Alberta Geological Survey
Alberta Geological Survey |
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Regional geology map of uppermost Cretaceous-Tertiary strata in the plains. In southeastern Saskatchewan, east of the distal limit of the Belly River Formation, and in southern Manitoba, partly correlative strata are included in the Campanian to Maastrichtian Riding Mountain Formation. |
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Major structural features, geographic areas of common nomenclature, lines of cross section and locations of reference logs. |
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Stratigraphic nomenclature for the uppermost Cretaceous-Tertiary - from the top of the Milk River/Chungo to the base of Laurentide drift. Column numbers refer to regions shown in the index map (Fig. 24.2). |
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Figure 24.4 a. Continent-wide transgression of the Pakowki sea (~83 Ma). b. Depositional setting of the initial stages of the first clastic wedge of western-derived sediments of the Foremost Formation (~78 Ma). c. Shift in source of sedimentation to the northwest during the later stages of Oldman Formation deposition (~76 Ma). d. Second clastic wedge depositing sediments (Horseshoe Canyon Formation) into a southeast-retreating Bearpaw Sea (~73-70 Ma). e. Depositional setting of a widespread lacustrine environment with local paleosol development, suggesting limited basin sedimentation during deposition of the Battle Formation (~66 Ma). f. Deposition of the third clastic wedge (lower Scollard, Frenchman formations) under widespread fluvial conditions, followed by extensive coal development during deposition of the upper Scollard and lower Ravenscrag formations (~63 Ma). g. Deposition of the final clastic wedge (Paskapoo/Porcupine Hills formations), prior to widespread erosion (~56 Ma).
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Section A*-A', located in south-central Saskatchewan, illustrates the thinning of the Judith River Formation clastic wedge to the southeast. Beyond the zero edge, the Bearpaw and Pakowki formations are part of the marine Riding Mountain Formation. |
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Section D-D*, from the foothills to the plains, shows the wedge-shaped geometry of the sediments of the Coalspur/Scollard formations, thinning from west to east. The Cretaceous-Tertiary boundary is marked (red line on the section) by the first laterally persistent coal seam above the barren zone of the lower Coalspur/Scollard strata. |
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Section L-L', through the southern plains, shows the diachronous contacts of the Belly River/Judith River and the underlying and overlying Pakowki and Bearpaw formations, respectively. To the east, beyond the Judith River zero edge, the Bearpaw and Pakowki belong to the Riding Mountain Formation. |
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Section H-H'. Note the northwest pinchout of the marine Bearpaw Formation and the uniform thickness of the Pakowki Formation, implying that the shoreline trends at the time of the Pakowki/Belly River contact were parallel to the section. |
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Section J-J'. The overall thickness (greater than 1800 m in this section) along the western edge of the basin suggests that the axis of the foreland basin was nearly parallel to section H-H'and perpendicular to this section. |
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Reference logs for the uppermost Cretaceous-Tertiary. The standard Atlas vertical scale (1:3000) is common to all three logs. a: Shown are, the abrupt lower disconformable contact of the transgressive Pakowki Formation; the regionally gradational contact between the Pakowki Formation and the overlying Belly River "basal sands"; and the sharp lower contact of the transgressive Bearpaw Formation with the underlying, laterally persistent Lethbridge coal zone of the Oldman Formation. b: Illustrated is the gradational upper Bearpaw Formation contact with the Horseshoe Canyon Formation and the easily recognizable lower contact of the Battle Formation overlying the widespread correlative Carbon-Thompson coal zone. c: Shown are, the contact between the Battle Formation and the overlying Scollard Formation; the boundary between the predominantly coal-barren lower Scollard and prolific coal-bearing upper Scollard, usually defined as the first laterally persistent correlative coal bed (commonly containing the Cretaceous-Tertiary boundary); and the poorly defined contact of the sandy basal Paskapoo Formation with the Scollard Formation. |
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Outcrop sections. Measured sections from the southern and central foothills illustrating the variability of facies due to climatic differences. The southern foothills strata were deposited in an arid environment, giving rise to widespread caliche and redbeds, whereas strata in the central and northern foothills were deposited in a more humid environment, leading to widespread development of coal. |
