The Geological Atlas of the Western Canada Sedimentary Basin

Chapter 19

Cretaceous Mannville Group

Major structural elements of the foreland basin during Mannville deposition. Numbers indicate the areas to which the columns of the correlation chart (Fig. 19.2) and the reference logs (Fig. 19.5) apply. Map scale 1:20 000 000.

Figure 19.2

Table of stratigraphic nomenclature for the Mannville Group and equivalent strata in the Western Canada Sedimentary Basin. Column numbers refer to map areas as shown on Figure 19.1. The heavy dashed line in columns 1 to 3 denotes the top of the Mannville-equivalent strata in areas where deposition occurred without significant interruption into the overlying Colorado interval. The dotted line is the boundary between the Lower Mannville and Upper Mannville units (Figs. 19.22, 19.24). In the southern foothills (column 8), the Pocaterra Creek is designated as the basal member of the Cadomin Formation, but is significantly older according to palynology; see Poulton et al. (this volume, Chapter 18) for further discussion.

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Figure 19.3

Structure map of the sub-Mannville unconformity surface. Symbol and colour coding indicate the age of strata underlying the unconformity. These strata become progressively older to the north and east.

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Figure 19.4

Isopach map of the total Mannville. Marine shale equivalents exist in the northern part of the basin but cannot be separated from the overlying section north of the edge of Upper Mannville sands. In the northeast, the top of the Mannville is behind borehole surface casing and is not logged. Most of the Mannville strata on the northeastern flank of the basin are buried beneath Quaternary cover. Control points in the Cordillera are outcrop sections palinspastically restored to their original positions. Mannville oil sands deposits are shown for reference.

Figure 19.5

Reference logs for subsurface sections throughout the basin. Gamma-ray (G) and sonic (S) logs are shown in each case, because they best reflect the range of Mannville lithologies. Bolder lines indicate the top of the Mannville and Lower/Upper Mannville boundary (where distinguishable). Vertical scale is Atlas standard 1:3000.

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Figure 19.6

Isopach map of the Cadomin Formation and Cut Bank Member. They are sharply bounded to the east by an escarpment that has been mapped in southern and northern regions, but not as accurately in the foothills of central Alberta. Section J-J' (Fig. 19.7) illustrates stratigraphic relations across the escarpment edge.

Figure 19.7

Cross section J-J' , showing the abrupt eastward pinchout of the Cadomin Formation and thinning of the Gething and Bluesky formations across the Fox Creek Escarpment. The line of section is shown on Figure 19.6.

Figure 19.8

Paleogeographic map illustrating facies relations in Cadomin/Gething strata of northwestern Alberta. A branch of the river system occupying the Edmonton Valley drained through the gap between the Keg River and Red Earth highlands, forming the Keg River Delta. Section K-K' (Fig. 19.9) illustrates facies relations across the area. After Smith (this volume, Chapter 17).

Figure 19.9

Cross section K-K' , depicting regional facies relations from the Edmonton Valley across the Red Earth Highlands and Keg River Delta. The line of section is shown on Figure 19.8.

Figure 19.10

Cross section L-L' , illustrating the stratigraphic framework of Blairmore-Luscar strata (Mannville-equivalent) in the southern and central foothills. In a simplistic sense, the succession can be divided into a basal non-marine unit (Cadomin and Gladstone), a medial brackish water to marine unit (Calcareous and Moosebar), and an upper marginal-marine to non-marine interval (Beaver Mines and Gates). In detail, the Moosebar is a complex shale/sandstone succession containing at least three and possibly four transgressive-regressive marine cycles, which are included in the Calcareous/Ostracod and Glauconitic/Bluesky intervals (see discussion).

Figure 19.11

Schematic cross section M-M' , showing approximate stratigraphic framework of the Mannville Group in southern and western Alberta. In southern Alberta, many Lower Mannville and Glauconitic sandstones fill valleys incised into older continental and brackish water strata. In central Alberta, a series of marine sandstones (Ellerslie, Ostracod, Bluesky and Glauconitic) are incised locally by mud- and sand-filled valleys. See Discussion for more detailed consideration of these correlations.

Figure 19.12

Cross section N-N' , illustrating stacked deltaic to marginal-marine successions of the lower Upper and upper Upper Mannville intervals in the central plains. The laterally continuous GP (General Petroleums), Sparky and McLaren sands are marginal-marine, wave-reworked sand sheets. The GP, Sparky and McLaren channels were cut by later distributary channels or during an erosive interval succeeding deposition of each member. Total length of section is about 3.5 km. After Gross (1980).

Figure 19.13

Cross section O-O' , depicting stacked prograding succession of the Falher (lower Upper Mannville) and Notikewin (upper Upper Mannville) of the Peace River Arch area. These strata reflect repeated transgressive/regressive events arising from the interplay of eustasy and Cordilleran tectonic events, which provided influxes of clastic debris while loading the basin edge and increasing accommodation space for sediments.

Figure 19.14

Index map for regional cross sections A-A' to G-G' , showing their positions with respect to paleogeography of the basin during the Cadomin/Gething interval. After Smith (this volume , Fig. 17.3). Map scale 1:10 000 000.

Figure 19.15

Regional cross section B-B*. See Figure 19.14 for line of section.

Figure 19.16

Regional cross section C-C' . See Figure 19.14 for line of section.

Figure 19.17

Regional cross section A-A'. See Figure 19.14 for line of section.

Figure 19.18

Regional cross section D-D' . See Figure 19.14 for line of section.

Figure 19.19

Regional cross section F-F*. See Figure 19.14 for line of section.

Figure 19.20

Regional cross section G-G' . See Figure 19.14 for line of section.

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Figure 19.21

Structure map on the top of the Mannville. Symbol and colour coding indicate the nomenclature used for the top-Mannville pick in the Atlas database.

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Figure 19.22

Isopach map of the Lower Mannville (see Fig. 19.2 for Lower/Upper Mannville subdivision). Hachured areas represent highlands at the beginning of Mannville deposition. Marine shale equivalents in the northern part of the basin cannot be distinguished from younger strata north of the edge of Lower Mannville sands, and hence are not mapped. Control points in the Cordillera are palinspastically restored to their original positions.

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Figure 19.23

Lower Mannville oil and gas fields. Isopach contours as per Figure 19.22.

Table 19.23a

Oil production from the Lower Mannville

Table 19.23b

Gas production from the Lower Mannville

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Figure 19.24

Isopach map of the Upper Mannville (see Fig. 19.2 for Lower/Upper Mannville subdivision). Marine shale equivalents in the northern part of the basin cannot be distinguished from older or younger strata north of the edge of Upper Mannville sands, and hence are not mapped. In the northeast, the top of the Mannville is behind borehole surface casing and is not logged. Control points in the Cordillera have been palinspastically restored to their original positions.