Date of Award

1-1-2011

Document Type

Campus Access Thesis

Department

Earth and Ocean Sciences

Sub-Department

Geology

First Advisor

Robert Thunell

Abstract

Several proxies for ocean temperature, ice sheet growth, and continental weathering analyzed from ODP Site 738 sediments off the coast of East Antarctica have offered insight into the variable climate of the Paleogene 'greenhouse.' In this study, I compile evidence from fine fraction carbonate, benthic foraminifera, fossil fish teeth, detrital sediment, and sea level records to build a case for the existence of a brief cooling event accompanied by the growth of an ephemeral ice sheet 37.15 Ma, three million years prior to the onset of early Oligocene Antarctic glaciation. The d18O values for both the fine fraction carbonate and benthic foraminifera (Cibicidoides spp.) increased ~0.6 ppm, reflecting a combination of ice sheet growth and deep water cooling. Fossil fish teeth and detrital sediments were analyzed for eNd, a proxy for continental weathering, revealing negative excursions of ~1 and 3 eNd units, respectively. These negative eNd excursions indicate an influx of older, crustal material into circum-Antarctic waters. Miller et al. (2005) reports a sea level drop of ~20 meters beginning 37.15 Ma. Collectively, the data from these proxies indicate the most likely explanation for these phenomena is the growth of an ice sheet during this short-lived cooling period 37.15-36.9 My.

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