8531

102

1048

Spo

t 108

0.32

0.07

150.

0016

0.16

660.

0023

1.64

200.

0374

0.05

050.

0018

0.60

8197

145

993

1398

714

996

3510

299

3

Spo

t 109

0.44

0.07

900.

0022

0.17

400.

0026

1.89

590.

0534

0.05

560.

0023

0.52

6111

7355

1034

1410

8019

1093

4588

1173

Spo

t 110

0.32

0.08

810.

0021

0.23

730.

0034

2.88

260.

0675

0.07

100.

0030

0.61

4113

8544

1373

1813

7718

1386

5799

1385

Spo

t 111

0.57

0.07

870.

0013

0.14

920.

0023

1.61

850.

0306

0.04

820.

0008

0.82

1511

6432

896

1397

712

951

1577

896

Spo

t 112

0.34

0.08

040.

0019

0.20

720.

0030

2.29

690.

0557

0.06

680.

0028

0.58

6712

0747

1214

1612

1117

1306

5310

112

07

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

92


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 113

0.57

0.08

280.

0015

0.19

670.

0033

2.24

640.

0458

0.05

760.

0011

0.81

5912

6634

1157

1811

9614

1131

2091

1266

Spo

t 114

0.51

0.07

620.

0014

0.17

450.

0023

1.83

190.

0353

0.05

420.

0017

0.69

6410

9937

1037

1310

5713

1067

3294

1099

Spo

t 115

0.27

0.07

230.

0013

0.14

970.

0024

1.49

150.

0300

0.05

000.

0011

0.77

9999

436

899

1392

712

986

2190

899

Spo

t 117

0.37

0.07

320.

0018

0.14

650.

0025

1.47

720.

0381

0.04

650.

0013

0.65

1710

1849

881

1492

116

919

2587

881

Spo

t 120

0.39

0.07

830.

0017

0.19

470.

0027

2.10

260.

0465

0.05

780.

0020

0.62

7111

5542

1147

1511

5015

1136

3899

1155

Spo

t 121

0.37

0.07

620.

0009

0.16

910.

0025

1.77

640.

0276

0.05

210.

0007

0.96

4711

0023

1007

1410

3710

1026

1392

1100

Spo

t 123

0.54

0.10

090.

0014

0.27

020.

0036

3.75

950.

0588

0.07

810.

0026

0.85

0016

4126

1542

1815

8413

1519

5094

1641

Spo

t 126

0.50

0.08

700.

0013

0.22

320.

0029

2.67

860.

0438

0.06

620.

0019

0.79

9513

6129

1299

1513

2312

1296

3695

1361

Spo

t 127

0.25

0.08

130.

0013

0.20

480.

0030

2.29

560.

0404

0.06

290.

0014

0.83

7812

2830

1201

1612

1112

1232

2698

1228

Spo

t 129

0.35

0.08

120.

0036

0.17

080.

0034

1.91

270.

0839

0.05

750.

0030

0.45

5312

2685

1017

1910

8629

1129

5783

1226

Spo

t 130

0.31

0.07

190.

0015

0.16

100.

0025

1.59

500.

0360

0.04

970.

0013

0.69

3798

243

962

1496

814

981

2598

962

Spo

t 134

0.34

0.09

490.

0018

0.22

690.

0035

2.96

730.

0614

0.06

770.

0018

0.75

1315

2536

1318

1913

9916

1324

3386

1525

Spo

t 137

0.33

0.08

230.

0020

0.18

210.

0030

2.06

710.

0520

0.05

510.

0018

0.64

3812

5347

1078

1611

3817

1085

3486

1253

Spo

t 138

0.28

0.07

880.

0017

0.18

380.

0029

1.99

660.

0457

0.05

530.

0017

0.68

1911

6643

1088

1611

1415

1088

3293

1166

Spo

t 139

0.62

0.08

700.

0017

0.21

060.

0032

2.52

650.

0518

0.06

090.

0012

0.75

1113

6136

1232

1712

8015

1196

2391

1361

Spo

t 147

0.57

0.08

280.

0015

0.18

970.

0029

2.16

500.

0433

0.05

750.

0011

0.76

9012

6435

1120

1611

7014

1131

2089

1264

Spo

t 149

0.27

0.07

970.

0012

0.18

390.

0027

2.01

960.

0340

0.05

710.

001 1

0.85

5611

8928

1088

1411

2211

1123

2092

1189

Spo

t 150

0.28

0.07

990.

0010

0.19

710.

0029

2.17

000.

0337

0.05

730.

0008

0.94

2311

9324

1160

1611

7211

1126

1697

1193

Spo

t 151

0.58

0.09

330.

0014

0.25

270.

0038

3.25

070.

0564

0.07

250.

0011

0.86

4914

9428

1453

1914

6913

1415

2297

1494

Spo

t 152

0.20

0.07

050.

0010

0.15

220.

0022

1.47

990.

0243

0.04

540.

0008

0.89

5494

327

913

1392

210

897

1697

913

Spo

t 155

1.04

0.12

950.

0015

0.37

720.

0055

6.73

240.

1003

0.09

980.

0011

0.98

4220

9120

2063

2620

7713

1923

2199

2091

Spo

t 161

0.27

0.07

420.

0010

0.16

530.

0024

1.69

050.

0276

0.04

800.

0008

0.89

3210

4627

986

1310

0510

948

1694

986

Spo

t 162

0.29

0.07

000.

0010

0.15

070.

0022

1.45

470.

0245

0.04

340.

0007

0.88

4592

928

905

1391

210

860

1497

905

Spo

t 164

2.43

0.12

100.

0015

0.34

560.

0051

5.76

540.

0891

0.09

150.

0010

0.95

6519

7121

1913

2519

4113

1770

1997

1971

Spo

t 167

0.61

0.11

420.

0013

0.33

670.

0050

5.30

150.

0795

0.08

780.

0011

0.98

1018

6720

1871

2418

6913

1701

2010

018

67

Spo

t 20.

380.

0783

0.00

140.

1952

0.00

302.

1067

0.04

100.

0562

0.00

110.

7930

1153

3411

5016

1151

1311

0622

100

1153

Spo

t 60.

300.

0796

0.00

100.

2020

0.00

282.

2170

0.03

340.

0578

0.00

080.

9313

1188

2411

8615

1186

1111

3616

100

1188

Spo

t 10

0.28

0.08

950.

0010

0.23

050.

0034

2.84

350.

0435

0.06

770.

0010

0.95

6114

1422

1337

1813

6711

1324

1895

1414

Spo

t 12

0.31

0.08

250.

0010

0.19

930.

0029

2.26

750.

0355

0.05

880.

0009

0.93

8912

5823

1172

1612

0211

1155

1693

1258

Spo

t 14

0.26

0.09

450.

0010

0.25

560.

0038

3.33

090.

0491

0.06

920.

0009

0.99

7215

1819

1468

1914

8812

1352

1697

1518

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BR

Z-01

93


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 15

0.31

0.08

370.

0010

0.20

510.

0030

2.36

670.

0367

0.06

150.

0009

0.94

9412

8523

1203

1612

3311

1206

1694

1285

Spo

t 16

0.11

0.07

660.

0009

0.18

020.

0025

1.90

290.

0272

0.06

510.

0010

0.96

1911

1122

1068

1410

8210

1275

1996

1111

Spo

t 17

0.61

0.13

280.

0015

0.15

480.

0022

2.83

430.

0411

0.06

230.

0009

0.96

2121

3619

928

1213

6511

1221

1743

928

Spo

t 18

0.52

0.11

630.

0017

0.16

520.

0023

2.64

970.

0434

0.05

960.

0016

0.85

8319

0126

986

1313

1512

1171

3152

986

Spo

t 19

0.24

0.07

040.

0014

0.15

520.

0023

1.50

570.

0325

0.04

900.

0014

0.69

3894

041

930

1393

313

967

2799

930

Spo

t 20

0.42

0.08

520.

0011

0.21

640.

0035

2.54

110.

0434

0.05

370.

0009

0.93

6713

1925

1263

1812

8412

1058

1896

1319

Spo

t 21

0.32

0.08

330.

0010

0.21

090.

0031

2.42

180.

0380

0.05

830.

0009

0.94

6012

7623

1234

1712

4911

1145

1797

1276

Spo

t 22

0.26

0.07

710.

0011

0.15

580.

0024

1.65

670.

0287

0.05

190.

0012

0.88

1511

2528

933

1399

211

1022

2383

933

Spo

t 23

0.25

0.07

640.

0010

0.17

610.

0026

1.85

360.

0310

0.05

050.

0009

0.89

5811

0427

1046

1410

6511

996

1795

1104

Spo

t 24

0.30

0.06

990.

0011

0.15

040.

0021

1.45

050.

0255

0.04

360.

0009

0.80

6892

732

903

1291

011

862

1697

903

Spo

t 25

0.56

0.09

630.

0012

0.27

250.

0039

3.61

520.

0545

0.07

290.

0010

0.94

2615

5322

1553

2015

5312

1423

1810

015

53

Spo

t 28

0.35

0.07

740.

0019

0.17

040.

0028

1.81

710.

0463

0.05

260.

0016

0.64

2511

3148

1014

1510

5217

1036

3190

1131

Spo

t 29

0.25

0.07

640.

0012

0.17

470.

0027

1.84

140.

0338

0.05

090.

0011

0.83

5311

0731

1038

1510

6012

1003

2194

1107

Spo

t 31

0.23

0.08

090.

0009

0.20

050.

0029

2.23

510.

0326

0.05

770.

0008

0.97

7212

1821

1178

1511

9210

1134

1597

1218

Spo

t 33

0.31

0.08

160.

0010

0.19

760.

0029

2.22

370.

0355

0.05

820.

0010

0.91

5312

3625

1163

1611

8911

1143

1894

1236

Spo

t 34

0.44

0.09

790.

0011

0.26

320.

0039

3.54

990.

0543

0.07

400.

0010

0.96

9015

8421

1506

2015

3812

1444

1995

1584

Spo

t 37

0.39

0.09

260.

0010

0.18

200.

0026

2.32

270.

0333

0.05

540.

0007

0.97

7814

7921

1078

1412

1910

1089

1373

1479

Spo

t 38

0.32

0.07

200.

0013

0.15

730.

0023

1.56

070.

0301

0.04

810.

0010

0.77

1698

535

942

1395

512

949

2096

942

Spo

t 39

0.21

0.07

180.

0008

0.15

240.

0021

1.50

860.

0216

0.04

480.

0006

0.97

3598

022

915

1293

49

886

1193

915

Spo

t 41

0.26

0.08

1 10.

0010

0.19

420.

0028

2.17

220.

0333

0.05

750.

0008

0.94

6612

2423

1144

1511

7211

1131

1693

1224

Spo

t 42

0.40

0.08

530.

0010

0.22

440.

0031

2.63

810.

0391

0.06

830.

0010

0.92

9913

2223

1305

1613

1111

1335

1899

1322

Spo

t 43

0.37

0.07

180.

0018

0.15

040.

0025

1.48

830.

0389

0.05

140.

0014

0.62

8998

050

903

1492

616

1013

2792

903

Spo

t 44

0.40

0.08

320.

0011

0.20

720.

0029

2.37

710.

0363

0.06

370.

0009

0.90

4712

7425

1214

1512

3611

1249

1895

1274

Spo

t 47

0.49

0.07

690.

0015

0.17

370.

0027

1.84

070.

0394

0.05

280.

0012

0.72

7211

1839

1032

1510

6014

1040

2292

1118

Spo

t 50

0.37

0.07

900.

0009

0.20

150.

0028

2.19

350.

0323

0.06

040.

0008

0.93

7711

7123

1184

1511

7910

1186

1610

111

71

Spo

t 52

0.15

0.07

060.

0010

0.15

910.

0022

1.54

860.

0246

0.05

010.

0011

0.85

8994

628

952

1295

010

989

2010

195

2

Spo

t 57

0.30

0.08

610.

0010

0.22

670.

0032

2.68

970.

0397

0.06

710.

0009

0.96

1913

4021

1317

1713

2611

1312

1798

1340

Spo

t 58

0.16

0.09

760.

0015

0.20

630.

0035

2.77

450.

0519

0.09

830.

0025

0.89

4915

7828

1209

1813

4914

1895

4577

1578

Spo

t 59

0.25

0.08

170.

0010

0.18

340.

0029

2.06

620.

0341

0.05

660.

0010

0.95

8612

3923

1086

1611

3811

1114

1988

1239

Spo

t 61

0.45

0.08

800.

0015

0.22

770.

0033

2.76

170.

0509

0.07

150.

0014

0.79

0813

8232

1322

1713

4514

1396

2696

1382

Spo

t 62

0.30

0.07

060.

0011

0.15

440.

0022

1.50

270.

0270

0.04

810.

0009

0.80

6394

632

926

1393

211

949

1898

926

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

94


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 63

0.28

0.07

650.

0010

0.17

020.

0024

1.79

570.

0289

0.05

500.

0009

0.87

7111

0927

1013

1310

4410

1083

1891

1109

Spo

t 64

0.40

0.08

130.

0013

0.20

410.

0030

2.28

800.

0415

0.06

210.

0012

0.80

5712

2931

1197

1612

0913

1217

2297

1229

Spo

t 65

0.25

0.08

190.

0010

0.21

780.

0032

2.45

870.

0397

0.06

480.

0011

0.92

2612

4324

1270

1712

6012

1270

2110

212

43

Spo

t 67

0.24

0.11

280.

0012

0.26

880.

0039

4.18

100.

0611

0.07

790.

0010

0.98

3218

4519

1535

2016

7012

1517

1983

1845

Spo

t 69

0.35

0.09

440.

0015

0.26

070.

0039

3.39

380.

0603

0.07

540.

0015

0.84

1415

1729

1493

2015

0314

1469

2898

1517

Spo

t 70

0.35

0.08

050.

0010

0.19

840.

0029

2.20

200.

0353

0.05

450.

0008

0.90

6212

1025

1167

1611

8211

1073

1696

1210

Spo

t 71

0.45

0.06

230.

0020

0.10

370.

0017

0.89

060.

0284

0.03

200.

0011

0.51

3868

667

636

1064

715

636

2193

636

Spo

t 72

0.58

0.07

370.

0012

0.17

340.

0025

1.76

130.

0325

0.04

820.

0008

0.79

0210

3333

1031

1410

3112

951

1610

010

33

Spo

t 73

0.38

0.08

010.

0010

0.19

990.

0028

2.20

610.

0336

0.05

490.

0008

0.91

5811

9824

1175

1511

8311

1080

1598

1198

Spo

t 74

0.17

0.07

790.

0009

0.17

710.

0026

1.90

260.

0294

0.05

380.

0008

0.96

1811

4423

1051

1410

8210

1059

1692

1144

Spo

t 75

0.59

0.08

400.

0010

0.22

160.

0032

2.56

540.

0388

0.05

610.

0007

0.94

6112

9223

1290

1712

9111

1104

1310

012

92

Spo

t 76

0.29

0.12

190.

0013

0.36

170.

0051

6.07

870.

0872

0.09

840.

0012

0.99

0219

8419

1990

2419

8713

1898

2210

019

84

Spo

t 77

0.34

0.07

980.

0009

0.20

220.

0029

2.22

590.

0336

0.05

390.

0007

0.94

5611

9323

1187

1511

8911

1061

1410

011

93

Spo

t 80

0.26

0.07

070.

0011

0.15

490.

0023

1.51

020.

0275

0.04

500.

0009

0.80

7995

032

928

1393

511

890

1898

928

Spo

t 83

3.76

0.07

400.

0023

0.15

610.

0029

1.59

120.

0500

0.03

880.

0006

0.58

5210

4061

935

1696

720

769

1290

935

Spo

t 85

0.28

0.08

430.

0019

0.19

720.

0034

2.29

080.

0563

0.05

500.

0017

0.70

7912

9944

1160

1812

1017

1081

3289

1299

Spo

t 86

0.36

0.08

170.

0015

0.20

700.

0032

2.33

150.

0468

0.06

240.

0014

0.75

8812

3835

1213

1712

2214

1224

2698

1238

Spo

t 90

0.31

0.07

030.

0017

0.16

840.

0026

1.63

170.

0396

0.05

070.

0016

0.64

1993

748

1003

1498

315

999

3010

793

7

Spo

t 91

0.39

0.08

120.

0010

0.18

130.

0028

2.03

010.

0337

0.05

260.

0009

0.92

3412

2725

1074

1511

2611

1036

1788

1227

Spo

t 92

0.18

0.08

180.

0010

0.21

740.

0031

2.45

100.

0379

0.06

470.

0012

0.90

7712

4025

1268

1612

5811

1266

2310

212

40

Spo

t 95

0.29

0.07

140.

0010

0.15

780.

0023

1.55

380.

0261

0.04

600.

0008

0.86

2697

029

945

1395

210

910

1597

945

Spo

t 97

0.36

0.08

160.

0009

0.20

960.

0030

2.35

680.

0352

0.05

660.

0007

0.96

7712

3522

1227

1612

3011

111 2

1499

1235

Spo

t 99

0.27

0.08

030.

0009

0.20

200.

0029

2.23

720.

0338

0.05

470.

0008

0.94

9612

0523

1186

1611

9311

1075

1598

1205

Spo

t 106

0.25

0.07

290.

0009

0.17

790.

0026

1.78

870.

0287

0.04

970.

0008

0.92

1010

1225

1055

1410

4110

980

1610

410

12

Spo

t 107

0.46

0.08

000.

0014

0.21

640.

0033

2.38

570.

0458

0.06

740.

0014

0.78

7611

9633

1263

1712

3814

1318

2710

611

96

Spo

t 109

0.51

0.08

840.

0011

0.24

320.

0035

2.96

400.

0459

0.07

470.

