Extensive MIS 3 glaciation in southernmost Patagonia revealed by cosmogenic nuclide dating of outwash sediments

Darvill, C. M., Bentley, M. J., Stokes, C. R., Hein, A. S. and Rodés, Á. (2015) Extensive MIS 3 glaciation in southernmost Patagonia revealed by cosmogenic nuclide dating of outwash sediments. Earth and Planetary Science Letters, 429, 157 - 169. (doi: 10.1016/j.epsl.2015.07.030)

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The timing and extent of former glacial advances can demonstrate leads and lags during periods of climatic change and their forcing, but this requires robust glacial chronologies. In parts of southernmost Patagonia, dating pre-global Last Glacial Maximum (gLGM) ice limits has proven difficult due to post-deposition processes affecting the build-up of cosmogenic nuclides in moraine boulders. Here we provide ages for the Río Cullen and San Sebastián glacial limits of the former Bahía Inútil–San Sebastián (BI-SSb) ice lobe on Tierra del Fuego (53–54°S), previously hypothesised to represent advances during Marine Isotope Stages (MIS) 12 and 10, respectively. Our approach uses cosmogenic 10Be and 26Al exposure dating, but targets glacial outwash associated with these limits and uses depth-profiles and surface cobble samples, thereby accounting for surface deflation and inheritance. The data reveal that the limits formed more recently than previously thought, giving ages of 45.6 ka (View the MathML source) for the Río Cullen, and 30.1 ka (View the MathML source) for the San Sebastián limits. These dates indicate extensive glaciation in southern Patagonia during MIS 3, prior to the well-constrained, but much less extensive MIS 2 (gLGM) limit. This suggests the pattern of ice advances in the region was different to northern Patagonia, with the terrestrial limits relating to the last glacial cycle, rather than progressively less extensive glaciations over hundreds of thousands of years. However, the dates are consistent with MIS 3 glaciation elsewhere in the southern mid-latitudes, and the combination of cooler summers and warmer winters with increased precipitation, may have caused extensive glaciation prior to the gLGM.

Item Type:Articles
Additional Information:The research was funded by a UK NERC Ph.D. studentship (NE/j500215/1) awarded to CMD at Durham Univer-sity. 10Be and 26Al analyses were supported by NERC CIAF grant 9127/1012, and we thank Delia Gheorghiu, Allan Davidson and Sheng Xu for their help at CIAF and SUERC AMS Laboratory.
Glasgow Author(s) Enlighten ID:Rodes, Dr Angel
Authors: Darvill, C. M., Bentley, M. J., Stokes, C. R., Hein, A. S., and Rodés, Á.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Earth and Planetary Science Letters
ISSN (Online):1385-013X
Published Online:27 August 2015
Copyright Holders:Copyright © 2015 The Authors
First Published:First published in Earth and Planetary Science Letters 429:157-169
Publisher Policy:Reproduced under a Creative Commons License

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