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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 157-157

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

The Basal Colorado Sandstone and Other Tidal Sandsheets Formed During the Joli Fou Transgression [Abstract]

Banerjee, I.1

ABSTRACT

A detailed subsurface sedimentological study of the Basal Colorado Sandstone (BCS) in the Cessford Field in southern Alberta has revealed various features of tidal deposition, such as mud couplets, tidal bundles, heterolithic bedding, flaser bedding, mud-draped foresets, etc. A facies model constructed from this study illustrates a northwest trending transgressive tidal sand sheet lying unconformably over the coastal swamplagoonal sediments of the Mannville Group. The sheet was deposited by a southeast flowing tidal current and was buried by the open marine black shales of the Joli Fou Formation.

Vertical sampling through the Mannville-BCS-Joli Fou interval reveals a trend of variation in diversity indices of foraminifers and dinoflagellates and glauconite content across the transgressive surface. This trend documents the relative rate of sea level rise.

Regional stratigraphic equivalents of the BCS were studied in the outcrop belts of the southern Foothills (Sunkay Member, Blackstone Formation and Mill Creek Formation, Blairmore Group) and in the Great Falls area of Montana (Lower Flood Member, Blackleaf Formation). All three rock units exhibit tidal structures similar to those found in the BCS and are of the same age, as documented by their dinoflagellate assemblages. From these data, reconstruction of regional paleogeography has been made and compared to a modern analogue in the Celtic Sea of Great Britain.

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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES

1 Geological Survey of Canada, Calgary T2L 2A7

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