Saskatchewan Geological Survey 1 Summary of Investigations 2015, Volume 2

Athabasca Group + Martin Group = Athabasca Supergroup? Athabasca Basin Multiparameter Drill Log Compilation and

Interpretation, with Updated Geological Map Sean A. Bosman 1 and Paul Ramaekers 2

Parts of this publication may be quoted if credit is given. It is recommended that reference to this publication be made in the following form: Bosman, S.A. and Ramaekers, P. (2015): Athabasca Group + Martin Group = Athabasca Supergroup? Athabasca Basin multiparameter drill log compilation

and interpretation, with updated geological map; in Summary of Investigations 2015, Volume 2, Saskatchewan Geological Survey, Saskatchewan Ministry of the Economy, Miscellaneous Report 2015-4.2, Paper A-5, 13p.

This report is associated with the Data File Report entitled: Bosman, S.A. and Ramaekers, P. (2015): Stratigraphy of the Jackfish, Cree and Mirror basins from multiparameter drill logs, Athabasca Basin, Saskatchewan

(parts of NTS 64E, 64L, 74E to 74P); Saskatchewan Geological Survey, Saskatchewan Ministry of the Economy, Data File 39.

Abstract Multiparameter drill logs are useful for describing and delineating the strata of the stacked Jackfish, Cree and Mirror basins that comprise the present-day Athabasca Basin region. This paper presents an update of the stratigraphy of these stacked basins based on examination of 427 multiparameter drill logs. Stratigraphic picks that resulted from this examination are tabulated in Data File 39, a separate publication associated with this paper. In addition to the stratigraphic picks, contacts for the Quaternary and Phanerozoic cover, intrusive mafic to ultramafic rocks, and crystalline basement rocks are shown in the Data File. The standardized core logging procedures of the EXploration science and TECHnology initiative (EXTECH IV) and subsequent Saskatchewan Geological Survey stratigraphy programs were utilized, with more than twice the number of drillholes used than in previous compilations. The new picks, and consideration of regional correlations, further document and develop the revision of the EXTECH IV stratigraphic scheme. The main results of the present study are:

1) raising the Athabasca Group to supergroup status to include several unmetamorphosed, stacked sedimentary basins including the Martin, Jackfish, Cree and Mirror basins;

2) the recognition that the Martin Group and Fair Point Group share similar lithological characteristics that are related to extensional processes taking place during the Trans-Hudson Orogen;

3) raising the Fair Point, Manitou Falls, Lazenby Lake and Wolverine Point formations to group status; 4) inclusion of the Locker Lake to Carswell formations in the McFarlane Group, which is correlative both temporally and

lithologically with the Dismal Lakes Group in Nunavut and the Northwest Territories, further supporting elevation of the Athabasca succession to that of supergroup;

5) the recognition that the Read Formation forms a southeast- to northwest-trending trough that is the structural and depositional axis of the Cree Basin;

6) the correlation of several strata (e.g., Warnes, Hodge, Clampitt-Dunlop) across the Cree Basin, rendering some Manitou Falls Formation subunit names obsolete; and

7) raising the stratigraphic rank of several other formations and members.

An updated geological map of the Athabasca Basin region with the provisional changes based on these stratigraphic picks is included with this report as an ESRI ArcGIS shapefile.

Keywords: Athabasca Basin, stratigraphy, Paleoproterozoic, Athabasca Group, EXTECH IV, Athabasca supergroup, Jackfish Basin, Cree Basin, Mirror Basin, Martin Group

1 Saskatchewan Ministry of the Economy, Saskatchewan Geological Survey, 1000-2103 11th Avenue, Regina, SK S4P 3Z8 2 MF Resources Inc., 832 Parkwood Drive SE, Calgary, AB T2J 3W7

Although the Saskatchewan Ministry of the Economy has exercised all reasonable care in the compilation, interpretation and production of this product, it is not possible to ensure total accuracy, and all persons who rely on the information contained herein do so at their own risk. The Saskatchewan Ministry of the Economy and the Government of Saskatchewan do not accept liability for any errors, omissions or inaccuracies that may be included in, or derived from, this product.

