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The Last Glaciation in Central Magellan Strait, Southernmost Chile

Published online by Cambridge University Press:  20 January 2017

Chalmers M. Clapperton
Affiliation:
Department of Geography, University of Aberdeen, Aberdeen AB9 2UF, Scotland, United Kingdom
David E. Sugden
Affiliation:
Department of Geography, University, of Edinburgh, Edinburgh EH8 9XP, Scotland, United Kingdom
Darrell S. Kaufman
Affiliation:
Department of Geology, Utah State University, Logan, Utah 84322-4505
Robert D. McCulloch
Affiliation:
Department of Geography, University of Aberdeen, Aberdeen AB9 2UF, Scotland, United Kingdom

Abstract

Glacial landforms and drift stratigraphy in central Magellan Strait, southernmost Chile, document repeated fluctuations during the last glacial cycle of outlet lobes from an ice cap centered over the southern Andes. The lobes developed comparatively low-gradient profiles because of low basal shear stresses over soft deformable beds and this made them sensitive to even small-scale changes in the mass balance. Such low profiles and rapid calving in deep proglacial lakes during deglaciation may have made the Magellan ice lobe particularly responsive to climatic fluctuations during the last glacial cycle, and to advance and retreat over considerable distances. Study of the glacial landforms and drift stratigraphy has led to the identification of at least five glacier advances to limits at and south of the Segunda Angostura. Fragments of mollusc shells contained in basal till indicate marine incursions between some advances, thus documenting extensive deglaciation. A partial chronology based on amino acid studies and radiocarbon dating suggests that five of these advances occurred during the last glacial cycle. The most extensive advances may have culminated during substages of marine isotope stage 5 (substage 5b or 5d) and/or during stage 4. Slightly less extensive advances occurred between ca. 28,000 and 14,000 yr B.P.

Type
Research Article
Copyright
University of Washington

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