Major tectonic processes illustrated with examples from the Geology of Norway. Intro and overview of the Late Proterozoic to Permian tectonic evolution Baltica becomes a tectonic entity The margins of Baltica Early deformation along the Caledonian margin Ophiolites and island arcs - PowerPoint PPT Presentation
Major tectonic processes illustrated with examples from the Geology of Norway • Intro and overview of the Late Proterozoic to Permian tectonic evolution • Baltica becomes a tectonic entity • The margins of Baltica • Early deformation along the Caledonian margin • Ophiolites and island arcs • Towards continental collision and the Scandian orogeny • Late to post-orogenic tectonic processes • Late Palaeozoic continental rifting • Start of a new Wilson cycle
Transcript
Major tectonic processesillustrated with examples from
the Geology of Norway
• Intro and overview of the Late Proterozoic to Permian tectonic evolution
• Baltica becomes a tectonic entity• The margins of Baltica• Early deformation along the
Caledonian margin• Ophiolites and island arcs• Towards continental collision and the
Scandian orogeny• Late to post-orogenic tectonic
processes• Late Palaeozoic continental rifting• Start of a new Wilson cycle
OUTBOARD ACTIVITY:From the Ægir Sea to the
Iapetus and Tornquist Oceans
The oldest supra-subduction zoneophiolites and island-arc complexesin the Scandinavian Caledonides(`Group 1´) formed in this time-spanin the Early to MiddleOrdovician (495 to 465 Ma) whileBaltica started to drift northwardswith velocities up to ~10 cm/yr
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From: Torsvik & Rehnström 2002
Timanian
Plate-tectonic velocitiesof Baltica quantified by pal-mag. data (Torsvik & coworkers)
The outboard terranes:Upper and UppermostAllochthons
(Upm A): continental margin rocks including marbles of
Evidence for Early-Caledonian deformation and metamorphism is common in the outboard terranes
from Nordkapp to Stavanger70 N
65 N
60 N
10 E
30 E
OsloBergen
Tromsø
Trondheim
Stavanger
Example, Uppermost allochthon, Troms
Nordkapp The Scandian collision produced a nappe stack which can be traced along the entire belt: The Lower,
Middle, Upper and Uppermost allochtons
Corfu et al. in 2006, in press
460 MaMiddle Ordovician
Tromsdalstind eclogite
Early-Caledonian events; where and when?
Corfu et al. 2003
Middle Ordovician unconformity over the Lyngen ophiolite (Up Alloch) Eclogite facies metamorphism and deformation in the Tromsø region (Upm Alloch)
These events clearly occurred outboard of Baltica, and the rocks containing their record was emplaced ‘piggy-back’ during the Scandian collision
`Group 1´ type ophiolites and island-arc complexes:• Situated within the Upper Allochton between Karmøy in the south and Lyngen in the north• Ages spanning 495 to 465 Ma (within uncertainty) with the Leka, Karmøy ophiolites as the oldest and arc-plutons and volcancs as the youngest• Both spreding axis and arc-magmatism have geochemical subduction zone signatures
Karmøy
Bømlo/Stord
Bergen
Trondheim area
Otta-Foldal
Leka
Narvik
Lyngen
Gjersvik
Roberts et al. 2002
Subduction polarityaway from Baltica, eventuallybuild-up of mature arcs
From: Roberts et al. 2002
From: Pedersen 1992
AGE OF GROUP-1 OPHIOLITES/ISLAND -ARCS
Arc-related plutons
A slide with Norwegian ophiolite summary
The outboard terranes:Upper and UppermostAllochthons
(Upm A): continental margin rocks including marbles of
Evidence for pre - Scandian deformation and metamorphism is common in the outboard terranes
from North-Cape to Stavanger70 N
65 N
60 N
10 E
30 E
OsloBergen
Tromsø
Trondheim
Stavanger
Example, North Cape
Nordkapp
The North Cape story, when? Sedimentation until Early Silurian (Aeronian-438 Ma); syn-tectonic gabbro and granites (438-433 Ma);Peak Barrovian metamorphism (~436 Ma)RAPID TECTONIC EVOLUTION!
