south reindeer lake quaternary project: glaciofluvial corridors … · 2019-01-18 · arc volcanic...

Saskatchewan Geological Survey 1 Summary of Investigations 2017, Volume 2

South Reindeer Lake Quaternary Project: Glaciofluvial Corridors and Reconnaissance-scale Kimberlite Indicator Mineral Sampling

(NTS 64D/10, with Parts of 64D/07, /08, /09 and /11) Michelle A. Hanson 1

Information from this publication may be used if credit is given. It is recommended that reference to this publication be made in the following form: Hanson, M.A. (2017): South Reindeer Lake Quaternary project: glaciofluvial corridors and reconnaissance-scale kimberlite indicator mineral sampling (NTS

64D/10, with parts of 64D/07, /08, /09 and /11); in Summary of Investigations 2017, Volume 2, Saskatchewan Geological Survey, Saskatchewan Ministry of the Economy, Miscellaneous Report 2017-4.2, Paper A-10, 25p.

This paper is associated with the map separates entitled: Hanson, M.A. (2017): Surficial geology of the Milton Island area, Reindeer Lake (NTS 64D/10, with parts of 64D/07 and /11); 1:100 000-scale preliminary map

with Summary of Investigations 2017, Volume 2, Saskatchewan Geological Survey, Saskatchewan Ministry of the Economy, Miscellaneous Report 2017-4.2-(3).

Hanson, M.A. and Dixon, D. (in press): Surficial geology of the Bleasdell Lake area (western NTS 64D/09, with part of 64D/08); 1:100 000-scale preliminary map.

Abstract As part of the South Reindeer Lake Quaternary project, samples for kimberlite indicator mineral (KIM) analysis were collected from glaciofluvial sediment in the Milton Island area of Reindeer Lake. This paper describes the distribution and characteristics of glaciofluvial corridors in this area and the locations of KIM and pebble samples collected during the 2017 field season.

A regional glacial meltwater drainage network existed in the study area during the last deglaciation. Six glaciofluvial corridors were identified, trending southwestward. These corridors are 0.3 to 2 km wide, separated by 10 to 15 km, forming a weakly dendritic pattern, and are characterized by eskers, glaciofluvial plains, kames and kettles, meltwater-scoured bedrock, winnowed and eroded till, and cobble-boulder fields. The lateral boundaries of the corridors are commonly sharp and areas between corridors are largely covered in subglacially deposited till.

Nineteen samples of glaciofluvial sediment were collected for KIM analysis. Samples were collected from esker crests, a kame, a glaciofluvial plain, from beaches formed from these deposits, and from glaciofluvial outwash fans. Medium- to coarse-sized sand was targeted, as were facies containing concentrations of heavy minerals, where present. At the time of publication, results from the analysis of the KIM samples were not available, but these results will be added to the Saskatchewan KIM database and the Saskatchewan Mining and Petroleum GeoAtlas once received.

Ten samples of pebbles were collected from glaciofluvial sediment, with the intent to determine sediment provenance and dispersal distance of glaciofluvial deposits. Whereas almost all of the pebbles are consistent with the local bedrock geology, many are also consistent with bedrock geology up to 100 km to the northeast, making it difficult to determine glaciofluvial sediment provenance and dispersal distance at this stage of the investigation. Typically, however, dispersal trains within eskers extend up to a maximum of 25 km, and planned analysis of pebble rock types in till as well as fine-fraction geochemical analysis of till in the study area might help determine glacial dispersal distances within the region and aid in the production of a glacial dispersal model for the area.

Keywords: kimberlite indicator minerals, KIM, Quaternary, Reindeer Lake, glaciofluvial corridor, drift prospecting, Late Wisconsinan, Reindeer Zone

1. Introduction As part of the South Reindeer Lake Quaternary project, samples for kimberlite indicator mineral (KIM) analysis were collected from glaciofluvial sediment in the Milton Island area of Reindeer Lake (Figure 1).

1 Saskatchewan Ministry of the Economy, Saskatchewan Geological Survey, 1000-2103 11th Avenue, Regina, SK S4P 3Z8 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.


Figure 1 – Lithostructural domainal map of northern Saskatchewan showing the 2017 project area; polygons highlighted in green are inliers of the buried Archean Sask craton. Saskatchewan Geospatial Imagery Collaborative (SGIC) orthophoto shows detailed view of the study area.


The South Reindeer Lake Quaternary project was designed to provide surficial geological data to assist with the assessment of the mineral potential and the application of drift prospecting in the area. Fieldwork for this project was initiated in 2017 and covered the extent of NTS 64D/10 and some adjacent areas in 64D/07, /08, /09 and /11. This project has four main components: 1) Surficial geology mapping at a scale of 1:100 000 and surficial sediment description; 2) Determination of ice-flow directions and chronological reconstruction; 3) Regional-scale till sampling for fine-fraction geochemical analysis, grain size determination and pebble rock type

determination; and 4) Reconnaissance-scale KIM sampling.

This paper deals mainly with the fourth component, describing the distribution and composition of glaciofluvial sediment and the location of KIM samples collected during the 2017 field season. At the time of publication, results from the analysis of the KIM samples had not been received, but these results will be added to the Saskatchewan KIM database (http://publications.gov.sk.ca/documents/310/96198-Kimberlite%20Indicator%20Minerals.pdf) once available.

The rationale for reconnaissance-scale KIM sampling in the area is twofold. First, recent discoveries of KIMs in exposed areas of the Sask craton, such as near Deschambault Lake (Figure 1), have spurred exploration for diamond-bearing kimberlites in the region. The current study area is within the vicinity of several Archean cratons at depth (Corrigan et al., 2005, 2007), the boundaries of which are not well defined, and thus has the potential for diamond-bearing kimberlites. Second, the study area has an abundance of ideal glacial landforms and sediments for reconnaissance-scale KIM sampling. Eskers—long ridges of gravel to sand sediments deposited by meltwater in subglacial channels—are the primary target for KIM sampling. On the Canadian Shield, eskers are very common; in the study area, they are particularly abundant and easily accessible for sampling.

