The Upper Cretaceous (Turonian) Second White Specks … · 2019. 1. 4. · 1 Geological Consultant, 252 Coldwell Road, Regina, SK S4R 4L2. Saskatchewan Geological Survey 2 Summary

Saskatchewan Geological Survey 1 Summary of Investigations 2005, Volume 1

The Upper Cretaceous (Turonian) Second White Specks Formation of Eastern Saskatchewan

J.E. Christopher 1 and M. Yurkowski

Christopher, J.E. and Yurkowski, M. (2005): The Upper Cretaceous (Turonian) Second White Specks Formation of eastern Saskatchewan; in Summary of Investigations 2005, Volume 1, Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2005-4.1, CD-ROM, Paper A-18, 12p.

Abstract The Upper Cretaceous (Turonian) Second White Specks Formation of eastern Saskatchewan consists of marine limestone and shales. It is subdivided into the lower bituminous limestone and marlstone Keld Member and the bituminous limestone and calcareous black shale Assiniboine Member. Bedding cycles identified within the Second White Specks are based on seven cores distributed throughout the study area, and on more than 3500 geophysical well log signatures. The Keld Member can be subdivided into three downlapping sequence sets which appear to be imbricated clinoforms that attenuate to the west and northwest. The basal sequence, Unit A, is capped by a regional unconformity. Units B and C are differentiated on the basis of a sharp irregular contact where recognized, as well as by changes in depositional patterns. The Assiniboine Member is recognized as a sequence of distal tongues of submarine banks that attenuate and increase in number towards west. The bipartite subdivision of the Second White Specks Formation becomes tenuous towards the west as depositional thinning, facies changes, and truncation of the beds by overlying units occurs. Regional variations in thickness can be attributed to major structural antecedents such as the Williston Basin, the Moosomin–Hudson Bay structural lineament, and the Punnichy Arch. Hydrocarbon potential in the study area is still unclear, in spite of several hydrocarbon shows, as the Second White Specks awaits the first commercial discovery.

Keywords: Turonian, Keld, Assiniboine, cyclic bedding, sequence sets, structural lineaments, Punnichy Arch, Second White Specks, Colorado Group, source rock, oil shale.

1. Introduction Mapping of the Phanerozoic formations in the eastern half of southern Saskatchewan was initiated in 2003 as part of a larger project known as the Williston Basin Architecture and Hydrocarbon Potential Targeted Geoscience Initiative (TGI II) Project. This trans-provincial mapping project is undertaken in conjunction with Manitoba Industry, Economic Development and Mines, and the Geological Survey of Canada in order to provide correlatable continuity for all of the major Phanerozoic stratigraphic units present in the region. This paper addresses the distribution and lithological characterization of the Second White Specks Formation in the Saskatchewan portion of the project area and is timely as industry turns its focus to shallow-gas exploration. Although no commercial gas production exists in the Second White Specks in the eastern part of the province, anecdotal evidence of gas shows has been recorded from time to time throughout the drilling history of the Williston Basin.

Though widely distributed in the outcrops of the Pasquia Hills in eastern Saskatchewan and the hills fronting the Cretaceous outcrop belt of southwestern Manitoba, the Second White Specks Formation in the subsurface of eastern Saskatchewan is scarcely noted in the literature. This no doubt arises from the paucity of cores through this formation. However, because of its calcareous distinctiveness, the formation is readily recognized in the thousands of geophysical well logs taken in drilling related to exploration for the deeper hydrocarbons and industrial minerals. The study area (Figure 1) covers Saskatchewan, east of Rge 4W3 to the boundary with Manitoba and from Tp 1 to the subcrop north of Tp 52. Mapping of the regional geology and interpretation of the sedimentology are based upon examination of cores from seven wells (one core per well) and more than 3500 geophysical wireline logs.

Turonian in age (McNeil and Caldwell, 1981), the Second White Specks Formation can be subdivided into two main lithological types: calcareous shale and calcarenitic limestone. It is correlative with the Favel Formation of Manitoba and the Greenhorn Formation of Montana and North Dakota.

1 Geological Consultant, 252 Coldwell Road, Regina, SK S4R 4L2.


Figure 1 - Map of eastern Saskatchewan showing the northern limit of the Second White Specks Formation; subcrop edge is indicated by a black dashed line, and outcrop edge by a solid line. Also shown are the locations of wells on cross section A-A′ (Figure 4) (modified from Beck, 1974).

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The Second White Specks Formation in the Canadian eastern portion of the Western Interior Seaway has been studied in great detail in the outcrops of the Manitoba Escarpment by many researchers since Dawson in 1859 assigned to it a Cretaceous age (McNeil and Caldwell, 1981). Other notable papers relevant to the Saskatchewan portion of the escarpment include those by Wickenden (1945) on the Mesozoic of the Eastern Plains and Beck (1974) on the surface economic geology of the Pasquia Hills area, particularly the oil shale and silica sand deposits. The report by McNeil and Caldwell (1981) on the Cretaceous of the Manitoba Escarpment is the most comprehensive to date; it refines the stratigraphy utilizing foraminiferal assemblages, detailed outcrop descriptions, and geophysical logs. Its definitions of the Assiniboine and Keld members were adapted for use in this mapping project and, therefore, in this paper. The report also contains a comprehensive review of the pre-1981 literature regarding the escarpment.

