Preliminary Investigation: Sedimentology and Provenance of the Wood Mountain Formation and Derived Glacial and Glaciofluvial Sediments – Context for Kimberlite Indicator Mineral Anomalies

Lynn Kelley and Gary Yeo

Kelley, L. and Yeo, G. (2004): Preliminary investigation: Sedimentology and provenance of the Wood Mountain Formation and derived glacial and glaciofluvial sediments – context for kimberlite indicator mineral anomalies; in Summary of Investigations 2004, Volume 2, Geological Survey, Sask. Industry Resources, Misc. Rep. 2004-4.2, CD-ROM, Paper A-12, 10p.

Abstract Garnet, diopside, and chromite with chemistries inferred to indicate mantle affinity are geochemical pathfinders exploited in prospecting for diamond. In southern Saskatchewan, these minerals are found in high abundances in gravel, sand, and poorly-consolidated conglomerate of the Wood Mountain Formation, and overlying tills and glaciofluvial deposits. Several campaigns have been mounted to explore for a potential kimberlitic source for these pathfinder minerals, but no satisfactory explanation for their presence has been put forward. This project is intended to provide geological context for the occurrences of kimberlite indicator minerals found in the Wood Mountain area, by examining the transport history and provenance of the strata containing them. This note summarizes preliminary observations on sediment transport data and sediment provenance from seven locations. Grain size analysis, detailed provenance studies, and analysis for kimberlite indicator minerals and detrital gold are pending, and will be reported upon in a future communication.

Keywords: Wood Mountain, kimberlite indicator, sediment provenance, paleocurrent.

1. Introduction a) Exploration History Southern Saskatchewan has been explored for diamond since at least 1963, when a De Beers affiliate discovered kimberlite indicator minerals in the Frenchman River Valley (Lehnert-Thiel et al., 1992). Kimberlite indicator mineral surveys carried out by various public agencies (Simpson, 1991; Gent, 1992; Swanson and Gent, 1993; Thorleifson and Garrett, 1993; Millard and Drever, 1994; Thorleifson et al., 1994; Millard and Day, 1996) confirmed the presence of indicator minerals in gravel, sand and poorly-consolidated conglomerate of the Wood Mountain Formation, and tills and glaciofluvial deposits of local provenance in southern Saskatchewan. The 1988 discovery by Monopros (then the Canadian exploration arm of De Beers) of the Sturgeon Lake kimberlite block, northeast of Prince Albert, was followed by an unprecedented staking rush. In addition to the central Saskatchewan staking activity that led to the discovery of the Fort à la Corne kimberlite field, Monopros, Cameco, and Better Resources staked ground in the southern part of the province. Better Resources confirmed some of the indicator mineral anomalies and flew a 5730 line-km aeromagnetic survey in search of local kimberlite sources (SIR Assessment Files 72-0005; 72G3-NE-0001; 72G6-SW-0001; 72H5-SW-0009; and 72J-0002). The company recognized several magnetic features as potential kimberlite targets, but failed to drill test any of them and most of the ground lapsed. Pure Gold Resources staked a large tract of ground in 1998, again confirmed some of the indicator mineral anomalies, and flew 16 152 km of aeromag (SIR Assessment File 72G-0001). Again, potential targets were not drill tested. Madison Exploration recently launched an exploration program in southern Saskatchewan centred on a northeast-trending linear magnetic anomaly near . The anomaly was identified from the Better Resources magnetic survey, but Better Resources was focused on circular structures as targets indicative of the classic kimberlite “pipe,” and ignored this linear feature. Madison has completed a Mobile Metal Ions survey over the anomaly, and plans further exploration, including drilling, in the fall of 2004. b) Previous Work Peridotitic garnet, G-10 garnet, chrome diopside, and chromite have been recorded in the Wood Mountain area (Figure 1). Peridotitic garnet abundances of 25 to more than 50 grains per sample are reported in six samples that form a northwest trend beginning just north of the village of . Most of these samples also contain multiple grains of chrome diopside; two samples on this trend, and another just to the southwest, contain single grains of high-chromium chromite. Another cluster of samples with high abundances of peridotitic garnets and chrome diopside were collected northeast of the West Block of . One sample in this cluster

