Abstract

A tributary of the Red Deer River in Dinosaur Provincial Park, southern Alberta, contains evidence of a sequence of valley cutting and the deposition of three alluvial fills and one eolian deposit. With the exception of the eolian deposit and minor amounts of Shield and Cordilleran rocks, the sediments are derived from local bedrock. Incision of the bedrock valley occurred in the early postglacial period about 14 000 – 12 000 BP by rapid drainage of proglacial lakes and meltwaters. The valley was subsequently partly infilled as locally fed stream discharges declined during the early to middle Holocene. By 6000–5000 BP alluvial fans had formed along the base of the valley walls. Fan development was followed by two phases of stream entrenchment and alluvial deposition, including the most recent phase of cutting and filling that began approximately 800 BP. The erosional and depositional events may reflect climatic changes as inferred in lacustrine deposits in southern Alberta and in valleys elsewhere in the Great Plains. Glacioisostacy conditions, however, at least in the early Holocene, may have had profound effects on stream base levels.

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