--> ABSTRACT: High-Frequency Sequences Reveal Tectonic Modulation of a Eustatic Transgression: Basal Kaskapau Formation, (Late Cenomanian), Western Canada Foreland Basin, by Guy Plint; #90906(2001)

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Guy Plint

Dept. Earth Sciences, University of Western Ontario, London, Ontario, Canada, N6A 5B7. [email protected]

ABSTRACT: High-Frequency Sequences Reveal Tectonic Modulation of a Eustatic Transgression: Basal Kaskapau Formation, (Late Cenomanian), Western Canada Foreland Basin.

The mudstone-dominated late-Middle Cenomanian to Middle Turonian Kaskapau Formation of the Western Canada Foreland Basin records the greatest eustatic transgression of the Cretaceous. The Kaskapau Fm. is wedge-shaped, thinning over 600 km from about 500 m in the most proximal, western part of the basin, to about 50 m in the east. This geometry indicates pronounced flexural subsidence during deposition. The stratigraphy and sedimentology of the Kaskapau Fm. have been studied over an area of about 100,000 km2 of NW Alberta and NE British Columbia, between township 50 in the south and the Peace River in the north, and from the 5th Meridian (114..W) in the east to the Rocky Mountain Foothills. Twenty outcrop sections, about 1700 well logs and 20 cores were used to establish stratigraphic and facies relationships.

The Kaskapau Fm. overlies the Early to Mid Cenomanian Dunvegan Formation which comprises deltaic units that prograded across the study area from NW to SE over about 2 my (Bhattacharya & Walker, 1991a,b; Plint, 2000). Ten major delta complexes are recognized within the Dunvegan Fm., each complex being separated by regional transgressive marine mudstones. The lower 8 complexes represent about 400 km of net coastal progradation by deltas building into water typically several tens of m deep. The upper two delta complexes record a succession of deltas that prograded into shallow water (typically < 15 m) which covered the drowning delta plain, and which collectively record about 270 km of shoreline backstep.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado