Distribution of Lower Paleozoic Strata in the Vicinity of the Meadow Lake Escarpment, West-Central Saskatchewan

F.M. Haid/

Haid!, F.M. (1989): Distribution of Lower Paleozoic strata in the vicinity of the Meadow Lake Escarpment, west-central Sas­ katchewan; in Summary of Investigations 1989, Saskatchewan Geological Survey; Saskatchewan Energy and Mines, Miscel­ laneous Report 89-4.

This study was undertaken to provide data necessary to (Figure 1). Stratigraphic correlations of and delineate the northern limits of Ordovician and Silurian carbonates were established using geophysical strata on maps generated for the New Geologic Atlas of logs and drill cuttings. Data from the and Or­ Western Sedimentary Basin, and to further on­ dovician elastic sequence are from Paterson (1971) and going research by the author on the Silurian sequence from an ongoing regional study by D.F. Paterson, who in Saskatchewan (Haid!, 1987, 1988). The paper sum­ kindly made available these new data. marizes results from 73 wells in an area encompassing Townships 47 to 64, Range 24W2 to the border

~ SUBCROP OF INTERLAKE FORMATION SUBCROP OF STONY MOUNTAIN FORMATION

~ [>. <)! SUBCROP OF STONEWALL FORMATION L...... :...J SUBCROP OF RED RIVER FORMATION - (HERALD /YEOMAN FORMATIONS)

Figure 1 - Suocrop map of Lower Paleozoic caroonatt,s in the study ama. The erosional edge of the Red River Formation defines the Meadow Lake Escarpment, a northwest-facing slope formed by differential erosion of Red River caroonates and Dead· wood/Earlie elastics. The location of cross section A·A' (Figure 2) is shown by a heavy black line.

Saskatchewan Geological Survey 125 1. Geologic Setting Meadow lake Escarpment, along the northeast-south­ west curvilinear trend of the erosional edge of the Red Lower Paleozoic strata in Saskatchewan were deposited River Formation (van Hees, 1958). Later transgression on the Interior Platform component of the Western of the sea southwards across the Escarpment resulted Canada Sedimentary Basin (Aitken, in press; Osadetz in deposition of the argillaceous dolomites, dolomitic and Haidl, in press). These deposits encompass the two shales. and minor anhydrites of the Ashern Formation lowermost major unconformity-bounded sequences of (van Hees, 1958; Buller 1958; uppermost beds, Meadow Sloss (1963), the Sauk Sequence and Tippecanoe Se­ Lake Fm., Fuzesy, 1980). At the close of Ashern deposi­ quence. In west-central Saskatchewan, Sauk Sequence tion, the Meadow Lake Escarpment was buried by strata are composed entirely of elastics (Deadwood and sediments (Figure 2). Earlie Formations) of Middle Cambrian to Early Or­ dovician age. A major unconformity separates these In the northeast corner of the study area (wells in Twp. elastics from the basal elastic unit of the Tippecanoe Se­ 61 and 64, Age. 24W2; Twp. 63, Age. 1W3, Table 1), quence, the Winnipeg Formation (Middle Ordovician), truncation of Devonian and Lower Paleozoic strata oc­ which is present only in the eastern portion of the study curred during the pre- erosion period. In this area (Table 1). The remainder of the Tippecanoe Se­ area, Lower Cretaceous sandstones of the Mannville quence is composed of carbonates of Late Ordovician Group overlie Ordovician carbonates. to Early Silurian age. This carbonate sequence was deposited in the ancestral Williston Basin with northern depositional limits that probably extended well beyond 2. the study area, but uplift on the northern margin during the pre-Devonian erosion period resulted in substantial a) Deadwood and Earlie Formations truncation of Lower Paleozoic strata (van Hees, 1958, 1964). At the erosional margin of resistant Ordovician Historically, the siltstones, shales, and sandstones which carbonates (Figure 2), more rapid erosion of less resis­ comprise the basal sedimentary sequence in western tant Deadwood/Earlie claS1ics formed a relatively steep Saskatchewan have been assigned to the Deadwood northwest-facing slope, the Meadow Lake Escarpment Formation (Fyson, 1961; Fuzesy, 1980). Recent work by (van Hees, 1958). North of this escarpment, pre­ Paterson (1988; this volume) suggests that the lower por­ Oevonian erosion also removed up to 300 m of Sauk Se­ tion of the sequence is Middle Cambrian in age and cor­ quence strata (van Hees, 1958, 1964). relates with the Earlie Formation defined in eastern Alber­ ta (Pugh, 1971). The remainder of the sequence corre­ Following the initial transgression of Middle Devonian lates with the which is assigned a seas, a complex sequence of evaporites. carbonates, Late Cambrian to Early Ordovician age (Paterson, 1988; and elastics (Meadow lake Fm., Fuzesy, 1980; Meadow Lefever et al., 1987; Pugh, 1971) . Lake Beds, van Hees, 1956; Buller, 1958) were deposited in the Lower Elk Point Basin. Distribution of In east-, the Earlie Formation is com­ these strata indicate that the approximate southern posed of "interbedded, glauconitic sittstones and fine­ shoreline of this basin was, at that time, formed by the grained sandstones and shales• (Pugh, 1971, p7) and the Deadwood Formation consists of interbedded