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Saskatchewan Geological Survey 2 Summary of Investigations 2004, Volume 2 contains a single grain of high chromium chromite. Samples containing G-10 garnets and eclogitic garnets occur throughout the area, but form no discernible pattern. The anomalous results occur more or less across the outcrop belt of the late Miocene Wood Mountain Formation, and include results from both the poorly consolidated Wood Mountain conglomerate and overlying glacioclastic sediments. The Wood Mountain Formation (and its stratigraphic equivalent in , the Flaxville Formation) is one of a series of Tertiary fluvial conglomerates in southern Saskatchewan. Paleographic reconstructions by Vonhof (1969), Whitaker (1980), and Leckie and Cheel (1989) suggested that the coarse siliciclastic deposits of the Wood Mountain Formation were formed by eastward transport of coarse gravels from the Eocene-Miocene Cypress Hills Formation and northward fluvial transport of sediment derived from the Belt Supergroup and the various Cenozoic intrusive and extrusive rocks of the Montana Alkaline Province (Hearn, 1989). Kjarsgaard (1995) compared compositional data for garnet and clinopyroxene from southern Saskatchewan tills with similar data for garnet and clinopyroxene derived from Montana Alkaline Province igneous rocks and found significant overlap. One interpretation is that the rocks of the Montana Alkaline Province, eroded and transported north and east by streams, might be the source of the kimberlite indicator minerals found in the Wood Mountain Formation. Overlying tills in the Wood Mountain vicinity inherited abundant indicator minerals from the latter. Kimberlites have been documented in at least two locations in the Montana Alkaline Province: the Williams Kimberlite of the Missouri Breaks diatremes is about 200 km southwest of the Wood Mountain area, and the recently discovered Homestead Kimberlite is in the Grassrange intrusion field, about 300 km to the southwest (Ellsworth, 2000; Doden et al., 2001). Hearn (1999) described peridotitic xenoliths in aillikitic rocks at Froze-to- Death Butte, Johnson Ranch, Gold Butte, and other locations in the Porcupine Dome, about 300 km south- southwest of the Wood Mountain area. Xenolithic (contained in peridotite xenoliths) and xenocrystic (liberated from xenoliths and in contact with matrix) garnets of G-9 composition were relatively common, but no G-10 or eclogitic garnets were found. Clinopyroxene containing greater than 1.5% Cr2O3 and chromite with Cr2O3 content in the 52 to 59% range were also noted.

Swanson and Gent (1993) advocated a local source for kimberlite indicator minerals in the Wood Mountain area. They noted that the abundance of kimberlite indicator minerals in till was highly variable and that there was little correlation between abundance of indicator minerals in tills and the relative proportion of locally-derived sediment (quartzite and chert cobbles) in the till. They described garnet grain surfaces from Wood Mountain area samples that showed virtually no abrasion due to sedimentary transport and in some instances also had kelyphitic rims or orange- peel textures. Furthermore, the senior author has observed euhedral prismatic bright green clinopyroxenes in tills between the two blocks of Grasslands National Park. These observations are at odds with the concept of fluvial transport from source rocks hundreds of kilometres away. Laboratory abrasion studies carried out on kimberlite indicator minerals by Atkinson (1989) and McCandless (1990) suggest that preservation of euhedral shapes or primary surface textures would be unlikely beyond a few tens of kilometres of fluvial transport.

Indicator minerals may have been transported to the Wood Mountain area in lithic boulders or cobbles and the indicator minerals liberated locally. Vonhof (1969) examined more than 4000 pebbles and cobbles from the Wood Mountain Formation. Fewer than 0.5% were classified as igneous in origin, and these were predominantly felsic porphyritic rocks. Vonhof described two pebbles of flow breccia similar to flow breccia pebbles present in the Cypress Hills Formation. If the flow breccia pebbles from the Wood Mountain Formation are indeed from the same source as those described from the Cypress Hills Formation, they are unlikely to be the source of indicator minerals, which are much more abundant in the Wood Mountain area than in the Cypress Hills.

2. Field Work Late in the 2004 field season, the authors undertook a detailed study of the Wood Mountain Formation and locally derived glacial sediments, focusing on the vicinities where anomalous kimberlite indicator minerals had been previously documented. Stratigraphic sections were measured and described at seven locations (Figure 2). The measured sections and other field data will form the basis of a paleogeographic reconstruction that is underway, partly as a B.Sc. honours project at the University of Saskatchewan by Amanda Perrot. Twelve bulk samples were collected for analysis for kimberlite indicator minerals and detrital gold, but results were not available at the time of writing.

