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GSA Bulletin; May 2008; v. 120; no. 5-6; p. 709-731; DOI: 10.1130/B26242.1
© 2008 Geological Society of America
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Late Cenozoic glacier-volcano interaction on James Ross Island and adjacent areas, Antarctic Peninsula region

Michael J. Hambrey1,{dagger}, John L. Smellie2, Anna E. Nelson2 and Joanne S. Johnson2

1 Centre for Glaciology, Institute of Geography & Earth Sciences, Aberystwyth University, Ceredigion, Wales SY23 3DB, UK
2 British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK

Correspondence: {dagger}E-mail: mjh{at}aber.ac.uk

The northern Antarctic Peninsula region has undergone ~10 m.y. of eruptive activity by basaltic volcanoes, mainly in subglacial settings. Spectacular exposures of lava-fed deltas, capped by basalt flows and commonly underlain by glacigenic sediments on top of a Cretaceous sedimentary "basement," characterize James Ross, Vega, and other islands and promontories in the region. Neogene strata are collectively known as the James Ross Island Volcanic Group and record a cryptic history of glaciation, with the timing of events determinable by argon-isotope dating. Focusing especially on the glacigenic sediments themselves, and their relationships with overlying or bounding volcanic rocks, we define facies associations related to (1) eruptions beneath thick ice (>200 m) that produced lava-fed deltas resting on, and intermingling with, diamictite; and (2) eruptions under marine conditions that typically culminated in the development of several tuff-cone successions, some on top of presumably relict glacially striated surfaces. A combination of provenance studies on clasts in the glacigenic sediments, some of which are derived from the Antarctic Peninsula, and geochronology, leads to the conclusion that an Antarctic Peninsula Ice Sheet extended over James Ross and Vega Islands at about the time that the main volcanic edifices began to grow, i.e., prior to ca. 6.2 Ma at least. Much of the subsequent development of the succession is attributed to the interaction between the growing volcanoes and local ice caps. Full resolution of glacial-interglacial events in this region promises to inform the debate about the stability of the most climatically sensitive part of the Antarctic Ice Sheet during the Neogene Period.

Key Words: Neogene glacial fluctuations • James Ross Island • Antarctic Peninsula Ice Sheet • glacier-volcano interaction • glacigenic sediments • lava-fed deltas • argon dating • strontium dating






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