0011

0.91

9413

9124

1403

1813

9812

1455

2010

113

91

Spo

t 110

0.33

0.09

400.

0015

0.20

310.

0032

2.63

240.

0500

0.07

950.

0016

0.83

3915

0830

1192

1713

1014

1546

3079

1508

Spo

t 113

0.79

0.08

710.

0015

0.24

920.

0040

2.99

300.

0593

0.06

640.

0012

0.81

6013

6332

1435

2114

0615

1299

2210

513

63

Spo

t 115

0.24

0.07

370.

0015

0.16

480.

0024

1.67

410.

0347

0.04

910.

0015

0.70

5810

3339

983

1399

913

970

2895

983

Spo

t 117

0.20

0.07

450.

0010

0.17

910.

0026

1.84

030.

0298

0.05

380.

0010

0.89

1010

5626

1062

1410

6011

1059

1910

110

56

Spo

t 118

0.37

0.08

200.

0010

0.20

570.

0029

2.32

710.

0364

0.06

140.

0010

0.91

1512

4624

1206

1612

2111

1205

1897

1246

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

95


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 119

0.40

0.07

440.

0014

0.17

420.

0029

1.78

760.

0384

0.04

290.

0010

0.76

9610

5338

1035

1610

4114

849

1998

1053

Spo

t 121

0.72

0.08

160.

0010

0.20

380.

0029

2.29

390.

0367

0.06

130.

0009

0.90

2012

3625

1196

1612

1011

1202

1697

1236

Spo

t 124

0.23

0.07

870.

0014

0.19

610.

0029

2.12

840.

0418

0.05

750.

0016

0.75

2611

6535

1154

1611

5814

1131

3099

1165

Spo

t 126

0.15

0.08

090.

0010

0.16

190.

0023

1.80

530.

0279

0.05

790.

0010

0.93

1512

1823

967

1310

4710

1139

1879

967

Spo

t 128

0.64

0.08

000.

0012

0.19

430.

0027

2.14

530.

0358

0.05

810.

0010

0.84

3011

9828

1145

1511

6412

1141

1996

1198

Spo

t 129

0.68

0.07

770.

0019

0.16

530.

0026

1.77

320.

0452

0.04

710.

0012

0.62

1811

4049

986

1410

3617

931

2387

986

Spo

t 131

0.36

0.07

150.

0012

0.15

130.

0022

1.49

110.

0282

0.04

630.

0010

0.77

2697

134

908

1292

711

915

1994

908

Spo

t 132

0.17

0.07

210.

0009

0.15

490.

0022

1.53

980.

0239

0.04

720.

0008

0.91

3398

825

929

1294

610

932

1694

929

Spo

t 133

0.33

0.12

460.

0013

0.10

570.

0015

1.81

650.

0265

0.05

710.

0007

0.98

0520

2419

648

910

5110

1123

1432

648

Spo

t 134

0.18

0.08

090.

0010

0.20

490.

0031

2.28

470.

0380

0.06

250.

0012

0.92

1112

1825

1202

1712

0812

1225

2399

1218

Spo

t 137

0.18

0.08

340.

0010

0.21

860.

0031

2.51

290.

0375

0.06

640.

0010

0.95

0712

7822

1275

1612

7611

1299

2010

012

78

Spo

t 140

0.21

0.08

370.

0010

0.19

620.

0028

2.26

400.

0345

0.04

970.

0009

0.92

9412

8623

1155

1512

0111

980

1790

1286

Spo

t 141

0.32

0.08

250.

0010

0.21

140.

0033

2.40

500.

0394

0.05

470.

0009

0.94

4512

5823

1236

1712

4412

1077

1798

1258

Spo

t 143

0.68

0.09

110.

0018

0.22

240.

0037

2.79

460.

0609

0.06

880.

0016

0.76

5714

4937

1295

2013

5416

1346

2989

1449

Spo

t 144

0.44

0.07

660.

0013

0.17

050.

0026

1.80

060.

0343

0.04

880.

0009

0.79

4011

1133

1015

1410

4612

962

1891

1111

Spo

t 10.

520.

0931

0.00

100.

2626

0.00

343.

3726

0.04

530.

0702

0.00

080.

9641

1490

2115

0317

1498

1113

7115

101

1490

Spo

t 20.

290.

0709

0.00

100.

1564

0.00

211.

5294

0.02

510.

0420

0.00

070.

8353

954

3093

712

942

1083

114

9893

7

Spo

t 41.

130.

1038

0.00

150.

2687

0.00

403.

8427

0.06

610.

0708

0.00

100.

8669

1692

2715

3420

1602

1413

8218

9116

92

Spo

t 50.

390.

0964

0.00

110.

2726

0.00

363.

6264

0.04

930.

0720

0.00

090.

9607

1556

2115

5418

1555

1114

0516

100

1556

Spo

t 60.

350.

0873

0.00

100.

2358

0.00

312.

8392

0.03

850.

0623

0.00

070.

9601

1367

2213

6516

1366

1012

2214

100

1367

Spo

t 70.

510.

0816

0.00

100.

2102

0.00

272.

3653

0.03

340.

0569

0.00

070.

9241

1235

2412

3015

1232

1011

1 813

100

1235

Spo

t 80.

730.

0951

0.00

100.

2656

0.00

333.

4824

0.04

450.

0315

0.00

040.

9755

1529

2015

1817

1523

1062

77

9915

29

Spo

t 90.

310.

0752

0.00

170.

1730

0.00

261.

7940

0.04

160.

0515

0.00

140.

6561

1074

4510

2914

1043

1510

1527

9610

74

Spo

t 10

0.73

0.09

290.

0011

0.25

960.

0034

3.32

730.

0460

0.06

750.

0007

0.94

7914

8622

1488

1714

8811

1321

1410

014

86

Spo

t 12

0.41

0.07

950.

0008

0.19

670.

0026

2.15

640.

0289

0.05

550.

0006

0.99

0811

8621

1158

1411

679

1091

1298

1186

Spo

t 14

0.30

0.07

430.

0010

0.17

610.

0023

1.80

340.

0266

0.04

760.

0007

0.88

9510

4926

1046

1310

4710

941

1310

010

49

Spo

t 15

0.26

0.09

570.

0010

0.26

370.

0035

3.47

830.

0470

0.07

300.

0009

0.98

3315

4220

1509

1815

2211

1424

1798

1542

Spo

t 16

0.31

0.08

750.

0009

0.23

250.

0031

2.80

490.

0373

0.06

220.

0007

0.99

6613

7220

1347

1613

5710

1219

1398

1372

Spo

t 17

0.38

0.08

670.

0011

0.23

220.

0030

2.77

520.

0402

0.06

740.

0010

0.90

0613

5324

1346

1613

4911

1319

1810

013

53

Spo

t 18

0.26

0.07

130.

0009

0.15

420.

0021

1.51

550.

0231

0.04

570.

0007

0.88

4696

626

924

1293

79

902

1496

924

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BR

Z-02

96


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 19

0.52

0.07

860.

0008

0.20

640.

0026

2.23

720.

0287

0.03

850.

0004

0.99

2211

6221

1210

1411

939

764

810

411

62

Spo

t 20

0.59

0.08

820.

0009

0.15

810.

0020

1.92

280.

0245

0.02

420.

0003

0.98

2413

8720

946

1110

899

484

668

946

Spo

t 22

0.32

0.08

010.

0011

0.19

600.

0027

2.16

290.

0333

0.05

730.

0009

0.88

3011

9926

1154

1411

6911

1126

1796

1199

Spo

t 23

0.33

0.09

560.

0010

0.27

170.

0036

3.58

350.

0476

0.07

100.

0008

0.98

6515

4120

1550

1815

4611

1386

1510

115

41

Spo

t 24

0.46

0.08

570.

0016

0.21

870.

0031

2.58

410.

0523

0.06

310.

0013

0.70

5113

3236

1275

1712

9615

1237

2496

1332

Spo

t 26

0.40

0.07

840.

0014

0.18

760.

0025

2.02

750.

0362

0.05

680.

0011

0.73

5411

5734

1108

1311

2512

1117

2296

1157

Spo

t 28

0.45

0.07

180.

0008

0.16

860.

0022

1.66

840.

0231

0.04

760.

0006

0.93

0798

024

1004

1299

79

940

1110

298

0

Spo

t 28b

0.67

0.09

830.

0016

0.27

520.

0037

3.72

780.

0646

0.07

200.

0013

0.77

7815

9231

1567

1915

7714

1404

2498

1592

Spo

t 30

1.00

0.09

670.

0011

0.20

350.

0026

2.71

250.

0353

0.01

930.

0002

0.96

7615

6121

1194

1413

3210

387

577

1561

Spo

t 32

0.17

0.07

860.

0009

0.20

290.

0026

2.19

980.

0298

0.05

890.

0009

0.93

4011

6323

1191

1411

819

1157

1810

211

63

Spo

t 33

0.45

0.09

240.

0011

0.24

860.

0031

3.16

540.

0434

0.07

240.

0010

0.91

5814

7523

1431

1614

4911

1413

1997

1475

Spo

t 35

0.24

0.07

280.

0014

0.17

070.

0023

1.71

200.

0345

0.05

130.

0015

0.67

3610

0739

1016

1310

1313

1012

2810

110

07

Spo

t 36

0.40

0.07

260.

0011

0.16

590.

0021

1.65

950.

0265

0.04

490.

0008

0.80

5510

0230

990

1299

310

888

1599

990

Spo

t 37

0.30

0.07

960.

0010

0.19

900.

0025

2.18

240.

0299

0.05

600.

0008

0.92

0411

8624

1170

1311

7510

1102

1699

1186

Spo

t 38

1.61

0.11

390.

0013

0.33

470.

0044

5.25

400.

0704

0.08

720.

0010

0.97

0318

6220

1861

2118

6111

1690

1810

018

62

Spo

t 39

0.40

0.09

830.

0012

0.28

660.

0036

3.88

410.

0526

0.08

340.

0012

0.93

8715

9222

1625

1816

1011

1620

2210

215

92

Spo

t 39r

0.17

0.09

840.

0013

0.28

310.

0036

3.83

970.

0556

0.07

750.

0018

0.88

8315

9424

1607

1816

0112

1509

3310

115

94

Spo

t 42

0.39

0.08

430.

0011

0.22

680.

0029

2.63

680.

0387

0.07

100.

0011

0.87

0613

0026

1318

1513

1111

1386

2110

113

00

Spo

t 45

0.50

0.09

420.

0011

0.26

610.

0033

3.45

370.

0451

0.08

110.

0010

0.95

5715

1121

1521

1715

1710

1575

1910

115

11

Spo

t 47

0.40

0.07

260.

0012

0.17

220.

0023

1.72

180.

0295

0.05

440.

0010

0.76

6010

0233

1024

1210

1711

1070

1910

210

02

Spo

t 49

0.30

0.07

050.

0009

0.15

430.

0020

1.49

930.

0219

0.04

900.

0008

0.87

4894

326

925

1193

09

966

1598

925

Spo

t 51

0.73

0.09

500.

0016

0.24

480.

0037

3.20

330.

0586

0.04

530.

0016

0.82

8915

2731

141 1

1914

5814

896

3092

1527

Spo

t 52

0.31

0.06

990.

0016

0.15

170.

0022

1.46

150.

0342

0.04

750.

0013

0.60

8992

546

910

1291

514

938

2698

910

Spo

t 55

0.28

0.07

820.

0010

0.19

240.

0025

2.07

270.

0306

0.05

830.

0009

0.89

0311

5125

1134

1411

4010

1145

1899

1151

Spo

t 56

0.39

0.08

740.

0010

0.23

810.

0031

2.86

770.

0382

0.07

060.

0009

0.96

3913

6921

1377

1613

7410

1378

1710

113

69

Spo

t 57

0.30

0.06

980.

0013

0.15

740.

0021

1.51

470.

0283

0.04

920.

0011

0.72

0192

336

942

1293

611

970

2110

294

2

Spo

t 60

0.23

0.07

740.

0009

0.19

620.

0025

2.09

410.

0274

0.05

120.

0007

0.96

3911

3222

1155

1311

479

1010

1410

211

32

Spo

t 61

0.32

0.09

990.

0012

0.28

760.

0038

3.96

210.

0563

0.08

580.

0013

0.92

0716

2323

1630

1916

2712

1663

2510

016

23

Spo

t 65

0.29

0.07

010.

0013

0.14

980.

0020

1.44

750.

0272

0.05

070.

0012

0.71

0193

137

900

1190

911

999

2297

900

Spo

t 69

0.37

0.09

630.

0013

0.24

690.

0035

3.27

480.

0526

0.06

020.

0013

0.89

3715

5425

1422

1814

7512

1182

2592

1554

Spo

t 70

0.28

0.08

050.

0011

0.19

690.

0027

2.18

410.

0349

0.03

970.

0008

0.87

1712

0827

1159

1511

7611

786

1696

1208

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

97


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 74

0.32

0.08

490.

0010

0.22

320.

0028

2.61

350.

0344

0.06

700.

0009

0.95

2013

1422

1299

1513

0410

1311

1899

1314

Spo

t 75

0.25

0.09

640.

0027

0.24

970.

0040

3.32

000.

0933

0.07

580.

0039

0.57

0315

5652

1437

2114

8622

1477

7392

1556

Spo

t 76

0.34

0.07

900.

0010

0.19

630.

0026

2.13

820.

0304

0.05

670.

0008

0.91

7611

7324

1155

1411

6110

1115

1699

1173

Spo

t 79

0.25

0.08

020.

0011

0.19

720.

0026

2.18

080.

0321

0.06

000.

0011

0.88

1312

0226

1160

1411

7510

1178

2097

1202

Spo

t 80

0.24

0.07

120.

0015

0.15

110.

0021

1.48

330.

0324

0.04

880.

0015

0.64

1596

343

907

1292

413

963

2894

907

Spo

t 81

0.38

0.09

070.

0012

0.24

250.

0032

3.03

090.

0461

0.06

910.

0012

0.87

1014

3925

1400

1714

1512

1351

2297

1439

Spo

t 82

0.70

0.09

370.

0012

0.25

390.

0034

3.27

840.

0484

0.07

300.

0010

0.89

4215

0124

1458

1714

7611

1423

1997

1501

Spo

t 85

0.28

0.08

050.

0010

0.19

420.

0026

2.15

470.

0312

0.05

750.

0009

0.91

3912

0924

1144

1411

6710

1131

1795

1209

Spo

t 86

0.38

0.07

250.

0012

0.15

380.

0021

1.53

590.

0269

0.04

790.

0009

0.77

5399

932

922

1294

511

946

1792

922

Spo

t 87

0.59

0.09

230.

0012

0.24

500.

0033

3.11

740.

0461

0.07

430.

0011

0.89

9814

7324

1413

1714

3711

1449

2096

1473

Spo

t 89

0.27

0.07

220.

0011

0.15

020.

0020

1.49

460.

0248

0.04

830.

0009

0.81

3599

130

902

1192

810

953

1791

902

Spo

t 93

0.29

0.09

430.

0011

0.24

830.

0033

3.22

940.

0444

0.07

440.

0011

0.95

7515

1521

1430

1714

6411

1451

2094

1515

Spo

t 94

0.22

0.08

580.

0010

0.22

580.

0030

2.67

140.

0376

0.06

250.

0010

0.95

7513

3422

1313

1613

2110

1225

1898

1334

Spo

t 95

1.29

0.09

950.

0015

0.24

550.

0033

3.36

690.

0553

0.03

130.

0007

0.80

8916

1429

1415

1714

9713

623

1388

1614

Spo

t 97

0.46

0.09

090.

0012

0.23

010.

0031

2.88

290.

0443

0.06

970.

0011

0.87

4814

4425

1335

1613

7812

1362

2092

1444

Spo

t 101

0.33

0.09

800.

0011

0.26

680.

0036

3.60

570.

0503

0.07

570.

0011

0.97

2215

8721

1525

1815

5111

1474

2096

1587

Spo

t 104

0.68

0.08

520.

0013

0.20

640.

0028

2.42

460.

0400

0.06

480.

0010

0.81

8613

2029

1210

1512

5012

1270

1992

1320

Spo

t 106

0.38

0.07

870.

0009

0.19

650.

0026

2.13

360.

0299

0.06

060.

0008

0.93

3111

6523

1157

1411

6010

1189

1699

1165

Spo

t 107

0.65

0.10

100.

0012

0.28

220.

0037

3.92

720.

0541

0.07

710.

0010

0.94

7616

4221

1602

1916

1911

1501

2098

1642

Spo

t 109

0.33

0.08

710.

0009

0.23

020.

0030

2.76

230.

0365

0.06

920.

0009

0.98

0213

6220

1335

1613

4510

1353

1798

1362

Spo

t 110

0.18

0.09

630.

0010

0.26

560.

0035

3.52

730.

0465

0.08

060.

0011

0.99

3515

5420

1518

1815

3310

1566

2198

1554

Spo

t 111

0.54

0.10

820.

0012

0.30

660.

0039

4.57

090.

0606

0.08

490.

0014

0.95

2717

6921

1724

1917

4411

1646

2697

1769

Spo

t 114

0.27

0.07

890.

0009

0.19

010.

0025

2.06

710.

0283

0.05

470.

0008

0.95

9011

6922

1122

1411

389

1076

1496

1169

Spo

t 115

0.46

0.08

640.

0010

0.22

270.

0029

2.65

270.

0359

0.06

290.

0008

0.97

1313

4821

1296

1513

1510

1232

1596

1348

Spo

t 116

0.20

0.07

490.

0009

0.16

890.

0023

1.74

410.

0247

0.04

980.

0008

0.95

4110

6623

1006

1310

259

982

1594

1066

Spo

t 118

0.47

0.08

040.

0017

0.19

460.

0031

2.15

560.

0489

0.05

320.