The Second White Specks Formation has been included in many biostratigraphic studies of the Colorado Group. North and Caldwell’s (1975) classic paper on the foraminiferal assemblages of Saskatchewan addresses the entire Cretaceous and refers to a thinning of the Second White Specks in the south-central portion of the province (near Saskatoon), as well as to discontinuities associated with the First and Second White Speckled Shales. Bloch et al. (1999) examined the sedimentology, micropaleontology, and geochemistry of the Colorado Group in context of the Western Canadian Sedimentary Basin from the foothills of Alberta to the Manitoba Escarpment. Their study contains numerous geochemical analyses, including RockEval on cores selected from across the basin. Schröder-Adams et al. (1999) supplemented this work in the Pasquia Hills in context of the recent descriptions of marine vertebrate fauna found near Carrot River and bone-bed conglomerates in Bainbridge Creek [see also Cumbaa and Tokaryk (1999) and Cumbaa and Bryant (2001)]. Collum (2000) reported on the molluscan fauna of the Colorado Group in the Pasquia Hills and its correlation to the North American Cenomanian-Turonian reference section in Pueblo, Colorado.

2. Structural Setting In the study area, the Second White Specks Formation crops out in the Pasquia Hills and subcrops against Quaternary sediments in a west-northwest–striking belt that dips to the south-southwest (Figure 2). A structure map on the formation (Figure 2) reveals the layout of a tri-partite southwesterly to south-southwesterly dipping monocline, sloping from 367 m (msl) in the northeast to -416 m (msl) at the International Border. Between Tps 18 and36 (approx.), the monocline is shaped by the multi-component Punnichy Arch comprising the Watrous and Wynyard domes, the graben-like Tabbernor lineament belt along Rges 4 to 7W2, and the Yorkton salient protruding west into the Wynyard Dome from the western front of the Moosomin-Hudson Bay structural trend (Christopher, 2003, p86, Figures 46 and 47).The monocline east of Rge 20W2 dips more steeply (0.6 m/km) southward into the central part of the Williston Basin. West of Rge 20W2, the surface of the Second White Specks is more flat lying and may in places be structurally influenced by the escarpment along the Middle Devonian Prairie Evaporite salt edge (Figure 2). These major structural forms have antecedents that exerted influence in the depositional basin of the Second White Specks Formation.

3. Lithologic Description McNeil and Caldwell (1981) correlated the core from the IMC Yarbo No. 17S (LSD 1-24-20-33W1) well with the outcrop belt, and this well serves as a reference section for eastern Saskatchewan (location of section is shown in Figure 1). It and the other available cores are linked in the correlation cross section of Figure 3.

Four wells from potash shaft or test holes have continuous core (Alwinsal Lanigan 3-28-33-23W2, SWP Bredenbury 11-36-22-1W2, IMC Yarbo No. 17S 1-24-20-33W1, and Sylvite Ste Marthe 13-22-17-30W1). The other three wells were drilled as oil and gas exploration wells and have more limited cored sections (Imperial Findlater 16-4-21-25W2, NAL Alida East 121/10-2-6-33W1, and Imperial Oxbow 15-36-2-3W2). The Second White Specks consists of an upper Assiniboine member (absent in Alwinsal Lanigan) and a lower Keld member. The Keld is subdivided into units A, B, and C on the basis of three identified downlapping sequences. The Morden is the lower black shale member of the Carlile Formation. The Niobrara is the equivalent of the First White Speckled Shale. The Govenlock, the basal member of the Niobrara Formation, is absent in the Imperial Findlater well.

Commonly referred to as shale or limestone, the Second White Specks Formation is a combination of bituminous, bioclastic, and calcarenitic limestone and marlstone, and calcareous grey and black shale. The Keld and Assiniboine members, recognizable in outcrops and in eastern Saskatchewan, lose their differences westward because of depositional thinning, facies change, and truncation under the Morden Member of the Carlile Formation. Even in the eastern region, the characteristic contact between the two members may be lacking, so picking the member boundary on geophysical logs tends to be based on an arbitrary interpretation of the resistivity signature, the Keld being the more resistive lower unit.


Figure 2 - Structure map on the top of the Second White Specks Formation in eastern Saskatchewan; contour interval is 50 m. Demarcated are the components of the Punnichy Arch: the Watrous and Wynyard domes, the Yorkton salient and the projected Tabbenor Lineament belt. Also shown are the Moosomin–Hudson Bay structural trend and two areas in which Prairie Evaporite salts have been totally dissolved.

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The composition of the calcarenite was exhaustively investigated by Bloch et al. (1999) and Schröder-Adams et al. (2001). These researchers found that, at Bainbridge Creek in the northern front of the Pasquia Hills, the calcarenite is dominated by comminuted pelecypod shell material and foraminiferal tests, and that some 54 nannofossil species make up the coccolithic white specks. The upper contact of the Second White Specks Formation with the Morden Member of the Carlile Formation, where intersected in the cores of this study, is seen to be erosional at all sites except IMC Yarbo No. 17S, where the material representing the contact zone is apparently lost. The lower contact of the formation is on the so-called “X Bentonite”, which is the defined top of the Belle Fourche Shale, though it should be noted that the bentonite intersects the transition from noncalcareous black shales typifying the Belle Fourche to calcareous speckled shales characteristic of the Second White Specks.