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Figure 2 - Cross S6Ction showing progressiw truncation of Lower Paleozoic carbonates from south to north. North of the Meadow Lake Escarpment, which formed at th6 erosional edge of the Rad River Formation, Middle Devonian strata (Meadow Lake Fm., Fuzesy, 1980; Meadow Lake &Ids and Ashem Formation, van HHs, 1958) infill the erosional low on th6 Dead· wood/ Earlie Formations. Location of the cross s6Ction Is shown in Figure 1. Logs used are gamma (G) and neutron (N) or sonic (S). Datum Is the top of the Ashem Formation ..

126 Summary of Investigations 1989 Table 1 - Well data. Wei/ location, kelly bushing elevation, and depth of tops of the Ashem Formation, Meadow Lake &

Saskatchewan Geological Survey 127 micaceous shales and micaceous and glauconitic tributed primarily to pre-Devonian erosion. However, pre­ sittstones (Pugh, 1971). Ordovician uplift and erosion on the eastern margin of the basin (van Hees, 1964) also contributed to removal Preliminary log correlations suggest that similar of a portion of this sequence. lithologies are present over much of western Sas­ katchewan. In the vicinity of the Meadow Lake Escarp­ b) Winnipeg Formation ment, stratigraphic correlation is less certain. The Dead­ wood Formation in this area contains coarse-grained The Winnipeg Formation (Middle Ordovician) unconfor­ siltstones and fine-grained sandstones (Pugh, 1971) mably overlies the Deadwood Formation in the eastern thus making it difficult to delineate the Deadwood/ Earlie half of the study area. It is composed predominantly of boundary. An additional correlation problem occurs at quartz sandstone with sub-angular to rounded grains the base of the elastic sequence directly overlying rocks ranging from very fine to coarse. The contact with the of Precambrian age. The Basal sandstone unit overlying carbonates of the Red River Formation is described by Pugh (1971) has not been defined in Sas­ described as conformable by some authors (e.g. katchewan and, therefore, the oldest Cambrian rocks Vigrass, 1971) and as unconformable by others (e.g. are included in the Deadwood/ Earlie sequence. Paterson, 1971; Kendall, 1976). The thin sheet (<3 m) of Winnipeg strata that blankets much of the study area In this study the Deadwood and Earlie Formations have (Figure 4 of Paterson, 1971 ), is interpreted by Kendall not been differentiated. An isopach map of net thick­ (1976) as the basal sandstone (or arenaceous dolomite) ness of the two formations illustrates both depositional commonly present at the base of the Red River Forma­ and erosional patterns associated with these strata (Fig­ tion. Maximum thickness (up to 55.1 m) of the Winnipeg ure 3). Deposition of this sequence took place in the Formation in the study area occurs in the northeast ·uoydminster Embayment•, a shallow depression which corner; the author's correlation of this thick sand unit as developed on the Interior Platform of the Western part of the Winnipeg Formation is tentative. Canada Basin during the Middle Cambrian (van Hees, 1964; Aitken, in press). South of the Meadow Lake Es­ c) Herald and Yeoman Formations (Red River carpment the distribution of strata reflects deposition within this embayment with maximum thickness Formation) (513.6 m) present in 10-24-53-25W3 in the southwest A thin remnant (16 m) of th e Yeoman Formation cored corner of the study area. Two periods of erosion have af­ in California Standard Fort Pitt 1-25-54-26W3 is com­ fected Deadwood/ Earlie strata. The dramatic thinning posed primarily of burrowed, mottled and commonly of Deadwood/Earlie rocks north of the Escarpment is at-

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Figure 3 - Jsopach map of undifferentiated Deadwood and Earlie Formations. Contour interval is 50 m.