0017

0.69

6212

0742

1146

1711

6716

1047

3395

1207

Spo

t 119

0.34

0.08

750.

0010

0.22

500.

0030

2.71

480.

0376

0.06

460.

0009

0.95

4213

7222

1308

1613

3310

1266

1795

1372

Spo

t 120

0.34

0.08

780.

0011

0.22

390.

0030

2.70

900.

0391

0.06

390.

0010

0.92

6113

7823

1302

1613

3111

1252

1895

1378

Spo

t 121

0.51

0.10

440.

0012

0.28

940.

0038

4.16

420.

0574

0.08

030.

0011

0.95

5717

0421

1638

1916

6711

1561

2196

1704

Spo

t 122

0.42

0.08

730.

0010

0.22

180.

0029

2.66

740.

0375

0.06

210.

0008

0.94

4013

6622

1291

1613

2010

1218

1695

1366

Spo

t 123

0.16

0.09

790.

0011

0.26

790.

0035

3.61

420.

0486

0.07

880.

0012

0.98

0215

8420

1530

1815

5311

1533

2297

1584

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

98


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 125

0.54

0.07

700.

0009

0.17

610.

0023

1.86

790.

0262

0.04

940.

0006

0.94

4911

2023

1045

1310

709

974

1293

1120

Spo

t 127

0.26

0.07

210.

0011

0.15

680.

0022

1.55

770.

0268

0.04

660.

0009

0.80

1698

831

939

1295

411

920

1795

939

Spo

t 129

0.62

0.08

190.

0009

0.20

110.

0027

2.27

010.

0314

0.05

290.

0006

0.97

2912

4321

1181

1512

0310

1041

1195

1243

Spo

t 130

0.39

0.07

530.

0013

0.16

800.

0024

1.74

510.

0337

0.05

040.

0010

0.72

7210

7735

1001

1310

2512

994

1993

1077

Spo

t 134

0.67

0.11

140.

0013

0.30

710.

0042

4.71

720.

0690

0.08

200.

0010

0.93

9218

2321

1726

2117

7012

1593

1995

1823

Spo

t 136

0.22

0.07

250.

0009

0.15

320.

0021

1.53

170.

0233

0.04

470.

0007

0.89

2410

0026

919

1294

39

884

1492

919

Spo

t 137

0.57

0.09

900.

0012

0.26

550.

0037

3.62

440.

0528

0.07

010.

0009

0.94

3216

0622

1518

1915

5512

1369

1695

1606

Spo

t 138

0.27

0.07

520.

0009

0.16

820.

0023

1.74

360.

0265

0.04

530.

0007

0.90

6510

7425

1002

1310

2510

896

1393

1074

Spo

t 139

0.41

0.07

780.

0014

0.17

340.

0025

1.86

060.

0368

0.04

760.

0010

0.72

0611

4236

1031

1410

6713

940

1990

1142

Spo

t 10.

380.

1028

0.00

120.

2698

0.00

353.

8217

0.05

280.

0803

0.00

110.

9356

1675

2115

4018

1597

1115

6120

9216

75

Spo

t 30.

290.

0954

0.00

100.

2754

0.00

403.

6245

0.05

360.

0793

0.00

120.

9895

1537

2015

6820

1555

1215

4323

102

1537

Spo

t 40.

420.

0974

0.00

120.

2852

0.00

373.

8273

0.05

520.

0781

0.00

120.

8896

1574

2316

1718

1599

1215

2022

103

1574

Spo

t 50.

410.

0806

0.00

160.

1978

0.00

272.

1975

0.04

560.

0580

0.00

140.

6649

1211

3911

6315

1180

1411

3926

9612

11

Spo

t 60.

390.

0965

0.00

120.

2801

0.00

363.

7278

0.05

350.

0832

0.00

130.

8927

1558

2315

9218

1577

1216

1524

102

1558

Spo

t 70.

390.

0936

0.00

110.

2478

0.00

333.

1972

0.04

690.

0702

0.00

110.

9200

1501

2314

2717

1457

1113

7020

9515

01

Spo

t 80.

700.

0967

0.00

140.

2736

0.00

363.

6454

0.05

930.

0782

0.00

120.

8137

1561

2815

5918

1560

1315

2323

100

1561

Spo

t 90.

460.

0956

0.00

130.

2719

0.00

363.

5848

0.05

510.

0754

0.00

120.

8588

1541

2515

5118

1546

1214

7023

101

1541

Spo

t 10

0.48

0.10

200.

0013

0.28

360.

0037

3.98

930.

0582

0.08

260.

0013

0.88

2416

6224

1609

1816

3212

1605

2497

1662

Spo

t 14

0.50

0.10

850.

0012

0.29

060.

0042

4.34

800.

0638

0.08

340.

0013

0.98

1117

7520

1644

2117

0312

1619

2493

1775

Spo

t 16

0.46

0.07

960.

0014

0.19

690.

0027

2.16

040.

0403

0.05

960.

0012

0.73

491 1

8634

1159

1511

6813

1170

2398

1186

Spo

t 18

0.37

0.07

250.

0013

0.15

760.

0022

1.57

460.

0304

0.04

800.

0011

0.70

9999

937

943

1296

012

947

2094

943

Spo

t 19

0.30

0.08

980.

0012

0.16

780.

0022

2.07

850.

0303

0.05

610.

0009

0.88

4514

2224

1000

1211

4210

1102

1870

1000

Spo

t 21

0.19

0.09

900.

0016

0.27

260.

0036

3.72

150.

0627

0.07

760.

0022

0.79

3216

0629

1554

1815

7613

1510

4197

1606

Spo

t 22

0.20

0.07

660.

0015

0.20

250.

0029

2.13

820.

0441

0.05

880.

0019

0.68

9811

1139

1189

1511

6114

1156

3610

711

11

Spo

t 23

0.37

0.07

540.

0008

0.19

050.

0027

1.97

970.

0286

0.05

840.

0008

0.97

6910

7922

1124

1511

0910

1148

1510

410

79

Spo

t 24

0.66

0.08

780.

0013

0.23

050.

0030

2.78

840.

0461

0.06

560.

0011

0.79

7613

7729

1337

1613

5212

1284

2197

1377

Spo

t 25

0.31

0.11

350.

0012

0.21

360.

0031

3.34

220.

0488

0.07

170.

0011

0.98

4418

5619

1248

1614

9111

1400

2067

1856

Spo

t 26

0.45

0.09

490.

0018

0.28

010.

0043

3.66

400.

0728

0.06

970.

0034

0.77

9515

2734

1592

2215

6416

1361

6510

415

27

Spo

t 27

0.50

0.08

710.

0013

0.24

220.

0038

2.90

950.

0522

0.07

430.

0015

0.86

5513

6328

1398

2013

8414

1449

2810

313

63

Spo

t 28

0.27

0.09

720.

0010

0.27

680.

0039

3.70

920.

0519

0.07

210.

0010

0.99

7015

7119

1575

2015

7311

1407

1910

015

71

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BR

Z-15

99


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 29

0.71

0.09

880.

0011

0.28

210.

0041

3.84

500.

0569

0.08

650.

0012

0.96

9816

0221

1602

2016

0212

1676

2310

016

02

Spo

t 30

0.43

0.08

500.

0013

0.22

660.

0030

2.65

400.

0428

0.06

450.

0012

0.81

6413

1528

1316

1613

1612

1263

2310

013

15

Spo

t 31

0.38

0.10

500.

0013

0.25

120.

0041

3.63

350.

0609

0.08

170.

0037

0.97

1917

1422

1444

2115

5713

1588

6984

1714

Spo

t 34

0.40

0.10

580.

0012

0.30

390.

0046

4.43

230.

0702

0.07

680.

0016

0.96

0017

2821

1710

2317

1813

1495

2999

1728

Spo

t 37

0.36

0.09

320.

0014

0.26

180.

0035

3.36

250.

0552

0.07

640.

0016

0.80

7814

9228

1499

1814

9613

1488

3010

114

92

Spo

t 38

0.30

0.07

950.

0013

0.19

870.

0027

2.17

700.

0384

0.05

910.

0014

0.75

5611

8432

1169

1411

7412

1161

2699

1184

Spo

t 39

0.58

0.11

110.

0013

0.29

730.

0047

4.55

630.

0739

0.08

540.

0023

0.96

4118

1821

1678

2317

4114

1657

4392

1818

Spo

t 40

0.66

0.09

160.

0014

0.24

910.

0033

3.14

360.

0520

0.07

200.

0013

0.79

9214

5829

1434

1714

4313

1406

2498

1458

Spo

t 41

0.27

0.07

860.

0009

0.20

340.

0029

2.20

460.

0327

0.06

490.

0010

0.96

4411

6222

1194

1611

8310

1272

1910

311

62

Spo

t 43

0.46

0.09

910.

0012

0.25

060.

0040

3.42

460.

0571

0.06

350.

0020

0.94

8416

0823

1442

2015

1013

1244

3790

1608

Spo

t 47

0.18

0.07

770.

0010

0.20

070.

0026

2.14

950.

0321

0.05

680.

0012

0.86

1711

4026

1179

1411

6510

1117

2310

311

40

Spo

t 48

0.43

0.10

830.

0013

0.29

420.

0037

4.39

280.

0600

0.07

650.

0013

0.92

0617

7122

1663

1817

1111

1489

2494

1771

Spo

t 53

0.86

0.09

840.

0019

0.25

550.

0038

3.46

430.

0697

0.07

050.

0018

0.74

3015

9435

1467

2015

1916

1378

3392

1594

Spo

t 55

0.27

0.09

730.

0011

0.27

190.

0036

3.64

550.

0509

0.07

580.

0013

0.93

7815

7321

1550

1815

6011

1477

2599

1573

Spo

t 60

0.49

0.09

390.

0015

0.24

560.

0033

3.17

800.

0537

0.06

710.

0013

0.80

0215

0629

1416

1714

5213

1313

2594

1506

Spo

t 63

0.36

0.07

640.

0016

0.17

370.

0027

1.82

890.

0407

0.05

200.

0013

0.68

5011

0542

1032

1510

5615

1025

2493

1105

Spo

t 65

0.40

0.09

540.

0011

0.27

080.

0036

3.55

950.

0497

0.07

510.

0009

0.96

2415

3521

1545

1815

4111

1463

1710

115

35

Spo

t 66

0.62

0.08

780.

0012

0.24

280.

0033

2.93

790.

0457

0.06

840.

0009

0.88

1413

7725

1401

1713

9212

1337

1710

213

77

Spo

t 67

0.28

0.07

350.

0011

0.17

210.

0024

1.74

440.

0296

0.05

060.

0009

0.81

9910

2830

1024

1310

2511

999

1810

010

28

Spo

t 68

0.32

0.09

790.

0011

0.27

190.

0036

3.67

050.

0500

0.07

940.

0009

0.98

2715

8520

1550

1815

6511

1544

1798

1585

Spo

t 69

0.11

0.08

900.

0010

0.16

190.

0022

1.98

500.

0286

0.09

050.

0013

0.96

0914

0321

967

1211

1010

1750

2369

967

Spo

t 77

0.41

0.10

720.

0011

0.30

270.

0041

4.47

260.

0609

0.08

190.

0009

0.98

4717

5219

1705

2017

2611

1591

1897

1752

Spo

t 79

0.31

0.09

230.

0011

0.25

350.

0035

3.22

340.

0471

0.07

710.

0011

0.94

9714

7222

1456

1814

6311

1502

2099

1472

Spo

t 81

0.33

0.07

950.

0011

0.20

260.

0029

2.22

040.

0352

0.05

740.

0009

0.89

0811

8526

1189

1511

8811

1128

1710

011

85

Spo

t 82

0.87

0.09

730.

0017

0.26

230.

0039

3.51

750.

0670

0.07

570.

0013

0.78

1315

7333

1501

2015

3115

1475

2495

1573

Spo

t 86

0.21

0.09

380.

0011

0.26

270.

0036

3.39

670.

0493

0.07

770.

0012

0.95

5415

0422

1503

1915

0411

1512

2210

015

04

Spo

t 92

0.35

0.09

760.

0010

0.24

150.

0033

3.25

010.

0445

0.06

530.

0008

0.99

7415

7919

1394

1714

6911

1278

1488

1579

Spo

t 95

0.39

0.08

600.

0011

0.22

930.

0031

2.71

750.

0402

0.06

820.

0010

0.92

5413

3823

1331

1613

3311

1334

1899

1338

Spo

t 96

0.24

0.07

980.

0013

0.19

500.

0028

2.14

580.

0386

0.05

660.

0013

0.79

4611

9332

1148

1511

6412

1113

2596

1193

Spo

t 100

0.42

0.09

990.

0011

0.28

420.

0039

3.91

430.

0556

0.07

770.

0010

0.95

9616

2221

1612

1916

1711

1513

1999

1622

Spo

t 101

0.71

0.09

560.

0010

0.25

230.

0034

3.32

520.

0457

0.07

450.

0009

0.98

1815

4020

1450

1814

8711

1452

1694

1540

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

100


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 104

0.41

0.09

150.

0011

0.24

920.

0034

3.14

380.

0453

0.07

110.

0009

0.94

9114

5722

1435

1814

4411

1388

1898

1457

Spo

t 108

0.17

0.07

060.

0007

0.15

510.

0021

1.50

880.

0207

0.04

690.

0006

0.98

0894

521

929

1293

48

927

1198

929

Spo

t 109

0.41

0.07

860.

0016

0.17

720.

0027

1.91

980.

0416

0.05

380.

0013

0.71

3611

6240

1052

1510

8814

1058

2491

1162

Spo

t 112

0.23

0.09

720.

0010

0.26

460.

0036

3.54

550.

0486

0.07

750.

0010

0.98

6915

7119

1513

1815

3711

1509

1896

1571

Spo

t 117

0.50

0.10

370.

0011

0.25

190.

0034

3.60

080.

0492

0.06

520.

0008

0.98

9916

9119

1448

1815

5011

1277

1586

1691

Spo

t 118

0.69

0.23

450.

0025

0.60

890.

0087

19.6

862

0.28

160.

1173

0.00

160.

9966

3083

1730

6635

3076

1422

4329

9930

83

Spo

t 119

0.54

0.10

450.

0011

0.29

930.

0041

4.31

410.

0595

0.06

890.

0008

0.98

7817

0619

1688

2016

9611

1348

1599

1706

Spo

t 120

0.52

0.08

470.

0012

0.21

530.

0030

2.51

350.

0407

0.06

320.

0010

0.86

8913

0827

1257

1612

7612

1239

1896

1308

Spo

t 121

0.44

0.09

700.

0011

0.27

040.

0038

3.61

530.

0526

0.06

290.

0009

0.95

6515

6721

1543

1915

5312

1234

1698

1567

Spo

t 127

0.63

0.08

730.

0010

0.23

700.

0033

2.85

120.

0411

0.06

800.

0008

0.95

3513

6622

1371

1713

6911

1329

1610

013

66

Spo

t 128

0.33

0.09

520.

0011

0.26

560.

0037

3.48

680.

0514

0.06

490.

0010

0.94

7815

3222

1519

1915

2412

1272

1899

1532

Spo

t 129

0.29

0.10

030.

0012

0.27

350.

0043

3.77

640.

0617

0.06

270.

0026

0.96

2716

2923

1558

2215

8813

1230

5096

1629

Spo

t 130

0.35

0.09

800.

0011

0.28

730.

0040

3.88

050.

0552

0.08

010.

0011

0.96

6215

8621

1628

2016

1011

1557

2010

315

86

Spo

t 131

0.56

0.08

180.

0013

0.20

260.

0031

2.28

370.

0421

0.05

550.

0010

0.81

6312

4032

1189

1612

0713

1092

1896

1240

Spo

t 133

0.39

0.07

960.

0010

0.19

970.

0028

2.19

210.

0340

0.05

780.

0008

0.90

3211

8725

1174

1511

7911

1135

1699

1187

Spo

t 135

0.33

0.07

400.

0015

0.15

730.

0023

1.60

520.

0346

0.04

660.

0012

0.69

1110

4241

942

1397

213

921

2390

942

Spo

t 139

0.55

0.08

030.

0011

0.21

250.

0030

2.35

160.

0368

0.05

990.

0008

0.89

2812

0326

1242

1612

2811

1176

1610

312

03

Spo

t 140

0.52

0.08

740.

0012

0.22

260.

0032

2.68

130.

0430

0.06

740.

0010

0.88

8313

6926

1296

1713

2312

1318

1995

1369

Spo

t 142

0.40

0.09

630.

0012

0.27

110.

0039

3.59

760.

0549

0.07

810.

0012

0.93

1315

5323

1546

2015

4912

1520

2210

015

53

Spo

t 147

0.64

0.09

580.

0012

0.26

950.

0038

3.55

870.

0542

0.07

430.

0010

0.92

4315

4423

1538

1915

4012

1448

1910

015

44

Spo

t 152

0.24

0.1 1

630.

0012

0.20

150.

0029

3.23

040.

0464

0.08

530.

0011

0.98

8719

0019

1184

1514

6511

1654

2162

1900

Spo

t 154

0.45

0.10

510.

0013

0.29

640.

0042

4.29

280.

0657

0.08

050.

0013

0.91

8917

1523

1674

2116

9213

1565

2498

1715

Spo

t 155

0.28

0.08

590.

0009

0.14

140.

0019

1.67

460.

0230

0.04

040.

0005

0.99

9013

3620

853

1199

99

801

1064

853

Spo

t 158

0.35

0.09

490.

0011

0.26

740.

0038

3.49

760.

0525

0.07

590.

0011

0.93

8415

2522

1528

1915

2712

1478

2110

015

25

Spo

t 162

0.28

0.09

470.

0011

0.26

570.

0037

3.46

980.

0502

0.07

660.