The descriptions of the stratigraphic sections of the seven wells identified on Figure 3 are therein generalized, largely on the basis of their bedding cycle sequences , which generally are thin, and number as many as 17. Bedding is generally cyclic, from deeper water, greyish black shale upward to shallower water calcarenite and bioclastic limestone, or the reverse. Bedding cycles of the Assiniboine Member represent a deeper water phase of the Keld. The bedding cycles apparently represent far-ranging clinoforms. Those of the Keld Member in the study area belong to three southwesterly downlapping sequence sets (Wagoner et al., 1987), here named units A, B, and C. The sequences of the Assiniboine, apparently represent distal tongues of submarine banks in the adjacent region of Manitoba; thus they attenuate and increase in number westward. Toward the northwest near longitude 106οW in south-central Saskatchewan, the Assiniboine is truncated under the sub-Morden disconformity. Stratigraphic data for the seven wells identified on Figure 3 are tabulated in Table 1.

a) IMC Yarbo No. 17S (1-24-20-33W1) The Second White Specks Formation in the IMC Yarbo No. 17S well is 23.75 m thick and both the Keld and Assiniboine members are present. The Keld Member, 9.75 m in thickness, displays seven cyclic beds. Bedding cycles 2 to 7 involve upward transitions of marlstone to very fine-grained calcarenite; they average 0.78 m in thickness and lack erosional upper or lower boundaries. These six bedding cycles are assigned to unit B. Unit A, the basal unit of the Keld, represents cycle 1. This cycle differs from the others in that, as a 4.3 m-thick transition through the “X” bentonite from the black shale of the Belle Fourche to the marlstone of the Keld, it is terminated by a 0.04 m thick, kaolinitic seat earth and remnant coal bed under an erosional surface. It also includes layers of fish-bone and fish-scale hash above the bentonite. The capping unconformity, although clearly documented in only two of the cores examined, is considered regional in extent. It is expressed in this well as a paleosol and in the Imperial Oxbow 15-36-2-3W2 well as a burrowed hardground. The “X” bentonite at this site is the uppermost of four bentonites which are interbedded with calcareous marlstone over an interval of 1.8 m.

The Assiniboine Member is 14 m thick, and features five bedding cycles which average 2.8 m in thickness, sharp contacts between cycles, and a more varied depositional style. Bedding cycles 1 and 2 deepen upward from current-bedded, fine-grained calcarenite laminated with subordinate marlstone, into marlstone laminated with subordinate greyish black, coccolithic shale. Cycles 3, 4, and 5 are upward shallowing, from greyish black shale to poorly sorted, shaly calcarenite and bioclastic limestone dominated by Inoceramus and subordinate fish-bone and fish-scale debris. There are also five beds of yellowish green bentonite, 0.01 to 0.02 m thick, the first of which is basal to the Assiniboine; the second, third, and fourth are included in cycle 4, and the fifth in cycle 5. The member underlies the Morden Member of the Carlile Formation at an erosional contact 245.7 m below Kelly bushing.

b) SWP Bredenbury 11-36-22-1W2 The Second White Specks Formation in the SWP Bredenbury 11-36-22-1W2 well has geophysical log signatures and thickness (24.5 m) that are similar to those of those of Yarbo No. 17S, but the stratigraphic layout in core is strikingly different.

Table 1 - Stratigraphic data for seven wells illustrated on cross-section A- A′ (Figure 3); wells are listed in order shown on cross section (from west to east). Values are given as depths below Kelly bushing.

Formation Location

AImperial Findlater

16-4-21-25W2

Alwinsal Lanigan

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SWP Bredenbury

11-36-22-1W2

IMC Yarbo No. 17S

1-24-20-33W1

Sylvite Ste Marthe

13-22-17-30W1NAL Alida East

121/10-2-6-33W1

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Imperial Oxbow15-36-2-3W2

Lea Park Pembina Mbr not present 288.1 m (945') 196.5 m (665') 182.4 m (598') 159.1 m (522') not present not presentNiobrara un-named mbr 415.1 m (1362') not present not present not present not present 562.0 m (1844') 690.7 m (2266')

Govenlock Mbr ??? 305.1 m (1001') 216.3 m (710') 202.1 m (663') 180.4 m (592') 571.1 m (1874') 735.1 m (2412')Carlile un-named mbr 470.6 m (1544') 308.5 m (1012') 232.6 m (763') 217.0 m (712') 198.9 m (651') 579.5 m (1901') 750.2 m (2461')

