--> Abstract: The Record of Basinwide Sea Level Fluctuation in Middle Cretaceous Viking and Bow Island Formations, Alberta, Canada, by G. E. Reinson, R. I. Campbell, and J. Cox; #90987 (1993).

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REINSON, GERALD E., and ROSS I. CAMPBELL, Geological Survey of Canada, Calgary, Alberta; and JOHN COX, Mount Royal College, Calgary, Alberta

ABSTRACT: The Record of Basinwide Sea Level Fluctuation in Middle Cretaceous Viking and Bow Island Formations, Alberta, Canada

Regional stratigraphic correlations combined with facies and sequence stratigraphic analyses indicate that the Albian Viking Formation and equivalent Bow Island Formation in central and southern Alberta contain evidence of significant eustatic sea level fluctuations. The effects of these fluctuations have been preserved in the sedimentary record of these formations as sequence boundaries separating regressive deposits from transgressive deposits. In the Viking Formation, two principal stratigraphic sequences are recognizable throughout central Alberta: a lower progradational succession or highstand systems tract and, an upper transgressive systems tract (including incised valley-fill). In the Bow Island Formation throughout southern Alberta, three readily recognizable depositional uni s are evident: a lower unit of stacked shelf-to-shoreface cycles, a middle coastal plain unit and, an upper shallow marine transgressive unit. The lower and middle units comprise the highstand systems tract, while the upper unit records the transgressive systems tract.

When the Viking and Bow Island sequence models are compared through detailed north-south oriented log correlations, it becomes evident that the sequence boundary within each formation is one and the same. The regional aspect of this sequence boundary, or "middle Viking" unconformity is, thought to represent a basinwide drop in sea level that occurred not only in Alberta but as far south as the Denver basin and other parts of the Western United States.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.