--> ABSTRACT: Sequence Stratigraphic Evolution of Upper Frasnian Platform to Basin Transitions; Front Ranges, Alberta, Canada, by P. K. Wong, J. A. W. Weissenberger, K. Potma, and G. Gilhooly; #91019 (1996)

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Sequence Stratigraphic Evolution of Upper Frasnian Platform to Basin Transitions; Front Ranges, Alberta, Canada

P. K. Wong, J. A. W. Weissenberger, K. Potma, and G. Gilhooly

Upper Devonian (Frasnian) platform edges are well exposed at Cripple Creek and Wapiabi Gap, west-north-west of Calgary. These two areas occur on the southern and northern edges, respectively, of the northeast-southwest trending basinal Cline channel. The entire Frasnian section at both location is approximately 1500 feet thick and can be subdivided into seven third order sequences.

At Cripple Creek, the lower three third order sequences display an overall backstepping, and at Wapiabi Gap, a mainly aggradational style of sedimentation. The stacking pattern of the platform edges in both areas can be attributed to high accommodation rates and an absence of basin filling shale within the Cline channel. However, during and following sequence four time, shale influx and diminishing accommodation produced a forestepping style of sedimentation.

The seven sequence boundaries also show a progressive evolution associated with changing accommodation. The lower three sequence boundaries, in the Leduc Formation, occur within thin, stacked, shallow lagoon to tidal flat parasequences, reflecting relatively high accommodation rates. With decreasing accommodation, the overlying three surfaces are defined by the presence of shallow water facies abruptly juxtaposed upon deeper water facies. The boundaries of the uppermost two sequences; at the base of the Calmar and in the Graminia Formation, lie within of a series of erosive surfaces and represent a time of minimum basin accommodation.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California