Morden Mbr 481.3 m (1579') 329.5 m (1081') 244.4 m (802') 232.6 m (763') 222.2 m (729') 614.0 m (2014') 787.6 m (2584')Second White Assinboine Mbr 487.5 m (1599') not present 259.7 m (852') 245.7 m (806') 236.8 m (777') 642.2 m (2107') 816.9 m (2680')Specks Keld Mbr 494.8 m (1623') 331.6 m (1088') 273.1 m (896') 259.7 m (852') 254.2 m (834') 655.7 m (2151') 827.2 m (2714')Belle Fourche 502.3 m (1648') 335.9 m (1102') 284.2 m (932') 265.2 m (870') 266.2 m (873') 665.0 m (2182') 845.8 m (2775')


The lower contact of the Keld Member is picked on the “X” bentonite and, though at 9.6 m the member is similar in thickness to that at Yarbo No. 17S, it displays three, rather than seven, bedding cycles. These three cycles are thicker, less well defined, and upward shallowing, and together display overall shallowing upward from marlstone (dominant in the lower half of the member) to medium-grained calcarenitic and coccolithic limestone in the upper. The basal contact is taken on the uppermost of five bentonites over a 1.2 m interval of shale assigned to the underlying Belle Fourche. Like the Yarbo well, bedding cycle 1 is 4.7 m thick, with bituminous, dark grey, coccolithic marlstone that contains abundant fish scales and bone fragments grading upward into capping medium-grained, current-bedded, well indurated coccolithic calcarenite. As well, the basal 10 cm includes two bone beds delineated by sharp contacts. It is assigned to unit A of the Keld, although a capping disconformity is not displayed. Cycles 2 and 3, respectively 1.7 and 3.2 m thick, are calcarenitic limestone with thin concentrations of fish debris. They represent Keld B. Unlike at Yarbo No. 17S, all bedding cycles include single bentonite partings.

The Assiniboine Member, its base picked on a thin bentonite at 273.1 m below Kelly bushing, is 14.9 m thick and features five bedding cycles. Most of the member is concentrated in bedding cycles 1 and 2. The upward-shallowing cycle 1 is a 6.4 m thick limestone with a narrow lithologic range: basal dark grey, bituminous, coccolithic, and pelecypod-rich bioclastic limestone grades upward into argillaceous limestone with subordinate coccolithic content and a compressed tree limb. In addition to the basal bentonite, the bed includes an upper bentonite, 1.4 m below the top. Bedding cycle 2, also 6.4 m in thickness, includes five bentonite beds, each less than 0.01 m thick. It grades upward from coccolithic and inoceramid shell-rich marlstone into cemented, bioclastic limestone featuring interlaminated inoceramid shell debris and calcarenite. Cycles 3 and 4 are vestigial beds of marlstone and calcarenitic limestone, 0.6 and 0.1 m thick, respectively. Cycle 5 is a 1.4 m thick marlstone with about 25% crenulated laminae of cemented inoceramid shells on a sharp contact. A pyrite-lined unconformable surface at 259.7 m below Kelly bushing marks the contact of the Assiniboine with the overlying Morden Shale. Though similar in thickness to the section at Yarbo No. 17S, the asymmetry in bedding mass reflects a more continuous accumulation of limestone at the Bredenbury site, and therefore the episodic buildup of submarine banks.

c) Sylvite Ste Marthe 13-22-17-30W1 The Second White Specks Formation at the Sylvite Ste Marthe 13-22 site is 29.4 m thick, which is around 5 m thicker than the formation at both Yarbo No. 17S and SWP Bredenbury. This increase in thickness corresponds to its more southerly position, closer to the depositional axis of the basin in southeastern Saskatchewan (Figures 3 and 4). Like at Yarbo No. 17S, the “X” bentonite consists of multiple beds, but here there are six, ranging in thickness from 0.005 m to 0.1 m, for a combined thickness of 0.25 m. These are intercalated with dark grey mudstone. The base of the Keld is picked on the uppermost of these bentonites.

Units A, B, and C are present in the 12 m thick Keld Member, which displays five bedding cycles with an average thickness of 2.4 m. Cycles 1, 2, 3, and 5 represent repetitive build-up of the depositional site into shallow banks. The 3.8 m thick cycle 1 is dominated by dark grey, argillaceous limestone with about 15% inoceramid debris at and near the base, 15% coccoliths, fish scales and fish bones in the middle part of the cycle, and coccolithic and calcarenitic limestone at the top. It corresponds to unit A, which thins southward from the Bredenbury site. Cycles 2 and 3 correspond to unit B and are marlstone to calcarenitic-coccolithic limestone transitions, 2.9 m and 1.8 m thick, respectively. Bedding cycles 4 and 5 are assigned to Unit C. Cycle 4 is upward deepening, 1.4 m thick, and is initiated by a 0.6 m thick, permeable, medium- to fine-grained, calcite-cemented, quartzose sandstone, incorporating a 0.1 m thick, basal grit of inoceramid shell debris on an erosional contact. The cycle is completed by an upward gradation into quartzose sandy, calcareous mudstone with abundant fish scales. Bedding cycle 5 is a 2.1 m thick upward transition into argillaceous limestone marked by an increase of shell calcarenite and coccoliths.