128 Summary of Investigations 1989 nodular dolomite. Geophysical log response and nificant increase in argillaceous content is apparent in samples suggest that this lithology is typical of the drill cuttings. Yeoman throughout the study area. The burrowed and mottled nature is characteristic of this unit throughout No cores were taken from this formation but samples the Williston Basin (Kendall, 1976, 1985; Haid!, 1988). In and geophysical log response indicate that this interval the Fort Pitt core (1-25-54-26W3) the dolomite sequence is composed of burrowed mottled dolomite with minor contains anomalous abundant lenses and irregular beds interbeds of argillaceous dolomite, similar to the of reddish-brown dolomitic shale and anhydrite over a lithologies observed in Stony Mountain cores from the 3.5 m interval approximately 5 m below the top of the Cumberland Lake area in east-central Saskatchewan Yeoman. The contacts between the dolomite and the (Haidl, 1988). shale clearly indicate infiltration by the shale of the over­ lying Ashern Formation into fractures and solution The upper contact of the Stony Mountain Formation is cavities developed in the carbonate during the pre- placed at the base of a thin argillaceous dolomite bed Devonian erosional period. Anhydrite was probably (commonly with quartz grains) which, where well­ precipitated in cavities in the Yeoman Formation at the developed, has a characteristic high gamma ray log same time as it formed in the Ashern Formation. reading. However, in several wells this marker bed is not well-defined, making accurate correlation of the The Herald Formation has not been cored in the study Stonewall/Stony Mountain boundary difficult (Figure 2). area but geophysical log response and samples indi­ cate that it is composed of microcystaJline dolomite with e) Stonewall Formation interbeds of argillaceous dolomite. The contact between the Herald Formation and the overlying Stony Mountain In west-central Saskatchewan the Stonewall Formation Formation is placed at the base of a marker bed charac­ is composed of microcrystalline, in places fossiliferous, terized by a marked deflection to the right (higher dolomite and cryptocrystalline dolomite. Prominent values) on gamma ray logs. This bed is composed of ar­ marker beds are present at the base, in the middle gillaceous dolomite, with interbeds of arenaceous ("t" horizon), and at the top of the formation. The dolomite. The presence of multiple argillaceous beds marker beds consist of argillaceous dolomite with inter­ with similar log response within the Herald Formation laminations of dolomitic shale. Quartz grains are com­ and within the lower portion of the Stony Mountain For­ monly observed in samples, usually as scattered grains mation often makes correlation of this contact difficult in argillaceous dolomite, but also as sandstone samples. (Figure 2). The entire Stonewall Formation is preserved in the In this study, the Yeoman and Herald Formations have southeastern portion of the study area where it ranges been mapped as one unit. The contact between the two in thickness from 14.1 min 7-26-51-25W2 to 19.8 min formations is described as gradational and is difficult to 13-19-51 -2W3. The subcrop of the Stonewall Formation pick even in areas with good well and core control (Ken­ is illustrated in Figure 1. dall, 1976; Haidl, 1988). For this reason the HeraldjYeoman contact has not been picked for the pur­ f) Interlake Formation pose of regional mapping. This undifferentiated HeraldjYeoman unit is equivalent to the Red River For­ Rocks of the Interlake Formation are preserved in the mation in adjacent areas of the Williston Basin. In the southeastern portion of the study area. The erosional study area, total thickness of HeraldjYeoman strata ran­ edge follows a northeast-southwest trend, parallel to the ges from 45.1 min 7-26-51-25W2 to zero along the subcrops of other Lower Paleozoic carbonate units (Fig­ erosional edge (Figure 1). Depositional thicknesses ure 1). (where penetrated) range from the maximum of 45.1 m in 7-26-51-25W2 to a minimum of 28.1 min 10-16-56- In Saskatchewan, the Interlake is subdivided into two in­ 14W3. formal stratigraphic units, Lower and Upper Interlake (Haidl, 1987). The lower Interlake contains several well­ d) Stony Mountain Formation defined marker beds, characterized by a high gamma ray log response, while there is a paucity of such beds The subcrop of the Stony Mountain Formation also fol­ in the Upper Interlake. In the study area, fossil frag­ lows a northeast-southwest trend, roughly parallel to the ments, coated grains, and microcrystalline,commonly Meadow Lake Escarpment (Figure 1). Data from wells laminated, dolomite observed in samples all suggest which penetrate the depositional thickness of these that the lithologic sequence is similar to that observed in strata indicate that maximum thickness of Stony Moun­ cores in east-central Saskatchewan (Haidl, 1988). tain strata (up to 34.2 m) occurs in the southwest por­ Samples and log response indicate the occurrence of a tion of the map area. The two wells (13-19-51-2W3 and number of marker beds composed of argillaceous 4-31-55-10W3) with minimum thickness (25.6 m) are lo­ dolomite with interbeds of dolomitic shale, arenaceous cated along a line running northwest from the city of dolomite and minor sandstone. Prince Albert. In 13-19-51-2W3, the decreased thickness of the Stony Mountain coincides with a thick Stonewall The basal metre of the Lower Interlake is cored in interval. The gamma ray log over the Stonewall/Stony 11-7-58-21W2, a well just east of the study area. The Mountain sequence in this well indicates a number of cored interval consists of a dolomitized coral anomalously high gamma responses. However, no sig- stromatoporoid(?) ftoatstone, a lithology characteristic of