Saskatchewan Geological Survey 2 Summary of Investigations 2015, Volume 2

1. Introduction The Athabasca Basin Ore Systems project is a multifaceted initiative of regional compilation work and new geoscience. The goal is to collect and interpret regional multidisciplinary data (e.g., stratigraphy, basement geology, clay mineralogy) from the Athabasca region and make them available as datasets compatible for GIS and 3-D display. This paper focuses on the Athabasca Stratigraphic Interpretation subproject, the goal of which is to construct a regional 3-D stratigraphic framework as a basis for other studies. Lithological data (e.g., maximum grain size of detritus, thickness of conglomerate units) collected through systematic logging of drillcore containing Proterozoic Athabasca Basin sedimentary rocks are the primary data used in this study. A detailed discussion regarding this logging method can be found in Bosman and Korness (2007). Lithological data are used to create multiparameter drill logs that provide a means to interpret and correlate the strata.

This paper discusses three results from this subproject: 1) a data file containing stratigraphic picks3 from the interpretation of multiparameter drill logs from the Athabasca Basin; 2) proposed4 nomenclature changes including elevation of Athabasca Group to supergroup; and 3) an updated geological map of the Athabasca Basin.

Discussion regarding the elevation of Athabasca Group status to supergroup is presented in section 3 of this paper; however, from this point forward the new term Athabasca supergroup5 will be used unless reference to the historical term is necessary.

2. Data File 39 a) Introduction Data File 39 (Bosman and Ramaekers, 2015) is a Microsoft® Excel spreadsheet containing stratigraphic picks for units of the Athabasca supergroup from 427 drillholes within the Athabasca Basin. This paper is based on the data contained in Data File 39 and, although it is being released as a separate product from this paper in order to permit future updates as new information becomes available, the reader is encouraged to download the data file and follow along while reading this paper.

b) Logging Method The stratigraphic picks in Data File 39 were determined from the multiparameter drill logs. This logging method, as applied to the Athabasca Group, was developed during EXTECH IV (Yeo et al., 2001) and was adopted by the Saskatchewan Geological Survey’s (SGS) Athabasca Basin stratigraphy programs. Some modifications to the logging technique have been made since EXTECH IV (Bosman and Korness, 2007; Bosman and Schwab, 2009), but the methods are sufficiently similar to allow the correlation of drill logs created during both programs. Within each logging interval (generally 1 to 3 metres), the following lithological parameters are recorded:

1) maximum transported grain size, representing the largest detrital grain in the interval; 2) intraclast thickness, measured by the total accumulated thickness of clay intraclasts; 3) total aggregate thickness of mudstones; 4) total aggregate thickness of interlaminated siltstones/mudstones and fine-grained sandstone (all referred to

as planar siltstones); 5) aggregate thickness of conglomerate, provided individual beds have a minimum thickness of 2 cm; and 6) number of fractures.

3 ‘Stratigraphic pick’ is an interpreted depth to the top and/or bottom of a stratigraphic horizon in a drillhole using geophysical, lithological or other data from the drill logs. 4 None of the changes to the stratigraphic hierarchy proposed in this paper have been formalized with the North American Commission on Stratigraphic Nomenclature (NACSN) (North American Commission on Stratigraphic Nomenclature, 2005); however, although terms such as ‘proposed’ or ‘suggested’ are only used sporadically in the text for ease of reading, the nature of the tentative hierarchy is nonetheless implied throughout the paper. 5 ‘Supergroup’ has not been formalized with the NACSN and therefore is not capitalized.

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c) SGS and EXTECH IV Drill Logs A total of 427 multiparameter drill logs were used in this study, of which 230 were generated by staff of the SGS since 2006. As part of the EXTECH IV research, data for roughly 250 drillcores were collected (Figure 1). Of these, 203 were logged using various forms of the EXTECH IV logging method, whereas the remaining 47 were logged in the more traditional way of picking intervals of varying lengths with consistent lithologic and sedimentologic characteristics. Of the 203 EXTECH IV drillcores logged, 197 were used in this study. The remaining 6 EXTECH IV multiparameter drill logs were relogged by the SGS. These duplicate drill logs were used to compare the logging techniques of the two programs, as discussed in Bosman and Korness (2007). Seventeen of the 47 drillholes logged in the traditional manner during the EXTECH IV program were relogged by staff of the SGS and included in the 230 count mentioned above. The raw systematic lithological logging data for all the multiparameter drill logs used in this study will be available in a future publication.

