Stratigraphic Characterization of an Early Cretaceous Channel-belt Avulsion: Implications for Paleoenvironmental Interpretations of the McMurray Formation, Alberta
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Abstract
Deposits of the Early Cretaceous McMurray Formation, in the southeast Athabasca Oil Sands Region (AOSR) Alberta, Canada, compose a world-class archive of fluvial-deltaic deposition. The integration of uniquely dense wireline well log and drill core data provides a unique opportunity to investigate the stratigraphic and spatial distribution of economically-important reservoir sandstone across a large area. A lithostratigraphic framework is used to map stratigraphically-associated deposits across >11,000 km^2. The youngest and best-preserved channel-belt is interpreted to contain the deposits of an ancient channel-belt-scale avulsion. An understanding of avulsion mechanics, derived from previous studies of modern or geologically-recent rivers, allows for investigation of the evolutionary history of the ancient river. This has implications for paleoenvironmental interpretations, including a possible recognition of the effects of the backwater length in a large, shallow Early Cretaceous fluvial-deltaic system. These deposits provide insight into the geologic history of the Western Interior Seaway, the preservation potential of large-scale fluvial features in the stratigraphic record, and their use in the reconstruction of ancient river systems.