Abstract

We present ground-penetrating radar (GPR) profiles that reveal the sedimentary architecture of an esker deposited during a surge-associated outburst flood at the Bering Glacier, Alaska. The wide, up-flow end of the esker contains a transition from large backset beds to large foreset beds interpreted to reflect composite macroform development in an enlarged part of the conduit. By contrast, the narrow, down-flow portion of the esker is dominated by plane beds interpreted to have been deposited where the conduit was constricted and the flow was faster. A previously studied outburst esker at Skeiðarárjökull, Iceland has a similar morphology and stratigraphic architecture. This suggests that outburst floods generate distinct depositional signatures in eskers, both in terms of morphology and sedimentary architecture. Identification of these distinct signatures in ancient eskers will help assess the paleohydraulic conditions under which ancient eskers formed and, by extension, the nature of meltwater drainage systems beneath the Laurentide and Eurasian ice sheets.

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