Origin of well-rounded gravels in glacial deposits from Brøggerhalvøya, northwest Spitsbergen: potential problems caused by sediment reworking in the glacial environment |
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| Authors: | DAVID HUDDART MATTHEW R BENNETT MICHAEL J HAMBREY NEIL F GLASSER KEVIN CRAWFORD |
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| Institution: | School of Education and Community Studies, I. M. Marsh Campus, Liverpool John Moores University, Barkhill Road, Liverpool L17 6BD, U.K.;School of Earth and Environmental Sciences, University of Greenwich, Medway Towns Campus, Pembroke, Chatham Maritime, Kent ME4 4AW, U.K.;School of Biological and Earth Sciences, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, U.K. |
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| Abstract: | Well-rounded gravels are described from moraine-mound complexes, diamicton forefields and modern englacial thrusts at the margins of four glaciers on the northern side of Brøggerhalvøya, northwest Spitsbergen. Their shape charcteristics are compared with modern and fossil glacigenic, modern beach and Early Weichselian beach gravels from this peninsula. The best discriminators of the well-rounded gravels have been found to be the percentage-frequency roundness histograms, the roundness mid-point and roundness range diagrams and the sphericity-roundness plots. It is concluded that the gravels have been derived by englacial thrusting from Early Weichselian or last interglacial beaches in the inner parts of the fjord and in the low level cirques when sea level reached at least 50m a.s.l. and deposited the beach gravels. The discrimination between gravel in basal diamictons, proglacial outwash and modern beaches is difficult as the reworking has resulted in little particle shape change. The potential major problem caused by reworking in the glacial environment is emphasised. especially when clast shape comparisons from modern environments to older sediments are used. |
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