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"Basal Belly River" cross section K-K'. The cross section represents a dip section, illustrating the Lea Park/Belly River transition in the Ferrier and Keystone oil and gas fields in west-central Alberta. The section clearly illustrates the diachronous nature of the strata of the basal Belly River Formation and the five distinct shoreface facies decreasing in age from southwest to northeast. Note that the vertical scale (1:2000) is considerably expanded from the Atlas norm (1:6000). |
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Structure contour map on the Lea Park/Pakowki formations. Structure contours illustrate the western dip of the strata in the foreland basin throughout much of Alberta; note the high contour density in southwestern Alberta. Structure contours in Saskatchewan, east of the Bow Island Arch, reflect the influence of the Williston Basin to the southeast and salt solution collapse structures in the underlying Paleozoic. |
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Structure contour map on the Battle/Kneehills Tuff marker. Contours indicate the westward dip of the strata; note the curving of the contours at the north and south ends of the mapped region, suggesting a downwarping of the basin along a northeast-southwest axis immediately southwest of Edmonton. |
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Isopach map of the upper Lea Park/Pakowki formations. Contours indicate a relatively constant gradient of thickness west of the Bow Island Arch. Immediately to the east of the arch isopach values increase dramatically. Variability of thickness in southern Saskatchewan can be attributed to the influence of the underlying salt-solution structures. |
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Isopach map of the Belly River/Judith River formations. Note the abrupt thinning of the Belly River wedge over the axis of the Bow Island Arch. North of the Bearpaw Formation "zero-edge", the Belly River Formation is part of the Wapiti Formation (Fig. 24.19). Significant oil production is from Belly River (and equivalent Wapiti) reservoirs, as shown. Note that the tabulation of oil production (Table 24.16a) includes data from fields in underlying Colorado Group strata (see Fig. 20.2). |
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Isopach map of the Bearpaw Formation. The Bearpaw Formation pinches out to the northwest and thickens markedly immediately south of Calgary. |
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Isopach map of the Horseshoe Canyon Formation (plus Whitemud and Battle). The Horseshoe Canyon Formation is part of the Wapiti Formation north and west of the Bearpaw "zero edge". South of about 50°ree;30'N, the Battle Formation is not recognized, and consequently mapping of the Horseshoe Canyon equivalents is problematic. Note that the Whitemud Formation is included in this Horseshoe Canyon Formation isopach, but it does not contribute substantially to the overall thickness. |
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Isopach map of the Wapiti Formation. Isopachs are restricted to the region north and west of the "zero edge" of the Bearpaw Formation and include strata equivalent to the Belly River and Horseshoe Canyon formations. |
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Isopach map of the interval from the present-day land surface (KB) to the Battle (Alberta)/Bearpaw (Saskatchewan). This map illustrates the wedge shape of the late Maastrichtian and Tertiary strata, including the Paskapoo and Scollard formations, in Alberta. In Saskatchewan, the isopach map represents the thickness of strata from surface (KB) to the Bearpaw Formation, including undifferentiated Eastend, Whitemud, Battle, Frenchman and Ravenscrag formations. Note that local isopach variations may be topographically controlled. |
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Cretaceous-Tertiary boundary localities. Illustrated are the locations of the "world class" outcrops of the Cretaceous-Tertiary in the Western Canada Sedimentary Basin. |
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Distribution and formation names of the consolidated and unconsolidated middle to upper Tertiary sediments. Saskatchewan Sands and Gravels are Pleistocene. |
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Schematic profiles of post-Paleocene deposits. The sections illustrate the amount of sediment removed by post-orogenic erosion, and the stratigraphic positions of remnant consolidated and unconsolidated middle to upper Tertiary sediments. a: Athabasca River section, illustrating the stratigraphic position of the Smoky Tower, Whitecourt Mountain, Swan Hills, Simonette River, Pelican Mountain and Avenir deposits. b: Red Deer River section, illustrating the stratigraphic position of the Red Deer, Hand Hills and Wintering Hills deposits. c: Oldman/Saskatchewan River section, illustrating the stratigraphic position of the Del Bonita Uplands, Fort Macleod, Magrath, Peigan, Kipp, Taber, Wolf Island and Cypress Hills deposits. |
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Alberta Geological Survey
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