0011

0.96

8615

2321

1519

1915

2011

1491

2010

015

23

Spo

t 164

0.49

0.09

810.

0013

0.25

020.

0036

3.38

380.

0532

0.07

240.

0011

0.90

8315

8924

1439

1815

0112

1413

2191

1589

Spo

t 166

0.73

0.09

720.

0015

0.27

140.

0042

3.63

870.

0664

0.07

780.

0014

0.83

9615

7229

1548

2115

5815

1514

2598

1572

Spo

t 167

0.64

0.08

820.

0011

0.15

270.

0022

1.85

650.

0282

0.04

810.

0007

0.93

5413

8723

916

1210

6610

949

1266

916

Spo

t 168

0.53

0.09

520.

0010

0.27

580.

0039

3.62

050.

0520

0.08

220.

0011

0.97

7315

3320

1570

2015

5411

1596

2010

215

33

Spo

t 20.

300.

0732

0.00

090.

1725

0.00

241.

7413

0.02

580.

0499

0.00

070.

9325

1020

2410

2613

1024

1098

414

101

1020

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

Sam

ple

BR

Z-24

101


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 30.

530.

0963

0.00

120.

2714

0.00

383.

6036

0.05

470.

0757

0.00

100.

9307

1554

2315

4819

1550

1214

7520

100

1554

Spo

t 40.

390.

0729

0.00

100.

1745

0.00

241.

7524

0.02

740.

0515

0.00

080.

8894

1010

2610

3713

1028

1010

1515

103

1010

Spo

t 50.

500.

0903

0.00

120.

2473

0.00

353.

0775

0.04

820.

0678

0.00

100.

8898

1431

2514

2518

1427

1213

2619

100

1431

Spo

t 60.

310.

0829

0.00

100.

2171

0.00

302.

4823

0.03

630.

0619

0.00

090.

9426

1268

2312

6716

1267

1112

1416

100

1268

Spo

t 70.

540.

0795

0.00

090.

2034

0.00

292.

2291

0.03

320.

0546

0.00

070.

9486

1185

2311

9415

1190

1010

7413

101

1185

Spo

t 90.

220.

0709

0.00

140.

1530

0.00

221.

4955

0.03

170.

0464

0.00

140.

6855

954

4191

812

929

1391

727

9691

8

Spo

t 10

0.28

0.08

680.

0010

0.23

100.

0032

2.76

210.

0401

0.06

710.

0009

0.95

5613

5522

1340

1713

4511

1313

1899

1355

Spo

t 11

0.28

0.07

340.

0009

0.17

500.

0024

1.77

080.

0260

0.04

960.

0007

0.94

0010

2524

1039

1310

3510

979

1310

110

25

Spo

t 12

0.26

0.09

610.

0010

0.27

450.

0038

3.63

560.

0503

0.07

080.

0008

0.98

9515

4919

1563

1915

5711

1383

1510

115

49

Spo

t 14

0.28

0.09

660.

0011

0.27

520.

0039

3.66

530.

0529

0.07

200.

0009

0.98

7515

6021

1567

2015

6412

1405

1710

015

60

Spo

t 15

0.35

0.09

640.

0010

0.27

430.

0038

3.64

330.

0507

0.07

550.

0009

0.98

7215

5520

1562

1915

5911

1471

1710

015

55

Spo

t 18

0.16

0.07

890.

0009

0.20

910.

0029

2.27

450.

0339

0.06

080.

0011

0.93

9811

7023

1224

1612

0411

1192

2010

511

70

Spo

t 20

0.37

0.07

310.

0013

0.17

090.

0025

1.72

220.

0324

0.05

020.

0010

0.76

7610

1734

1017

1410

1712

989

1910

010

17

Spo

t 22

0.59

0.06

040.

0018

0.10

000.

0016

0.83

350.

0254

0.03

100.

0008

0.52

1262

064

615

961

614

617

1699

615

Spo

t 23

0.29

0.06

940.

0008

0.15

560.

0021

1.48

760.

0220

0.04

550.

0007

0.92

8691

025

932

1292

59

899

1310

293

2

Spo

t 24

1.11

0.07

050.

0012

0.15

860.

0023

1.54

230.

0283

0.04

680.

0007

0.78

3294

334

949

1394

711

925

1210

194

9

Spo

t 25

0.35

0.09

480.

0010

0.26

930.

0037

3.52

030.

0481

0.07

020.

0008

0.99

4815

2419

1537

1915

3211

1371

1510

115

24

Spo

t 27

0.25

0.07

860.

0010

0.20

030.

0028

2.16

910.

0324

0.05

290.

0008

0.93

821 1

6124

1177

1511

7110

1041

1510

111

61

Spo

t 28

0.74

0.07

040.

0010

0.15

600.

0022

1.51

350.

0247

0.04

120.

0005

0.87

9194

028

934

1293

610

816

1099

934

Spo

t 29

0.16

0.08

990.

0011

0.24

930.

0035

3.09

040.

0467

0.07

550.

0014

0.93

3414

2323

1435

1814

3012

1470

2510

114

23

Spo

t 30

0.48

0.09

540.

0011

0.26

920.

0039

3.53

860.

0532

0.06

900.

0009

0.95

3215

3522

1537

2015

3612

1348

1710

015

35

Spo

t 33

0.69

0.09

610.

0012

0.27

170.

0039

3.59

720.

0547

0.06

950.

0009

0.93

3715

4923

1549

2015

4912

1358

1710

015

49

Spo

t 34

0.47

0.06

280.

0010

0.12

110.

0017

1.04

820.

0182

0.03

460.

0006

0.81

4670

132

737

1072

89

687

1110

573

7

Spo

t 36

0.31

0.09

490.

0012

0.27

230.

0039

3.56

330.

0547

0.07

300.

0012

0.92

7615

2623

1553

2015

4112

1424

2310

215

26

Spo

t 37

0.34

0.08

090.

0010

0.20

680.

0028

2.30

640.

0338

0.05

810.

0008

0.92

8512

1924

1212

1512

1410

1142

1699

1219

Spo

t 38

0.65

0.10

800.

0013

0.31

590.

0046

4.70

440.

0716

0.07

790.

0011

0.95

0417

6722

1770

2217

6813

1516

2010

017

67

Spo

t 39

0.52

0.09

480.

0010

0.27

290.

0039

3.56

510.

0509

0.06

520.

0007

0.99

8615

2420

1555

2015

4211

1276

1410

215

24

Spo

t 41

0.32

0.07

270.

0010

0.16

990.

0024

1.70

190.

0275

0.04

450.

0007

0.88

5610

0427

1012

1310

0910

880

1410

110

04

Spo

t 42

0.35

0.07

830.

0009

0.20

360.

0028

2.19

840.

0317

0.05

510.

0007

0.96

1711

5522

1194

1511

8110

1084

1410

311

55

Spo

t 43

0.62

0.08

910.

0012

0.24

680.

0035

3.03

040.

0481

0.06

600.

0010

0.88

9114

0526

1422

1814

1512

1292

1910

114

05

Spo

t 45

0.38

0.08

200.

0014

0.20

280.

0030

2.29

290.

0430

0.05

880.

0012

0.77

5112

4633

1190

1612

1013

1156

2495

1246

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

102


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 46

0.30

0.08

050.

0010

0.19

880.

0028

2.20

530.

0339

0.05

810.

0009

0.91

2512

0925

1169

1511

8311

1142

1797

1209

Spo

t 47

0.61

0.08

580.

0010

0.22

830.

0032

2.70

050.

0392

0.06

700.

0008

0.95

1713

3422

1325

1713

2911

1310

1699

1334

Spo

t 48

0.86

0.10

940.

0012

0.31

260.

0043

4.71

470.

0663

0.08

820.

0011

0.96

8617

8920

1754

2117

7012

1708

2098

1789

Spo

t 49

0.54

0.06

960.

0012

0.15

730.

0023

1.50

990.

0291

0.04

470.

0008

0.75

2291

836

942

1393

412

884

1610

394

2

Spo

t 52

0.42

0.07

150.

0014

0.16

770.

0024

1.65

270.

0341

0.04

960.

0011

0.70

3497

239

999

1399

113

979

2210

399

9

Spo

t 53

0.61

0.08

020.

0012

0.19

460.

0028

2.15

190.

0372

0.05

930.

0010

0.84

4212

0329

1146

1511

6612

1165

1895

1203

Spo

t 55

0.34

0.09

550.

0010

0.26

450.

0037

3.48

340.

0486

0.07

580.

0010

0.98

8615

3820

1513

1915

2411

1476

1898

1538

Spo

t 56

0.25

0.08

270.

0011

0.20

710.

0029

2.36

140.

0361

0.06

060.

0010

0.91

4012

6224

1213

1512

3111

1190

2096

1262

Spo

t 58

0.49

0.08

060.

0012

0.19

880.

0028

2.20

910.

0364

0.05

830.

0009

0.85

8012

1228

1169

1511

8412

1146

1896

1212

Spo

t 59

0.35

0.07

970.

0011

0.19

530.

0028

2.14

550.

0339

0.05

950.

0010

0.89

1311

8926

1150

1511

6411

1169

1897

1189

Spo

t 62

0.30

0.08

370.

0013

0.21

580.

0031

2.48

980.

0430

0.06

640.

0013

0.82

8912

8530

1260

1612

6913

1299

2598

1285

Spo

t 63

0.42

0.08

330.

0011

0.20

880.

0029

2.39

680.

0380

0.06

320.

0010

0.88

6212

7626

1222

1612

4211

1239

1996

1276

Spo

t 67

0.25

0.07

470.

0009

0.16

250.

0023

1.67

380.

0246

0.05

000.

0007

0.94

8710

6023

971

1399

99

986

1492

971

Spo

t 69

0.28

0.07

300.

0010

0.16

890.

0024

1.69

870.

0276

0.05

090.

0009

0.86

6610

1328

1006

1310

0810

1003

1799

1013

Spo

t 71

0.46

0.10

590.

0012

0.30

840.

0042

4.50

290.

0630

0.08

930.

0012

0.96

9517

3020

1733

2117

3212

1729

2210

017

30

Spo

t 73

0.83

0.08

660.

0011

0.22

360.

0031

2.66

840.

0412

0.06

640.

0009

0.90

6213

5125

1301

1613

2011

1299

1896

1351

Spo

t 75

0.27

0.07

370.

0009

0.16

850.

0024

1.71

240.

0259

0.05

100.

0008

0.92

3810

3424

1004

1310

1310

1005

1597

1034

Spo

t 78

0.46

0.10

800.

0012

0.32

200.

0045

4.79

530.

0694

0.08

720.

0012

0.96

9417

6621

1800

2217

8412

1689

2210

217

66

Spo

t 79

0.31

0.08

000.

0011

0.19

930.

0028

2.19

860.

0349

0.05

810.

0010

0.88

6111

9826

1172

1511

8111

1142

1998

1198

Spo

t 82

0.23

0.08

650.

0009

0.24

400.

0033

2.91

080.

0401

0.06

740.

0009

0.99

0113

5020

1408

1713

8510

1317

1710

413

50

Spo

t 83

0.48

0.10

840.

0012

0.32

010.

0044

4.78

170.

0673

0.08

520.

001 1

0.98

2917

7220

1790

2217

8212

1653

2010

117

72

Spo

t 84

0.42

0.08

200.

0010

0.21

150.

0030

2.39

110.

0355

0.05

460.

0007

0.94

8012

4523

1237

1612

4011

1074

1499

1245

Spo

t 86

0.41

0.09

080.

0012

0.24

920.

0036

3.11

870.

0485

0.06

410.

0010

0.91

8014

4224

1434

1814

3712

1256

1899

1442

Spo

t 88

0.26

0.07

240.

0008

0.16

460.

0023

1.64

220.

0240

0.04

290.

0006

0.96

4399

723

982

1398

79

850

1198

982

Spo

t 90

0.91

0.11

980.

0017

0.33

040.

0051

5.45

480.

0923

0.07

750.

0012

0.90

6419

5325

1840

2518

9415

1508

2394

1953

Spo

t 91

0.32

0.08

730.

0010

0.22

940.

0033

2.76

190.

0410

0.05

830.

0008

0.95

6313

6822

1332

1713

4511

1145

1597

1368

Spo

t 93

0.11

0.07

690.

0009

0.16

550.

0025

1.75

300.

0274

0.04

950.

0009

0.97

1411

1823

987

1410

2810

977

1788

987

Spo

t 96

0.27

0.07

160.

0010

0.15

860.

0023

1.56

540.

0262

0.04

210.

0007

0.86

4697

529

949

1395

710

833

1497

949

Spo

t 97

0.84

0.10

930.

0013

0.31

650.

0047

4.76

700.

0730

0.08

020.

0010

0.96

5017

8721

1773

2317

7913

1560

1999

1787

Spo

t 99

0.24

0.09

350.

0010

0.25

790.

0036

3.32

410.

0472

0.06

760.

0009

0.98

8714

9820

1479

1914

8711

1323

1699

1498

Spo

t 100

0.67

0.20

350.

0026

0.54

960.

0087

15.4

177

0.24

560.

1016

0.00

200.

9881

2854

2028

2436

2841

1519

5636

9928

54

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

103


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 104

0.26

0.08

210.

0010

0.22

700.

0033

2.56

930.

0386

0.05

960.

0009

0.95

8712

4823

1319

1712

9211

1170

1610

612

48

Spo

t 110

0.25

0.08

210.

0010

0.20

580.

0030

2.32

750.

0361

0.05

440.

0008

0.94

0312

4724

1206

1612

2111

1071

1697

1247

Spo

t 113

0.57

0.08

970.

0011

0.24

350.

0035

3.01

120.

0468

0.06

480.

0009

0.91

9914

1924

1405

1814

1112

1269

1799

1419

Spo

t 116

0.23

0.08

210.

0010

0.21

580.

0032

2.44

290.

0375

0.05

360.

0009

0.96

5012

4822

1260

1712

5511

1056

1710

112

48

Spo

t 121

0.27

0.08

180.

0009

0.20

530.

0029

2.31

480.

0342

0.05

720.

0008

0.96

0512

4022

1204

1612

1710

1124

1597

1240

Spo

t 125

1.71

0.10

940.

0016

0.31

400.

0046

4.73

410.

0794

0.08

300.

0012

0.86

4117

8926

1760

2217

7314

1611

2298

1789

Spo

t 126

0.33

0.09

140.

0012

0.24

830.

0038

3.12

860.

0524

0.04

850.

0010

0.91

6814

5426

1430

2014

4013

957

1998

1454

Spo

t 127

0.23

0.07

280.

0009

0.16

930.

0024

1.69

870.

0258

0.04

980.

0007

0.94

8310

0824

1008

1310

0810

982

1410

010

08

Spo

t 130

0.50

0.07

260.

0016

0.16

220.

0025

1.62

450.

0377

0.05

200.

0012

0.66

6510

0445

969

1498

015

1025

2397

969

Spo

t 131

0.75

0.11

740.

0014

0.34

660.

0050

5.60

790.

0840

0.09

630.

0012

0.96

5019

1621

1918

2419

1713

1858

2310

019

16

Spo

t 132

0.38

0.08

760.

0010

0.23

220.

0033

2.80

320.

0416

0.06

760.

0009

0.95

8513

7322

1346

1713

5611

1322

1798

1373

Spo

t 133

0.07

0.08

130.

0009

0.17

840.

0026

2.00

060.

0290

0.08

250.

0012

0.99

3612

3021

1058

1411

1610

1603

2286

1230

Spo

t 135

0.29

0.07

240.

0009

0.16

380.

0023

1.63

500.

0249

0.04

790.

0007

0.93

4099

724

978

1398

410

945

1498

978

Spo

t 137

0.41

0.07

390.

0012

0.16

740.

0024

1.70

420.

0310

0.04

740.

0009

0.79

5710

3833

998

1310

1012

936

1796

998

Spo

t 142

0.59

0.07

990.

0011

0.19

730.

0029

2.17

140.

0358

0.05

600.

0008

0.90

3311

9326

1161

1611

7211

1101

1697

1193

Spo

t 143

0.45

0.07

060.

0010

0.15

850.

0023

1.54

230.

0257

0.04

630.

0007

0.85

0894

629

948

1394

710

915

1410

094

8

Spo

t 146

0.35

0.07

770.

0010

0.19

630.

0028

2.10

280.

0328

0.05

690.

0009

0.90

821 1

4025

1155

1511

5011

1119

1710

111

40

Spo

t 150

0.30

0.07

290.

0012

0.16

850.

0025

1.69

300.

0317

0.04

570.

0010

0.78

0510

1034

1004

1410

0612

902

1999

1010

Spo

t 151

0.38

0.08

250.

0009

0.21

160.

0030

2.40

670.

0341

0.05

980.

0007

0.99

0712

5820

1237

1612

4510

1175

1498

1258

Spo

t 153

0.56

0.07

600.

0010

0.18

690.

0027

1.95

870.

0309

0.05

030.

0007

0.90

7310

9626

1104

1411

0111

993

1310

110

96

Spo

t 154

0.36

0.07

870.

0009

0.20

190.

0028

2.18

990.

0319

0.05

480.

0007

0.96

7411

6422

1185

1511

7810

1078

1410

211

64

Spo

t 155

0.29

0.07

940.

0009

0.19

670.

0028

2.15

240.

0314

0.05

280.

0007

0.96

8911

8222

1157

1511

6610

1040

1398

1182

Spo

t 157

0.23

0.08

130.

0010

0.20

810.

0029

2.33

310.

0346

0.05

940.

0009

0.93

7712

2923

1219

1512

2211

1166

1899

1229

Spo

t 158

0.58

0.07

300.

0014

0.16

870.

0025

1.69

850.

0337

0.04

790.

0009

0.73

8510

1537

1005

1410

0813

945

1799

1015

Spo

t 159

0.59

0.10

950.