2. Regional Setting a) Bedrock Geology The bedrock geology of the area (Figure 2) is discussed in detail by Maxeiner et al. (2004, 2005, and references therein). The bedrock is part of the Reindeer Zone, which comprises mainly 1.92 to 1.83 Ga subduction-generated arc volcanic and plutonic rocks and marginal basin sedimentary rocks. These rock units are thought to have formed in a Pacific-scale ocean basin, the Manikewan Ocean (Stauffer, 1984), that occupied the region between the Rae-Hearne, Superior, and Sask cratons prior to terminal collision and formation of the 1.8 Ga Trans-Hudson Orogen (Saskatchewan Geological Survey, 2003). These cratons formed the root of the region. The northwestern Reindeer Zone, including the study area, forms a north-northwest–dipping imbricate stack of Paleoproterozoic juvenile arc, sedimentary and plutonic rocks of various ages and tectonic settings that have been metamorphosed to amphibolite facies (Maxeiner et al., 2004). Rocks in the study area are predominantly part of the Lawrence Point (1.92 Ga), Reed Lake (?1.88 to 1.87 Ga), Milton Island (~?1.87 Ga), Duck Lake (~1.87 Ga), and Levesque Point assemblages, and the Sickle/McLennan groups (~1.84 Ga), and include mafic to ultramafic igneous rocks, felsic to intermediate volcanic rocks, pelitic to psammitic turbidites, and derived migmatites (Maxeiner et al., 2004).

b) Late Wisconsinan Glacial Chronology Northern Saskatchewan underwent numerous glaciations throughout the Quaternary Period, but it is primarily the record of the last, the Late Wisconsinan, that is well preserved. During the last glaciation, the Laurentide Ice Sheet (LIS) advanced and flowed generally southwestward over Saskatchewan from a dispersal centre in the Keewatin Sector, in Nunavut (Prest et al., 1968; Prest, 1984; Dyke and Prest, 1987; Dyke et al., 2002). Nineteen to 23 thousand calendar years before present (cal. ka BP; ~18.0 14C ka BP2; Mix et al., 2001; Dyke, 2004), at the maximum extent of the LIS, most of Saskatchewan was covered by ice, which would have been greater than 3000 m

2 Because radiocarbon ages are based on the radioactive decay of 14C and the level of atmospheric 14C has not been constant over time, radiocarbon ages need to be calibrated in order to determine an age in calendar years. A radiocarbon age is a fixed age but a calendar age may change based on the calibration curve used. Both ages are reported here for clarity. Calendar years reported are taken directly from referenced publications and have not been recalibrated.

http://publications.gov.sk.ca/documents/310/96198-Kimberlite%20Indicator%20Minerals.pdf


thick over the study area (Dyke et al., 2002). Widespread retreat of the LIS throughout North America was underway by 16.8 cal. ka BP (14.0 14C ka BP; Dyke et al., 2003; Dyke, 2004). In Saskatchewan, ice retreated generally to the northeast. In the study area, chronological control on ice sheet retreat is non-existent. Reconstructions of regional ice sheet retreat indicate that generally by 10.2 cal. ka BP (9.0 14C ka BP; Dyke et al., 2003) ice had retreated north of the study area and the area was inundated by a proglacial lake. This lake was ~90 m higher than the current Reindeer Lake (Campbell, 2004) and covered the entire area, except perhaps a high point to the east of the isthmus between Asimwok and Numakoos bays (Figure 1). It is likely that this lake later became part of the larger glacial Lake Agassiz (Schreiner, 1983; Teller et al., 1983; Dyke et al., 2003; Leverington and Teller, 2003), but some more recent reconstructions do not connect the two lakes (e.g., Teller and Leverington, 2004). By 8.45 cal. ka BP (7.7 14C ka BP) the glacial lake had drained and Reindeer Lake was likely near its current extent (Schreiner, 1983; Dyke et al., 2003; Dyke, 2004).

Figure 2 – 1:250 000-scale bedrock geology map of the study area; geology is from the Saskatchewan Mining and Petroleum GeoAtlas (https://gisappl.saskatchewan.ca/Html5Ext/index.html?viewer=GeoAtlas; accessed 13 October 2017). The black polygon outlines the area covered in this study.

https://gisappl.saskatchewan.ca/Html5Ext/index.html?viewer=GeoAtlas


c) Ecoregion The study area lies within the Churchill River Upland ecoregion, which is part of the Boreal Shield ecozone (Padbury and Acton, 1994). Generally, black spruce forests dominate the region, especially in areas of thin fine-grained till, varying from open to closed canopy with increasing sediment thickness (Acton et al., 1998). Jack pine forests are prevalent on sandy to gravelly glaciofluvial sediments (Acton et al., 1998). Mixed-wood forests of trembling aspen (or poplar), white spruce, balsam fir and white birch, with sparse black spruce and jack pine, are found on fine-grained glaciolacustrine sediments (Acton et al., 1998). Low-lying bogs are commonly perennially frozen, supporting black spruce. Small stands of trembling aspen are found on well-drained slopes (Acton et al., 1998). Common soils are Brunisolic on well-drained slopes; Gleysols, Organics, and local Cryosols in small, poorly drained swales and flat-lying areas; and Gray Luvisols on fine-grained glaciolacustrine deposits (Acton et al., 1998).

Small parts of the study area have burned in the past 20 years: the northern tip of Milton Island in 2016; the area west of Fleming Bay in 2010 and 2012; the southern end of Mooney Island and the northern part of Wapus Island in 2006; the east and southern sides of Bleasdell Lake in 2005; and Reynolds Peninsula in 2003 (Saskatchewan Wildfire Management Atlas, accessed 3 October 2017; Figure 1).

3. Previous Research Prior to this project, there was limited surficial geological work done in the study area in terms of surficial mapping. Quaternary surficial deposits and landforms were mapped at a scale of 1:250 000 as part of a Quaternary reconnaissance-scale mapping program of the Canadian Shield of Saskatchewan by the Saskatchewan Research Council (Alley and Schreiner, 1984; Schreiner, 1984). ArcMap data for the surficial mapping are available on the Saskatchewan Mining and Petroleum GeoAtlas (GeoAtlas). During this previous study, 22 sites were visited: 15 surficial sediment observation and sample sites, 6 seismic sites, and 1 photographed site. Three of these sites (DA-393, -521 and -525; Alley and Schreiner, 1984; Figure 3) relate to glaciofluvial deposits, but original field data is not available.

Figure 3 – Locations of previous sediment sample sites (locations approximate to within a few hundreds of metres; Alley and Schreiner, 1984) and previously collected KIM samples (Swanson, 1996; GeoAtlas, accessed 11 October 2017). Note that the whitish areas in the photo are areas of the lakes covered by ice. The black polygon outlines the area covered in this study.


No public-domain KIM samples were collected within the study area prior to this project. As part of a reconnaissance-scale sampling program of eskers, eight samples (FS-92-14, FS-93-05, -06, -07, -08 and -09, and FS-95-63 and -64; Swanson, 1996; Figure 3) were collected to the north, northwest, west and southwest of the study area. These samples contained chrome diopsides, ilmenites, pyropes, and/or spinels. Additionally, three samples (SIR 0261-36, -87 and -99; Figure 3) were collected by Saskatchewan Geological Survey field crews in 2002, approximately 25 km to the northeast of the study area; these samples also contained spinels. Data for all of these samples is accessible on the GeoAtlas and in the Saskatchewan KIM database.

