The internal sediment architecture of a drumlin,Port Byron,New York State,USA |
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| Institution: | 1. Université de Lorraine, Faculté des Sciences et Technologies, Département des Géosciences, UMR 7359 GéoRessources, BP 70239, 54506 Vandoeuvre-lès-Nancy, France;2. 6D Avenue General de Gaulle, 05100 Briançon, France;3. Université de Strasbourg, EOST, 1 rue Blessig, 67084 Strasbourg cedex, France;1. Institute of Geophysics and Geoinformatics, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 12, 09596 Freiberg, Germany;2. Institute of Numerical Analysis and Optimization, TU Bergakademie Freiberg, Akademiestraße 6, 09596 Freiberg, Germany;3. Federal Institute for Geosciences and Natural Resources BGR, Stilleweg 2, 30655, Hannover, Germany;1. Federal Institute for Geosciences and Natural Resources, Stilleweg 2, 30655 Hannover, Germany;2. Institute of Geophysics and Geoinformatics, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 12, 09596 Freiberg, Germany;3. Institute of Numerical Analysis and Optimisation, TU Bergakademie Freiberg, Gustav-Zeuner-Str. 12, 09596 Freiberg, Germany |
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| Abstract: | An exposure within the central portion of a large drumlin at Port Byron, New York State, USA, part of the large New York drumlin field, reveals a sequence of steeply dipping cemented sands and gravels of proglacial, ice-contact deltaic origin overlain by a thin till veneer. The sands and gravels appear to have been deposited within the proximal proglacial environment during a late retreat phase of the Laurentide Ice Sheet sometime prior to being overridden by subsequent ice and drumlinized. During deposition of the ice-contact delta, escaping subglacial regelation-meltwater permeated the proximal deltaic sediment pile and calcium carbonate was released, in a series of pulses, to form pore-occluding calcite cement within the sand and gravel porespaces. The calcium carbonate precipitated into the sands and gravels due to a reduction in hydrostatic pressure and CO2 outgassing of the meltwater as it exited from beneath the ice sheet. Once cemented, these deltaic sediments were considerably stronger and acted afterward as an obstacle around which the future ice advance streamed and, in turn, produced the characteristic drumlin shape. In overriding the ice-contact deltaic sediments, the ice sheet emplaced a thin layer of till which exhibits syndepositional deformation features indicative of being emplaced as a deforming bed layer beneath the advancing ice sheet. Micromorphological analysis of the overlying till shows that no interstitial or intraclastic calcite occurs within the till. |
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