North cape
Andersen 1981
GarStaur
Kya
Sil
Corfu et al. in 2006, in press
Syn-tectonic gabbro
Syn-metamorphic granite
Early-Caledonian events; where? The Honningsvåg Igneous Complex has primary magnetization and is well dated (437.5-438.9 Ma)!
Flysch sedimentation, deformation, plutonism and metamorphism of early Silurian age near North Cape
The HIC palaeomagnetic data from Torsvik et al. 1992, reinterpreted with the new precise U/Pb ages from:
Corfu et al. 2006, JGS (in press)
THESE DATA SUGGEST THAT THE POSITION OF THE MAGERØY ROCKSIN THE LOWER SILURIAN WAS EQUATORIAL, AND MOST LIKELY CLOSE
TO THE LAURENTIAN MARGIN
440 Ma
Kirkland et al. 2005
The ‘Finnmarkian’ orogeny as originally proposed by Sturt, Ramsay and co-workers (including me) does not exist. The ‘Finnmarkian’ complexes comprise late-Proterozoic rocks related to the Timanian orogeny and pre-Caledonian rifting (now positioned in the Middle Allochthon) as well as overlying outboard rocks (Magerøy, Hellefjord, Lyngen) that belongs to the Upper Allochthon
MATURE ISLAND-ARCVOLCANIC AND COMPOSITEPLUTONIC COMPLEXESBUILD DURING THE MIDDLETO LATE ORDOVICIAN
Smøla-HitraUp Hovind Gp.
Sunnhordland
Bindal-Helgeland
First Scandian HP metamorphism ~ 424 ±
5Ma
U/Pb ages of intrusives and some volcanics,
compiled by Corfu et al. 2006, in press.
Outboard activity related to magmatic arcs and back-arc spreading in the Iapetus ocean
“Soft docking” of Avaloniabefore the Late Ordovician ?
Closure of the Tornquist Ocean
INTRA-ARC INCONFORMITIESBELOW MID-LATE SILURIAN
OR DEVONIAN CONGLOMERATES(UCF-3) IN SUNNHORDLAND
The telescoped Caledonian margin of Baltica
EARLY-CALEDONIAN (PRE-SCANDIAN) TECTONIC EVENTS ALONG THE
CALEDONIAN MARGIN OF BALTICA? 1 1) W-Finnmark, type area for
‘Finnmarkian’ now discredited. Caledonian deformation and metamorphism Finnmark is Scandian
22) Nordbotn (~500 Ma eclogites, these need to be dated again by more precise methods)
6
6) Jæren (eclogites of unknown age in Jotun nappe type rocks, same as Bergen eclogites, ie. early-Scandian or Baltica-Avalonia collision?)
7
7) Stratigraphy in foreland, clastic cromite, most likely from ophiolite in the lower middle Ordovician?
3
3) Seve-Jämtland (~454±4 Ma eclogites same age as Tromsø! Are these really in rocks of Baltic origin or are they outboard?)
4) Otta-Foldal-Røros (pre-470 Ma)
4
5) Atløy, W. Norway (Ar-450 Ma + strat.)
5
5) Atløy, W. Norway (Ar-450 Ma + strat.)
Silurian fossils
Def/met450 Ma
Stratigraphic (ucf + fossils) and geochronological evidence (Ar)for an early Caledonian event at 450 Ma, Sunnfjord area, W.Norway
Brekke and Solberg 1987Andersen et al. 1990, 1998,
Eide et al. 2000
1640 Maolder than450 Ma
443 Ma
428 Ma
5 km
Early-Caledonian events; the Baltica-Avalonia assembly
Tornquist Sea closure bysubduction under E-Avalonia
in ~455-440.
Geological evidence?Fauna provinciality between
Baltica and Avalonia disappears
Mid-Ordovician metamorphicages (Ar) in North-Sea
basement
Subduction magmatism in England - Wales
Kinnekulle K-bentonitea ~455Ma super-
volcano eruption producing~1000km3 ash
Deformation/metamorphismin nappes of SW.Norway
(Atløy, Jæren)?
From Torsvik & Rehnström 2003
IAPETUS IS CLOSING AND CONTINENTALCOLLISION TAKES OVER FROM THE WENLOCK
THE LATE-SILURIANFULL SCALE COLLISONBETWEEN BALTICA AND