4. Methods and Analyses a) Mapping and Sediment Description Interpretation of 1:60 000-scale aerial photographs and Saskatchewan Geospatial Imagery Collaborative (SGIC) orthophotos provided the basis for the preliminary surficial mapping, which was followed by ground truthing in the field. Glaciofluvial sediment descriptions are from 71 pits dug with a shovel to an average depth of 58 cm (maximum of 124 cm), 47 beaches, and 26 vertical exposures of sediment (Figure 4). Winnowed and eroded till descriptions are from 35 pits dug with a shovel to an average depth of 50 cm (maximum of 80 cm; Figure 4). Till pit depths were constrained by thin sediment over bedrock, frozen sediment in June and early July, local high water tables, and lag deposits that made it difficult to dig. Sediment descriptions include, where applicable, sediment type (e.g., sand, gravel, etc.), unit thickness, nature of the contact between units, grain size3, sorting, structure, compaction, clast framework, clast size and shape, sedimentary structures, and associated landforms. These sites were spaced approximately 1 site per 4 km2, with closer spacing in areas of difficult air photo interpretation and higher landform variability; vertical exposure sites were described wherever found. Field sites were restricted to sites accessible by boat and foot traverse, with a very small number accessed by float plane.

Figure 4 – Location of all field sites of glaciofluvial sediment and winnowed and eroded till that are described and discussed in this paper. Note that some sites are too close to each other to be distinguished separately at the scale of this image.

3 Grain size was determined in the field based on the Wentworth classification.


b) Kimberlite Indicator Minerals Nineteen samples (Table 1, Figure 5) of glaciofluvial sediment were collected for KIM analysis. Medium- to coarse-sized sand was targeted because KIMs are most commonly this grain size (Hozjan and Averill, 2009), as were facies containing concentrations of heavy minerals, where present (Figure 6, Table 1). The grain size of all facies containing concentrations of heavy minerals was assessed in the field and found to be at or below the threshold between fine- and medium-grained sand. Thus, most of these grains are below the common grain size of KIMs. Nonetheless, samples of these facies were collected alongside those of appropriate grain sizes. All samples were sieved in the field using a 1 cm sieve to remove larger particles where necessary, and collected in new, clean 12 L pails. Where possible, samples of pebbles (average of 105 pebbles, ~3 cm diameter; Table 1) were collected to help determine sediment provenance and dispersal distance. Ten pebble samples were collected from glaciofluvial sediments, seven alongside KIM samples, and three from separate glaciofluvial sediment sites.

Table 1 – KIM and pebble sample locations and general descriptions. Refer to Figure 5 for mapped locations.

Sample Landform Geographic Location Collected Grain Size (Field Observations)

Heavy Minerals Present

KIM Sample

Pebble Sample

MH17-004* Glaciofluvial veneer Southeast of ‘Duck Lake’ **

Pebbles only N/A No Yes

MH17-018 Esker crest Jones Peninsula Pebbles only N/A No Yes MH17-022 Beach derived from esker ‘Peanut Island’ Fine to very coarse sand Yes Yes Yes

MH17-026 Glaciofluvial veneer East of Hodgson Island Pebbles only N/A No Yes MH17-031 Beach derived from esker ‘Bikini Beach’ Fine to medium sand Yes Yes Yes

MH17-038 Esker crest ‘Duck Lake’ Fine to coarse sand No Yes No

MH17-042 Beach derived from esker Fleming Bay Medium to coarse sand Yes Yes No

MH17-103 Beach adjacent to esker Southwest Lawrence Bay

Fine to coarse sand Yes Yes No

MH17-106 Esker crest Jones Peninsula Fine to coarse sand No Yes No

MH17-111 Esker crest Southwest Butler Island

Medium to very coarse sand

No Yes Yes

MH17-188 Beach derived from esker Southwest Mooney Island

Medium to coarse sand Yes Yes No

MH17-196 Beach in glaciofluvial corridor Numakoos Bay Medium to coarse sand Yes Yes No

MH17-228 Beach on an outwash fan Loon Bay Fine to coarse sand No Yes Yes

MH17-251 Esker crest Wetmore Lake

Fine to very coarse sand, granules, pebbles

No Yes Yes

MH17-252 Beach adjacent to esker Bleasdell Lake Fine to coarse sand No Yes Yes

MH17-253 Beach in glaciofluvial corridor Bleasdell Lake Medium to coarse sand No Yes No

MH17-254 Beach formed on esker Lowdermilk Bay Coarse sand No Yes No

MH17-257 Glaciofluvial plain Asimwok Bay Fine to coarse sand No Yes No

MH17-281 Glaciofluvial kame Numakoos Bay Fine to very coarse sand, granules, pebbles

No Yes Yes

MH17-292 Beach on an outwash fan ‘North-South Bay’ Coarse sand No Yes No

MHA17-030 Beach adjacent to esker North of Milton Island Medium sand Yes Yes No

MHA17-089 Esker crest Wapusis Lake Medium to coarse sand No Yes No

* Italics indicates pebble sample only. ** Names in quotation marks are unofficial names.


Figure 5 – KIM and pebble sample locations. Note that ‘Duck’ (unofficial name) and Wapusis lakes are not separate lakes, but part of the larger Reindeer Lake. Refer to Table 1 for more information on each sample.

Figure 6 – Well-sorted fine to coarse sand beds with heavy mineral beds and laminations (dark layers), ‘Bikini Beach’ (unofficial name; UTM 629555E, 6267051N). Heavy mineral layers arise from sorting by present-day lacustrine waves.

KIM sampling was conducted in the study area at a reconnaissance scale. Within a glaciofluvial corridor (see ’Discussion - Glaciofluvial Corridors’), samples were spaced every 5 to 8 km, where possible. Where tributaries met, attempts were made to sample above the confluence to help narrow down source material should KIMs be present. The landforms and geographic locations of sample sites are listed in Table 1. Samples were collected from 1) esker


crests (5 sites; Figure 7A); 2) beaches formed directly on eskers (5 sites; Figure 7B); 3) beaches adjacent to eskers, but not clearly derived from eskers (3 sites); 4) beaches within identified glaciofluvial corridors (2 sites); 5) a kame immediately adjacent to an esker (1 site; Figure 7C); 6) a glaciofluvial plain adjacent to an esker (1 site; Figure 7D); and 7) beaches on outwash fans (2 sites). Esker crests were the primary target because they are commonly enriched in heavy minerals compared to other glacial sediments due to reworking and sorting within the subglacial channel. Similarly, beaches derived directly from eskers are ideal target sites because wave reworking may lead to further concentration of heavy minerals (Figure 6). Where these first two options were not available, other geomorphic sites such as other beaches and esker-adjacent glaciofluvial landforms (kames and plains) were chosen because their processes of formation can concentrate heavy minerals, if present. The samples from the beaches on the outwash fans were chosen to ensure regular spacing with other sites, even though the source of one of the fans could not be conclusively determined (see ’Discussion - Glaciofluvial Corridors’).