Saskatchewan Geological Survey 129 the basal Lower Interlake in the Cumberland Lake area (Figure 4). There has been speculation that the Escarp­ (Haidl, 1968). ment coincides with basement faulting which may have had both vertical and lateral movements (van Hees, The full depositional thickness of the Lower Interlake 1958, 1964). D.M. Kent (pers. comm.) speculates that unit is penetrated in only five wells where values range this feature, particularly at its northeast extremity, may from 25.3 m to 29.8 m (Table 1). The erosional remnant be associated with an extension of the Stanley Fault of the Upper Interlake in these wells has a maximum (Figure 1 of Padgham, 1968). thickness of 19.5 m in 8-3-48-5W3. 4. Further work 3. Structure This study was originally undertaken as a regional map­ Structure contours on the top of the Precambrian base­ ping project based primarily on geophysical logs. More ment define a homodine which dips to the southwest at detailed work is required to fully understand deposition­ approximately 4.5 m per kilometre (Figure 4). No major al and erosional features and their relationship to such anomalies are observed on this surface in the map area factors as eustatic sea level changes and basement tec­ and preseot well control is insufficent to define minor tonics. structures. a) Stratigraphic correlation north of the The map of structure contours on the top of Dead­ wood/Earlie Formations (Figure 5) illustrates strata in Meadow Lake Escarpment the southern portion of the study area dipping to the Interpretation of depositional and erosional features in south-southwest at approximately 4.5 m per kilometre. this area requires detailed stratigraphic correlation Along the Meadow lake Escarpment, erosional relief on based on comprehensive knowledge of the lithologies these strata disrupts the regional trend. Here contours of the various formations. The basal elastic sequence re­ define a west-southwest trending •nose•, roughly parallel quires further study in order to differentiate the "Basal to the Escarpment. A similar pattern is defined by con­ sandstone•, and the Deadwood, Earlie and Winnipeg tours on the top of the sub-Devonian unconformity (Fig· Formations. The complex lithologies of the Meadow ure 3 of Buller, 1958). Lake Formation must also be mapped in detail in order that a sandy facies of the Meadow Lake Formation can The principal reason for the trend of the Escarpment is more readily be distinguished from the underlying Dead­ not clear. There appears to be no evidence of sig­ wood or Earlie Formations, or a Meadow Lake dolomite nificant faulting on the present-day Precambrian surface from a remnant of the Red River Formation.

Figure 4 - Structure contours on the top of the Precambrian. Contour interval is 100 m; datum is mean sea level.