The 17.4 m thick Assiniboine Member has five bedding cycles and, in keeping with the depositional style of the member, they are erratic in thickness. Cycles 1 to 4 are upward shallowing, and 2.4 m, 4.3 m, 2.1 m, and 0.9 m thick, respectively. They are upward transitions from dark grey, marlstones to coccolithic and shell bioclastic limestone. Cycle 1 includes two bentonitic laminae, and cycle 3 contains four. The bentonites range in thickness between 0.01 m and 0.06 m. Cycle 5 is upward deepening and 7.7 m thick. It is mostly bituminous, greyish black and dark grey marlstone with abundant fish bones and teeth interstratified with subordinate centimetre-scale interbeds of white, coarsely crystalline, inoceramid-rich, bioclastic limestone, capped by a 2 m thick black, noncalcareous shale with abundant fish bones. Four bentonitic layers are present in the upper half of the cycle. The Assiniboine Member is terminated under the Morden Shale Member by an irregular contact, marked by a 0.03 m thick rubble of pyrite-encrusted nodules, green silty and tan mudstone flakes and granules, and black mudstone granules.

d) NAL Alida East 10-2-6-33W1 At the NAL Alida East 121/10-2-6-33W1 well, the Second White Specks Formation lies between 642.19 and 665.0 m below Kelly bushing, but only the upper 13.81 m are cored. It is thinned to 22.8 m from the 29.4 m at the Ste Marthe site, and is divided into the Assiniboine and Keld members at 655.70 m. Thus the core mostly exhibits


Figure 4 - Isopach map of the Second White Specks Formation in eastern Saskatchewan; contour interval is 2 m. Demarcated are the Watrous and Wynyard domes, the projected Tabbenor Lineament belt, the pre-Cantuar Moosomin Paleo-upland, and the Jurassic erosional edge (Christopher, 2003). Also shown are the following early Mannville paleovalleys (indicated in red): 1, Assiniboia; 2, Weyburn; 3, Estevan; 4, Northgate; and 5, Kamsack.

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T23

T24

T25

T26

T27

T28

T29

T30

T31

T32

T33

T34

T35

T36

T37

T38

T39

T40

T41

T42

T43

T44

T45

T46

T47

T48

T49

T50

T51

T52

T53

T54

T55

1

1

1

1

2

3

4

5

Pre

-Cantu

ar

Moosom

in

Pale

o-u

pla

nd

sic Ers

oa

sr

iou

na

J

l Edge

Tab

ben

or lin

eam

en

t belt (p

roje

cte

d)

Regina

Weyburn

Estevan

00

0

16

38

24 26

28

34

WatrousDome Wynyard

Dome

6

8

16

16

26

16

16

16

6

6

6

6

6

6

paleovalleys0 50 100 150

Scale in kilometres

N


an Assiniboine facies, which here consists of 14 thin-bedded (0.05 m to 5.27 m thick), bituminous, coccolithic and bioclastic limestone and black shale sequences on sharp or erosional contacts. Graded laminites of limestone and shale dominate the thicker cycles in the lower half of the member, especially the 5.27 m thick bedding cycle 4. The upper portion of the section displays metre-thick or less, upward-shallowing bedding cycles, with intercalated minor channel cut-and-fill, cemented, inoceramid bioclasts. The contact with the black shale of the Morden is sharp and irregular, under a 0.2 m thick, cemented layer of inoceramid bioclasts.

e) Imperial Oxbow 15-36-2-3W2 In the Imperial Oxbow 15-36-2-3 W2 well, the southernmost well on the cross section, the Second White Specks Formation is 28.9 m thick of which 23.4 m is cored (4.8 m of the Assiniboine and all of the 18.6 m thick Keld section).The Keld section displays eleven bedding cycles, which on the basis of sharp, irregular contacts can be grouped into the three units, or parasequence sets, A, B, and C. The bedding cycles are all interpreted as upward shallowing, except cycle 2, and five of them are less than a metre thick.

Keld A is a single bed, 0.7 m thick, of well-cemented, dense, medium-grained, coccolithic calcarenite, penetrated by vertical burrows and intercalated at 10 cm spacing with greyish black shale partings. The basal contact is on the “X” bentonite of the Belle Fourche Formation. The burrowed upper contact zone lies directly below a disconformity, equivalent to that seen on Unit 1 of Yarbo No. 17S.

Keld B is 13.0 m thick, and incorporates bedding cycles 2 to 6. Bedding cycle 2 is a 5.1 m, upward transition of dark grey marlstone laminated with approx. 20% inoceramid-rich bioclastic limestone through marlstone and calcareous shale, to a capping, bioturbated silty limestone. Bedding cycles 3 and 4 are l.5 m and 0.8 m thick respectively, and marlstone to calcareous, greyish black shale transitional to medium-grained coccolithic calcarenite. Bedding cycle 5 is 4.4 m thick and dominated by dark grey coccolithic marlstone with abundant fish scales and bone fragments. It is terminated in sharp contact with cycle 6. Cycle 6 is medium grey, argillaceous bioclastic limestone, 1.1 m thick, and capped by 0.07 m thick, burrowed (Glossifungites), calcite-cemented, very fine-grained quartzose sandstone.