Figure 7 – Examples of KIM sample locations: A) A low, flat-topped esker, ‘Duck Lake’ (unofficial name; UTM 625196E, 6271135N). The KIM sample was collected from the crest. B) KIM sampling on a beach formed on an esker, ‘Bikini Beach’ (unofficial name; UTM 629555E, 6267051N). Note the multiple layers of darker, heavy minerals on the beach surface. C) A rounded, steep-sided kame immediately adjacent to an esker, Numakoos Bay (UTM 655636E, 6280507N). D) A flat to gently undulating glaciofluvial plain in the lowland between a scoured outcrop ridge in the distance and bouldery glaciofluvial hill in the foreground, Fleming Bay. This particular glaciofluvial plain was not sampled, but it was difficult to photograph the plain that was sampled because of vegetation cover.

The KIM samples were submitted to the Saskatchewan Research Council’s (SRC) Geoanalytical Laboratories for KIM analysis and gold grain counts4. Results will be added to the Saskatchewan KIM database, once available. Pebble rock types were identified in the field and are discussed below.

4 Please note that this reconnaissance-scale sampling program was designed for KIM sampling, not for gold grains, even though gold grains are being counted at SRC. A proper drift prospecting sampling program for gold grains would have required 1) closer sample spacing because visible gold grain dispersal trains are generally short (<2 km; e.g., McClenaghan, 2001), and 2) collection of smaller grain sizes because gold grains in till are commonly silt sized (e.g., McClenaghan, 2001; McMartin, 2009).


c) Ecosite Classification At each site, field crews attempted to determine ecosite classifications based on the Field Guide to the Ecosites of Saskatchewan’s Provincial Forests (McLaughlan et al., 2010). Determining relationships between ecosites and sediment type can provide quick information for planning field mapping and sediment sampling surveys. The type of vegetation at a site is highly dependent upon the substrate; for example, variations in grain size affect moisture retention in the soil, which affects dominant vegetation type. Ecosites were classified by non-biologists at ~80% of the sites; at some sites, recent burns prevented identification, and at others, the ecosite could not be confidently identified.

5. Results This section describes and interprets the landforms and sediments observed in the study area and groups them based on whether they are depositional or erosional and whether they are ice-contact or proglacial, as well as distinguishing postdepositional landforms (beaches). Pebble rock types are also listed, at the end of this section. The regional context of these sediments and a discussion of the pebble rock types follows in the ‘Discussion’ section.

a) Ice-contact Glaciofluvial Landforms and Sediment Ice-contact glaciofluvial landforms and sediment are deposited by glacial meltwater on, within, or beneath a glacier. This sediment is present discontinuously but fairly pervasively throughout the study area, varying in morphology and composition. Field descriptions of ice-contact glaciofluvial landforms, their composition and ecosites are presented in Table 2 and their locations are shown on Figure 8.

The most prominent landforms are eskers, which were mapped from air photo interpretation and field ground truthing. The eskers form regional weakly dendritic and local anabranching patterns (Table 2, Figures 8, 9A and 9B). Regionally, the eskers flow down slope through structurally controlled bedrock valleys. For example, they were deposited in both broad valleys that are currently occupied by Reindeer Lake, or narrow valleys between two steep bedrock ridges (e.g., between Wapus Bay and Wapusis Lake; Figure 8). There are two local exceptions to this. First, the esker trending from Lowdermilk Bay to near the southern part of Asimwok Bay (Figure 8), although it follows the regional bedrock topography, it was deposited on an upward-trending slope grading 0.7% over ~7.5 km. Secondly, the esker trending from ‘Duck Lake’ toward Jones Peninsula (Figure 8) follows an upward-trending 8% slope instead of through a narrow valley ~70 m to the southeast, at the south end of ‘Duck Lake.’ This indicates that both of these esker segments were deposited by subglacial meltwater that was flowing upslope.

Eskers are commonly flanked by 1) glaciofluvial plains (Figure 9B, Table 2), which are composed of flat to undulating thick stratified sediment; 2) kames (Figure 7C, Table 2), which are uneven, steep-sided hills; and 3) kettles (Figure 9B), which are depressions formed by the melting out of ice blocks. Additionally, glaciofluvial blanket sediments (Table 2) are categorized as thick (>2 m) sediments, not associated with a specific landform, that mask the underlying topography, and glaciofluvial veneers (Table 2) are thin sediments (≤2 m thick) that commonly overlie till, bedrock, and other glaciofluvial sediments and can reflect the underlying topography. The veneer is present in two forms: mostly as moderately well- to well-sorted sediment (Figure 9C, Table 2), but also as a diamicton (Table 2). These esker-adjacent landforms could have been deposited in minor subglacial meltwater conduits and/or cavities adjacent to the major esker conduits (Brennand, 1994; Utting et al., 2009). Many of them, however, could have been deposited as proglacial outwash. As the ice front retreated, exposing the esker, outwash deposits could have been deposited adjacent to, and on top of, the eskers (cf., Cummings et al., 2011, and references therein). Without any identifying stratigraphic relationships, all, except for two sites, were categorized as ice-contact and are assumed to be contemporaneous with esker deposition.


Table 2 – Field descriptions of ice-contact glaciofluvial landforms and sediments. Ecosite classification codes from McLaughlan et al. (2010).

Esker (Crests and Flanks) Plain Kame Blanket Veneer

Figure 9A Figure 9B Figure 7C Sorted

Figure 9C

Diamicton

No. of Sites 25 8 1 14 31 14

Sediment Fine to very coarse sand, gravelly sand, boulder-cobble gravel, diamicton

(Silty)* fine to medium sand

Fine to very coarse sand, pebbly sand

Silt, very fine to fine sand, pebbly to cobbly sand, boulder-cobble gravel

Silty very fine to fine sand, pebbly sand

(Silty) very fine to coarse sand with gravel

Sorting Poorly to moderately well Well (moderately well) Poorly (Poorly to) well Moderately well to well Unsorted to moderately

Compaction Loose Loose Loose Loose Loose (moderate)

Clast Content (%) 10 to 25 (0 to 80) Negligible (35) 35 <5 (up to 30) Negligible (<40) 10 to 25 (1 to 50)

Clast Size Granule to boulder Granule, pebble, cobble Granule, pebble, cobble Granule, pebble, cobble Granule, pebble, cobble Granule, pebble, cobble (boulder)

Clast Roundness Well rounded (subangular to well rounded) Subrounded to well rounded Rounded (subangular to well rounded)

Subrounded to rounded (angular to well rounded)

Subangular to subrounded Subrounded (subangular to well rounded)

Sedimentary

Structures

Massive, (irregularly, cross-) bedded (normal and reverse grading, rippled, rip-up clasts)

Massive, (irregular) bedding Irregular stratification Massive (reverse and normal grading; lenses; irregular stratification)

Massive (normal and reverse grading, irregular stratification, rip-up clasts)

Massive (normal and reverse grading; irregular stratification)

