Preliminary Report: Lithostratigraphic Investigations of the North and Northeast Athabasca Basin, Saskatchewan Sean A. Bosman and Matthew Schwab 1 Bosman, S.A. and Schwab, M. (2009): Preliminary report: lithostratigraphic investigations of the north and northeast Athabasca Basin, Saskatchewan; in Summary of Investigations 2009, Volume 2, Saskatchewan Geological Survey, Sask. Ministry of Energy and Resources, Misc. Rep. 2009-4.2, Paper A-6, 13p. Abstract Multi-parameter digital plots of diamond drill cores are a simple, quick, objective, and effective method of delineating the lithostratigraphy of the Athabasca Basin. During 2009, 61 diamond drill holes from several understudied areas of the Athabasca Basin were documented using multi-parameter digital plots. The focus of the summer program was to log drill holes located in the north and northeast parts of the basin. The techniques and logging parameters closely followed those developed by the EXploration science and TECHnology initiative (EXTECH IV) Athabasca Uranium Multidisciplinary Study. Gamma-ray data integrated with the multi-parameter logging method were used in the EXTECH IV research and this study to help define several stratigraphic contacts including the one between the Read Formation and the Bird Member and/or Raibl Member of the Manitou Falls Formation. These new quantitative logs guided the repositioning of several unit contacts. The summer findings also suggest that there is a significant fining of the conglomerates in the lower stratigraphic units towards the north and northeast parts of the Athabasca Basin. This fining may indicate a more southerly contact between the central Ahenakew deposystem and the northern Moosonees deposystem than previously identified. Keywords: Athabasca Basin, Athabasca Group, lithostratigraphy, stratigraphy, Manitou Falls Formation, Read Formation, Lazenby Lake Formation, Wolverine Point Formation, Raibl Member, EXTECH IV, sandstone, conglomerate, mudstone, digital logging, core logging. 1. Introduction Regional core logging of the Athabasca Basin continued during 2009. This was the third year of this project which remained focused on revising, redefining, and repositioning the lithostratigraphy of the Athabasca Group. These modifications to the lithostratigraphic contacts will be used as the framework for a 3-D model of the Athabasca Basin. This study builds on the work completed in 2007 (Bosman and Korness, 2007), 2008 (Bosman et al., 2008), and that of the 2000-04 EXploration science and TECHnology initiative (EXTECH IV) project. EXTECH IV was a multi-disciplinary collaboration between industry, federal and provincial geological surveys, and universities to better understand targeted geological, geochemical and geophysical aspects of the Athabasca Basin and to develop exploration technology. As part of EXTECH IV, a stratigraphy subproject was designed to refine and develop a better understanding of Athabasca Group lithostratigraphy, sedimentological processes, sequence stratigraphy, and their relationships to unconformity-associated uranium deposits. Using 2-D models of the Athabasca Group and new diamond drill hole data, the main goal of this multi-year study will be to develop a 3-D model of the Athabasca Basin. The model will advance our lithostratigraphic knowledge of the Athabasca Basin by: 1) presenting more accurately positioned contacts; 2) improving our understanding of the basinal fault systems, their timing, location and development; 3) assisting in interpreting basin geometry and evolution; and 4) will be an important step in analyzing the basin in the 4th dimension (i.e., xyz and time). Advancements in our understanding of reactivated fault systems are important criteria for discovering uranium and other ore deposits. During the three years of this study, 136 drill holes have been logged from many areas of the Athabasca Basin (Figure 1). The methods for recording the data have remained consistent during this study allowing for comparison between drill holes. Each drill hole is logged in 3 m intervals recording the following five sedimentary parameters: maximum transported grain (MTG) size, total thickness of conglomerate, mudstone and planar siltstone beds which is subsequently converted to a percent for the digital plots, and the total thickness of clay intraclasts 2. These five 1 Department of Geology, University of Saskatchewan, 114 Science Place, Saskatoon, SK S7N 5E2. 2 Staying consistent with EXTECH IV, clay intraclasts are plotted using cm/m; however, percentages of clay intraclasts are used in the definitions of the lithostratigraphic units. Saskatchewan Geological Survey 1 Summary of Investigations 2009, Volume 2 150000 m E 110°W 250000 m E 350000 m E 450000 m E 105°W 550000 m E m m N m N MFc 6600000 FP 6600000 Figure 2 FP ! !! Lake Athabasca A AA! MFc-p LZd A A! A! A! A! Black A! MFr-cr Lake A! MFr-lp MFb-l MFd-p LLb A!! A ! MFr-up LLm !A !! ALZd !AA A MFc-p MFb-u m m N m N LLb W MFd-p A! LZl Ob C D W LLs D Oa A! ! 