Keld C contains cycles 7 to 11 that are 0.4 to 1.4 m thick, and are mostly marlstone to calcarenite over the lower half of the unit, and marlstone and bioclastic limestone in the upper. Inoceramid shells appear in all cycles up to 15% by volume. Two bentonitic laminae are present in bedding cycle 7. The basal contact of Keld C is sharp and irregular, and the upper contact is sharp under a green bentonite taken as the base of the Assiniboine Member.

The Assiniboine Member displays the thin-bedded, sharp-contact bounded, cyclic bedding character of the northern wells. Bedding cycle 1 is a coarse- to medium-grained calcarenite transition, 0.4 m thick, whereas bedding cycle 2, is a 1.9 m thick, medium-grained calcarenite on basal dark grey marlstone. Bedding cycles 3, 4, and 5 appear to be attenuated by erosion. Thus, the 1.6 m thick, inoceramid-rich marlstone (cycle 3), the 0.5 m thick coccolithic calcarenite to dark grey shale pair (cycle 4), and the 0.1 m thick, bioclastic limestone to marlstone transition (cycle 5) are juxtaposed by sharp, bounding contacts. Thin green laminae of bentonite occur in bedding cycles 1, 2, and 3.

f) Imperial Findlater 16-4-21-25W2 The thickness of the Second White Specks Formation at this site, 240 km west of IMC Yarbo No. 17S, is reduced to 14.8 m. Most of the Keld Member, picked on the “X” bentonite is made up of the basal, 6.2 m thick, upward-deepening bedding cycle 1, a coccolithic, current-bedded calcarenite with approximately 15% coarse laminae of inoceramid debris that grades over the upper half into argillaceous limestone and interbedded calcareous shale. Bedding cycles 2 and 3 are vestigial. Bedding cycle 2 is a 0.8 m thick, dark grey, calcareous shale-marlstone transition. Bedding cycle 3 is 0.5 m thick, and transitional to dark grey, argillaceous limestone. The three bedding cycles are considered components of Keld B, which here is comparable in format to that at Imperial Oxbow 101-15-36-2-3W2. Neither Keld A nor Keld C is recognized here. The absence of Keld A is apparently because the Findlater site lies west of the unit’s attenuated edge.

The 7.3 m thick Assiniboine Member features seven bedding cycles that range from 0.2 to 1.4 m thick except cycle 3, which is 4.1 m thick. The cycles represent upward-deepening, sharp-based, condensed couplets of well-cemented, current-bedded coccolithic and calcarenitic limestone, gradational into black coccolithic marlstone. There are four bentonite beds, two of which are in the 0.8 m thick bedding cycle 1. The contact with the Morden Member is marked by a thin (0.03 m) calcareous, coarse-grained sandstone rich in fish teeth, scales, and bone fragments on a sharp, irregular contact.

g) Alwinsal Lanigan 3-28-33-23W2 Some 65 km northwest of the Imperial Findlater well, the Second White Specks Formation at the Alwinsal Lanigan 3-28-33-W2 site has thinned to 4.3 m and is reduced to two upward-shallowing bedding cycles, 2.4 m and 1.9 m


thick, respectively. These are composed of dark grey, argillaceous, coccolithic limestone transitional to well-cemented, dark grey and greyish black, current-bedded coccolithic calcarenite and bioclastic limestone. The base of the formation is placed on the “X” bentonite, which is the highest of three bentonites found over a 0.07 m interval. The sharp, irregular contact with the Morden Shale at 331.6 m is marked by a white-speckled, argillaceous calcarenite with bone fragments above a bentonite in black shale. Bentonite beds are absent from the Second White Specks Formation at this site. It is assumed that the Keld Member is in contact with the “X” bentonite, and that northwesterly loss of section in the formation has occurred, not only by attenuation in the Assiniboine Member as seen at the Imperial Findlater site, but also by erosion under the Morden Member of the Carlile Formation at the Lanigan site. Keld C is also deduced to have been lost to the overlying unconformity. The Lanigan site, like Findlater, lies west of the feather edge of Keld A. Thus only Keld B is present here.

h) Regional Distribution On the line of section in Figure 3, the Keld A and B parasequences, are traced through core observations and geophysical log signatures from Imperial Oxbow 101-15-36-2-3W2, north through NAL Alida East 121/10-2-6-33W1, Sylvite Ste Marthe 13-22-17-30W1, IMC Yarbo No. 17S (LSD 1-24-20-33W1) to SWP Bredenbury 11-36-22-1W2. Parasequence C, however, is traceable only to Sylvite Ste Marthe 13-22 and is apparently overlapped by the Assiniboine Member to the north and west. The bedding cycles differ in number, thickness, and facies distribution from well to well, and so indicate an imbrication of lenticular bodies at a given horizon. Their attenuated extensions can extend from the main body for many miles. For instance, westward from the Imperial Oxbow well, the Keld A unit which is thinned to 0.7 m from the 3.8 m at Ste Marthe 13-22, is traceable along Tp 3 as a thinning pavement to Rge 20W2, a distance of 175 km. The feather edge of Keld A is apparently north-aligned along Rge 20W2, thus the unit is not seen at the Findlater and Lanigan wells, which lie beyond it to the west. At Yarbo No. 17S and Bredenbury 11-36, the submarine bank supporting Keld A became sufficiently emergent that island coastal facies developed and culminated in the formation of pedosol and coal at Yarbo No. 17S. The general loss and attenuation of the Keld bedding cycles northwestward suggest subaqueous planing by an initially transgressing Assiniboine sea. The absence of massive Assiniboine limestone bodies in the study area, and the general distribution of attenuated inoceramid bioclastic limestone and black bituminous shale couplets in eastern Saskatchewan, indicate that massive, parent facies of limestone and shale exist elsewhere, probably in Manitoba or the Dakotas. The Assiniboine depositional floor must have been relatively flat and at the base of the marine photic depth. Finally, the upper contact of the Second White Specks Formation with respect to the Morden Member of the Carlile Formation, where seen, is invariably erosional, and so indicates a significant hiatus between the two formations; thus, the common usage of the top of the Second White Specks Formation as a stratigraphic datum may be tenuous in regional chrono-stratigraphic correlations.

