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The AAPG/Datapages Combined Publications Database

CSPG Bulletin

Abstract


Bulletin of Canadian Petroleum Geology
Vol. 38 (1990), No. 1. (March), Pages 183-183

C.S.P.G. 1990 Convention, "Basin Perspectives"

Cambrian Facies and Paleogeography, Subsurface of Southern Alberta [Abstract]

Tawadros, E.1

ABSTRACT

Cambrian rocks in Western Canada occur in three facies belts; an inner detrital belt, a middle carbonate belt, and an outer detrital belt. The Cambrian in the Rocky Mountains and Front Ranges displays a cyclical pattern in which strata characteristic of the inner detrital and middle carbonate belts formed "grand cycles". The grand cycles can be recognized in well data from the westernmost part of Southern Alberta. However, as the carbonates give way eastward to clastics, the cycles become difficult to recognize. Nine lithofacies have been recognized in the Cambrian rocks of this region: 1. mottled dolomitic mudstone and wackestone; 2. mudstone, wackestone, and packstone; 3. oolitic grainstone; 4. cryptalgalaminates and cryptalgalaminate breccia; 5. flat-pebble conglomerate; 6. glauconitic sandstone; 7. quartzarenite; 8. hybrid sandstone and iron formations; and 9. coquina. These facies were deposited in environments ranging from supratidal to subtidal, with storms playing a major role in sediment distribution. Iron typically occurs in amounts exceeding 15 per cent by volume of the iron-formation facies and is interpreted to be diagenetic in origin.

Facies mapping of the Cambrian in the subsurface of southern Alberta shows that the paleogeography during the Cambrian consisted of a very shallow basin surrounded by shoal areas on three sides. The shoal areas bordered the Peace River Arch, the West Alberta Ridge, and the Sweetgrass Arch. The shallow basin was dominated by glauconitic sandstone and shale, quartzarenite, flat-pebble conglomerate, coquina and minor carbonate. Shoal areas were dominated by mottled dolomitic mudstone to packstone, oolitic grainstone, cryptalgalaminate, flat-pebble conglomerate, coquina, and minor clastics. Mud cracks are abundant, especially in the shoal area on the south side of the Peace River Arch.

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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES

1 ET Geological Consultants, Calgary T1Y 4A3

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