Figure 1 – Geological map of the Athabasca Basin region showing the distribution of drillholes presented in Data File 39. Drillcore logged by SGS staff are shown as blue circles; red circles are drillholes logged during the EXTECH IV program. Mines are denoted by yellow circles. Areas of Phanerozoic cover are shown by cross-hatching. Stratigraphic codes in this figure are explained in Table 1. Dark blue lines represent selected roads.

d) Compilation Process and Content To maintain a consistent interpretation between logs, the stratigraphy in each drill log was correlated to all neighbouring drill logs, as opposed to relying on correlation along drillhole fences, as is done in a cross-section. In some cases, correlated drillholes were only hundreds of metres apart; however, in the central and some other parts of the basin, the separation between correlated drillholes is commonly tens of kilometres to a maximum of 90 kilometres. Drillholes are also usually drilled in clusters with linear distributions, reflecting the locations of the target basement conductors. For these reasons, the standard stratigraphic practice of basing correlations on loops, rather than fences, of drillholes is not always practical, but this remains the goal. In addition to the units of the Jackfish,

Saskatchewan Geological Survey 4 Summary of Investigations 2015, Volume 2

Cree and Mirror basins, Data File 39 contains data on, if present, the depth of water, and thicknesses of overburden, intrusive mafic to ultramafic rocks, Phanerozoic rocks and crystalline basement, as well as the drillhole identification and location.

Still to be completed as part of the Athabasca Stratigraphic Interpretation subproject are basin-wide isopach maps, which may lead to further modifications of the stratigraphic picks presented in Data File 39; therefore, the authors suggest that the stratigraphic picks in Data File 39 be used as an interim dataset.

Table 1 – Stratigraphic column for the Athabasca supergroup. ‘Quaternary’, ‘Phanerozoic’ and ‘Crystalline Basement’ have been added to the table as a reference for Figure 1. WCSB – Western Canada Sedimentary Basin.

Basin Sequence Athabasca supergroup

Higher Rank [rock code]

Group [rock code]

Formation [rock code]

Member [rock code]

General Lithofacies Description

Quaternary [Q]

Glacial deposits

WCSB Phanerozoic [P]

Rocks of the Devonian and Cretaceous

Mirror III

Atha

basc

a sup

ergr

oup

McFarlane [MC]

Carswell [C] Siliciclastics and stromatolitic carbonate

Douglas [D] Mudstone, fine- to very fine-grained quartz arenite

Otherside [O]

Davy [Od] Pebbly quartz arenite and quartz arenite

Birkbeck [Ob] Quartz arenite

Archibald [Oa] Pebbly quartz arenite, quartz arenite

Locker Lake [LL]

Marsin [LLm] Pebbly quartz arenite Brudell [LLb] Conglomeratic quartz arenite Snare [LLs] Lower pebbly quartz arenite

Cree

II-4

Wolverine Point [W]

Claussen [Wc] Clay-rich quartz arenite, mudstone; arenite much more abundant than mudstone

Brule [Wb] Mudstone ± quartz arenite ± phosphatic hardgrounds, replaced tuff

Lazenby Lake [LZ]

Larter [LZl]

Pebbly quartz arenite, quartz arenite, siltstone + mudstone; arenite much more abundant than siltstone + mudstone

Shiels [LZs] Quartz arenite with pebbly layers

II-3

Manitou Falls [MF]

Clampitt-Dunlop [MFcl, MFd]

Upper

Clay-intraclast–rich quartz arenite, siltstone + mudstone (Dunlop and Upper Clampitt members); arenite more abundant than siltstone + mudstone

Lower Quartz arenite, minor pebbly quartz arenite, minor clay intraclasts

Hodge [MFh] Pebbly quartz arenite ± conglomerate

II-2

Warnes [MFw] Clay-intraclast–rich quartz arenite

Collins [MFc] Sandy member Quartz arenite Pebbly member Pebbly quartz arenite

Bird [MFb] Conglomeratic quartz arenite; one to five fining-up cycles

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Basin Sequence Athabasca supergroup

Higher Rank [rock code]

Group [rock code]

Formation [rock code]

Member [rock code]

General Lithofacies Description

II-1

Read [MFr] Three informal members

1) Conglomerate to mudstone; 2) quartz arenite; 3) quartz arenite with intraclasts. Multiple fining-up cycles proximally.