4. The Depositional Basin From minima of 2 to 8 m in the north, the Second White Specks Formation thickens to over 40 m on the northern flank of the Williston Basin in the southeast (Figure 4). The steepened isopach gradient from 25 m to 40 m reflects an active depositional centre to the south of the Canada–U.S. border. Thickening of the section at Imperial Oxbow 101-15-36-2-3W2 suggests that much of this accelerated accommodation increase occurred during Keld B and Assiniboine times. Both units are twice as thick as their equivalents north along the eastern segment of the section shown in Figure 3. A subsidiary site of depositional activity projects into the study area from southwestern Manitoba, between Tps 7 and 24 and the northerly trending front along Rge 4W2. It is suggested here that this northerly depositional thickening corresponds to the Moosomin–Hudson Bay Structural Lineament, which also controlled the erosional escarpment of Jurassic strata that formed during the Early Cretaceous (Christopher, 2003). The eastern wells from SWP Bredenbury 11-36 to Sylvite Ste Marthe 13-22 are located on this escarpment, and thus the Keld banks sat on topographic highs in the photic zone of the depositional basin. The escarpment is flanked to the west along Rge 4W2 by the Tabbernor Lineament Zone as projected south from the Precambrian Shield. The Keld tongue of thickening coincides with the buried early Mannville southern Assiniboia, Estevan, and Weyburn paleovalley fill along this lineament, and accommodation may, therefore, have occurred by compactional effects on Mannville sediments, or by re-activation of basement subsidence along the western edge of the buried Precambrian Superior Province (Christopher, 2003). The broad region of thinning to the northwest corresponds in great part to the Watrous and Wynyard domes on the Punnichy Arch, which, in the Second White Specks Formation, is signified by attenuation of the Assiniboine Member and erosional overlap by the Carlile Formation (Figure 3). Local thicks and thins within a range of 12 m, both isolated and linked, are present, especially in the southwestern part of the study area. Blanketing of a low-relief structural terrace overlooking the Williston Basin is indicated. Southward thickening across the Canada–U.S. border apparently hinged on a contemporaneously subsiding depocentre.


5. Hydrocarbon Potential of the Second White Specks Formation Total organic carbon (TOC) values over a 17 m thick interval in the Second White Specks Formation range from 3.95 to 9.92% in the US Borax and Chemical 5-22-34-1W3 well just west of the study area. At well SWP Bredenbury 11-36-22-1W2, TOC values are between 0.82 and 12.62% over a 17.2 m thick interval (Bloch et al., 1999). Macauley (1984) also measured high, but internally variable TOC values for the Second White Specks and interpreted the kerogen as a mixture of Types II and III. The Second White Specks Formation in the study area is considered to be a potential source rock because of its high percentage of organic matter (Macauley, 1984; Bloch et al., 1999).

Macauley (1984) measured Tmax values between 400°C to 425°C using samples from 10 wells within the study area, and Bloch et al. (1999) reported Tmax values from 396°C to 419°C at SWP Bredenbury 11-36-22-1W1 and US Borax and Chemical 5-22-34-1W3 just west of the study area. Tmax values in this range are traditionally interpreted to indicate immature organic matter that is unlikely to have generated significant hydrocarbons. Hydrocarbons sourced from within the Second White Specks would most probably exist as biogenic gas or possibly as oil shale. There is no current commercial production from the Second White Specks in eastern Saskatchewan. Drill stem test results from 18 wells show primarily mud recoveries, although minor amounts of gas were recovered at CNRL Assiniboine 6-14-16-12W2, and well-site geologists who work the Williston Basin are aware of gas kicks that are often observed at the Second White Specks level. It is because of these indications that these strata are now commonly tested. Thus from Stone Castle Big Beaver 06-16-03-24W2, which was drilled in December 2003, gas chromatograph profiles show an increase in gas count above a background of 100 units to about 180 units in the Second White Specks interval. This well is standing cased. Simpson (1970) also reported several instances of gas and oil shows in the ‘Favel’, most notably around the Kamsack, Kackwa, and Hudson Bay areas.

