The sedimentary architecture of outburst flood eskers: A comparison of ground-penetrating radar data from Bering Glacier, Alaska and Skeidararjokull, Iceland

摘要

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 Skeidararjokull, Iceland has a similar morphology and stratigraphic architecture. This suggests that outburst floods generate distinct deposi-tional signatures in eskers, both in terms of morphology and sedimentary architecture. Identification of these distinct signatures in ancient eskers will help assess the paleo-hydraulic conditions under which ancient eskers formed and, by extension, the nature of meltwater drainage systems beneath the Laurentide and Eurasian ice sheets.