Abstract

Early-late Cenomanian rocks of the Doe Creek unit are near the base of the Kaskapau Formation and were deposited in a broad, very shallow embayment that occupied the foredeep of the Western Canada foreland basin. The Doe Creek unit consists of 13 upward-shoaling sequences, typically 3–10 m thick. Subsurface correlation shows that sequences can be traced for 100–350 km from the fore-deep toward the forebulge. On the proximal and distal margins of the embayment, each sequence is capped by a flooding surface, commonly underlain by a paleosol developed in marine mudstone. In the center of the embayment, most sequences are capped by one or more isolated, sharp-based sandstone bodies interpreted as lowstand delta-front deposits. Flooding surfaces on top of each sequence are continuously traceable in well logs from the foredeep to the vicinity of the forebulge, implying simultaneous transgression across the basin. Every sequence shows an abrupt upward shallowing, usually to emergence, that was caused by accommodation loss, not sediment accumulation. A vertical relative sea-level excursion of ∼10 m on a time scale spanning a maximum range of ∼9–74 k.y. is estimated for each sequence. Because transgressions and regressions appear to be in phase across the basin, sequences are better explained by eustasy rather than by flexural reciprocal sedimentation: a glacioeustatic mechanism provides the most likely explanation.

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