Oil shale crops out in the Pasquia Hills as Niobrara and Second White Specks shale. In 1913, tests done on the shales indicated 7 gallons (imp.)/ton (35 l/t) (McInnes, 1913). A 1964-65 assay carried out by Sun Oil Company determined that the oil was 11.5 API, highly aromatic and hydrogen-deficient (Macauley, 1984). Beck (1974) calculated that approximately 413 million m3 (2.6 billion barrels) of petroleum reserves were in place along the north flank of the Pasquia Hills. Macauley (1984), while in agreement with Beck as to the best location for production possibilities, downgraded that estimate due in part to lower grade intervals at the top and base of the pay zone and estimated in situ reserves, based on a 14 m thick pay zone, to be 200 million m3 (1.25 billion barrels). Canwest Petroleum Corporation recently acquired 850 000 acres and has drilled 44 test holes in the Pasquia Hills (Oil and Gas Journal, 2005) to test the economic viability of these oil shales.

6. References Beck, L.S. (1974): Geological Investigations in the Pasquia Hills Area; Sask. Dep. Miner. Resour., Rep. 158, 16p.

Bloch, J.D., Schröder-Adams, C.J., Leckie, D.A., Craig, J., and McIntyre, D.J. (1999): Sedimentology, Micropaleontology, Geochemistry and Hydrocarbon Potential of Shale from the Cretaceous Lower Colorado Group in Western Canada; Geol. Surv. Can., Bull. 531, 185p.

Christopher, J.E. (2003): Jura-Cretaceous Success Formation and Lower Cretaceous Mannville Group of Saskatchewan; Sask. Industry Resources, Rep. 223, CD-ROM.

Collum, C.J. (2000): High-resolution stratigraphy, regional correlation and report of molluscan faunas: Colorado Group (Cenomanian-Coniacian interval, Late Cretaceous) east-central Saskatchewan; in Summary of Investigations 2000, Volume 1, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 2000-4.1, p82-97.

Cumbaa, S.L. and Bryant, H.N. (2001): Stratigraphic position of a Late Cretaceous (Cenomanian) bonebed, east-central Saskatchewan; in Summary of Investigations 2001, Volume 1, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 2001-4.1, p121-124.

Cumbaa, S.L. and Tokaryk, T.T. (1999): Recent discoveries of Cretaceous marine vertebrates in the eastern margins of the Western Interior Seaway; in Summary of Investigations 1999, Volume 1, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 99-4.1, p57-63.

Macauley, G. (1984): Cretaceous Oil Shale Potential of the Prairie Provinces, Canada; Geol. Surv. Can., Open File Rep. OF 977, 61p.

McInnes, W. (1913): The Basins of Nelson and Churchill Rivers; Geol. Surv. Can., Mem. 30, 68p.


McNeil, D. and Caldwell, W.G.E. (1981): Cretaceous Rocks and their Foraminifera in the Manitoba Escarpment; Geol. Assoc. Can., Spec. Pap. 21, 439p.

North, B.R. and Caldwell, W.G.E. (1975): Foraminiferal faunas in the Cretaceous system of Saskatchewan; in Caldwell, W.G.E. (ed.), The Cretaceous System of North America, Geol. Assoc. Can., Spec. Pap. 13, p303-331.

Oil and Gas Journal (2005): CanWest Petroleum updates Pasquia Hills Oil Shale project; Oil and Gas Journal, http://www.oilonline.com/news/headlines/ephotline/20050125.CanWest_.16959.asp, accessed 17 Feb 2005.

Schröder-Adams, C.J., Cumbaa, S.L., Bloch, J., Leckie, D.A., Craig, J., Seif El Dein, S.A., Simons, D., and Kenig, F. (2001): Late Cretaceous (Cenomanian to Campanian) paleoenvironmental history of the eastern Canadian margin of the Western Interior Seaway: Bonebeds and anoxic events; Palaeogeo. Palaeoclim. Palaeoecol., v170, p261-289.

Schröder-Adams, C.J., Leckie, D.A., Craig, J., and Bloch, J. (1999): Upper Cretaceous Colorado Group in Pasquia Hills, northeastern Saskatchewan: A multidisciplinary study in progress; in Summary of Investigations 1999, Volume 1, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 99-4.1, p52-56.

Simpson, F. (1970): Low depth Saskatchewan Prospect; Oilweek, v58, 30 Mar 70, p14-15.

Wagoner, J.E., Mitchum, R.M., Posamentier, H.W., and Vail, P.R. (1987): Part 2: Key definitions of seismic stratigraphy; in Bally, A.W. (ed.), Atlas of Seismic Stratigraphy, Amer. Assoc. Petrol. Geol., Tulsa, OK, p11-14.

Wickenden, R.T.D. (1945): Mesozoic Stratigraphy of the Eastern Plains, Manitoba and Saskatchewan; Geol. Surv. Can., Mem. 239, 87p.

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The Upper Cretaceous (Turonian) Second White Specks … · 2019. 1. 4. · 1 Geological Consultant, 252 Coldwell Road, Regina, SK S4R 4L2. Saskatchewan Geological Survey 2 Summary