0012

0.31

660.

0044

4.77

880.

0688

0.08

680.

0011

0.96

9217

9120

1773

2217

8112

1683

2199

1791

Spo

t 160

0.53

0.08

870.

0011

0.23

250.

0033

2.84

410.

0423

0.06

670.

0009

0.94

2113

9923

1347

1713

6711

1304

1796

1399

Spo

t 161

0.43

0.07

300.

0009

0.16

610.

0023

1.67

210.

0254

0.04

840.

0007

0.91

2010

1425

991

1399

810

955

1398

991

Spo

t 162

0.50

0.09

180.

0011

0.24

910.

0035

3.15

340.

0458

0.07

080.

0009

0.95

8414

6322

1434

1814

4611

1382

1798

1463

Spo

t 164

0.18

0.08

430.

0011

0.21

920.

0031

2.54

890.

0393

0.06

320.

0012

0.91

7213

0024

1278

1612

8611

1238

2298

1300

Spo

t 165

0.23

0.07

110.

0011

0.15

720.

0023

1.54

150.

0276

0.04

860.

0010

0.80

6096

132

941

1394

711

959

2098

941

Spo

t 166

0.51

0.09

130.

0013

0.24

800.

0036

3.12

230.

0507

0.07

090.

0011

0.88

2314

5326

1428

1814

3812

1384

2198

1453

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

104


Tabl

e 1.

(con

tinue

d)

Ana

lysi

sTh

/U20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Rho

b20

7 Pb/

206 P

b±

1σ20

6 Pb/

238 U

± 1σ

207 P

b/23

5 U±

1σ20

8 Pb/

232 Th

± 1σ

Con

c.c

Spo

t 167

0.24

0.10

270.

0011

0.29

080.

0040

4.11

730.

0574

0.08

490.

0011

0.99

2016

7419

1645

2016

5811

1647

2098

1674

Spo

t 168

0.46

0.08

220.

0010

0.21

200.

0030

2.40

100.

0358

0.06

160.

0008

0.94

0612

4923

1239

1612

4311

1209

1599

1249

Spo

t 169

0.30

0.08

600.

0011

0.22

590.

0031

2.67

790.

0403

0.06

420.

0010

0.92

0513

3824

1313

1613

2211

1257

1998

1338

Spo

t 170

0.41

0.07

910.

0011

0.19

220.

0028

2.09

720.

0353

0.05

430.

0009

0.86

4411

7628

1133

1511

4812

1068

1796

1176

Spo

t 172

0.53

0.09

610.

0011

0.26

250.

0038

3.47

650.

0511

0.07

250.

0009

0.97

1215

4921

1503

1915

2212

1414

1797

1549

a Dis

play

ed ra

tios

and

ages

are

unc

orre

cted

for c

omm

on P

b.b E

rror

cor

rela

tion;

def

ined

as

[(err.

206 P

b/23

8 U)/(

mea

sure

d 20

6 Pb/

238 U

)]/[(e

rr. 20

7 Pb/

235 U

)/(m

easu

red

207 P

b/23

5 U)].

c D

egre

e of

con

cord

ance

(%);

defin

ed a

s 10

0 ×

[(206 P

b/23

8 U a

ge)/(

207 P

b/20

6 U a

ge)]

d Effe

ctiv

e ag

e; fo

r age

s <1

000

Ma

and

>100

0 M

a, th

is c

orre

spon

ds to

cal

cula

ted

206 P

b/23

8 U a

nd 20

7 Pb/

206 P

b ag

es, r

espe

ctiv

ely.

Isot

opic

Rat

iosa

Age

Est

imat

esa (M

a)E

ff.A

ged

105


Tabl

e 2.

Hf I

soto

pic

data

Ana

lysi

s17

6 Hf/17

7 Hf

2SE

176 Lu

/177 H

f17

6 Yb/17

7 Hf

Effe

ctiv

eA

geH

f iε H

f1S

ET D

M (G

a)T D

M (c

rust

al)

z002

0.28

2202

0.00

0021

0.00

1087

0.05

0804

1260

0.28

2176

6.85

0.75

1.49

1.62

z020

0.28

1917

0.00

0036

0.00

1012

0.04

7264

1359

0.28

1891

-1.0

21.

281.

882.

18

z021

0.28

2095

0.00

0047

0.00

1688

0.09

0459

1423

0.28

2050

6.05

1.64

1.66

1.79

z026

0.28

2216

0.00

0034

0.00

0918

0.04

6655

953

0.28

2200

0.82

1.20

1.46

1.75

z032

0.28

2037

0.00

0043

0.00

0846

0.03

7086

1414

0.28

2014

4.60

1.52

1.70

1.87

z035

0.28

1941

0.00

0060

0.00

1939

0.08

7501

1373

0.28

1891

-0.7

12.

101.

892.

17

z039

0.28

2079

0.00

0018

0.00

1046

0.04

8973

1332

0.28

2053

4.12

0.62

1.65

1.84

z040

0.28

1702

0.00

0026

0.00

1298

0.05

8879

1829

0.28

1657

1.32

0.92

2.19

2.39

z044

0.28

1832

0.00

0018

0.00

0718

0.03

4082

1515

0.28

1812

-0.3

10.

631.

982.

25

z049

0.28

1719

0.00

0020

0.00

1277

0.05

5006

1852

0.28

1674

2.45

0.69

2.17

2.34

z050

0.28

1977

0.00

0115

0.00

3233

0.14

4551

1359

0.28

1894

-0.9

14.

031.

912.

17

z053

0.28

2009

0.00

0081

0.00

2476

0.09

5874

1204

0.28

1953

-2.2

92.

831.

822.

14

z054

0.28

2121

0.00

0043

0.00

1790

0.07

8769

643

0.28

2099

-9.6

51.

491.

632.

17

z055

0.28

2605

0.00

0027

0.00

1980

0.08

2720

533

0.28

2585

5.14

0.96

0.94

1.16

z056

0.28

1753

0.00

0130

0.00

5146

0.22

3508

637

0.28

1691

-24.

234.

542.

363.

06

z058

0.28

1453

0.00

0017

0.00

1127

0.04

9282

1905

0.28

1412

-5.6

50.

602.

522.

87

z076

0.28

1915

0.00

0043

0.00

1532

0.06

8208

640

0.28

1897

-16.

881.

521.

912.

61

z077

0.28

1921

0.00

0033

0.00

0641

0.03

0235

1233

0.28

1906

-3.3

11.

151.

852.

22

z078

0.28

2095

0.00

0043

0.00

1416

0.06

8720

1238

0.28

2061

2.31

1.50

1.65

1.88

z086

0.28

2250

0.00

0051

0.00

3090

0.12

8135

1086

0.28

2186

3.33

1.79

1.50

1.70

z089

0.28

1928

0.00

0017

0.00

0732

0.03

2237

1593

0.28

1906

4.78

0.59

1.85

2.00

z091

0.28

2124

0.00

0017

0.00

0754

0.03

9016

1261

0.28

2106

4.39

0.59

1.58

1.77

z094

0.28

2158

0.00

0041

0.00

1825

0.07

7317

631

0.28

2137

-8.5

71.

431.

582.

09

z104

0.28

2013

0.00

0027

0.00

1310

0.06

0983

564

0.28

1999

-14.

940.

931.

762.

44

z121

0.28

3147

0.00

3372

0.00

1951

0.08

8610

651

0.28

3123

26.7

911

8.02

0.15

-0.1

2

z142

0.28

1566

0.00

0035

0.00

1264

0.05

2733

1875

0.28

1521

-2.4

51.

232.

382.

66

z143

0.28

1965

0.00

0022

0.00

0689

0.03

0555

1265

0.28

1948

-1.1

00.

761.

802.

11

z154

0.28

2051

0.00

0090

0.00

1603

0.05

6675

682

0.28

2031

-11.

213.

161.

722.

29

z156

0.28

2244

0.00

0019

0.00

1230

0.05

9379

528

0.28

2232

-7.5

00.

681.

431.

95

z159

0.28

2046

0.00

0017

0.00

0870

0.04

0722

1294

0.28

2024

2.24

0.59

1.69

1.93

z163

0.28

1896

0.00

0089

0.00

2420

0.09

2515

598

0.28

1869

-18.

783.

121.

982.

70

z165

0.28

1610

0.00

0016

0.00

0666

0.02

9699

1918

0.28

1586

0.81

0.57

2.28

2.49

Lu d

ecay

con

stan

t 1.8

65 x

10-1

1 Sch

erer

et a

l. (2

001)

BD

M01

106


ble

2. (c

ontin

ued)

Ana

lysi

s17

6 Hf/17

7 Hf

2SE

176 Lu

/177 H

f17

6 Yb/17

7 Hf

Effe

ctiv

eA

geH

f iε H

f1S

ET D

M (G

a)T D

M (c

rust

al)

z170

0.28

1819

0.00

0119

0.00

3533

0.22

6737

948

0.28

1756

-15.

004.

182.

162.

72

z173

0.28

2144

0.00

0041

0.00

2254

0.12

5614

1163

0.28

2095

1.78

1.43

1.62

1.85

z176

0.28

2098

0.00

0022

0.00

2219

0.11

1463

1379

0.28

2040

4.73

0.76

1.68

1.84

z180

0.28

2044

0.00

0032

0.00

0957

0.04

7635

1429

0.28

2018

5.06

1.13

1.70

1.86

z183

0.28

2302

0.00

0052

0.00

0819

0.04

1151

1015

0.28

2286

5.26

1.82

1.34

1.53

z184

0.28

2206

0.00

0051

0.00

1299

0.04

8133

1042

0.28

2181

2.13

1.78

1.49

1.74

z185

0.28

1595

0.00

0015

0.00

0317

0.01

3594

1950

0.28

1583

1.44

0.52

2.28

2.48

z187

0.28

2198

0.00

0046

0.00

0854

0.03

8270

608

0.28

2188

-7.2

61.

621.

482.

00

z188

0.28

2457

0.00

0047

0.00

0919

0.03

9194

548

0.28

2447

0.56

1.63

1.12

1.46

z195

0.28

1542

0.00

0018

0.00

0956

0.04

6765

1805

0.28

1509

-4.4

90.

632.

392.

72

z002

0.28

1198

449

1.26

013E-‐05

0.00

0666

673

0.02

4058

936

1896

0.28

1174

46-‐14.31

0.44

2.84

3.38

z003

0.28

1846

299

1.32

359E-‐05

0.00

0584

277

0.02

2597

468

1594

0.28

1828

667

2.08

0.46

1.95

2.17

z023

0.28

1917

098

1.54

824E-‐05

0.00

0680

529

0.03

1225

898

1571

0.28

1896

866

3.97

0.54

1.86

2.03

z026

0.28

2235

369

1.51

202E-‐05

0.00

0536

581

0.02

4725

043

1031

0.28

2224

951

3.46

0.53

1.42

1.65

z033

0.28

1755

376

2.41

959E-‐05

0.00

1385

999

0.05

0535

5217

990.28

1708

095

2.44

0.85

2.12

2.30

z037

0.28

2230

021.67

906E-‐05

0.00

1194

964

0.05

5464

069

1065

0.28

2206

038

3.56

0.59

1.45

1.67

z040

0.28

1927

467

1.80

277E-‐05

0.00

0643

0.02

8184

145

1433

0.28

1910

057

1.31

0.63

1.85

2.09

z045

0.28

2270

054

2.21

982E-‐05

0.00

1475

649

0.07

3237

775

1090

0.28

2239

758

5.30

0.78

1.40

1.58

z047

0.28

1963

203

1.37

276E-‐05

0.00

0472

302

0.01

7876

1114

170.28

1950

559

2.39

0.48

1.79

2.01

z049

0.28

1767

418

1.97

465E-‐05

0.00

1056

833

0.03

9243

8217

380.28

1732

603

1.93

0.69

2.09

2.29

z051

0.28

1923

918

1.54

809E-‐05

0.00

0639

252

0.02

3712

565

1411

0.28

1906

868

0.72

0.54

1.85

2.11

z053

0.28

1910

673

1.33

45E-‐05

0.00

0100

845

0.00

4211

988

0.28

1908

797

-‐8.70

0.47

1.84

2.37

z054

0.28

1979

908

3.02

6E-‐05

0.00

2012

451

0.06

5451

331

1565

0.28

1920

324.66

1.06

1.84

1.99

z057

0.28

1854

972

1.52

719E-‐05

0.00

0884

616

0.03

4979

682

1580

0.28

1828

519

1.75

0.53

1.96

2.18

z062

0.28

2226

515

2.04

087E-‐05

0.00

0622

793

0.02

0020

348

1032

0.28

2214

407

3.11

0.71

1.43

1.67

z067

0.28

1910

779

2.82

427E-‐05

0.00

1866

978

0.07

8865

716

1559

0.28

1855

717

2.23

0.99

1.93

2.13

z069

0.28

2069

785

3.24

699E-‐05

0.00

0730

167

0.02

8320

051

987

0.28

2056

223

-‐3.51

1.14

1.65

2.05

z077

0.28

1822

501

2.02

217E-‐05

0.00

1203

747

0.04

1507

378

1682

0.28

1784

154

2.48

0.71

2.02

2.21

z080

0.28

2171

773

1.44

958E-‐05

0.00

0358

675

0.01

3337

603

1056

0.28

2164

641

1.87

0.51

1.50

1.77

z082

0.28

2109

346

1.56

94E-‐05

0.00

0677

782

0.02

8489

474

1271

0.28

2093

094

4.15

0.55

1.60

1.79

z083

0.28

2201

425

1.60

781E-‐05

0.00

0723

140.03

3280

903

968

0.28

2188

251

0.75

0.56

1.47

1.77

z093

0.28

1747

644

1.86

922E-‐05

0.00

0736

706

0.02

8861

295

1688

0.28

1724

082

0.49

0.65

2.10

2.33

BP

UG

02

Lu d

ecay

con

stan

t 1.8

65 x

10-1

1 Sch

erer

et a

l. (2

001)

107


Tabl

e 2.

(con

tinue

d)

Ana

lysi

s17

6 Hf/17

7 Hf

2SE

176 Lu

/177 H

f17

6 Yb/17

7 Hf

Effe

ctiv

eA

geH

f iε H

f1S

ET D

M (G

a)T D

M (c

rust

al)

z095

0.28

1850

029

1.72

039E-‐05

0.00

0726

335

0.03

1164

761

1518

0.28

1829

168

0.38

0.60

1.96

2.21

z099

0.28

2151

041

1.58

664E-‐05

0.00

0694

906

0.02

9749

521

1215

0.28

2135

117

4.39

0.56

1.54

1.73

z100

0.28

1803

771.78

194E-‐05

0.00

0986

177

0.03

7105

666

1540

0.28

1775

045

-‐1.06

0.62

2.03

2.32

z101

0.28

1852

686

1.42

79E-‐05

0.00

0621

789

0.02

7034

267

1511

0.28

1834

910.43

0.50

1.95

2.20

z103

0.28

1961

61.75

476E-‐05

0.00

1060

497

0.04

1795

096

1351

0.28

1934

540.34

0.61

1.82

2.09

z104

0.28

1864

189

1.54

122E-‐05

0.00

0628

553

0.02

8582

558

1546

0.28

1845

798

1.60

0.54

1.93

2.16

z107

0.28

1720

712

1.65

859E-‐05

0.00

1131

310.04

1563

894

1765

0.28

1682

855

0.78

0.58

2.16

2.38

z116

0.28

1837

023

2.30

291E-‐05

0.00

1607

313

0.07

7190

484

1668

0.28

1786

252

2.23

0.81

2.02

2.21

z119

0.28

1872

116

2.24

953E-‐05

0.00

1139

20.03

8115

237

1467

0.28

1840

52-‐0.38

0.79

1.95

2.22

z120

0.28

1919

837

5.92

85E-‐05

0.00

4567

115

0.25

0930

823

1545

0.28

1786

369

-‐0.55

2.07

2.07

2.29

z122

0.28

1477

598

1.91

382E-‐05

0.00

1460

856

0.05

8625

428

1975

0.28

1422

8-‐3.69

0.67

2.51

2.81

z127

0.28

1834

734

1.55

062E-‐05

0.00

0542

084

0.01

9933

195

1487

0.28

1819

487

-‐0.66

0.54

1.97

2.25

z128

0.28

2209

728

0.00

0014

590.00

0628

777

0.02

4605

466

1015

0.28

2197

707

2.14

0.51

1.46

1.72

z002

0.28

2128

832.86

058E-‐05

0.00

1499

696

0.05

3242

807

1153

0.28

2096

224

1.63

1.00

1.60

1.86

z010

0.28

2042

698

2.58

833E-‐05

0.00

1508

621

0.06

2566

707

1414

0.28

2002

373

4.18

0.91

1.73

1.90

z014

0.28

2004

338

3.08

782E-‐05

0.00

1931

120.06

7832

575

1518

0.28

1948

871

4.63

1.08

1.80

1.95

z016

0.28

2076

376

3.04

149E-‐05

0.00

0595

632

0.02

2121

893

1111

0.28

2063

907

-‐0.46

1.06

1.64

1.95

z019

0.28

2236

996

1.67

778E-‐05

0.00

0446

606

0.02

0787

8893

00.28

2229

184

1.34

0.59

1.41

1.70

z024

0.28

2251

134

2.22

346E-‐05

0.00

0691

847

0.03

4108

537

903

0.28

2239

381.11

0.78

1.40

1.70

z025

0.28

1809

992.33

802E-‐05

0.00

0795

543

0.03

2342

213

1553

0.28

1786

617

-‐0.35

0.82

2.01

2.28

z029

0.28

2239

465

2.90

863E-‐05

0.00

0626

874

0.03

0447

154

1107

0.28

2226

392

5.20

1.02

1.42

1.60

z034

0.28

2025

061

2.84

811E-‐05

0.00

1288

760.05

9254

381

1584

0.28

1986

433

7.44

1.00

1.74

1.83

z038

0.28

2250

654

3.38

477E-‐05

0.00

0962

862

0.03

4538

843

942

0.28

2233

594

1.77

1.18

1.41

1.69

z042

0.28

2039

987

1.76

383E-‐05

0.00

0475

210.02

2063

018

1322

0.28

2028

125

3.01

0.62

1.68

1.90

z043

0.28

2239

671

4.72

318E-‐05

0.00

1121

641

0.03

8838

128

903

0.28

2220

620.44

1.65

1.43

1.74

z057

0.28

1896

053

0.00

0132

738

0.00

1268

197

0.04

3865

043

1340

0.28

1863

965

-‐2.41

4.65

1.92

2.25

z061

0.28

2006

993

2.22

668E-‐05

0.00

0988

032

0.04

4939

097

1382

0.28

1981

194

2.70

0.78

1.75

1.97

z062

0.28

2191

779

2.92

242E-‐05

0.00

0441

161

0.02

1137

678

926

0.28

2184

097

-‐0.35

1.02

1.47

1.81

z069

0.28

2030

859

3.44

692E-‐05

0.00

0753

643

0.03

0500

4715

170.28

2009

235

6.74

1.21

1.71

1.82

z071

0.28

2283

362

3.14

719E-‐05

0.00

0715

422

0.03

6069

356

636

0.28

2274

826

-‐3.58

1.10

1.36

1.79

z072

0.28

2160

312

2.48

33E-‐05

0.00

0422

275

0.02

1612

204

1033

0.28

2152

101

0.91

0.87

1.52

1.81

z073

0.28

2117

685

3.15

021E-‐05

0.00

1260

846

0.04

5374

0711

980.28

2089

192.39

1.10

1.61

1.84

BR

Z01

Lu d

ecay

con

stan

t 1.8

65 x

10-1

1 Sch

erer

et a

l. (2

001)