Morphology Undulatory, sinuous, dendritic, anabranching, discontinuous; flat-topped, round-crested;

shallow (small) to steep sided (larger); 150 m to 3 km long, 2 to 25 m high, 20 to 200 m wide

Flat to gently undulating; thick enough (>2 m) to mask underlying

topography

Small circular to ovate hills; thick enough (>2 m) to mask underlying

topography; <20 m high, <40 m wide

Thick enough (>2 m) to mask underlying topography

Thin enough (≤2 m) to reflect underlying topography

Ecosite Highly variable (BS3, 4, 5, 6, 7, 9, 12, 14, 15) BS3: jack pine/blueberry/lichen (BS7, 9, 17, recent burn)

BS3: jack pine/blueberry/lichen BS3: jack pine/blueberry/lichen (burnt; BS6, 9)

BS9: black spruce – jack pine/feathermoss (BS4, 5, 7, 17,

recent burn)

BS9: black spruce – jack pine/feathermoss (BS3, 6, 7,

and 17, recent burn)

Other Features Local downflow fining; one site had a veneer of till

Overlies (winnowed/ eroded) till, bedrock, and other glaciofluvial

sediments; can be deposited within cobble-boulder lag; in places overlain

by till

Overlies bedrock and sorted glaciofluvial sediment

* Parentheses and italics indicate characteristics that are present but not dominant.


Figure 8 – Locations of esker ridges, glaciofluvial field sites (grouped by landform), and glaciofluvial outwash deposits.

Figure 9 – Examples of ice-contact glaciofluvial landforms and sediment (refer to Figure 8 for geographic locations): A) Oblique aerial photograph of an esker ridge (arrows), trending from bottom left to central right in photograph, Wapusis Lake. B) Oblique aerial photograph of an esker ridge (dashed orange line), trending from top right to central left, flanked by ice-contact glaciofluvial plains (p), and kettles (k), between Lawrence Bay and Cowie Lake. C) Glaciofluvial ice-contact veneer of well-sorted silty very fine to fine, normally graded sand overlies partly clast-supported winnowed till. Some of the clasts (e.g., the one in the centre of the photo) form part of a lag deposit around and over which the veneer was deposited (UTM 654428E, 6273601N).


b) Glaciofluvial Outwash Sediment Glaciofluvial outwash is sediment deposited by glacial meltwater in front of a glacier. As noted above, there could be considerably more outwash sediment within the study area than what was identified. Without more vertical exposures, however, it is difficult to discern the relationship among glaciofluvial landforms and sediments.

Two sites with glaciofluvial outwash were noted in the study area: 1) west of Milton Island, here informally called ‘North-South Bay’; and 2) in Loon Bay (Figure 8). These sediments are thick enough to mask the underlying topography and have gently undulating upper surfaces, but do not have any specific landform.

Numerous vertical faces (0.5 to 2.6 m high) of the outwash deposits were eroded by wave action along the shoreline, permitting detailed observations. The ‘North-South Bay’ deposits were described from one 40-m-long exposure. These deposits comprise 1) planar-inclined (≤22°) and horizontal, crudely bedded, normally or reversely graded, poorly to well sorted, massive to ripple-cross-laminated (type A) coarse to very coarse sand (Figure 10A); and 2) planar-inclined, clast-supported, pebble-cobble gravel sheets, crudely stratified with gravelly coarse sand (Figures 10B and 10C). Overall, beds coarsen upwards (Figure 10B) and in the downflow direction. The Loon Bay deposits were described at several exposures on the southwest side and one exposure on the northeast side of an island. On the southwest side, these deposits display considerable lateral variability: poorly to well-sorted, bedded and laminated, horizontal and planar-inclined, silty very fine to very coarse sand is interbedded with poorly sorted pebbly sand and poorly sorted clast-supported granule to cobble-boulder gravel sheets. One of these exposures displays considerable soft-sediment deformation of silty very fine to fine sand and diamicton, including convolute bedding, rip-up clasts, and loading structures (Figures 10D and 10E). The northeast exposure consists of horizontally bedded and laminated medium to coarse sand and planar-cross-bedded medium to coarse, pebbly sand interbedded with granule to pebble gravels (Figure 10F). At all sites, contacts between beds are conformable or erosive, and clasts are dominantly subrounded to well rounded.

Paleocurrent measurements of cross-beds in the ‘North-South Bay’ site indicate flow was mainly toward the southeast (120 to 147°), with some variation toward the east (081°). Ripples in some beds are consistent with these directions (Figure 10A), whereas ripples (paleocurrent not measured) in other stratigraphically higher beds appear to indicate flow in near-opposite directions. Paleocurrent measurements in exposures at the southern end of the Loon Bay site show a wide variation in flow from east-northeast to south-southeast (060 to 160°), whereas one exposure at the northern end of the site indicates flow northward (360°; Figure 11).

The two glaciofluvial outwash deposit sites are interpreted as subaqueous outwash fans that were deposited in a proglacial lake where meltwater exited from subglacial tunnels at the ice margin directly into deep water. Because of a sudden decrease in velocity, the sediment load was deposited rapidly, creating the fans. These fans mark former ice-margin positions.

These two deposits blanket the underlying terrain, but neither have the shape of outwash fans. Likely, postdepositional erosion in the proglacial and current lakes has modified the original landforms, making it difficult to interpret them from remotely sensed data alone. The ‘North-South Bay’ fan was originally mapped from air photos as till (Alley and Schreiner, 1984), whereas the Loon Bay fan was mapped as an esker trending southward (Alley and Schreiner, 1984).

The crudely stratified, normally graded, locally erosive, poorly sorted, matrix-supported gravel sheets at both sites indicate deposition by high-density, cohesionless debris flows, hyperconcentrated flows, or traction carpets near the apex of the fan (Benn, 1996; Benn and Evans, 2010; Hanson and Clague, 2015). Finer gravel and sand beds were deposited by non-channelized sheet flows moving more distally across the fans, whereas better-sorted cross-bedded and cross-laminated sands record channelized or turbulent underflows (Benn and Evans, 2010; Hanson and Clague, 2015). The variable directions of the ripples (Figure 10A) at the ‘North-South Bay’ site are common in dynamic ice-marginal settings where meltwater effluxes vary laterally. Soft-sediment deformation structures (Figures 10D and 10E) are also common in such dynamic environments, particularly at more distal sites in finer-grained sediments. The diamicton clasts at the Loon Bay site (Figure 10E) could have originated as diamicton (remobilized till) emerging near the ice margin, mass-wasting sediments in an unstable proglacial lake, or till from iceberg dumps, any of which became entrained in the soft-sediment deformation. The paucity of fine to medium sand, silt and clay at these sites indicates that much of it was removed by underflows and by overflow plumes and deposited more distally. The


coarsening upward and in the downflow direction of the beds at the ‘North-South Bay’ fan indicates progradation of the fan, possibly from an increase in meltwater flow or from lateral migration of meltwater channels at the ice front. These fan sediments could drape previously deposited eskers and other landforms or deposits as the ice front retreated.

