Semester of Graduation

Summer 2018

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

The Uranium (U) isotopic system can be used to model the extent of global-scale ocean anoxia by utilizing the 238U/235U ratios as a paleo-redox indicator (δ238U). While recent studies have shown promise with the use of this novel proxy, variability is seen in modern carbonate sediment samples suggesting that more work is needed in order to understand elemental U uptake during early marine diagenesis. This thesis utilizes a sequential extraction methodology in order to understand the distribution of authigenic U within carbonate sediments.

This thesis consists of four parts, (1) an evaluation and modification of a sequential extraction methodology for U uptake in modern carbonate sediments, (2) application of the modified sequential extraction method to the study U distribution within chemical fractions within Bahamian bulk sediments, (3) the application of the modified methodology to study the U distribution across the Permian–Triassic boundary from the Lung Cam section in Northern Vietnam, and (4) the implications of authigenic U toward the δ238U paleo-redox marker.

Results show that a sequential extraction can be successful within carbonate sediments. The results of this sequential extraction shows that the majority of authigenic U is found within the exchangeable and carbonate fraction. This thesis hypothesizes that this U component is a non-crystalline U(IV) species. Furthermore, this authigenic U component was also found within the Permian–Triassic section located in Lung Cam, Vietnam, thus illustrating preservation of heavy authigenic U within the rock record.

Date

4-28-2018

Committee Chair

Herrmann, Achim

DOI

10.31390/gradschool_theses.4712

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