108


ble

2. (c

ontin

ued)

Ana

lysi

s17

6 Hf/17

7 Hf

2SE

176 Lu

/177 H

f17

6 Yb/17

7 Hf

Effe

ctiv

eA

geH

f iε H

f1S

ET D

M (G

a)T D

M (c

rust

al)

z075

0.28

2014

393

3.13

864E-‐05

0.00

1430

319

0.05

8773

3812

920.28

1979

512

0.61

1.10

1.76

2.03

z076

0.28

1453

358

2.42

648E-‐05

0.00

0729

206

0.03

2184

588

1984

0.28

1425

869

-‐3.36

0.85

2.50

2.79

z077

0.28

2117

568

1.82

341E-‐05

0.00

0866

721

0.03

8045

109

1193

0.28

2098

066

2.59

0.64

1.59

1.83

z080

0.28

2257

984

2.48

379E-‐05

0.00

0539

668

0.02

5473

086

928

0.28

2248

561

1.99

0.87

1.39

1.66

z086

0.28

2167

384

4.18

179E-‐05

0.00

0961

641

0.03

4320

089

1238

0.28

2144

915

5.27

1.46

1.53

1.70

z095

0.28

2262

397

2.36

917E-‐05

0.00

0862

248

0.03

3846

586

945

0.28

2247

074

2.31

0.83

1.39

1.66

z097

0.28

2062

042

2.75

152E-‐05

0.00

0925

814

0.03

4522

738

1235

0.28

2040

465

1.50

0.96

1.67

1.93

z109

0.28

1971

637

2.53

614E-‐05

0.00

0887

777

0.03

4261

948

1391

0.28

1948

305

1.73

0.89

1.80

2.03

z115

0.28

2230

848

2.49

233E-‐05

0.00

0783

521

0.03

3674

217

983

0.28

2216

346

2.08

0.87

1.43

1.70

z119

0.28

2219

52.69

084E-‐05

0.00

0386

145

0.01

8563

489

1053

0.28

2211

839

3.49

0.94

1.43

1.67

z124

0.28

2127

797

2.42

206E-‐05

0.00

1026

069

0.04

7867

183

1165

0.28

2105

256

2.22

0.85

1.59

1.83

z131

0.28

2160

651

1.98

365E-‐05

0.00

0572

007

0.02

5571

331

908

0.28

2150

878

-‐1.91

0.69

1.52

1.89

z137

0.28

2003

415.01

035E-‐05

0.00

0795

252

0.02

8944

545

1278

0.28

1984

231

0.46

1.75

1.75

2.02

z001

0.28

1978

011

2.21

08E-‐05

0.00

1008

060.03

9684

995

1490

0.28

1949

614.01

0.77

1.79

1.97

z002

0.28

2254

733

2.02

35E-‐05

0.00

0771

837

0.03

3111

552

937

0.28

2241

128

1.93

0.71

1.40

1.67

z005

0.28

1890

821.64

433E-‐05

0.00

0710

051

0.03

1044

902

1556

0.28

1869

912.68

0.58

1.90

2.10

z006

0.28

1971

043

1.91

757E-‐05

0.00

0749

104

0.03

0001

075

1367

0.28

1951

71.31

0.67

1.79

2.04

z008

0.28

1922

777

1.34

642E-‐05

0.00

0753

490.03

2182

815

290.28

1900

979

3.17

0.47

1.86

2.05

z009

0.28

2259

757

2.15

51E-‐05

0.00

0753

70.02

9793

427

1074

0.28

2244

513

5.11

0.75

1.39

1.58

z010

0.28

1974

645

1.87

146E-‐05

0.00

1368

487

0.05

6009

954

1486

0.28

1936

183

3.45

0.66

1.82

2.00

z014

0.28

2159

011.62

013E-‐05

0.00

0541

704

0.02

1737

318

1049

0.28

2148

313

1.13

0.57

1.52

1.81

z015

0.28

1769

011.25

155E-‐05

0.00

0290

995

0.00

8836

5715

420.28

1760

519

-‐1.52

0.44

2.04

2.35

z016

0.28

2001

071

2.01

9E-‐05

0.00

0951

293

0.03

8662

163

1372

0.28

1976

408

2.31

0.71

1.76

1.98

z001

0.28

1933

601

2.55

857E

-05

0.00

1180

871

0.04

9372

636

1675

0.28

1896

6.29

0.9

1.86

1.97

z005

0.28

2112

553

1.57

486E

-05

0.00

0667

681

0.02

5080

651

1211

0.28

2097

2.98

0.6

1.59

1.82

z008

0.28

1842

321

2.39

767E-‐05

0.00

1260

253

0.03

3879

5515

610.28

1805

0.48

0.8

1.99

2.24

z010

0.28

1891

877

1.70

357E

-05

0.00

0444

611

0.01

3905

318

1662

0.28

1878

5.35

0.6

1.89

2.02

z018

0.28

2191

386

1.95

546E

-05

0.00

0984

524

0.02

9382

254

943

0.28

2174

-‐0.31

0.7

1.50

1.82

z021

0.28

2099

167

2.60

518E

-05

0.00

0829

115

0.02

5039

099

1606

0.28

2074

11.05

0.9

1.62

1.63

z023

0.28

2300

267

2.79

392E

-05

0.00

3389

237

0.13

2016

232

1079

0.28

2231

4.75

1.0

1.44

1.61

z028

0.28

1884

754

2.02

307E

-05

0.00

1380

370.05

0848

513

1571

0.28

1844

2.09

0.7

1.94

2.15

BR

Z-02

BR

Z-15

Lu d

ecay

con

stan

t 1.8

65 x

10-1

1 Sch

erer

et a

l. (2

001)

109


Tabl

e 2.

(con

tinue

d)

Ana

lysi

s17

6 Hf/17

7 Hf

2SE

176 Lu

/177 H

f17

6 Yb/17

7 Hf

Effe

ctiv

eA

geH

f iε H

f1S

ET D

M (G

a)T D

M (c

rust

al)

z029

0.28

1835

929

2.40

006E

-05

0.00

1306

754

0.05

1569

794

1602

0.28

1796

1.11

0.8

2.01

2.23

z030

0.28

2001

571

2.03

108E

-05

0.00

0731

965

0.02

6229

733

1315

0.28

1983

1.27

0.7

1.75

2.00

z038

0.28

2101

222.57

444E

-05

0.00

0826

485

0.02

5051

249

1184

0.28

2083

1.84

0.9

1.61

1.87

z039

0.28

1829

806

2.44

952E

-05

0.00

2028

568

0.07

5118

008

1818

0.28

1760

4.72

0.9

2.05

2.18

z041

0.28

2118

468

2.64

991E

-05

0.00

1363

816

0.04

0582

7811

620.28

2089

1.55

0.9

1.61

1.87

z047

0.28

2119

484

1.76

207E-‐05

0.00

0854

461

0.03

0333

816

1140

0.28

2101

1.50

0.6

1.59

1.85

z055

0.28

1926

681

2.88

956E

-05

0.00

1431

529

0.04

4180

015

1573

0.28

1884

3.56

1.0

1.89

2.06

z065

0.28

1859

137

1.47

598E

-05

0.00

0473

805

0.01

6723

603

1535

0.28

1845

1.33

0.5

1.93

2.17

z066

0.28

1826

167

1.88

446E

-05

0.00

0898

224

0.03

2327

113

770.28

1803

-‐3.74

0.7

2.00

2.36

z067

0.28

2111

291.78

618E

-05

0.00

0585

167

0.01

7869

367

1028

0.28

2100

-‐1.03

0.6

1.59

1.93

z068

0.28

1889

223

1.35

799E

-05

0.00

0754

573

0.02

7968

005

1585

0.28

1867

3.22

0.5

1.90

2.09

z077

0.28

1529

861.75

019E

-05

0.00

0827

754

0.02

9623

744

1752

0.28

1502

-‐5.92

0.6

2.40

2.77

z086

0.28

1989

521

2.94

685E

-05

0.00

1214

236

0.03

3025

171

1504

0.28

1955

4.53

1.0

1.79

1.95

z095

0.28

1983

762

1.46

077E

-05

0.00

0405

816

0.01

3709

231

1338

0.28

1974

1.43

0.5

1.76

2.01

z100

0.28

1858

419

1.52

701E

-05

0.00

1220

402

0.04

4543

192

1622

0.28

1821

2.44

0.5

1.97

2.17

z108

0.28

2206

473

2.40

785E

-05

0.00

1212

394

0.03

3667

486

929

0.28

2185

-‐0.22

0.8

1.48

1.80

z118

0.28

0612

452

5.75

019E

-05

0.00

1117

398

0.03

0218

106

3083

0.28

0546

-‐9.29

2.0

3.67

3.98

z119

0.28

1831

948

4.93

342E

-05

0.00

2604

770.08

1523

025

1706

0.28

1748

1.74

1.7

2.08

2.27

z120

0.28

1915

548

0.00

0016

963

0.00

0569

652

0.02

0596

762

1308

0.28

1901

-‐1.80

0.6

1.86

2.18

z127

0.28

1839

921

1.71

499E

-05

0.00

0703

904

0.02

3094

505

1366

0.28

1822

-‐3.32

0.6

1.97

2.32

z131

0.28

2122

839

2.15

485E

-05

0.00

0861

477

0.02

5217

513

1240

0.28

2103

3.80

0.8

1.59

1.79

z133

0.28

2079

280.00

0025

60.00

0808

091

0.02

3959

257

1187

0.28

2061

1.16

0.9

1.64

1.91

z135

0.28

2211

664

1.45

567E

-05

0.00

0601

586

0.02

1055

476

942

0.28

2201

0.61

0.5

1.45

1.76

z139

0.28

2015

083

2.08

102E

-05

0.00

0723

391

0.02

1269

626

1203

0.28

1999

-‐0.71

0.7

1.73

2.04

z147

0.28

1792

216

3.47

648E

-05

0.00

0859

946

0.02

5285

9915

440.28

1767

-‐1.25

1.2

2.04

2.33

z158

0.28

1854

719

1.58

543E

-05

0.00

0766

039

0.02

8239

269

1525

0.28

1833

0.66

0.6

1.95

2.20

z162

0.28

1948

596

1.78

788E

-05

0.00

0830

411

0.02

8547

289

1523

0.28

1925

3.87

0.6

1.83

2.00

z005

0.28

1827

232.11

152E-‐05

0.00

0520

396

0.02

3607

077

1431

0.28

1813

158

-‐2.17

0.74

1.98

2.30

z006

0.28

2058

161.93

916E-‐05

0.00

0629

767

0.02

6841

575

1268

0.28

2043

093

2.32

0.68

1.67

1.90

z007

0.28

2128

234

2.72

961E-‐05

0.00

0750

940.03

2738

824

1185

0.28

2111

462.87

0.96

1.57

1.80

z009

0.28

2226

832

3.38

412E-‐05

0.00

0575

057

0.02

3395

464

918

0.28

2216

903

0.64

1.18

1.43

1.74

z015

0.28

1867

985

1.65

014E-‐05

0.00

0520

903

0.02

3376

455

1555

0.28

1852

662.04

0.58

1.92

2.14

BR

Z-24

Lu d

ecay

con

stan

t 1.8

65 x

10-1

1 Sch

erer

et a

l. (2

001)

110


ble

2. (c

ontin

ued)

Ana

lysi

s17

6 Hf/17

7 Hf

2SE

176 Lu

/177 H

f17

6 Yb/17

7 Hf

Effe

ctiv

eA

geH

f iε H

f1S

ET D

M (G

a)T D

M (c

rust

al)

z020

0.28

2183

834

1.73

334E-‐05

0.00

0491

068

0.02

4949

610

170.28

2174

435

1.34

0.61

1.49

1.77

z022

0.28

2271

988

1.86

501E-‐05

0.00

0537

760.02

4937

914

615

0.28

2265

788

-‐4.37

0.65

1.37

1.82

z023

0.28

2200

172

1.75

432E-‐05

0.00

0835

290.04

0204

263

932

0.28

2185

526

-‐0.15

0.61

1.48

1.80

z027

0.28

2095

472

1.66

23E-‐05

0.00

0694

861

0.03

2275

514

1161

0.28

2080

261.24

0.58

1.62

1.89

z028

0.28

2154

648

1.43

712E-‐05

0.00

0419

130.01

8735

481

934

0.28

2147

282

-‐1.46

0.50

1.52

1.88

z030

0.28

1847

641

1.69

888E-‐05

0.00

0793

785

0.03

2709

185

1535

0.28

1824

590.59

0.59

1.96

2.21

z034

0.28

2097

012

1.77

455E-‐05

0.00

0489

485

0.02

2228

686

737

0.28

2090

238

-‐7.88

0.62

1.61

2.13

z037

0.28

2129

357

1.38

878E-‐05

0.00

0510

464

0.02

0558

369

1219

0.28

2117

616

3.87

0.49

1.56

1.77

z038

0.28

1546

161.96

952E-‐05

0.00

0986

088

0.04

1878

389

1767

0.28

1513

132

-‐5.21

0.69

2.39

2.74

z041

0.28

2225

895

1.64

372E-‐05

0.00

0665

252

0.03

0921

518

1004

0.28

2213

318

2.44

0.58

1.44

1.69

z047

0.28

2145

357

2.35

393E-‐05

0.00

1447

215

0.07

5056

178

1334

0.28

2108

903

6.14

0.82

1.58

1.72

z049

0.28

2147

744

1.48

591E-‐05

0.00

0362

306

0.01

6141

752

942

0.28

2141

326

-‐1.51

0.52

1.53

1.89

z055

0.28

1863

244

1.52

271E-‐05

0.00

0875

815

0.03

7530

102

1538

0.28

1837

752

1.14

0.53

1.95

2.18

z058

0.28

2074

451.76

259E-‐05

0.00

0728

349

0.03

0412

769

1212

0.28

2057

797

1.59

0.62

1.65

1.90

z062

0.28

2074

451.76

259E-‐05

0.00

0728

349

0.03

0412

769

1285

0.28

2056

782

3.20

0.62

1.65

1.86

z071

0.28

1831

448

2.07

086E-‐05

0.00

0967

468

0.04

4511

878

1730

0.28

1799

722

4.13

0.72

1.99

2.15

z079

0.28

2135

704

1.71

096E-‐05

0.00

0616

412

0.02

7351

2311

980.28

2121

782

3.53

0.60

1.56

1.77

z084

0.28

2089

312

1.61

23E-‐05

0.00

0679

821

0.03

0568

744

1245

0.28

2073

337

2.89

0.56

1.63

1.85

z091

0.28

2035

447

1.65

051E-‐05

0.00

0935

264

0.03

9804

688

1368

0.28

2011

283

3.44

0.58

1.71

1.91

z096

0.28

2216

111

1.67

121E-‐05

0.00

0413

965

0.01

8880

685

949

0.28

2208

721

1.04

0.58

1.44

1.74

z099

0.28

1939

656

1.59

746E-‐05

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Chapter 6: An inconvenient truth: Multiple geomagnetic reversals in the Neoproterozoic–Cambrian Alto Paraguay Group, Amazonian Craton, Brazil.This chapter is under review as:McGee, B., Trindade, R.I.F., Collins, A.S. and Tohver, E., Under review. An inconvenient truth: Multiple geomagnetic reversals in the Neoproterozoic–Cambrian Alto Paraguay Group, Amazonian Craton, Brazil. Precambrian Research.

