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theses

The Paleocene-Eocene Thermal Maximum (PETM) was an abrupt warming of about 5°C that lasted ~170-220 kyr. The PETM is recognized by the Carbon Isotope Excursion (CIE), represented by a ~2.5-4 ‰ decrease in planktonic foraminiferal δ13C values in open ocean cores (Kennett and Stott, 1991; Zachos et al., 2003). The New Jersey coastal plain contains thick (~15 m) sections recording the PETM. Kopp et al. (2009) proposed an enhanced hydrologic cycle to explain the widespread clay deposition on the mid-Atlantic continental shelf during the PETM, suggesting an Appalachian Amazon analog. An increased flux of fresh water to the shelf would have lowered salinities substantially. I tested this hypothesis by measuring changes in salinity in the PETM section in the Millville, New Jersey core (ODP Leg 174AX). I used two paleothermometers to constrain temperature changes associated with planktonic foraminiferal δ18O variations, with the residual attributed to salinity-induced δ18Owater changes. Using the TEXH86 calibration of Kim et al. (2010), I compute a 5.5°C warming across the CIE at Millville from 30°C to 35.5°C; using the TEXL86 calibration, I compute a 7°C warming, but cooler temperatures (23-30°C). Mg/Ca ratio of planktonic foraminifera shows less warming of ~5°C from 29.5°C to 34.3°C. TEX86 shows a possible precursor warming at Wilson Lake and Bass River, NJ (Zachos et al., 2006; Sluijs et al., 2007). I compare TEX86 at Wilson Lake Hole A, Bass River, and Millville and conclude that the precursor warming may be spurious because it only occurs in TEXH86 and not TEXL86. Intermediate dwelling (Subbotina) planktonic foraminifera show a large decrease in δ18O values (~2.26 ‰) across the CIE. Use of the TEXH86 calibration and Mg/Ca ratio calibration (Anand et al., 2003) requires unrealistic salinities exceeding 44 psu. The TEXL86 calibration requires realistic salinity estimates and a ~4 psu salinity decrease associated with the CIE. This suggests a freshening of surface and intermediate waters during the CIE due to an enhanced hydrological cycle as proposed by Kopp et al. (2009). I attribute changes in surface to deep dwelling planktonic δ18O values to a breakdown of the thermocline caused by increased storm intensity during the PETM.

ETD_5193

M.S.

Includes bibliographical references

by Maria Makarova

doi:10.7282/T3ZC80Z5

ETD graduate

The author owns the copyright to this work.