Smart [MFs] Quartz arenite, much of it fine grained, horizontally bedded

Jackfish I Fair Point [FP]

Beartooth [FPb] Pebbly quartz arenite Lobstick Island [FPl]

Conglomeratic quartz arenite

Martin

Extending sequences into the Martin Group will be considered in the future

Martin [MG]

Melville Lake Sandstone, siltstone, minor conglomerate

Seaplane Base Sandstone, conglomerate, minor siltstone

Gillies Channel Conglomerate, sandstone, mafic flows

Beaverlodge Conglomerate, arkose, minor siltstone

Taz Sandstone and conglomerate Pebble Island Conglomerate and sandstone Charlot Point Conglomerate, sandstone Jug Bay Siliceous sandstone/arkose

Crystalline Basement [CB]

Rocks pre-dating deposition of the Athabasca Group

Reilly Reilly [RY] Conglomeratic quartz arenite in the

Reilly Basin (deposition interpreted as contemporaneous with Manitou Falls Group)

3. Proposed Modifications to Athabasca Group Stratigraphy Since the EXTECH IV study, the understanding of the stratigraphy in the Athabasca Basin has improved and revisions have been proposed to the existing stratigraphic nomenclature (Ramaekers et al., 2010). Although a detailed paper regarding this updated classification has not yet been completed, Table 1 shows a preliminary version of the updated stratigraphic nomenclature. The stratigraphic order and codes in Table 1 correspond to those on the updated geological map (Figure 1) discussed in section 4 of this paper; however, both are currently considered preliminary in that several of the updated names need further study. The proposed changes include the merging of units, removal of repeated units, and elevating the stratigraphic rank of groups, formations and members. Many of the proposed changes outlined below were introduced in Ramaekers et al. (2010) and are expanded upon herein.

a) Changes in Stratigraphic Rank due to Raising the Athabasca Group to a Supergroup 1) The regional structure of the present-day Athabasca Basin consists of three superimposed basins—the

Jackfish, Cree and Mirror basins—separated by unconformities that mark major basin reconfiguration as originally defined by Ramaekers (1980). Since then, the basin shapes have been better defined as more drillhole data became available. The Jackfish Basin is now recognized as a northeast-trending trough underlying the west part of the Athabasca region; the Cree Basin has been defined as a northwest-trending trough that extends throughout the region; and the Mirror Basin, also trending northwest, is recognized as possibly a half-graben with its active margin along the southwestern side of the basin.

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2) In the earliest descriptions of the greenschist facies to non-metamorphosed sedimentary successions of northern Saskatchewan (Alcock, 1920, 1936; Blake 1956), the modern-day Thluicho Lake (-Nonacho), Martin and Athabasca groups were all lumped together as parts of an ‘Athabasca Series’. Although these three successions were subsequently distinguished from one another based on their degree of metamorphism and deformation, their current lithological make-up, and their different geographic locations, recent work has provided new ways of defining their stratigraphic relationships. The Thluicho Lake Group has been metamorphosed to greenschist facies, deformed numerous times, and is attributed to tectonic activity associated with the 2.0 to 1.9 Ga Taltson orogeny (Bethune et al., 2010). In contrast, the Martin Group has not been subjected to metamorphic conditions, has been regionally deformed only once, and is attributed to tectonic activity associated with the 1.9 to 1.7 Ga Trans-Hudson orogeny (Hajnal et al., 1996). With the exception of the phase of regional deformation, these characteristics have much in common with the former Athabasca Group. Therefore, one way of thinking of the Martin Group is that it represents sedimentary fill of the earliest of four stacked basins resulting from the Trans-Hudson orogeny; the latter three being the Jackfish, Cree and Mirror basins that comprise the current Athabasca Basin. Viewed this way, it makes sense to incorporate the Martin Group into the former Athabasca Group, which, together with the other stratigraphic changes suggested below, justifies elevation of the Athabasca Group status to supergroup. It has been previously suggested that the Martin Group is broadly correlative with the Baker Lake Group of the Dubawnt Supergroup of Nunavut and the Northwest Territories (Rainbird et al., 2003; Ashton et al., 2009), just as the Athabasca Group is considered to be correlative with the Thelon Group (Barrensland Formation of the Dubawnt Supergroup; Rainbird et al., 2003). Thus, the new Athabasca supergroup (ca. 1.84 to ca. 1.54 Ga; Creaser and Stasiuk, 2007; Ashton et al., 2009) comprising the Martin, Jackfish, Cree and Mirror basins is analogous to the 1.85 to 1.50 Ga Dubawnt Supergroup of the Baker Lake area of Nunavut (Rainbird and Hadlari, 2000; Rainbird et al., 2007; Chamberlain et al., 2010). The Dismal Lakes Group of the Hornby Bay Basin in Nunavut and Northwest Territories (Baragar and Donaldson, 1973) is a close correlative in time and lithological make-up to sequence III (Table 1) of the Athabasca supergroup, which contains the Locker Lake to Carswell formations (Ramaekers et al., 2010). The difference in lithology between Athabasca sequences II and III is enough to warrant a separate McFarlane Group, and to elevate the Athabasca Group to supergroup status, but doing so makes inter-regional comparisons easier as well. To accommodate this change, a number of formations are raised to group status, and most members are raised to formation status. Here we mainly restrict the discussion in this paper to the strata of the Jackfish, Cree and Mirror basins.

