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Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control

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Graham, A. G. C. , Larter, R. D. , Gohl, K. , Hillenbrand, C. D. , Smith, J. A. and Kuhn, G. (2009): Bedform signature of a West Antarctic palaeo-ice stream reveals a multi-temporal record of flow and substrate control , Quaternary Science Reviews., 28 , pp. 2774-2793 . doi: 10.1016/j.quascirev.2009.07.003
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The presence of a complex bedform arrangement on the sea floor of the continental shelf in the westernAmundsen Sea Embayment, West Antarctica, indicates a multi-temporal record of flow related to theactivity of one or more ice streams in the past. Mapping and division of the bedforms into distinctlandform assemblages reveals their time-transgressive history, which implies that bedforms can neitherbe considered part of a single downflow continuum nor a direct proxy for palaeo-ice velocity, as suggestedpreviously. A main control on the bedform imprint is the geology of the shelf, which is dividedbroadly between rough bedrock on the inner shelf, and smooth, dipping sedimentary strata on themiddle to outer shelf. Inner shelf bedform variability is well preserved, revealing information about local,complex basal ice conditions, meltwater flow, and ice dynamics over time. These details, which are notapparent at the scale of regional morphological studies, indicate that past ice streams flowed across theentire shelf at times, and often had onset zones that lay within the interior of the Antarctic Ice Sheettoday. In contrast, highly elongated subglacial bedforms on sedimentary strata of the middle to outershelf represent a timeslice snapshot of the last activity of ice stream flow, and may be a truer representationof fast palaeo-ice flow in these locations. A revised model for ice streams on the shelf capturescomplicated multi-temporal bedform patterns associated with an Antarctic palaeo-ice stream for the firsttime, and confirms a strong substrate control on a major ice stream system that drained the WestAntarctic Ice Sheet during the Late Quaternary.

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