Figure 10 – Examples of glaciofluvial outwash sediment (refer to Figure 8 for geographic locations): A) Type A rippled coarse sand (middle bed), interbedded with horizontally bedded coarse sand, ‘North-South Bay’ (unofficial name; UTM 641548E, 6287805N). B) Planar-inclined coarse sand, gravelly sand, and pebble-cobble beds, ‘North-South Bay’ (UTM 641548E, 6287805N). C) Inclined pebble-cobble gravel beds, ‘North-South Bay’ (UTM 641548E, 6287805N). D) Convoluted bedding and sediment loading of overlying grey silty very fine sand into underlying beige fine sand, Loon Bay (UTM 658942E, 6291094N). E) Soft-sediment deformation and diamicton rip-up clasts (arrows), Loon Bay (UTM 658942E, 6291094N). F) Planar-cross-bedded coarse sand to pebbly sand with multiple reactivation surfaces, Loon Bay (UTM 659473E, 6292744N).


The ‘North-South Bay’ deposits are dominated by ecosite BS7, which comprises black spruce, blueberry, and reindeer lichens (McLaughlan et al., 2010). The Loon Bay deposits are characterized by ecosite BS3, which is dominated by jack pine, blueberries, and reindeer lichens (McLaughlan et al., 2010). Both ecosites are common on relatively sandy substrates.

c) Beaches Postdepositional erosion of the glaciofluvial ice-contact and outwash sediments described above formed beaches in many places. The majority of beaches are moderately well- to well-sorted, fine to coarse sand with negligible clast content (Figure 7B). These beaches display beds and/or laminations (Figure 6), normal and reverse grading, and some clast imbrications. Where heavy mineral grains are present, there is clear sorting by wave action (Figure 6). At a few locations, gravel beaches are present. These beaches are commonly matrix-free, moderately well- to well-sorted, subangular to subrounded, granule-pebble, or cobble gravel (Figures 12A and 12B). It is not clear that all of these gravel beaches formed directly from glaciofluvial sediment, but most do seem to be spatially associated with the glaciofluvial landforms and sediment (Figure 13).

Figure 12 – Examples of gravel beaches (refer to Figure 13 for geographic locations): A) Pebble beach, island north of Reynolds Peninsula (UTM 653232E, 6283146N). B) Pebble-cobble beach, Levesque Bay (UTM 645605E, 6270663N).

Figure 11 – Paleocurrent directions (arrows) measured from vertical exposures, Loon Bay glaciofluvial outwash deposits (yellow oval).


Figure 13 – Locations of esker ridges, ice-contact glaciofluvial landform sites, glaciofluvial outwash fans, and beach sites.

d) Glaciofluvial Erosional Features Glaciofluvial landforms and sediments in the study area are spatially associated with erosional features such as scoured, exposed bedrock, winnowed till, cobble-boulder lags, cobble-boulder fields, and patchy, eroded till (Figure 14).

Scoured bedrock is mapped in Figure 14 from aerial photographs and field sites. It is characterized by large meltwater-scoured regions (hundreds of metres wide) with a notable paucity (i.e., patchy, eroded till), or complete lack, of glacial sediment (Figure 15A). Exposed bedrock is present up to several kilometres laterally beyond the eskers and other glaciofluvial landforms (Figure 14).

Winnowed till (Figure 15B) is very common throughout the study area and is the product of removal of fine-grained particles (clay, silt and fine to medium sand) from the till matrix by water. Cobble-boulder fields (Figure 15C) are formed by the same winnowing processes to the extent that the matrix is entirely removed; they are commonly spatially associated with winnowed till and are up to a few tens of metres in diameter. It must be noted that winnowing can occur from both glaciofluvial meltwater and wave and current action within a proglacial lake. Figure 14 shows the distribution of winnowed till and cobble-boulder fields, both mapped in the field; some sites are clearly spatially related to the glaciofluvial landforms and sediments, whereas others are more distal. These latter ones are likely the product of glaciolacustrine winnowing, whereas the former are likely the product of both glaciolacustrine and glaciofluvial processes. At some sites proximal to the glaciofluvial landforms, the winnowed till is overlain by the glaciofluvial veneer, confirming a glaciofluvial origin.


Figure 14 – Locations of esker ridges, ice-contact glaciofluvial landform sites, glaciofluvial outwash fans, beach sites, scoured bedrock ridges, winnowed and eroded till, and cobble-boulder fields.

Winnowed till is commonly cobbly and bouldery at the surface, forming a lag deposit, which can be partly infilled with the glaciofluvial veneer. Depths of the winnowed till are on average at least 50 cm, but were noted up to 80 cm; however, in many cases, it was too difficult to dig through the winnowed lag to confirm maximum depths. Winnowed till composition is a function of the original till composition and the amount of subsequent winnowing. Commonly, it is massive, unsorted, loose to moderately compact, matrix to clast supported, with a matrix of silty very fine to fine sand, but with notably lower silt contents than non-winnowed tills. Clast content is highly variable depending on the amount of winnowing, ranging from 35% up to 100% in the cobble-boulder fields. Clasts are commonly angular to subrounded, ranging up to 50 cm in diameter (b-axis). Winnowed till was observed to overlie non-winnowed, undisturbed till in a few locations (Figure 15B), and likely overlies undisturbed till in many places. It was difficult, however, to test this because the high clast concentration made it difficult and inefficient to dig below the winnowed till.

Ecosites related to the winnowed till are highly variable, likely due to variable composition of the original till and the variable amount of subsequent winnowing. Overall, these sites have a higher proportion of deciduous trees than non-winnowed till sites. On fine-grained tills with a moderate amount of winnowing, a black spruce to jack pine and feathermoss ecosite dominates (BS9; McLaughlan et al., 2010). At sites with highly winnowed tills accompanied by substantial lag deposits, a trembling aspen to white birch with green alder ecosite dominates (BS15; McLaughlan et al., 2010).

Eroded till was rarely recognized in the area (Figure 14), partly as a function of there being fewer traverses in areas of known scoured bedrock, but, where noted, it was most common in small, local, protected areas. Eroded till differs from winnowed till in that it does not form a lag deposit with notable boulders and cobbles at the surface. Instead, it


has an upper erosional contact and is either unconformably overlain by the glaciofluvial veneer or is found as thin patches in areas of scoured bedrock. Not enough eroded till sites were documented to provide useful ecosite information.