115

Chapter 6 An inconvenient truth: multiple geomagnetic reversals in the Alto Paraguay Group

An inconvenient truth: Multiple geomagnetic reversals in the Neoproterozoic–Cambrian Alto Paraguay Group, Amazonian Craton, Brazil

Ben McGee*a, Ricardo I.F. Trindadeb, Mariana Rossafab, Alan S. Collinsa, Eric Tohverc

*Corresponding author. Tel: +61 8 8303 4971, fax: +61 8 8303 4347, email: [email protected] for Tectonics, Resources and eXploration (TRaX), School of Earth and Environmental Sciences, Mawson Building, The University of Adelaide, SA 5005, AustraliabDepartamento de Geofísica, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, 05508-090, São Paulo, BrazilcSchool of Earth and Environment, University of Western Australia, 35 Stirling Highway, Crawley, WA, 6009, Australia

A B S T R A C T

We present new palaeomagnetic data from the siliciclastic Alto Paraguay Group (northern Paraguay Belt, Brazil) that overlies Marinoan-aged glacial diamictites and cap carbonates of the SE Amazonian craton. The sandstones and mudstones of the Raizama, Sepotuba and Diamantino formations preserve a dual polarity palaeomagnetic direction (Component A) that is similar to that reported from the underlying cap carbonate rocks. Given the large duration of time between these deposits, a negative fold test, and their similarity to the Mesozoic-to-present day field direction, we interpret these results to represent a secondary magnetisation, likely acquired during regional emplacement of Jurassic basalt. This finding is significant because results from the cap carbonate have been used to suggest Amazonia was at low latitudes during the Ediacaran, which has implications for the snowball earth hypothesis and the tectonic evolution of the Paraguay Belt. A second palaeomagnetic direction (component B) is present in only four samples of the Diamantino Formation, but does not correspond to any known or expected direction for the Amazon craton. A third palaeomagnetic direction (component C) isolated from the E-W trending portion of the curved Paraguay Belt is similar to a late-Cambrian overprint observed in the carbonates of the underlying Araras Group. The presence of this dual polarity, post-folding result in the Raizama Formation indicates that the Raizama Formation had already been deposited, folded, and remagnetised prior to oroclinal bending of the Paraguay Belt.

Keywords:

Gondwana

Palaeomagnetism

Paraguay Belt

snowball Earth

Alto Paraguay Group

1. Introduction

Since its development, palaeomagnetism has provided us with information about Earth’s ancient magnetic field stored in rocks, enabling us to track the movement of tectonic plates and giving an understanding of Earth’s

palaeogeography. The global reference frame provided by the ancient geomagnetic field has been used in tracking the assembly and break-up of supercontinents such as Gondwana (e.g. Collins and Pisarevsky, 2005; Tohver et al., 2006). In addition to their role in developing the theory of plate tectonics, more recently

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palaeomagnetic results have been used as part of the snowball earth hypothesis to suggest that low latitude continents and their associated glacial deposits provide evidence that the earth was completely covered in ice at least twice during the Neoproterozoic (Hoffman et al., 1998). The putative severity that these glaciations were so vast rests almost entirely on palaeomagnetic data, notably the existence of low-latitude, sea-level glacial deposits (Hoffman and Li, 2009). The hypothesis is that if ice sheets occurred at sea level in the warmest regions of the surface ocean (i.e. the equator), then higher latitudes and topography must have also been covered in ice.

To date, there are only a few palaeomagnetic results that locate Marinoan glacial deposits at low-latitudes. Palaeomagnetic data from the Elatina Formation in South Australia define a palaeopole and indicate that grounded ice near sea-level occurred in equatorial palaeolatitudes (Schmidt and Williams, 1995; Sohl et al., 1999). Evidence for glacial rocks at the palaeoequator are found in the Huqf Supergroup in Oman where glacial tillites and their associated cap carbonates have been found to be deposited within the tropics (Kilner et al., 2005). A third piece of evidence for low-latitude glaciation has been presented from the cap carbonate of the glaciogenic Puga Formation in Brazil (Trindade et al., 2003). This work suggested that the presence of stratabound reversal stratigraphy and high unblocking temperatures in the Araras Group carbonates meant that the observed magnetic remanence was primary, despite the close proximity of the observed direction to the present day field (PDF).

Here, we report new palaeomagnetic data from above the Araras Group, in the siliciclastic Alto Paraguay Group. We define three components from these data and show that the most well defined direction is similar to the pole presented by (Trindade et al., 2003) suggesting that this magnetisation is not ancient but more likely Jurassic in age. The other components are also presented and discussed in the context of the evolving Paraguay orocline.

2. Geological Setting

The northern Paraguay Belt, the focus of this work, is an oroclinal orogeny that is part of a large suture zone involving the Pampean Belt to the south and Araguiaia Belt to the north (Trindade et al., 2006). To the north of the belt lies the south-eastern margin of the Amazon Craton, but basement rocks do not outcrop in the belt itself. The belt is composed of folded and weakly metamorphosed (lowest greenschist facies) Neoproterozoic passive margin sedimentary strata, which occurred as the result of collision between Amazonia and proto-Gondwana. The siliciclastic rocks of the upper Alto Paraguay Group that were deposited in the foreland of the Paraguay Orogen record the final stages of this collision (Bandeira et al., 2011). This occurred during the Cambrian Period (Trindade et al., 2003), with the end of orogenesis marked by the intrusion of the post-tectonic granites into the base of the strata at 518 Ma (McGee et al., 2012). Palaeozoic sedimentary deposits of the Paraná Basin to the SW of the study region mark a period of intracratonic subsidence that lasted until the early Mesozoic. Early Jurassic tholeiitic basalt flows are also present, Tapirapuã Formation is intrusive into the north-western part of the belt (Figure 1a) and the Anari Formation lies some 400 km to the northwest (Monteslauar et al., 1994).

The strata comprising the northern Paraguay Belt are divided into three groups. The older pelites, diamictites and siliciclastics of the roughly 4–6 km thick Cuiabá Group lie in the core of the orogen (Barros et al., 1982). The relationship between the Cuiabá Group and glacial diamictites of the Puga Formation is currently poorly established, due to non-exposure of the contact. Consequently the two formations have been interpreted as either correlative, representing lateral facies variations along the continental slope (Alvarenga et al., 2009) or as unconformable (Nogueira et al., 2007). A maximum depositional age of 706 Ma for the Puga Formation is based on U-Pb SHRIMP ages from the Puga diamictite from the southern Paraguay Belt (Babinski et al., In press).

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Fig. 1. (a) Geological map showing lithostratigraphic relationships within the northern Paraguay Belt, modified from CPRM Cuiabá 1:1000000 map sheet (Barros et al., 1982). Formation codes correspond to those used in the CPRM map sheet. (b) Schematic stratigraphic section for the northern Paraguay Belt showing sample locations. Note: thicknesses of units are not to scale.

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A thick package of carbonates belonging to the Araras Group overlie the Puga Formation and are subdivided into four formations. The basal cap carbonate, the Mirrasol d’Oeste Formation, is followed by limestone and shale of the Guia Formation, dolostone and dolomite breccias of the Serra do Quilombo Formation and dolostone, chert, sandstone and lime mudstone of the Nobres Formation. The base of the Araras Group is constrained by Pb-Pb whole-rock isochron ages of 627 ± 30 Ma (Babinski et al., 2006) and 633 ± 25 Ma (Alvarenga et al., 2009), consistent with chemostratigraphic correlation to the post Marinoan glaciation (Nogueira et al., 2007).

The glacially influenced Serra Azul diamictite rests unconformably on top of the Araras Group carbonates and is inferred to be related to the Gaskiers glaciation (Alvarenga et al., 2007; McGee et al., Under review). Mudstones overlying the Serra Azul diamictite signify a postglacial transgression and the coarsening upward nature of this sequence indicates a progressive filling of the basin with a gradual transition to the overlying siliciclastics of the Alto Paraguay Group. The Raizama Formation is composed of siltstones, sandstones and pebble conglomerates deposited on a storm and tidally influenced platform. Marine deposition ceased shortly after this and final deposition within the restricted Diamantino lake is recorded by red shales, siltstones and arkoses of the Diamantino Formation (Bandeira et al., 2011).

The age of the Alto Paraguay Group is poorly constrained due to the lack of volcanic layering, however, a recently reported maximum depositional age from prograding deltaic lobes of the Diamantino indicated they formed after 541 Ma (Bandeira et al., 2011). No fossils or trace fossils have been reported from the Alto Paraguay Belt. While few direct age constraints are available for the Paraguay Belt, the maximum depositional age of the Puga diamictite is 706 ± 9 Ma based on the age of the youngest detrital zircon (Babinski et al., In press).This result precludes it from being Sturtian in age and suggests that it is a correlative of the ~635 Ma Marinoan glaciation. This conclusion is supported by

both the δ13C (5.0‰) and the 87Sr/86Sr (0.7080) ratios from carbonates directly overlying the diamictites (Nogueira et al., 2003). Available radiometric ages for the Alto Paraguay Group include a Rb-Sr clay age of 569 ± 20 Ma from the Sepotuba and Diamantino formations (Cordani et al., 1978) and a detrital U-Pb age for the upper Diamantino Formation of 541 ± 7 Ma (Bandeira et al., 2011).

Previous palaeomagnetic work in the Paraguay Belt has focused on the carbonates overlying the Marinoan Puga diamictite (Tohver et al., 2010; Trindade et al., 2003). Trindade et al. (2003) provided evidence for multiple geomagnetic reversals in this group and used their results to imply a low-latitude Amazonia at ca. 520 Ma. Tohver et al. (2010) showed that early thrusting in the Paraguay Belt was associated with clay mineral transformations and chemical remagnetisation of carbonates in the Araras Group at ca. 528 Ma. Tohver et al. (2010) also showed that oroclinal bending of the Paraguay Belt was caused by a 90° clockwise rotation of the east-limb some time after 528 Ma.

This curvature results in NNW-SSE structural trends in the south to NNE-SSW and east-west structural trends in the north of the belt (Figure 1a). Structurally, the belt can be divided into two domains; the undeformed to weakly-deformed fringe at the edge of the Amazonian Craton where primary layering is often only gently tilted by 10–20°. The second domain in the core of the orogeny hosts tight regional scale folds and thrusts (Figure 1a). Here, we have divided the belt into three structural sectors; sector 1, the NNE-SSW trending part of the belt, sector 2, the NE-SW trending part of the belt and sector 3, the E-W trending portion of the belt.

3. Methods

Palaeomagnetic samples were collected in the field both as oriented hand samples and Pomeroy drill cores. Sample sites were selected based on their stratigraphic (temporal) position (Figure 1b) within the Alto Paraguay Group and lateral position within the northern Paraguay Belt. Spatial cover of the belt is

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good with data from the southernmost part of the belt to its inflection point and out to the east (Figure 1a). Only sites with fresh rock were sampled. All samples were oriented in the field using a magnetic compass and sun compass. Laboratory work was conducted at the Institute of Geophysics at the University of São Paulo in Brazil. Hand samples were drilled into cores of 2.2 cm diameter and cut to the same length. Drilled core samples were cut to the same length.

The natural remanent magnetism (NRM) for all specimens was subsequently measured using an Agico JR6A Spinner Magnetometer, set to manual mode (4 positions, velocity = 87.7 rev./sec.) to allow for increased sensitivity. This information was used to separate 3 specimens from each site with the highest NRM to conduct a pilot study. Two specimens were thermally demagnetised, in 18 steps, at increments of 100°C, 50°C and 20°C respectively up to 700°C where necessary. The other specimen was demagnetised in 13 steps, at increments of 5−10 mT up to a maximum of 100 mT in an alternating field using an Agico LDA3A demagnetiser in tumbling mode. After each demagnetisation step the direction and intensity of magnetisation was measured on the spinner magnetometer. At the completion of this pilot study these data were used to decide which sites were suitable for AF demagnetisation (i.e. those that completely demagnetised in the AF) and which sites required demagnetising thermally (sites that didn’t demagnetise completely under the AF).

The direction and magnetic intensity of specimens in the second suite of samples were measured using a 2G cryogenic magnetometer. AF demagnetisations were also conducted on this instrument, this time in 25 steps, with intervals of 2−10 mT. The increments for thermal treatment remained the same as in the pilot study.

Data processing and principal component analysis was conducted using Agico’s Remasoft 3.0. Linear segments were chosen from Zijderveld plots and used to calculate vectors for each specimen. The segment corresponding to a stable magnetization was selected whilst concurrently considering the

demagnetisation path on both orthogonal plots and equal area projections.

Thermomagnetic properties were measured with a CS4 apparatus coupled to an Agico Kappabridge KLY-4 in order to characterise the magnetic carriers in the samples. One specimen per site was selected for analysis and magnetic susceptibility was measured in a step-wise fashion in a low temperature domain (-200°C−0°C) and high temperature domain (0°C−700°C) over a period of 60 minutes in an Argon atmosphere.

4. Results

4.1 Demagnetisations

Demagnetisations for the Alto Paraguay Group samples are presented in Figures 2 – 4. The samples generally carry a weak natural remnant magnetisation (NRM) of around 0.5–1 x 10-3 Am-1. 226 of the samples (287 samples from 29 sites) yielded stable magnetisations, with three principal clusters observed. In the following discussion, clusters of similar palaeomagnetic directions are presented together, and these clusters generally correspond to geographic location of the sites.

Demagnetisation of specimens of the Raizama and Sepotuba formations in sector 1 produced 71 stable results. The stable magnetisation is commonly uni-vectorial (Figure 2) and general ranges for the unblocking temperature are typically between 500°C and 580°C. Orthogonal plots generally show tightly clustered, stable demagnetisations despite their low NRM (Figure 2). The resulting directions are predominantly moderately upward plunging to the north or shallowly plunging to the south/south-east (Figure 2). Grouping these results together reveals a single magnetic component that is stable until temperatures of 640 °C (Figure 2).

Specimens from sector 2 of the Raizama and Diamantino formations revealed 73 stable magnetisations. The range of unblocking temperatures is typically 500°C – 600°C or up to 50mT. Both single and bi-vectorial magnetisations were found in specimens from

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Fig. 2. Demagnetisation patterns for Alto Paraguay Group samples from sector 1 that comprise component A. Open and closed circles represent positive and negative directions in stereonets and vertical and horizontal directions in orthogonal plots respectively.

sector 2 (Figure 3 a–c and d–f respectively). The uni-vectorial magnetisations are shallowly northward dipping, upward or downward, and have steady demagnetisation patterns. The bi-vectorial specimens also preserve this shallow, northward dipping component in addition to a high temperature secondary component that is slightly steeper and dips west-northwest. The demagnetisation patterns revealed in the stereograms in Figure 3d–f are characteristic of progressive removal of a magnetic overprint to reveal a more ancient magnetisation.

Specimens from sector 3 belong to the Raizama and Sepotuba formations and produced 82 stable magnetisations. The stable magnetisations are a both uni-vectorial (Figure 4b,c & e) and multi-vectorial (Figure 4a, d & f). Unblocking temperatures are usually high at around 580°C – 680°C and directions are typically tightly clustered in the stereograms until these temperatures are reached (Figure

4). The characteristic directions revealed by these sites are dual polarity, either steep and upward to the northwest and downward to the southeast.

4.2 Magnetic Mineralogy

Despite low susceptibility values for the majority of the Alto Paraguay Group samples, it is still possible to infer information about their mineralogy from thermomagnetic and demagnetisation curves. In the high temperature curves, a number of sites reveal one prominent inflection at around 600°C (Figure 5a & b). After this point, susceptibility values drop significantly to near-zero at around 680°C—the Curie temperature of hematite. The Morin transition at -20°C—indicative of hematite—is observed in a number of the corresponding low temperature curves (e.g. Figure 3a and b). Thermal demagnetisation

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Fig. 3. Demagnetisation patterns for Alto Paraguay Group samples from sector 2 that comprise components A and B (represented by grey rectangles in orthogonal plots). Open and closed circles represent positive and negative directions in stereonets and vertical and horizontal directions in orthogonal plots respectively.

curves presented in Figure 5a and b show that complete removal of the magnetic field from these samples is only achieved after 680°C, confirming hematite as the magnetic carrier in these samples. These specimens correspond to those discussed previously in section 4.1 indicating that hematite is the carrier for the secondary magnetic component in Figure 3d–f.

The AF demagnetisation curve presented in Figure 5c shows a significant decay in intensity from 0−20 mT, typical of the mean destructive field of magnetite. Coupling these observations with the lack of a Morin transition in the low temperature curve but a Curie temperature of 680°C suggests that both magnetite and hematite are the magnetic carriers. A portion of the high temperature curves display non-reversible behaviour (e.g. Figure 5d). In this example the cooling curve in the high

temperature plot exhibits a Curie temperature of 580°C. A subtle Verway transition (-153°C) is observed in the low temperature curve and the complete loss of magnetic intensity by 100°C indicates the growth of secondary magnetite during heating.

4.3 Magnetic Components

Characteristic directions for each sector were selected and are represented in Figure 6 with the corresponding data in Table 1. 120 of the 226 stable samples were used to define three magnetic components.

The combination of directions from sector 1 and sector 2 (Figure 6a) produce a dual polarity component (A), with an upward directed cluster at -14/350 and a downward cluster at 20/164. These data fail the fold test (Figure 7) indicating component A is an overprint

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younger than the regional folding and rotation of the Paraguay Belt. Sector 2 data also contain a weakly defined, high temperature hematite component (B) at 17/309 (Figure 6b). These data also fail the fold test (Figure 7), owing to the small sample population defining this component. Sector 3 defines a steep dual-polarity component C (Figure 6c), dipping upward at 85/300 and downward at 75/160. While the tilt corrected data are more tightly clustered, signified by a higher kappa value after 100% tilt correction (Figure 7), they do not fall within the range of which kappa is statistically significant at the 95% confidence level and thus produce a negative test. This indicates that magnetisation of component C was most likely acquired after tilting.