3. Preliminary Results a) Sediment Provenance Wood Mountain Formation pebble count data are summarized on Figure 3 and Table 1. Clasts in the Wood Mountain Formation, in order of abundance, include: light coloured fine- to medium-grained quartzite; pink, red,

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Saskatchewan Geological Survey 4 Summary of Investigations 2004, Volume 2 N % ilometres k 0 a Ogema Saskatchewan Wood Mountain Wood Study Area 09 indicated on Figure 2. on Figure indicated ' '' ''' 06 Rockglen Assiniboia % % ' '' '''' le locations. Locations are Locations locations. le

Wood Mtn. 03 % Legend Outcrop of WoodMtn. Formation Lafleche ''' % '' ' ''' Grasslands National Park ' Figure 3 - Pie charts of pebble counts posted to samp Pie Figure 3 - Cadillac % %

Saskatchewan Geological Survey 5 Summary of Investigations 2004, Volume 2 Table 1 - Wood Mountain Formation pebble count data. WR, well rounded; SA, sub-angular; R, rounded; and SR, sub- rounded. Clast Dimensions (mm) Rounding No. % Avg. Max. Min. S.D. Location 04AP-1 Willow Bunch ? (451313E, 5470401N) Light tan to buff meta-quartzite WR 75 61 52 110 20 17.7 Pink, red, and brown meta-quartzite WR 13 10.6 40 65 15 17.4 Argillite WR 7 5.7 26 45 10 13 Chert WR 11 8.9 28 60 5 16.2 Gritstone WR 14 11.4 60 90 35 18.4 Conglomerate WR 1 0.8 30 30 30 Silicified wood SA 2 1.6 28 40 15 17.7 Felsic volcanic Vein quartz ALL CLASTS 123 100 47 110 5 9.9

Location 04AP-2 Willow Bunch (451313E, 5470401N) Light tan to buff meta-quartzite WR 80 63 48.4 130 15 27.4 Pink, red, and brown meta-quartzite WR 8 6.3 33.1 70 15 16.9 Argillite WR 10 7.9 17.5 25 10 5.4 Chert WR 8 6.3 25.6 40 10 9.4 Gritstone WR 17 13 41.8 75 25 14.4 Conglomerate RW 1 0.8 35 35 35 Silicified wood SA 3 2.4 56.7 115 25 50.6 Felsic volcanic Vein quartz ALL CLASTS 127 100 42.8 130 10 27.4

Location 04AP-9 Mankota Community Pasture (351192E, 5453886N) Light tan to buff meta-quartzite WR 95 70 33 95 10 15.6 Pink, red, and brown meta-quartzite R 8 6 29 55 15 14 Argillite R 16 12 19 35 8 8.7 Chert SR 8 6 26 48 12 12.7 Gritstone WR 7 5 47 105 15 29 Conglomerate Silicified wood Felsic volcanic SR 1 1 25 25 25 Vein quartz SR 1 1 50 50 50 ALL CLASTS 136 100 32 105 8 16.5

Location 04AP-12 Glentworth Quarry (377640E, 5461162N) Light tan to buff meta-quartzite WR to R 28 58.3 53 95 22 19.9 Pink, red, and brown meta-quartzite R to WR 8 16.7 32 45 20 8.8 Argillite SR 4 8.3 21 25 15 5.1 Chert SR to R 5 10.4 35 45 25 9.1 Gritstone R 3 6.3 51 90 25 34.4 Conglomerate Silicified wood Felsic volcanic Vein quartz ALL CLASTS 48 100 45 95 15 20.7

Location 04AP-13 South of Mankota (338044E, 5443490N) Light tan to buff meta-quartzite WR to SR 57 59 31.3 65 10 15 Pink, red, and brown meta-quartzite R 12 12 24.2 55 8 13.9 Argillite SR 7 7.2 12.9 20 8 4.3 Chert SR 8 8.2 17.9 30 12 6.3 Gritstone WR to SR 10 10 43.1 80 28 17.7 Conglomerate Silicified wood SR 1 1 40 40 40 Felsic volcanic R to SR 2 2.1 30 40 20 Vein quartz ALL CLASTS 97 100 29.3 80 8 15.7