6500000 A 6500000 ! C A! A ! ! ! Cluff Lake Mine A A A LZh "J Pasfield LZs A! A! Lake AA!!A! A! A!"JA "J LLm A! ! "J "J FP LZl !A!A! A A ! ! A!A Wollaston 58°N A Lake LLs LLb ! Cigar Lake Mine W LZd !A !"J ! RD LZl A ! A A LZl ! A! A! A! AA! A! A! !A A! 58°N LZs ! A A! A S A!! ! A! MFw-s A ! A ! A A LZc A MFc MFb-u m N m m N ! MFw-lp A ! A!A! A! A A! RD !MFc "J A McArthur River Mine A! ! ! 6400000 A! A ! 6400000 A MFw-up ! A A! ! !A A MFw-cr A!AA! MFd ! A! A Alberta ! !! MFc Cree Lake ! MFw-up ! A RD!AA MFw-up A! ! A A ! A! ! MFb-l Saskatchewan ! MFw-cr MFw-cr!A! ! MFw-upMFc ! A AA!!A! AA! A! !A MFw-cr A! A! ! A!! MFw-s !A AA! ! ! A A!A A!!!A MFw-lp A MFw-sA AA! ! A!AA MFw-lp A MFw-s 0 20 40 60 80 MFw-lp MFw-cr km Key Lake Mine "J RY 150000 m E 110°W 250000 m E 350000 m E 450000 m E 105°W 550000 m E Figure 1 - Current geological map of the Athabasca Basin including lithostratigraphic contacts of formations, members, and subunits (modified from Figure 1 of Ramaekers et al., 2007 and Figure 1 of Bosman et al., 2008). Lithostratigraphic codes are explained in Table 1. Red, pink, and purple drill hole symbols (circle with superimposed ‘+’ sign) show locations of drill holes logged during this study in 2007, 2008, and 2009, respectively. Small red circles are those logged during EXTECH IV. Pink squares show locations of selected uranium mines. Dark blue lines represent selected roads. Heavy box is the outline of Figure 2. Coordinates are in UTM NAD83, Zone 13. Saskatchewan Geological Survey 2 Summary of Investigations 2009, Volume 2 Table 1 - Third-order depositional sequences, major unconformities, and lithostratigraphic units of the Athabasca Group (modified after Ramaekers et al., 2007, Table 1). Lithostratigraphic codes displayed on all figures are referenced to this table. Formation [code] Member [code] Informal subunit (designated by dominant lithofacies or position) Overburden [OB] Includes Quaternary glacial deposits and other unconsolidated sand and gravel upper subunit [Cu] (stromatolitic to massive dolostone) Carswell [C] 4 lower subunit [Cl] (siliciclastic interbeds, stromatolite, oolite) Douglas [D] (mudstone, fine- to very fine-grained quartz arenite) Birkbeck [Ob] (quartz arenite) Otherside [O] Archibald [Oa] (pebbly quartz arenite, quartz arenite) Marsin [LLm] (upper pebbly quartz arenite) Sequence Sequence Locker Lake [LL] Brudell [LLb] (conglomeratic quartz arenite) Snare [LLs] (lower pebbly quartz arenite) Unconformity Claussen [Wc] (clay-rich quartz arenite » mudstone) Wolverine Point Wb-sm (quartz arenite > mudstone) 3 [W] Brule [Wb] Wb-s (nearly all quartz arenite) Wb-m (mudstone > quartz arenite » tuff) Dowler [LZd]1 (quartz arenite, siltstone + mudstone) Larter [LZl] (quartz arenite » siltstone + mudstone) Lazenby Lake [LZ] Shiels [LZs] (quartz arenite with pebbly layers) Sequence Sequence Clampitt [LZc] (quartz arenite > siltstone + mudstone) Hodge [LZh] (pebbly quartz arenite + conglomerate) Basal unconformity to Mirror Basin Dunlop [MFd] MFd-p (pebbly Dunlop in Moosonees Deposystem) (quartz arenite with ≥0.6%3 clay intraclasts) MFd quartz arenite only in most areas Collins [MFc] MFc quartz arenite only in most areas (quartz arenite) MFc-p (pebbly quartz arenite) Warnes [MFw]2 MFw-up (upper quartz-pebbly quartz arenite) (quartz arenite: non- MFw-cr (≥0.6%3 clay-intraclast–rich quartz arenite) pebbly, pebbly and MFw-s (quartz arenite) Manitou Falls [MF] ±clay intraclasts) MFw-lp (lower quartz-pebbly quartz arenite) MFr-up (upper quartz-pebbly quartz arenite) 2 Raibl [MFr]2 MFr-cr (≥0.6%3 clay-intraclast–rich quartz arenite) (quartz arenite: pebbly MFr-pcr (quartz-pebbly ≥0.6%3 clay-intraclast–rich quartz arenite) ±clay intraclasts) MFr-s (pebbly quartz arenite, quartz arenite; clay interbeds near base) MFr-lp (lower pebbly quartz arenite); clay interbeds near base Bird [MFb] (≥1.2%3 MFb-u (upper conglomeratic quartz arenite) Sequence Sequence conglomerate) MFb-l (lower conglomeratic quartz arenite) Local unconformity separates overlying units from Read and Smart formations S-u (upper quartz arenite), informal Shea Creek beds Smart [S] S-l (lower quartz arenite) (previously MFa) S-mp (local pebbly mudstone) Smart appears to be a lateral equivalent of Read RD-s (low-angle bedded quartz arenite) Read [RD] RD-cg (conglomerate) (previously MFa) RD-mp (local pebbly mudstone) Reilly [RY] RYcg (conglomeratic quartz arenite outliers east of Athabasca Basin) Basal unconformity to Cree Sub-basin (within Athabasca Basin) and to Reilly Basin (east of Athabasca Basin) Beartooth [FPb] (pebbly quartz arenite) FPl-cs (conglomeratic quartz arenite) Fair Point [FP] FPl-cg (conglomerate) Lobstick [FPl] FPl-ps (pebbly quartz arenite) FPl-mp (mudstone, pebbly) Sequence 1 No formal designation BL (basal lag, pebbles to boulders) Basal unconformity to Jackfish Basin Basement: metamorphosed Archean granitoid gneiss, Paleoproterozoic paragneiss and late intrusions Notes: 1 LZd is the distal, finer-grained, northeastern equivalent of the four other members (LZh, LZc, LZs, LZl) in the southwestern proximal region.