Figure 15 – Examples of glaciofluvial erosional features (refer to Figure 14 for geographic locations): A) A meltwater-scoured bedrock plateau with thin, patchy sediment cover, southwest end of ‘Duck Lake.’ An esker is ~200 m from the bottom right corner of the photo. B) Winnowed till overlying unmodified till. The winnowed till is coarser, with more clasts than the underlying till (UTM 640339E, 6264491N). C) Matrix-free cobble-boulder field of subrounded to rounded cobbles and boulders (UTM 634575E, 6289063N).

e) Pebble Rock Types Table 3 groups and lists the rock types of pebbles identified in the 10 pebble samples; Table 4 displays percentages of each group of rocks by sample. Samples are either dominated by plutonic rocks or metasedimentary rocks. The majority (92.7%) of the pebbles have compositions consistent with the local geology. A small percentage (2.7%) of the pebbles was not identifiable due to weathering or oxidation. Potential exotic clasts identified were quartz syenites and syenites (4.6%).

Table 3 – Percentages of each rock type identified from the pebble samples that were associated with glaciofluvial sediment.

Igneous (Plutonic) % Igneous (Volcanic) % Metasedimentary % Other %

Calc-silicate rock 0.1 Amphibolite 11.8 Pelite 13.7 Garnetite 0.3

Diorite 6.4 Intermediate volcanic

0.5 Psammite 7.6 Gneiss 2.3

Gabbro 2.2 Psammopelite 7.6 Graphite (oxidized) 0.1

Granite 19.7 Quartzite 3.9 Mylonite 1.0

Granodiorite 6.1 Quartz syenite/syenite 4.6

Leucogranite/aplite 0.7 Quartz vein 1.7

Pegmatite 2.1 Schist 5.0

Tonalite 0.1 Unidentifiable* 2.7

* Due to oxidation and/or weathering


Table 4 – Percentages of each rock grouping, listed by sample (bold indicates dominant rock type in each sample).

Sample % Igneous (Plutonic) % Igneous (Volcanic) % Metasedimentary % Other

MH17-004 22 28 38 12

MH17-018 49 9 14 28

MH17-022 29 11 46 14

MH17-026 48 13 17 21

MH17-031 30 9 47 14

MH17-111 35 21 26 18

MH17-228 41 6 27 26

MH17-251 47 16 22 15

MH17-252 29 7 48 15

MH17-281 66 8 18 8

6. Discussion a) Glaciofluvial Corridors The retreat and melting of ice sheets produces large amounts of water near the ice margin that entrains antecedent glacial deposits (commonly till), sorts them, and redeposits them. Glaciofluvial corridors are attributed to subglacial, channelized meltwater flow, and are commonly dendritic, regularly spaced, 0.3 to 2 km wide, with sharp lateral boundaries (St-Onge, 1984; Rampton, 2000; Utting et al., 2009). These corridors are characterized by sandy and gravelly glaciofluvial sediments (e.g., eskers and veneers), bouldery winnowed till and boulder lags, partially to completely eroded till, and scoured bedrock, among other features not identified within the current study area (St-Onge, 1984; Rampton, 2000; Cummings et al., 2011).

From the descriptions of glaciofluvial ice-contact depositional and erosional features and mapping of their distribution (Figure 14), it is apparent that a regional drainage system existed during the last glacial ice sheet retreat in the study area. For the most part, the ice-contact glaciofluvial landforms and sediments, as well as the erosional features, form multiple glaciofluvial corridors (Figure 16). Generally, the corridors are a few hundreds of metres wide, rarely exceeding 2 km. Some combine to form weakly dendritic patterns. The central component of each corridor is an esker ridge, which is commonly discontinuous and commonly deposited within pre-existing bedrock valleys. Within the corridors, eskers are flanked by glaciofluvial plains, kames and kettles, as well as scoured bedrock, winnowed and eroded till, and cobble-boulder fields (Figure 17). Not all of the erosional features mapped in the study area and shown in Figure 16 are part of the glaciofluvial corridors; likely the ones adjacent to the ice-contact glaciofluvial landforms and sediment are (e.g., the scoured bedrock, winnowed till, and cobble-boulder fields between Cowie Lake and Lawrence Bay; Figure 17), whereas more distal ones (e.g., winnowed till in the northeast arm of Lawrence Bay; Figure 16) are likely the product of winnowing in the proglacial lake. None of the depositional glaciofluvial landforms appear to be deformed, indicating that they likely originated subglacially, as opposed to supra- or englacially (if not proglacially). Adjacent to the corridors, the ground is mostly till covered.

Four well-defined glaciofluvial corridors extend northeast-southwest through the study area (Figure 16). This direction is subparallel to the direction of former ice flow (unpublished data collected in 2017), reflecting meltwater flow toward the ice margin. The main axes of the corridors are separated from each other by approximately 10 to 15 km. From east to west, the corridors are: 1) Bleasdell Lake to Wetmore Lake; 2) Lowdermilk Bay to Wetmore Lake; 3) northern Milton Island to ‘Bikini Beach’; and 4) Cheadle Lake to Jones Peninsula. Although discontinuous in places, the Milton–Bikini and the Lowdermilk–Wetmore corridors can be traced for over 30 km within the study area, and the latter extends to the north and south of the area (Alley and Schreiner, 1984). One, smaller, less well-defined corridor is clear in Fleming Bay and extends to the south (Alley and Schreiner, 1984) and, based on additional glaciofluvial sediment and erosional features, may have originated to the north, near Ochankugahe Island.


Figure 16 – General locations of glaciofluvial corridors. For simplicity, the main axis (commonly eskers) of the corridors (orange lines) is plotted as opposed to the entire width of the corridor, but corridors include nearly all of the ice-contact glaciofluvial landform and sediment sites (red, pink, orange and yellow symbols) and some of the adjacent erosional feature sites (blue and green symbols). For example, the scoured bedrock and winnowed till between Cowie Lake and Lawrence Bay is part of a glaciofluvial corridor (see Figure 17), but the winnowed till along the northeast arm of Lawrence Bay (circled in light grey) is likely the product of winnowing in the proglacial lake.

The ‘North-South Bay’ outwash deposits possibly originate from a corridor flowing southward from north of the area; this is not clear based on information within the study area, but eskers were mapped by Alley and Schreiner (1984) immediately to the north. The Loon Bay outwash fan, however, is difficult to associate with a known corridor. The paleocurrent directions are incongruous with the general direction of glaciofluvial corridors throughout the area; instead they indicate an ice front to the west of the deposit. More investigation of sediments to the north and northwest of this fan might aid in putting this landform into a regional context.

b) Drift Prospecting for Kimberlite Indicator Minerals At a reconnaissance scale, the study area is ideal for drift prospecting for kimberlite indicator minerals. It has abundant glaciofluvial sediment, in particular eskers, which are the most commonly sampled landform at this scale (Cummings et al., 2011, and references therein). Ten of the 19 KIM samples were collected directly from eskers or from beaches derived from them. In order to achieve a reasonable distribution of samples, it was necessary to sample glaciofluvial sediment not directly from eskers. Samples were thus collected from other beaches, from plains and kames within the glaciofluvial corridors, as well as the two subaqueous outwash fans (Figure 5). These different glaciofluvial landforms and sediments have different compositions than the eskers and might not be as ideal a sample material. No systematic study has been completed yet determining whether or not other sediment within glaciofluvial corridors is similarly as useful as that from eskers (cf., Cummings et al., 2011).