Location 04AP-14 Northwest of Lisieux (420412E, 5462405N) Light tan to buff meta-quartzite R to WR 70 69 30 105 8 17.8 Pink, red, and brown meta-quartzite WR to SR 10 10 21 30 10 6.7 Argillite SR 4 4 16 25 10 Chert SR 7 7 20 30 12 Gritstone WR to SR 3 3 26 30 17 Conglomerate R 1 1 30 30 30 Silicified wood Felsic volcanic R to SR 2 2 32 38 25 Vein quartz SR 4 4 16 28 8 ALL CLASTS 101 100 27 105 8 15.9

Location 04AP-16/17 Quantock Road (419978E, 5431537N) Light tan to buff meta-quartzite R to WR 62 57.9 25 45 12 8.4 Pink, red, and brown meta-quartzite R to WR 18 16.8 23 48 10 10.6 Argillite SR to R 5 4.7 17 20 10 Chert SR to R 10 9.3 14 25 9 4.9 Gritstone R to WR 8 7.5 36 52 22 Conglomerate Silicified wood Felsic volcanic WR to SR 2 1.9 25 30 20 Vein quartz R to WR 2 1.9 30 40 20 ALL CLASTS 107 100 24 52 9 9.7

Location 04AP-21 Fir Mountain Road (387756E, 5456968N) Light tan to buff meta-quartzite WR to SR 73 68 27.1 90 12 16.2 Pink, red, and brown meta-quartzite R 9 8.3 27.8 52 15 Argillite SR to WR 3 2.8 12.3 18 8 Chert SR 9 8.3 15.1 20 10 Gritstone SR to WR 9 8.3 30.1 60 18 Conglomerate R 1 0.9 25 25 25 Silicified wood SR to R 2 1.9 20.5 26 15 Felsic volcanic R 1 0.9 12 12 12 Vein quartz R 1 0.9 18 18 18 ALL CLASTS 108 100 25.6 90 8 14.9

Saskatchewan Geological Survey 6 Summary of Investigations 2004, Volume 2 and brown quartzite; very coarse-grained sandstone and gritstone; black argillite; chert; silicified wood; felsic igneous rock; pebble conglomerate; and vein quartz (Table 1; Figure 3). As noted by Vonhof (1969), tan to white quartzite is by far the dominant component, making up 58 to 70% of the gravel, while the last four clast types are not present in all samples. The clasts are mainly rounded to well rounded, except for silicified wood, which is typically subangular. Light coloured quartzite is particularly abundant at the Mankota Community Pasture, Fir Mountain Road, and Lisieux sites. This may reflect systematic regional variation. Silicified wood is typical of the more northerly sites, whereas felsic igneous rocks (mainly quartz-feldspar porphyries) are typical of the southwesterly sites. Very coarse-grained sandstone and gritstone, with average sizes ranging from 25.7 to 51 mm, are typically the largest clasts, while argillite clasts, with average sizes ranging from 12.3 to 25.7 mm, are typically the smallest. As Vonhof (1969) observed, average clast size does not become systematically smaller towards the east, with increased distance from source, as might be expected (e.g., Reid and Frostick, 1994). Average clast size is smallest at three central sites, Fir Mountain Road, Lisieux, and Quantock Road, and largest at the most easterly and westerly sites, Willow Bunch and Mankota Community Pasture, respectively. The quartzites, gritstones, and argillites were likely derived from late Proterozoic strata exposed in the eastern Rocky Mountains. Quartz feldspar porphyries are a distinctive feature of the Wood Mountain gravels (Vonhof, 1969) and are likely derived from early Tertiary volcanic complexes in west-central Montana. The characteristic angularity of the silicified wood suggests a more proximal source for that constituent as well. The observed variation in average clast size may reflect variation in regional stream gradient, with larger clasts at the westernmost and easternmost sites suggesting steeper gradients in those areas. b) Sediment Transport Data The most stable orientation for clasts in gravel bars is dipping upstream, subparallel to the flow direction (Collinson and Thompson, 1982). Mean clast imbrication values reported here from the Wood Mountain Formation suggest bars with axes trending 023º to 146º and indicate generally easterly gravel transport (Figure 4, Table 2). The predominance of gravel deposits and relatively low sediment transport variance variation (Miall, 1974) are typical of braided river systems.