3) Sequence I (Table 1), consisting solely of the Fair Point Formation, is raised to group status. The Fair Point Group consists of the Lobstick Island and Beartooth formations, both raised from member status. Note that the name Lobstick of Ramaekers et al. (2007) is here amended to Lobstick Island, because the Lobstick Member of the Late Devonian Nisku Formation has priority (Glass, 1990). The Fair Point Group comprises the fill of the Jackfish Basin, a northeasterly trending trough underlying the western part of the overlying Cree Basin. The precise age of the Fair Point Group is currently unknown but it has a maximum depositional age constraint of 1810 Ma, based on the youngest detrital 207Pb/206Pb zircon age (Rainbird et al., 2007). At the time of deposition it had an arkosic composition (Ramaekers, 1981) similar to that of the Martin Group, but after intense diagenesis now contains abundant clay pseudomorphs of the original feldspars, whereas the Martin Group still contains abundant feldspathic detritus. This contrasts with the material infilling the Cree and Mirror basins, which was largely quartz arenites and sublithic arenites at their time of deposition (Ramaekers, 1981). The Jackfish Basin’s northeast-trending structural orientation is similar to that of the largest known exposures of the Martin Group, which outcrop along the northeast-trending Black Bay fault; however, the Taz Formation (Table 1, Figure 1) of the Martin Group has a more west- to northwest-trending orientation, suggesting the regional extent of the Martin Group was once much larger. The Fair Point Group is not deformed to the same degree as the Martin Group, with the latter being much more fault controlled. Although a precise deposition age for the Fair Point Group has not been documented, sedimentation may have coincided with an extensional period related to intrusion of the Kivalliq Igneous Suite between 1.77 and 1.73 Ga (Peterson et al., 2015) inboard of margins of the Trans-

Saskatchewan Geological Survey 7 Summary of Investigations 2015, Volume 2

Hudson Orogen undergoing postcollisional deformation further to the east and southeast (Machado, 1990; Hajnal et al., 1996). Timing of Martin Group deposition is similarly uncertain but may have been initiated through extension due to the east-west shortening during accretion of the Nahanni-Fort Simpson terrane ca. 1.84 Ga (ibid.). Deposition continued through to 1.82 Ga, the time of the emplacement of the Gillies Channel mafic rocks, and ceased prior to the completion of D4 deformation (Ashton et al., 2009).

4) The sequence overlying the Fair Point Group includes the Manitou Falls, Lazenby Lake and Wolverine Point groups (all raised from formation status), which comprise the material infilling the Cree Basin (Table 1). The Manitou Falls Group consists, from base to top, of the Smart, Read, Bird, Collins, Warnes, Hodge and Clampitt-Dunlop formations. All these formations were raised from member status except Smart and Read, which were previously formations. These formations together represent the original Manitou Falls Group as first defined (Ramaekers, 1979, 1990), and represent all the main alluvial fans. The Lazenby Lake Group consists of the Shiels and Larter formations, raised from member status, and are interpreted as paralic deposits (alluvial plain, coastal deposits). The Wolverine Point Group consists of the Brule and Claussen formations, raised from member status, and are interpreted as deltaic, lacustrine, sabkha, and minor eolian deposits.

5) The McFarlane Group, introduced in Ramaekers et al. (2010), consists of the Locker Lake, Otherside, Douglas and Carswell formations. The McFarlane Group is correlative to the Dismal Lakes Group of the Hornby Bay Basin in Nunavut and Northwest Territories. This group comprises the fill of the initially rapidly subsiding Mirror Basin.

6) The Reilly Formation is preserved near the contact between the Wathaman Batholith and the Rottenstone Domain, and consists of fluvial pebbly quartz arenites similar in lithology to the Bird and Collins formations of the Manitou Falls Group. Its location and southwest paleocurrent directions show that it did not form part of the Cree Basin, and it is regarded here as the only known remnant of the Reilly Basin (Table 1).

b) Changes due to Improved Correlation Between the Eastern and Western Athabasca Basin Stratigraphic correlations in the Athabasca Basin are based on linear interpolation of lithological data, paleocurrent data, and the assumption that the area was generally not deformed. Since the EXTECH IV program, increased availability of drillcore has permitted better correlation across the basin. Details of these changes are discussed below and shown in Table 2.