Figure 17 – SGIC photo showing some aspects of glaciofluvial corridors in the study area: eskers, kettles, glaciofluvial ice-contact blankets and veneers, scoured bedrock, eroded till, and cobble-boulder fields. Dashed lines show some approximate corridor boundaries, with till dominating the terrain adjacent to the corridor.

Glaciofluvial deposits commonly originate from the erosion of antecedent till and the subsequent transportation and deposition of these eroded materials. Thus, if KIMs are found in these 19 samples, their source will need to be traced initially to till deposits up-ice, before subsequently being traced to a bedrock source farther up-ice (e.g., Cummings et al., 2011 and references therein). The sample collected from the Loon Bay outwash fan might be difficult to trace to its source because it is currently difficult to situate this landform in a regional context. The other sites, however, should be somewhat more straightforward. Within the study area, the winnowing of fines in till (from both glaciofluvial and glaciolacustrine processes) could produce a higher concentration of heavy minerals in the lag deposits than in the undisturbed till, providing potentially useful sample material for the next stage of drift prospecting.

An assessment of the pebble samples commonly helps to determine glaciofluvial sediment provenance and dispersal distance. A simple assessment of this small dataset indicates that nearly all of the clasts (92.7%) could be of local origin and the glaciofluvial sediment may not have been transported very far. Typically, dispersal trains within eskers extend up to a maximum of 25 km (Cummings et al., 2011, and references therein). Eskers within the region of the study area trend generally to the southwest. Following this trend in the up-ice direction, a large portion of the pebbles are also consistent with bedrock geology up to 100 km to the northeast of the study area (Manitoba Energy and Mines, 1989; Corrigan, 2000), and whereas this is a considerable distance for clasts to have been transported, it cannot be precluded that some of the clasts could have come from this far away. In fact, streamlined landforms mapped in NTS sheet 64F in Manitoba (Kaszycki and Way Nee, 1990) could indicate fast ice flow to the north-northeast of the study area that could have transported many distal clasts within reach of the study area where they could have been entrained by the subglacial glaciofluvial corridors. This makes it difficult at this stage to conclude whether glaciofluvial sediment in the area is of local or distal origin. Planned analysis of pebble rock types in till and fine-fraction geochemical analysis of till in the study area might help determine glacial dispersal distances within the region.


Determining the origin of the exotic clasts (quartz syenite and syenite) is difficult. It is possible that these pebbles were misidentified in the field; for example, they could possibly be clasts from local pegmatites. Assuming they were correctly identified, however, the only known potential source rock to the north or northeast for over 100 km is the Patterson Island pluton, exposed on Patterson Island, Reindeer Lake (Figure 1), ~100 km directly north of the study area (Corrigan, 2001). The dominant direction of flow of glaciofluvial corridors in the study area and to the north (Alley and Schreiner, 1984) is generally to the southwest, which is not consistent with the transportation of clasts from the Patterson Island pluton to the study area. More specifically, dominant ice-flow directions in the Patterson Island area are to the south-southwest (205° to 210°; Campbell, 2003), although one older, more southerly direction was recorded in that area (~190°; Campbell, 2003). This southerly direction has not been documented very far south of Patterson Island, however (Campbell, 2003), and this direction is still difficult to reconcile with these pebbles in the study area, as it is only southerly enough to transport the clasts to the very northwestern corner of the study area, if at all. Additionally, there is no known dominant south-southeastward ice-flow direction in the study area (unpublished data collected in 2017) or to the north (Alley and Schreiner, 1984) that could postdate the Patterson Lake 190° direction to subsequently bring these pebbles into the study area. It also cannot be discounted that a previous glaciation transported these clasts to within the range of the study area. The source of these clasts is at present unconfirmed.

c) Ecosites Ecosites were recorded at most sites in order to help with identifying sediment type more quickly, both from remotely sensed images and in the field. However, the high variability of the glaciofluvial sediment leads to a wide range of ecosites, making it difficult to draw many useful conclusions from this dataset. Generally, sites with glaciofluvial sediment at the surface tend to have more jack pine and deciduous trees than sites that have till at the surface. Black spruce trees prefer finer-grained sediment, such as silty fine sand, whereas jack pine and deciduous trees prefer coarser-grained sands. Areas that are highly winnowed, dominated by cobble-boulder lags to cobble-boulder fields, were almost exclusively characterized by open stands of aspen with lots of leaf litter.

7. Future Work This paper deals with only one component of the South Reindeer Lake Quaternary project. Results from analysis of the KIM samples submitted to SRC’s Geoanalytical Laboratories are imminent and will be added to the Saskatchewan KIM database and the GeoAtlas once available. Other products from this project will include two 1:100 000-scale surficial geological maps and a data file of the fine-fraction till geochemistry and grain size determination results once they are available. Several upcoming reports will address other aspects of the surficial geology, such as till and glaciolacustrine sediment distribution and composition, and ice-flow directions and chronology. All of these products combined will aid in the production of a glacial dispersal model for the region to better assist with drift prospecting in the area.

8. Conclusions A regional subglacial meltwater drainage network dominated the study area during the last deglaciation. Six glaciofluvial corridors have been identified, flowing generally from the northeast to the southwest. These corridors are 0.3 to 2 km wide, separated by 10 to 15 km, forming a weakly dendritic pattern, and are characterized by eskers, glaciofluvial plains, kames and kettles, scoured bedrock, winnowed and eroded till, cobble-boulder fields, and distinct lateral boundaries.

Nineteen samples of glaciofluvial sediment were collected for KIM analysis. At the time of publication, results from the analysis of the KIM samples were not available, but they will be added to the Saskatchewan KIM database and the GeoAtlas once available. Ten samples of pebbles were collected from glaciofluvial sediment, with the intent to determine dispersal distance of the sediment. Whereas almost all of the pebbles are consistent with the local bedrock geology, some are also consistent with bedrock geology up to 100 km to the northeast, making it currently difficult to determine glaciofluvial sediment dispersal distance.


9. Acknowledgments Field assistance was provided by D. Dixon and R. Mohrbutter, with contributions from K. Cunningham, P. Kelley and J. Schmidt, all of whom are thanked for their hard work. D. Robertson and the staff at Robertson Trading Ltd., A. Thompson and the staff and pilots at Osprey Wings Ltd., P. Engen at the Lawrence Bay Lodge, and D. Clarke at Lawrence Bay Airways are all acknowledged for superlative logistical support throughout the summer. R. Maxeiner is thanked for helpful discussions about the regional bedrock geology, pebble rock types and pebble provenance; J. Dale is thanked for a thorough and critical review of this paper that much improved it; and K. Ashton is thanked for a thorough review that helped clarify the discussion.

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