At five of the seven sites, foreset azimuths in cross-bedded sand were measured as well as clast imbrication. In most cases, relatively few foresets could be measured; hence the data show more scatter than clast imbrication. Mean foreset orientations reported here range from 343° to 094°, but are generally oblique to the mean transport direction of gravel at the same sites. The foresets probably represent transverse or diagonal sand bars or longitudinal gravel bars developed during waning flood episodes (i.e., water draining off the high gravel bars) (Collinson, 1986).

4. Future Work Stratigraphic sections were measured and described at seven locations during the 2004 field season. The measured sections and other field date will form the basis of a paleogeographic reconstruction that is underway, partly as a B.Sc. honours project by Amanda Perrot. Results for the bulk samples currently being processed for kimberlite indicator minerals will be archived on-line in the Saskatchewan Kimberlite Indicator Mineral Database at http://www.ir.gov.sk.ca/dbsearch/SaskKimbQuery/. Interpretation of the indicator mineral results in light of the paoleogeographic reconstruction will be the subject of a further paper.

5. References Atkinson, W.J. (1989): Diamond exploration philosophy, practice and promises: A review; in Ross, J. (ed.), Kimberlites and Related Rocks, Volume 2: Their Mantle/Crust Setting, Diamonds and Diamond Exploration, Blackwell Scientific, Victoria, Australia, p1075-1107. Collinson, J.D. (1986): Alluvial Sediments; in Reading, H.G. (ed.), Sedimentary Environments and Facies, Blackwell Scientific, Oxford, p20-62. Collinson, J.D. and Thompson, D.B. (1982): Sedimentary Structures; George Allen Unwin, London, 194p. Doden, A.G., Ellsworth, P.C., Gold, D.P., and Sicree, A.A. (2001): Lamprophyre and kimberlite intrusions from the Grassrange Field, central Montana; Geol. Soc. Amer., http://gsa/confex.com/gsa/2001AM/finalprogram/ abstract_26354.htm, accessed 15 Nov 2004.

Saskatchewan Geological Survey 7 Summary of Investigations 2004, Volume 2

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Saskatchewan Geological Survey 8 Summary of Investigations 2004, Volume 2 Table 2 - Location of sample sites and statistics for Wood Mountain Formation paleocurrent measurements. All UTM locations are NAD83, Zone 13.

Site Sections Structures Easting Northing Mean (o) n Standard Confidence Deviation (%) Interval (o)

Wood Mountain Formation Willow Bunch 04AP-2 Imbrication 451313 5470401 072* 62 7.2 13 04AP-5 451312 5470443 04AP-2 Cross-beds 451313 5470401 020 20 3.3 57 Mankota 04AP-7 Imbrication 351224 5453909 079* 76 4.1 17 Community 04AP-8 351207 5453898 Pasture 04AP-9 351192 5453886 04AP-9 Cross-beds 351192 5453886 011 7 5.8 113 Glentworth Quarry 04AP-10 Imbrication 377728 5460908 103* 102 4.9 12 04AP-11 377784 5460897 04AP-12 377640 5461162 04AP-10 Cross-beds 377728 5460908 030 9 5.4 51 04AP-11 377784 5460897 South of Mankota 04AP-13 Imbrication 338044 5443490 16* 11 2.9 31 Northwest of Lisieux 04AP-14 Imbrication 420412 5462405 104* 35 2.1 12 Quantock Road 04AP-15/16 Imbrication 419978 5431537 023* 51 5.1 12 04AP-17 Cross-beds 419976 5431568 094 11 4.7 64 04AP-18 419977 5431584 Fir Mountain Road 04AP-21 Imbrication 387756 5456968 106* 24 4.9 72 04AP-21 Cross-beds 387756 5456968 343 3 0 92 Ravenscrag Formation

St. Victor 04AP-6 Cross-beds 451313 5470444 342 6 7.5 41 Mankota 04AP-7 Cross-beds 351224 5453909 122 22 8 18 Community 04AP-8 351207 5453898 Pasture 04AP-9 351192 5453886 * For ease of comparison between mean foreset and clast imbrication measurements, the latter are reported as reciprocals of mean clast dip azimuth. Ellsworth, P.C. (2000): Homestead Kimberlite: New discovery in central Montana: Guidebook; 25th Annual Tobacco Root Geol. Soc. Field Conference, Butte, p14-20.

