Sedimentological and oceanographic change in the Northwest Atlantic Ocean across the Eocene Oligocene Transition

Abstract

The Eocene-Oligocene Transition (EOT) marks the most pivotal interval in Earth’s Cenozoic transition from warm, relatively ice-free ‘greenhouse’ conditions to a cooler ‘icehouse’ climate. The EOT saw the rapid growth of a large East Antarctic Ice Cap, global cooling, and a reorganisation of ocean currents at ~33-34 Ma, but little is known about how these events affected the Northern Hemisphere. The traditional view is that glaciation of the northern continents occurred much later than on Antarctica, but recent studies have, controversially, suggested that large northern ice sheets formed across the EOT. This thesis documents an investigation into this and related problems, taking advantage of rapidly deposited sediment drifts overlying the Southeast Newfoundland Ridge (SENR) recovered during Integrated Ocean Drilling Program (IODP) Expedition 342. Detrital sand and sedimentological features found in EOT-aged sediments on the SENR were interpreted at the time of their discovery to be evidence of ice rafting, and so could support the idea of bipolar glaciation. Provenance, surface texture, and sedimentological analyses presented in this thesis,
however, show that icebergs did not deposit these grains. Instead, the presence of these grains is attributed interplay between deep-water currents and glacioeustatic sea level change, through the use of grain flux, grain size, stable isotope, and spectral analyses. Industrial well and seismic data, together with a palaeogeographic digital elevation model, are used to reconstruct the geometry of the SENR, and show that its sedimentary history was often linked to larger-scale oceanographic changes along the Newfoundland Margin. These findings support the hypothesis that significant Northern Hemisphere glaciation did not occur across the EOT.

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ORCID for Paul Wilson: orcid.org/0000-0001-6425-8906

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