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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 5. (May)

First Page: 605

Last Page: 605

Title: Early Cretaceous Edmonton Channel in Alberta: ABSTRACT

Author(s): J. Ross McLean

Article Type: Meeting abstract

Abstract:

The Edmonton channel forms part of an extensive Early Cretaceous drainage system on the Alberta plains. Local topographic relief in excess of 160 m was infilled by the Lower Cretaceous Mannville Group. The pre-Mannville unconformity juxtaposes Lower Cretaceous strata on Devonian, Mississippian, Jurassic, and possibly earlier Cretaceous sediments. Erosion was prevalent over sedimentation between the Pennsylvanian and Early Cretaceous Periods, a time of about 150 m.y. This ultimately produced a broad, low-relief alluvial plain with a southwestern dip, blanketed by easterly derived quartzose sandstones.

A prominent lowering of sea level, possibly associated with a worldwide eustatic sea-level fall at about 130 m.y., caused widespread erosion and dissection of the alluvial plain. The north-south oriented Edmonton channel was cut at this time, incorporating elements of an earlier drainage pattern. Flow was to the south and then west to join the Spirit River system which flowed northwest subparallel to the Columbian orogenic belt.

Southward transgression of the sea in Aptian(?)-Albian time led to lowering of stream gradients, deposition of coarser bed load where available, and inundation of the previously established drainage system. The Edmonton channel became a small adjacent sea with somewhat restricted circulation to the main seaway during its early infilling. Numerous estuaries formed in tributaries to the main channel. Sedimentology and paleontology of the Lower Mannville Group sediments in the Edmonton channel indicate deposition is a standing body of brackish water directly upon, or only slightly above, the unconformity. Sedimentation associated with continuing transgression and a subsequent regression accounted for most of the infilling of the Edmonton channel. Local lithostratigraphic nomenclature doe not adequately reflect the nature and complexities observed in this sedimentary sequence.

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