Gent, M.R. (1992): Diamonds and precious gems of the Phanerozoic Basin, Saskatchewan: Preliminary investigations; Sask. Energy Mines, Open File Rep. 92-2, 67p.

Hearn, B.C. (1989): Montana high-potassium igneous province; in Field Trip Guidebook T346, 28th International Geological Conference, Amer. Geophys. Union, Washington, July, p1-5.

______(1999): Peridotite xenoliths from Porcupine Dome, Montana, USA: Depleted subcontinental lithosphere samples in an olivine-phlogopite-carbonate magma; in Gurney, J.J., Gurney, J.L., Pascoe, M.D., and Richardson, S.H. (eds.), Proceedings of the VIIth International Kimberlite Conference, Volume 1 – The J.B. Dawson Volume, Red Roof, Cape Town, April, 11 to 17, 1998, p353-360. Kjarsgaard, B.A. (1995): Research on kimberlite and application of diamond exploration techniques in Saskatchewan; in Richardson, D.G. (ed.), Investigations Completed by the Saskatchewan Geological Survey and the Geological Survey of under the Geoscience Program of the Canada-Saskatchewan Partnership Agreement on Mineral Development (1990-1995), Geol. Surv. Can., Open File 3119, p213-226. Leckie, D.A. and Cheel, R.J. (1989): The Cypress Hills Formation (Upper Eocene to Miocene): A semi-arid braidplain deposit resulting from intrusive uplift; Can. J. Earth Sci., v26, p1918-1931. Lehnert-Thiel, K., Loewer, R., Orr R.G., and Robertshaw, P. (1992): Diamond-bearing kimberlites in Saskatchewan, Canada: The Fort à la Corne Case History; Explor. Mining Geol., v1, p391-403. McCandless, T.E. (1990); Kimberlite xenocryst wear in high-energy fluvial systems: Experimental studies; J. Geochem. Expl., v37, p323-331.

Saskatchewan Geological Survey 9 Summary of Investigations 2004, Volume 2 Miall, A.D. (1974): Paleocurrent analysis of alluvial sediments: A discussion of directional variance and vector magnitude; Jour. Sed. Pet., v44, p1174-1185. Millard, M. and Day, R. (1996): Bulk sampling for diamonds in southwestern Saskatchewan; in Summary of Investigations 1996, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 96-4, p153-156. Millard, M.J. and Drever, G. (1994): Kimberlite indicator mineral sampling in west-central Saskatchewan, Canada; Sask. Resear. Counc., Publ. No. R-1200-3-D-94, 1p. Reid, I. and Frostick, L.E. (1994): Fluvial sediment transport and deposition; in Pye, K. (ed.), Sediment Transport and Depositional Processes, Blackwell Scientific, Oxford, p89-155. Simpson, M. (1991): Kimberlite indicator minerals in southwestern Saskatchewan; Sask. Resear. Counc., Publ. No. R-1210-8-E-91, 13p and 4 appendices on diskette. Slimmon, W.L. (2002): Geological Atlas of Saskatchewan; Sask. Industry Resources, CD-ROM, version 5. Swanson, F.J. and Gent, M.R. (1993): Results of reconnaissance sampling for kimberlite and lamproite indicator minerals, Saskatchewan; Sask. Energy Mines, Open File Rep. 93-4, 179p. Thorleifson, L.H. and Garrett, R.G. (1993): Prairie kimberlite study – till matrix geochemistry and preliminary indicator mineral data; Geol. Surv. Can., Open File Rep. 2745, 1 diskette. Thorleifson, L.H., Garrett, R.G., and Matile, G. (1994): Prairie kimberlite study indicator mineral geochemistry; Geol. Surv. Can., Open File Rep. 2875, 13p and 1 diskette.

Vonhof, J.A. (1969): Tertiary gravels and sands in the Canadian Great Plains; unpubl. Ph.D. thesis, Univ. Saskatchewan, 170p.

Whitaker, S.A. (1980): The Flaxville Formation in the Scobey-Opheim area, northeastern Montana; unpubl. M.Sc. thesis, Univ. Colorado, 113p.

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