Graduation Semester and Year

2017

Language

English

Document Type

Thesis

Degree Name

Master of Science in Earth and Environmental Science

Department

Earth and Environmental Sciences

First Advisor

Elizabeth M Griffith

Abstract

Early Eocene hyperthermal events can be an analog for global warming. Pelagic marine barite in deep sea sediment is a proxy for marine export production of organic matter into the deep ocean. Pelagic marine barite accumulation rates (BAR) were reconstructed over the Paleocene – Eocene Thermal Maximum (PETM; ~55.5 million years ago), Eocene Thermal Maximum 2 (ETM2; ~53.7 Ma) and ETM3 (~52.4 Ma) from ODP Sites 1209, 1215 and 1263. Northern Atlantic samples (with high detrital content) were acid digested and analyzed to reconstruct biogenic Ba (Ba/Al, Ba/Ti) and compare with elemental data from high resolution X-ray fluorescence. This data was used to test the following hypotheses: 1. Export production increases globally after the minimum carbon isotope excursion (CIE) defining the hyperthermal events due to increased surface production; 2. If driving mechanism(s) for ETM2 and ETM3 are similar to the PETM, then all three events should have similar trends in export production inferred from marine barite accumulation with lower magnitudes for ETM2 and ETM3; and 3. Enhanced remineralization in the thermocline will reduce the amount of exported organic matter that reaches the seafloor, potentially due to increased microbial metabolisms from temperature increases that consume organic material at faster rates resulting in less organic material sinking to the seafloor. Despite reduced or unchanged surface productivity, export production (inferred from BAR) increased during the PETM, ETM2 and ETM3. Generally, maximum export production occurred during the CIE minimums from increased organic carbon export efficiency from increased surface temperatures and/or increased aggregation from microbial transparent exopolymer particles. Export production was proportional to the CIE magnitude: highest after onset of the PETM and smallest after the onset of ETM3. Remineralization rates can be inferred from the difference between benthic foraminiferal data and export production. Low benthic foraminiferal accumulation (or high oligotrophic taxa) appear to be caused by low oxygen and nutrients in the deep ocean due to high remineralization rates from warm intermediate depths and less ballasting. Low oxygen levels in intermediate water depths suggest high oxygen utilization rates from remineralization supporting this interpretation.

Keywords

Barite, Paleocene-Eocene thermal maximum, Biogeochemical cycling

Disciplines

Earth Sciences | Physical Sciences and Mathematics

Comments

Degree granted by The University of Texas at Arlington

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27951-2.zip (3731 kB)
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