1) The Smart Formation unconformably overlies the Fair Point Group and underlies the Read Formation. It may represent the dominantly eolian and fluviatile reworking of the underlying Fair Point Group (Bosman et al., 2013).

2) The Read Formation is the first fully developed compound fining-up sequence of the Manitou Falls Group. It developed in a northeast-trending trough that forms the base of the Cree Basin, with the greatest thickness and much of the conglomeratic material more or less confined to this trough. Three informal members may be identified: 1) basal conglomeratic quartz arenite with interbedded mudstones, 2) a quartz arenite–dominated member that has the widest lateral extent of the Read Formation, and 3) an upper quartz arenite member with some clay intraclasts that is mainly confined to the central trough. The Read Formation is relatively easy to trace through the northwest trough to the western third of the basin. Farther northwest, similar to the overlying Bird Formation, the grain size of the Read Formation becomes finer, and both units become more difficult to correlate, although they do seem to extend to the northern side of Lake Athabasca. Ongoing work suggests that the Read Formation does not extend to the northeast quarter of the Cree Basin. The Smart and Read formations form the first major sub-sequence of the Cree Basin fill (Sequence II-1: Table 1).

3) The Bird Formation may be traced through most of the Cree Basin, with its defining conglomerates ranging from medium pebble conglomerates in the east of the basin to granule conglomerates at its western limit. From one to five fining-up cycles are present in cores, with many cores showing a distinct sandier section in

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the middle of the fining-up cycles. The Bird Formation in the northern third of the basin was deposited in the Moosonees deposystem (Ramaekers et al., 2007), in which pebble sizes are smaller overall compared to the Ahenekew and Karras deposystems, but in which small pebbles were carried in all units of the Manitou Falls Group. Ongoing work suggests that the Bird is the basal unit of the Athabasca supergroup in the northeastern part of the Cree Basin.

4) The Collins Formation (Ramaekers et al., 2007; equivalent to MFc of Ramaekers, 1979, 1980, 1990) is a fining-up unit with a basal pebbly member and an upper sand-dominated member. It forms the distal upper parts of the Bird Formation fluvial fans, and grades into the overlying Warnes Formation. At the time of assembling Data File 39, the Collins Formation was not included; this will be amended in future updates to this data file.

5) The complex packages of the Warnes and Raibl formations interpreted during the EXTECH IV program has been restricted (Ramaekers et al., 2010; Bosman, 2014) to the clay-intraclast–rich upper unit of these packages. The beds of the Warnes Formation (previously Warnes Member) were correlated through the eastern and northern parts of the region and shown to be identical to the Raibl Member of the EXTECH IV study, making the latter name unnecessary. The basal units of the former Warnes member in the eastern part of the basin were shown to be part of the Collins Formation, whereas the upper pebbly unit of the former Warnes member has proven to be equivalent to the Hodge Formation. The strata from the Bird to the Warnes form the second major sub-sequence in the Cree Basin (Sequence II-2: Table 1).

6) The Hodge Formation was first recognized during the EXTECH IV study as a prominent pebbly and conglomeratic section in the western part of the basin. This unit was then miscorrelated to the type section of the pebbly Lazenby Lake Group (now shown to be the Shiels Formation). Since the EXTECH IV program, this prominent pebbly unit in the west (Figure 2) has been shown to be traceable eastward and fines dramatically in the eastern part of the Cree Basin, where it can be distinguished as a granule to fine pebbly sandstone near the base of what was formerly mapped as the Manitou Falls Formation, Dunlop Member (MFd), and upper pebbly subunit of the Warnes Member. In the northeast, the lower contact of the Hodge Formation with the underlying clay-intraclast–rich unit of the Warnes Formation commonly shows a clear but small decrease over several metres in the maximum transported grain size. With the overlying Clampitt and Dunlop formations, the Hodge Formation forms the pebbly base of a third major fining-up sub-sequence in the Cree Basin (Sequence II-3: Table 1). The coarse material of this third cycle is derived largely from the south, unlike the coarse material from the underlying two cycles, which is derived largely from the east. These changes in grain size distribution, thickness of units and paleocurrent directions indicate a progressive waning of tectonism to the east of the Athabasca Basin, and increasing tectonism toward the south. Similar change in direction of the thermotectonic activity in the core of the Trans-Hudson Orogen was also noted by Machado (1990).