In addition to the above precision tests for components A–C, stability tests were carried out on components A and C by determining if the mean of their normal and reversed-

polarity constituents were non-unique. Figure 8 shows the results of these reversal tests with the normal polarity analyses plotted against the transposed reversed-polarity analyses and their means represented by large black and grey circles respectively, surrounded by their α95 circles. Component A (Figure 8a) passes the reversal test for both the in situ and tilt corrected data—since the means are not distinct at the 5% significance level—indicating that the two means in each stereonet represent the same population. Component B fails the reversal test for the in situ data but gives a positive reversal test for the tilt corrected data (Figure 8b).

5. Discussion

The negative fold tests outlined in Figure 7 indicate that all of the palaeomagnetic components defined here were obtained

Fig. 4. Demagnetisation patterns for Alto Paraguay Group samples from sector 3 that comprise component C. Negative and positive vectors are represented by open and closed circles respectively.

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Fig. 5. Selected thermomagnetic curves (high and low temperature domains) and demagnetisation curves for Alto Paraguay Group samples, showing predominance of hematite. In high temperature plots, heating and cooling curves are represented in black and grey respectively.

prior to folding within the northern Paraguay Belt. Component A (Figure 6a), which is defined from sectors 1 and 2, is similar to the Mesozoic-to-present day field directions shown in Figure 9. This component is also similar to the ‘component A’ presented by Trindade et al. 2003 from the cap carbonate of the Puga Formation. Based upon the available ages for this sequence and given that the results presented here from the Alto Paraguay Group lie stratigraphically at least 1500 m above the cap carbonates of the Puga Formation,

we estimate a maximum time gap of ~70 Ma between these components. Two main possibilities exist to explain these observed similarities, the first being that the position of the Amazon Craton was the same at the time of deposition of both the cap carbonate to the Puga Formation and the overlying Alto Paraguay Group sediments. This could either be through lack of movement of the craton or through a drift history that re-located it into a similar position.

The second possibility, the one we find more

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Fig. 6. Characteristic remanent directions from individual specimens defined by principal component analysis, both in situ (left) and tilt cor-rected (right). Small open and closed circles represent negative and positive vectors respectively, black and grey circles are from sector 1 and 2 respectively. (a) Component A from sector 1 and 2. (b) Component B from sector 2. (c) Component C from sector 3.

Fig. 7. Fold tests for Alto Paraguay Group components. Open squares, triangles and circles represent components A, B and C respectively.

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Fig. 8. Reversal tests for components (a) A and (b) C. Negative and positive vectors are represented by open and closed circles respectively.

likely given the large duration of time between these deposits, a negative fold test, and their similarity to the Mesozoic-to-present day field directions, is that these results represent a secondary magnetisation. We propose that this magnetisation was acquired during regional emplacement of the Tapirapuã tholeiitic basalt at around 197 Ma, which intrudes into the north-western margin of the northern Paraguay Belt (Figure 1a). A Jurassic age for remenance acquisition is consistent with the observation of multiple reversals, given the large number of polarity shifts during this geological period (Ogg et al., 2008).

The observation of multiple polarity reversals in the Puga Formation cap carbonate was used as evidence by Trindade et al. (2003) to suggest that magnetisation was primary and that their occurrence over ~20 m of the cap carbonate suggested a large time interval for deposition, much larger than that hypothesised by the rapid deglaciation model of Hoffman et al. (1998). The apparent stratabound reversals of Trindade et al. (2003) could well have

obtained this pattern of magnetisation during the Jurassic given the chances for multiple overprints by the changing magnetic field.

The pole produced from the results of Trindade et al. (2003) has been used as evidence to suggest that Amazonia and the related glaciogenic deposits of the Puga Formation were deposited at low-latitudes. A fundamental requisite of the snowball earth hypothesis is that if glaciers existed at low latitudes they would produce a runaway albedo feedback effect that would see the whole world covered in ice (Hoffman et al., 1998). Our results suggest that the data presented by Trindade et al. (2003) should be used with caution when assigning a low latitude position for the Amazon Craton.

Component B is certainly resolvable in some samples of the Raizama and Diamantino from sector 2. However, at this stage it is poorly resolved with too few data points to be regarded as an accurate recorder of the geomagnetic field. In addition, its failure of a fold test leads us to decline from draw

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conclusions about its meaning.The final component resolved here,

component C from sector 3, also produced a negative fold test, and as such we interpret that magnetisation was acquired after regional folding within the northern Paraguay Belt. However, the reverse component represented by these data are at ~90° to the 525 Ma reference direction presented by Tohver et al. (2010). Tohver et al. (2010) used their results from the underlying Araras Group to show that oroclinal bending of the Paraguay Belt was caused by a 90° clockwise rotation of the east-limb some time after 528 Ma. Our results corroborate these data and as such, we interpret that the Raizama Formation in sector 3 was deposited, folded and remagnetised with the Araras Group. Subsequently this whole package was rotated about a vertical axis by ~90° producing the presently observed orocline, most likely in response to the shape of the Amazon Craton. Due to a lack of fresh outcrop it was not possible to sample the Diamantino Formation in sector 3, which may have facilitated an investigation of the timing of deposition and rotation of the Diamantino Formation. Recent stratigraphic work by McGee et al. 2012 does, however, indicate that the Alto Paraguay Group is a continuous sequence with no obvious unconformities. This observation suggests that the Diamantino was also deposited, folded, magnetised and

rotated with the Araras Group.

6. Conclusions

This study presents new palaeomagnetic data from siliciclastic rocks of Alto Paraguay Group, overlying Marinoan cap carbonates, from the northern Paraguay Belt in Brazil. Component A, which fails the fold test and is nearly identical to the PDF and other Mesozoic-to-present day directions is also similar to the directions provided by Trindade et al. (2003). The pole of Trindade et al. (2003) has been used to suggest Amazonia was at low latitudes at the time of the Puga (Marinoan) glaciation and also has implications for the timing of Gondwana amalgamation (Trindade et al., 2006). Our results indicate that care should be taken when interpreting this magnetisation as primary, and thus the significance of the associated pole, given that we obtained similar results much higher in the stratigraphy of the Alto Paraguay Group. We advocate a much younger age for remagnetisation during the Jurassic, a reasonable conclusion given to the presence of a large tholeiitic basaltic intrusion into the north-west margin of the northern Paraguay Belt.

The other important conclusion of this work is that the results from the Raizama Formation in the east-limb of the belt (sector 3) corroborate with the post-folding, 90° rotation of the east limb of the northern Paraguay Belt found by Tohver et al. (2011).

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Pinho, F.E.C., 2007. Glacial diamictites of Serra Azul Formation (Ediacaran, Paraguay belt): Evidence of the Gaskiers glacial event in Brazil. Journal of South American Earth Sciences 23, 236-241.

Alvarenga, C.J.S.d., Boggiani, P.C., Babinski, M., Dardenne, M.A., Figueiredo, M.F., Santos, R.V., Dantas, E.L., 2009. The Amazonian Palaeocontinent, in: Gaucher, C., Sial, A.N., Halverson, G.P., Frimmel, H.E. (Eds.), Neoproterozoic-Cambrian Tectonics, Global Change and Evolution: a focus on southwestern Gondwana. Elsevier, pp. 15-28.

Babinski, M., Boggiani, P.C., Trindade, R.I.F., Fanning, C.M., In press. Detrital zircon ages and geochronological constraints on the

Fig. 9. Expected palaeomagnetic directions for Amazonia from the Cambrian to present day after Van der Voo (1993).

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Neoproterozoic Puga diamictites and associated BIFs in the southern Paraguay Belt, Brazil. Gondwana Research.

Babinski, M., Trindade, R.I.F., Alvarenga, C.J.S., Bogiani, P.C., Liu, D., Santos, R.V., Brito Neves, B.B., 2006. Chronology of Neoproterozoic ice ages in central Brazil, V South American Symposium on Isotope Geology, Punta del Este, Uruguay, pp. 303-306.

Bandeira, J., McGee, B., Nogueira, A.C.R., Collins, A.S., Trindade, R.I.F., 2011. Closure of the Neoproterozoic Clymene Ocean: sedimentary and detrital zircon geochronology evidence from the siliciclastic upper Alto Paraguai Group, northern Paraguay Belt, Brazil. Gondwana Research.

Barros, A.M., Silva, R.H., Cardoso, O.R.F.A., Freire, F.A., Souza Jr., J.J., Rivetti, M., Luz, D.S., Palmeira, R.C.B., Tassinari, C.C.G., 1982. Geologia. MME-SG: Levantamento de Recursos Naturais, Rio de Janeiro.

Collins, A.S., Pisarevsky, S.A., 2005. Amalgamating eastern Gondwana: The evolution of the Circum-Indian Orogens. Earth-Science Reviews 71, 229-270.

Cordani, U.G., Kawashita, K., Thomaz-Filho, A., 1978. Applicability of the rubidium-strontium methods to shales and related rocks, in: Cohee, G.V., Glaessner, M.F., Hedberg, H.D. (Eds.), Contributions to the Geologic Time Scale. American Association of Petroleum Geologists, Tulsa.

Hoffman, P.F., Kaufman, A.J., Halverson, G.P., Schrag, D.P., 1998. A Neoproterozoic snowball earth. Science 281, 1342-1346.

Hoffman, P.F., Li, Z.X., 2009. A palaeogeographic context for Neoproterozoic glaciation. Palaeogeography Palaeoclimatology Palaeoecology 277, 158-172.

Kilner, B., Mac Niocaill, C., Brasier, M., 2005. Low-latitude glaciation in the Neoproterozoic of Oman. Geology 33, 413-416.

McGee, B., Collins, A.S., Trindade, R.I.F., 2012. G’day Gondwana - the final accretion of a supercontinent: U-Pb ages from the post-orogenic Sao Vicente Granite, northern Paraguay Belt, Brazil. Gondwana Research 21, 316-322.

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Nogueira, A.C.R., Riccomini, C., Sial, A.C., Moura, C.A.V., Trindade, R.I.F., Fairchild, T.R., 2007. Carbon and strontium isotope fluctuations and paleoceanographic changes in the late

Neoproterozoic Araras carbonate platform, southern Amazon craton, Brazil. Chemical Geology 237, 168-190.

Nogueira, A.C.R., Riccomini, C., Sial, A.N., Moura, C.A.V., Fairchild, T.R., 2003. Soft-sediment deformation at the base of the Neoproterozoic Puga cap carbonate (southwestern Amazon craton, Brazil): Confirmation of rapid icehouse to greenhouse transition in snowball Earth. Geology 31, 613-616.

Ogg, J.G., G., O., Gradstein, F.M., 2008. The Concise Geologic Time Scale. Cambridge University Press, Cambridge.

Schmidt, P.W., Williams, G.E., 1995. The Neoproterozoic climatic paradox: equatorial paleolatitude for Marinoan glaciation near sea-level in South Australia. Earth Planet. Sci. Lett. 134, 107-124.

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Tohver, E., Cawood, P.A., Rosello, E.A., Jourdan, F., 2011. Closure of the Clymene Ocean and formation of West Gondwana in the Cambrian: evidence from the Sierras Australes of the southernmost Rio de la Plata craton, Argentina. Gondwana Research this volume.

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Tohver, E., Trindade, R.I.F., Solum, J.G., Hall, C.M., Riccomini, C., Nogueira, A.C.R., 2010. Closing the Clymene ocean and bending a Brasiliano belt: Evidence for the Cambrian formation of Gondwana, southeast Amazon craton. Geology 38, 267-270.

Trindade, R.I.F., D’Agrella-Filho, M.S., Epof, I., Brito Neves, B.B., 2006. Paleomagnetism of Early Cambrian Itabaiana mafic dikes (NE Brazil) and the final assembly of Gondwana. Earth Planet. Sci. Lett. 244, 361-377.

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Chapter 7: Key Outcomes and Future Research

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The following discussion outlines the key findings of this study, establishing the current field of knowl-edge regarding the break-up of Rodinia, the subsequent amalgamation of the supercontinent Gondwana and the glacial events of the time. It also outlines the potential future directions for further research within the context of this thesis.

The rift-related, Cryogenian-aged Toekems Sub-basin provides a unique exposure of the Nauuwpoort and Chuos formations and insight into the inter-relationship between Rodinian rifting and glaciation. The 763 Ma pegmatite cross-cutting the basal breccia adds to the suite of ages constraining initial rifting and open-ing of the basin. The overlying package of dominantly siliciclastic marine sediments that fills the Toekems Sub-basin is most likely equivalent to the Chuos Formation, based on apparent glacial influence, the pres-ence of iron-formation and stratigraphic position beneath the Rasthof cap carbonate. This correlation im-plies that the Naauwpoort Formation and Ugab Subgroup, are almost completely absent in this section, and hence that the unconformity spans a significant amount of time. Our new data provide evidence for multi-phase, middle Neoproterozoic extension on the south-western margin of the Congo Craton. Future studies in this area should focus on dating the felsic intrusives in the region to better constrain rifting and sedimentation within these basins.

The key outcome of chapter 2 is placing a minimum age constraint on the cessation of orogenesis within the northern Paraguay Belt. The Paraguay Belt in central South America is part of a larger chain of orogenic belts, including the Araguaia Belt to the northeast and potentially the Pampean Belt to the south that are interpreted amongst the youngest of the Gondwana amalgamation orogens. Placing a minimum age con-straint on this deformation is achieved via dating the post-orogenic São Vicente Granite, which crops out in the northern Paraguay Belt and cuts the basal unit of the deformed and metamorphosed sediments of the belt. Based on LA-ICPMS dating of more than 100 zircons from three separate samples we interpret a robust crystallisation age for the São Vicente batholith at 518 ± 4 Ma. This age constrains the termination of deformation within the Paraguay Belt and the final accretion of the supercontinent Gondwana. Dating crystallisation of this important intrusion proved challenging due to the presence of considerable common-Pb. Future studies should focus on removing this uncertainty from the age of this intrusive.

Chapter 3 of this thesis outlines the current field of knowledge for glacial deposits that are potentially of Gaskiers age (ca. 580 Ma) using the northern Paraguay Belt as a locality to document new evidence for glaciation at this time. Based on the observations in this chapter we infer that the canyon found at the São Sebastião section was most likely formed by a combination glacioeustatic drawdown and isostatic uplift due to glacial erosion. Given current geochronologic constraints and its stratigraphic location it appears that this glaciation is mid-Ediacaran in age and most likely associated with the ~582 Ma Gaskiers Forma-tion glaciation. Without suggesting that the Gaskiers glaciation was global in extent, the geological record certainly indicates a global record of glaciation and potentially related glacially incised valleys. In order to illu-minate our knowledge of this period, future work should focus on increasing the palaeomagnetic database for cratonic blocks at this time to gain a better understanding of their palaeogeography. A better idea of the stratigraphic relationships between these glacial deposits would also be beneficial, which could be made possible by an increased number of geochronological, chemo-stratigraphic and bio-stratigraphic studies.

In addition to elaborating on the sedimentology and stratigraphy of the previous chapter, chapter 4 also provides the first age constraints on the glacial sediments of the northern Parguay Belt, the Serra Azul Formation. The key finding is that these ages, when considered with other data, that the Serra Azul Formation developed in a mid-Ediacaran glaciation consistent with that expressed in the Gakiers Forma-tion of Newfoundland, Canada. Another key outcome is the presentation of a tectonic model based the new ages and sedimentological work showing the transition from a marine passive margin environment to a compressional setting where the Paraguay Belt developed as a peripheral bulge in the lithosphere of the Amazonian Craton.

Chapter 5 provides additional ages constraints on the northern Paraguay Belt, presenting the first com-prehensive detrital zircon study from the region. The ages from the top of this sequence, the Diamantino Formation, indicate final sedimentation in the Paraguay Belt began no earlier than 527 Ma. Based on the integrated U-Pb and Hf isotope data of detrital zircons presented here, potential sources for these sedi-ments are consistent with a predominantly Amazonian source until the early-Neoproterozoic at which point the signal becomes significantly more evolved and influence from the Paranapanema, and Goiás Massif to the east are inferred. Available evidence from Chapters 4 and 5 suggests that final sedimentation, defor-mation and metamorphism in the Paraguay Belt occurred between 540 and 510 Ma. Despite providing an excellent regional overview of the provenance of the sediments within the northern Paraguay Belt, a further study could certainly focus on finding volcanic horizons to provide more concise age constraints on sedi-mentation and glaciation within the belt.

The final chapter of this thesis presents new palaeomagnetic data from siliciclastic rocks of Alto Para-

Key Findings

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guay Group, overlying Marinoan cap carbonates. Our results indicate that care should be taken when inter-preting magnetisation of rocks in this region as primary, given that we obtained similar results to an earlier study much lower in the stratigraphy of the Alto Paraguay Group. We advocate a much younger age for remagnetisation during the Jurassic, a reasonable conclusion given to the presence of a large tholeiitic ba-saltic intrusion into the north-west margin of the northern Paraguay Belt. Future research in this area should focus on placing better constraints on the timing of magnetisation within these rocks.

Chapter 8: AppendixThe U-Pb zircon analyses and data presentation and interpretation were conducted by the PhD candidate and this chapter is published as:

Bandeira, J., McGee, B., Nogueira, A.C.R., Collins, A.S. and Trindade, R.I.F., 2012. Closure of the Neo-proterozoic Clymene Ocean: sedimentary and detrital zircon geochronology evidence from the siliciclastic upper Alto Paraguai Group, northern Paraguay Belt, Brazil. Gondwana Research.

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Chapter 8 Sedimentological and provenance response to the Cambrian closure of the Clymene Ocean

A Bandeira, J., McGee, B., Nogueira, A.C.R., Collins, A.S. & Trindade, R. (2012) Sedimentological and provenance response to Cambrian closure of the Clymene ocean: The upper Alto Paraguai Group, Paraguay Belt, Brazil. Gondwana Research, v. 21(2-3), pp. 323-340

NOTE:



http://dx.doi.org/10.1016/j.gr.2011.04.006

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