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Willems, B.A., 2009

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Bibliographic Reference

Willems, B.A., 2009, Quaternary glacial and climatic history of southern Alaska using high-resolution seismic reflection records: DeKalb, Illinois, Northern Illinois University, Ph.D. dissertation, xxi, 338 p., (some color) illust., maps.

Abstract

The ultra-high- and high-resolution seismic reflection data in a temperate glacimarine environment provides insight into glacimarine, marine, climatic, and tectonic processes of the Gulf of Alaska margin. Objectives of the dissertation were to improve our understanding of: (1) modern depositional processes operating in temperate glacimarine systems, and (2) the glacial dynamics of the Cordilleran Ice Sheet. These objectives have been met from investigations in Disenchantment Bay and Muir Inlet, as well as the Bering Trough and Yakutat Sea Valley areas on the Alaska shelf. Disenchantment Bay is similar to other glacimarine systems that have high sediment flux and rates of denudation despite the advance of Hubbard Glacier. Glacimarine varves can be recognized in Huntec seismic reflection profiles in proximal portions of the fjord and provide a high-resolution chronology from which depositional processes can be described. Annual accumulations of sediment measured from Huntec seismic reflection data cannot be used as a proxy of climate variability due to inadequate vertical resolution. Outburst sediments from the 1986 and 2002 outburst floods in Disenchantment Bay deposited laminated mud, thin beds of sand, and beds of diamicton. Depositional processes and sedimentary volumes are similar between the two outburst flood events. Their volumes are of similar magnitude to marine sediments derived from Icelandic jokulhlaups and are potentially analogous to marine ending outburst events. Fjord strata reveal differences in sediment preservation and fjord geometry and may collectively represent glacial processes throughout the glacial cycle from alpine to coastal settings. LIA, Neoglacial, and LGM deposits are thought to occur in Muir Inlet and provide new insight into the past glacial history. Strata in Disenchantment Bay reveal the dynamic nature of Hubbard Glacier and the dominance of Malaspina Glacier in the depositional system of Yakutat Bay. Glacimarine sequences on the shelf are dominantly composed of ice-proximal and ice-contact sediments. Sequence geometries reveal transition from aggradational to progradational style that is interpreted to represent the shift into the 100 k climate cycle. This transition is marked by a steady shift into shelf-edge progradation and subsequent ice streaming conditions as opposed to an abrupt transition.

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