Date of Award

1-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Stefanie Brachfeld

Committee Member

Matthew Gorring

Committee Member

Sandra Passchier

Subject(s)

Sedimentary rocks--Magnetic properties--Antarctica--Antarctic Peninsula, Sedimentary rocks--Antarctica--Antarctic Peninsula-- Analysis, Paleoclimatology--Antarctica, Magnetic susceptibility

Abstract

Two sediment cores were recovered from the Joinville-d’Urville Trough on the Northeastern Antarctic Peninsula (AP) during United States Antarctic Program cruise LMG04-04. KC3 was recovered from a sediment drift off Joinville Island. KC16 was recovered from a small basin west of the drift. Both cores show a two-part magnetic susceptibility profile: the upper section shows regularly spaced highs and lows, followed by a large amplitude drop. The susceptibility profiles of these two cores are similar to those found on the western side of the AP. The purpose of this study is to determine whether the same processes drive magnetic susceptibility on both sides of the AP. Susceptibility in KC16 is inversely correlated with diatom abundance, as expected. However, susceptibility in KC3 and KC16 is positively correlated with Si abundance and inversely correlated with Fe abundance. Susceptibility is also positively correlated with Ca and Al, suggesting that magnetite inclusions in silicates such as plagioclase may be a strong control on both the susceptibility and geochemical signals. Susceptibility peaks and troughs in KC16 and KC3 all exhibit a magnetic order/disorder transition at ~117 K, which we interpret as the magnetite Verwey transition. Curie temperature analyses also confirm the presence of slightly oxidized magnetite in both cores. Particle size analyses of KC16 and KC3 show a progressive coarsening of magnetite down core. Medium to fine silt-sized particles dominate in both cores, as well as in surface samples collected throughout the study area. Therefore, the magnetic coarsening is not related to bulk sediment grain size, and is a function of diagenesis. The susceptibility drops in KC3 and KC16 are dated at 390 yr BP and 2050 yr BP, respectively. These features are interpreted as climate transitions. The 390 yr BP feature in KC3 represents the termination of the Medieval Warm Period and the onset of the Little Ice Age. The 2050 yr BP feature in KC16 is interpreted as the onset of the Neoglacial interval on the northernmost Antarctic Peninsula.

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