7) The Dunlop Formation (Ramaekers et al., 2007; MFd of Ramaekers, 1990) and the Clampitt Formation (Ramaekers et al., 2007, where it was mistakenly grouped with the Lazenby Lake Formation) have been shown to be correlative (Ramaekers et al., 2010). In the southeastern part of the Cree Basin—the type area of the Dunlop Formation—the entire unit is clay-intraclast–rich, and has very little material coarser than 2 mm. A relatively narrow middle unit with fewer clay pebbles may mark the boundary between upper and lower fining-up cycles in the Clampitt Formation to the west. In the Moosonees deposystem in the northeast, coarser pebbles may mark the base of the upper member.

8) The Clampitt Formation is correlative to the Dunlop Formation and forms two overall fining-up cycles (upper and lower), each with basal pebbly beds in the western part of the Cree Basin. Near its source area in the southwest, the lower cycle shows further subsidiary fining-up cycles in places. The lower member is more pebble-rich, and intraclast-poor, having only sparse clay intraclasts in many drillcores. The upper member is more clay-intraclast–rich, yet rarely achieves the more uniform and greater percentages of clay intraclasts seen in the Dunlop Formation. With future work, it may be possible to trace the division between

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upper and lower members of the Clampitt Formation through the Dunlop Formation with more confidence. Preservation of more mudstone in the Dunlop suggests the eastern part of the Cree Basin subsided slightly more rapidly.

9) The Lazenby Lake Group consists of two fining-up sequences that are now recognized as the Shiels and Larter formations. The pebbly units in these formations are more variable and the sequences are more difficult to correlate than those of the underlying Manitou Falls Group, suggesting a change from a fluvial fan to an environment with lower slopes and more established and permanent channels. Most notable in the Larter Formation, pebbly units may become rare in some drillcores, and bedded silt and clay become more common, which is why these units were previously grouped with the Wolverine Point Formation (Ramaekers 1979, 1980; Ramaekers and Catuneanu, 2004). These units represent a paralic environment, and together with the overlying deltaic, lacustrine, eolian and sabka deposits of the Wolverine Point Group, form the fourth major sub-sequence of the Cree Basin (Sequence II-4: Table 1). Because the Shiels and Larter strata can now be traced throughout the basin, the Dowler Member (undivided Lazenby Lake of the EXTECH IV interpretation) is no longer necessary and becomes obsolete.

Table 2 – Stratigraphic changes between the EXTECH IV study and this report.

EXTECH IV This Report

Formation Member Formation Group

Wolverine Point Claussen Claussen Wolverine Point

Brule Brule

Lazenby Lake Dowler correlative to Hodge through to Larter

Larter

• Dowler removed

Lazenby Lake

Larter

Shiels Shiels

Clampitt Clampitt-Dunlop

• correlative

Manitou Falls

Hodge

Manitou Falls Dunlop

Dunlop (lower)

Collins

Warnes – upper pebbly Hodge includes

• Warnes – upper pebbly Warnes – all other subunits Warnes restricted to intraclast-

bearing unit

• Raibl; synonym of Warnes Raibl

Collins Collins

Bird Bird

Smart Read

Read Smart

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Figure 2 – Multiparameter drill log of diamond drillhole RS0604 drilled by Dejour Enterprises Ltd. The log contains the stratigraphic picks for this study, including the coarse-grained unit of the Manitou Falls Group, Hodge Formation. Each horizontal histogram represents a 3 m logging interval in which the following parameters are logged: maximum transport grain size (MTG); intraclast thickness - the total accumulated thickness of clay intraclasts; mudstone - aggregate thickness of mudstones; planar siltstone - aggregate thickness of laminated siltstones/mudstones and fine-grained sandstone; conglomerate - aggregate thickness of conglomerate, provided individual beds have a minimum thickness of 2 cm.

4. Geological Map The geological map of the Athabasca Basin (Figure 1) has been updated based on the interpreted stratigraphic picks presented in Data File 39. The map shows the Athabasca supergroup subcrop units. Phanerozoic cover is located mainly in the southwest part of the map. Upper and lower members of the Clampitt Formation (of the Manitou Falls Group) and formations of the Wolverine Point Group have not been subdivided on the map. The Collins and Dunlop were not included in the drill log interpretation and therefore not included in Data File 39 or the updated map (to be amended in the future). The Martin Group geology has not been modified and is based on the 1:250 000-scale geology of Mazimhaka and Hendry (1984, 1985) and Ashton and Hartlaub (2008). In addition to the ESRI ArcGIS shapefile associated with this paper, any subsequent updates for this map will be available on the Geological Atlas of Saskatchewan (URL <http://www.infomaps.gov.sk.ca/website/SIR_Geological_Atlas/viewer.htm>).