130 Summary of Investigations 1989 Figure 5 - Structure contours on the top of undifferentiatfKJ Deadwood/Earlie Formations. Contour inteNal is 50 m; datum is mean sea level. b) Depositional Trends Fuzesy, LM. (1980): Geology of the Deadwood (Cambrian), Meadow Lake and Winnipegosis (Devonian) Formations in Analysis of depositional trends requires that the area of west~ntral Saskatchewan; Sask. Miner. Resour., Rep. study be extended away from the erosional edges of 180, 64p. the various formations. More detailed lithologic data Fyson, W.K. (1961): Deadwood and Winnipeg stratigraphy in must be acquired to improve understanding of deposi­ southwestern Saskatchewan; Sask. Miner. Resour., Rep. tional sequences within both the elastic and carbonate 64, 37p. units. Integration of these data with geophysical data may enhance understanding of the relationship of Haid!, F.M. (1987): Stratigraphic and lithologic relationships, depositional and erosional features to basement tec­ Interlake Formation (Silurian), southern Saskatchewan; in tonics. Summary of Investigations 1987, Sask. Geol. Surv., Misc. Rep. 87-4, p187·193. One depositional trend observed in this study warrants - ~ ~- (1988): Lithology and stratigraphy of lower more detailed analysis. The southeast-northwest trend­ Paleozoic strata: new information from cores in the Cum­ ing depositional thin in the Stony Mountain Formation to berland Lake area, east-central Saskatchewan; In Sum­ the northwest of Prince Albert possibly extends to the mary of Investigations 1988, Sask. Geol. Surv., Misc. Rep. southeast to Township 37, Range 9W2 where a similar 88-4, p202-210. feature exists (Figure 19 of Kendall, 1976). It is of inter­ est to note that the Sturgeon Lake kimberlite discovery Kendall, A.C. (1976): The Ordovician carbonate succession (Twp. 51, Rge. 1W3) Hes along this trend. (Bighorn Group) of southeastern Saskatchewan; Sask. Miner. Resour., Rep. 180, 185p.

-....,..,...-- (1985): Depositional and dlagenetic alterations of 5. References Yeoman (Lower Red River) carbonates from Harding Co., Aitken, J.D. (in press): The Sauk Sequence - Cambrian to South Dakota; in Longman, M.W ., Shanley, K.W., Lindsay, Lower Ordovician: the birth of a Lower Paleozoic passive R.F. and Eby, D.E. (eds ). Rocky Mountain Carbonate margin; in Ricketts, B. (ed.), Basin Analysis - the Western Reservoirs - A Core Workshop; Soc. Econ. Paleon. Canada Sedimentary Basin; Can. Soc. Petrol. Geo!., Spec. Mineral., p95-124. Publ. 30. Lefever, R.O., Thompson, S.C. and Anderson, D.S. (1987): Ear­ Buller, J.V. (1958): On the Sub-Ashern stratigraphy of an area liest Paleozoic history of the Williston Basin in North in the northwestern part of the sedimentary basin of Sas­ Dakota; in Fifth International Williston Basin Symposium; katchewan; Oil in Canada, v10, No. 23, p34-44. Sask. Geol. Soc./N. Oak. Geol. Soc., Spec. Pub!. 9, p22- 36.

Saskatchewan Geological Survey 131 Osadetz, K.G. and Haldl, F.M. (in press): Tippecanoe Se· Sloss, L.L. (1963): Sequences in the cratonic interior of North quence: Middle Ordovician to Lowest Devonian vestiges America; Bull. Geol. Soc. Am., v74, p93--114. of a great epeiric sea; In Ricketts, B. (ed.), Basin Analysis - the Western Canada Sedimentary Basin; Can. Soc. van Hees, H. (1956): The Elk Point Group; Jour. Alta. Soc. Petrol. Geol., Spec. Publ. 30. Petrol. Geol., v4, No.2, 29-30p.

Padgham, W.A. (1968): The geology of the Deschambault --~- (1958): The Meadow Lake Escarpment - its Lake District; Sask. Dep. Miner. Resour., Rep . 114, 92p. regional significance to Lower Palaeozoic stratigraphy; In Second International Williston Basin Symposium; N. Oak. Paterson, D.F. (1971): The stratigraphy of the Winnipeg Forma· Geol. Soc./Sask. Geol. Soc., p70-78. tion (Ordovician) of Saskatchewan; Sesk. Dep. Miner. Resour., Rep. 140, 57p. (1964): Cambrian; in McCrossan, A.G. and --,G""'la._,i...,st-er, R.P. (eds.), Geological History of Western (1988): Review of regional stratigraphic relation· Canada; Alta. Soc. Petrol. Geol., Calgary, p20·28. --s..,..h..... lp-s-of the Winnipeg Group (Ordovician), the Deadwood Formation (Cambro-Ordoviclan) and underlying strata in Vigrass, L.W. (1971): Depositonal framework of the Winnipeg Saskatchewan; in Summary of Investigations 1988, Sask. Formation in Manitoba and eastern Saskatchewan; Geol. Geol. Surv., Misc. Rep. 88-4, p224-225. MSOC. Can., Spec. Pap. 9, p225-234.

Pugh, D.C. (1971): Subsurface Cambrian stratigraphy ln southern and central Alberta; Geol. Surv. Can., Pap. 70- 10, 33p.

132 Summary of Investigations 1989