--> Paleogeography of Marine Shales of the Albian to Turonian Western Canada Sedimentary Basin, by J. Bloch, C. Schroder-Adams, D. A. Leckie, and D. J. McIntyre; #90986 (1994).

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Abstract: Paleogeography of Marine Shales of the Albian to Turonian Western Canada Sedimentary Basin

J. Bloch, C. Schroder-Adams, D. A. Leckie, D. J. McIntyre

Sedimentological, biostratigraphic and geochemical data from marine shale of the lower Colorado Group in the Western Canada Sedimentary Basin (WCSB) are integrated to build paleoenvironmental reconstruction's of the Albian to Turonian Western Canada Sedimentary Basin.

The upper Albian Westgate Formation was deposited in the rising Mowry Sea with sediment sourced primarily from the rising Cordillera to the west. Foraminiferal and dinoflagellate assemblages are Boreal in affinity. Well-laminated sediment, a limited species diversity, and a predominance of Type III organic matter give way up section to a more bioturbated substrate and diverse faunal assemblage. This suggests a transition from a stressed, brackish environment to more fully marine conditions in the latest Albian.

The lower Cenomanian Fish Scales Formation was deposited under a stratified water column with anoxic bottom-water conditions. It is barren of Foraminifera but contains abundant algal cysts with limited species diversity. Organic matter is a mixture of Types II and III. The thin, tabular, fine-grained nature of the Fish Scales, coupled with the increased organic matter content suggest limited sediment input characteristic of a condensed section.

The Cenomanian Belle Fourche Formation was deposited in the Western Interior Seaway and contains fauna of Gulfian affinity. Sediment was sourced primarily from the Dunvegan delta in the northwest part of the basin.

The upper Cenomanian to Turonian Second White Specks Formation was deposited as a condensed section under a deeper, stratified water column during the global sea level highstand. Fully marine conditions existed over all of the WCSB. Winnowing by oceanic currents created localized marine unconformities below the Second White Specks and Fish Scales formations.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994