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5. Conclusions The primary reason for this paper is to present a record of the many recently studied multiparameter drill logs and, in conjunction with previous data from the EXTECH IV study, update the interpretation of the stratigraphy of the study area, which is now based on 427 drillholes, more than twice the number used in the EXTECH IV study. The results of this compilation and interpretation are available in Data File 39, which contains stratigraphic picks for all the interpreted multiparameter drill logs, including, where present, Quaternary, Phanerozoic, mafic to ultramafic intrusive rocks, Athabasca supergroup (and its subdivisions), and crystalline basement geology. The stratigraphic picks will be incorporated into the Athabasca Basin 3-D model (http://www.er.gov.sk.ca/3dfiles) to create an updated geological framework, which is the main goal of the Athabasca Stratigraphic Interpretation subproject.

The updated geological map and the resulting digital ESRI shapefile are available as an associated digital file and will be available on the Saskatchewan Geological Atlas in the future.

The compilation and interpretation of Data File 39 has resulted in fewer, and better defined, stratigraphic units that can be traced throughout the Cree Basin. The new mapping more clearly shows the structural development of the Jackfish, Cree and Mirror basins. The stratigraphic reassignments of the old Athabasca Group within the supergroup framework better illustrates the regional correlation with other basins such as in the Baker Lake and Hornby Bay regions. This helps to focus on the crustal-scale extensional events that resulted in the formation of the stacked Athabasca basins, and in establishing the conditions under which the Athabasca unconformity-type orebodies were emplaced.

6. Acknowledgements The authors are appreciative of the support from the staff at the Saskatchewan Subsurface Geological Laboratory in arranging examination tables for our drillcore logging and sample needs. Taylor Forsyth provided support for the compilation work. Arden Marsh assisted with formatting of the table in Data File 39. Ken Ashton, Colin Card, Ryan Morelli and Michelle Hanson are thanked for their insightful discussions and comments during the reviewing process of this paper, which greatly improved the content. Heather Brown was paramount in getting this document to publication.

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Bosman, S.A. and Ramaekers, P. (2015): Stratigraphy of the Jackfish, Cree and Mirror basins from multiparamater drill logs, Athabasca Basin, Saskatchewan (parts of NTS 64E, 64L, 74E to 74P); Saskatchewan Geological Survey, Saskatchewan Ministry of the Economy, Data File 39.

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Rainbird, R.H. and Davis, W.J. (2007): U-Pb detrital zircon geochronology and provenance of the late Paleoproterozoic Dubawnt Supergroup: linking sedimentation with tectonic reworking of the western Churchill Province, Canada; GSA Bulletin, v.119, p.314-328.

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Ramaekers, P., Catuneanu, O., Bosman, S. and Jefferson, C.W. (2010): Athabasca Basin, Saskatchewan and Alberta; update on stratigraphy; GeoCanada 2010 – Working with the Earth, JACC (Joint Annual Convention Committee of CSPG, CSEG and CWLS) - Canadian Society of Petroleum Geologists - Canadian Society of Exploration Geophysicists - Canadian Well Logging Society - Geological Association of Canada - Mineralogical Association of Canada - Canadian Chapter of the International Association of Hydrogeologists, Canadian Federation of Earth Sciences, Geoscientists Canada, Calgary, Alberta, May 10 to 14, abstract 934, 3p.

Ramaekers, P., Jefferson, C.W., Yeo, G.M., Collier, B., Long, D.G.F., Drever, G., McHardy, S., Jiricka, D., Cutts, C., Wheatley, K., Catuneanu, O., Bernier, S., Kupsch, B. and Post, R.T. (2007): Revised geological map and stratigraphy of the Athabascan Group, Saskatchewan and Alberta; in EXTECH IV: Geology and Uranium EXploration TECHnology of the Proterozoic Athabasca Basin, Saskatchewan and Alberta, Jefferson, C.W. and Delaney, G. (eds.), Geological Survey of Canada Bulletin 588 / Saskatchewan Geological Society Special Publication 18 / Geological Association of Canada, Mineral Deposits Division, Special Publication 4, p.155-191.

Yeo, G., Jefferson, C.W., Ramaekers, P. and Tong, K. (2001): From Palm to Plot: core logging in the EXTECH IV Athabasca Basin stratigraphy sub-project; in Summary of Investigations 2001, Volume 2, Saskatchewan Geological Survey, Saskatchewan Energy and Mines, Miscellaneous Report 2001-4.2, Section D, p.314-319.