Graduation Year

2004

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Geology

Major Professor

Eric A. Oches, Ph.D.

Committee Member

Philip van Beynen, Ph.D.

Committee Member

Peter Harries, Ph.D.

Keywords

Loess, Paleoclimate, Amino Acid Geochronology, Paleothermometer, Nussloch, Germany

Abstract

Racemization kinetics of amino acids, determined for the commonly occurring fossil gastropod Succinea, facilitates the ability to construct an accurate and precise paleothermometer to estimate paleotemperatures over specific time intervals during the last 150,000 years in parts of Central Europe. Racemization within the carbonate shell of Succcinea is induced at high temperatures over increasing intervals of time in the laboratory and measured for aspartic acid (asp), glutamic acid (glu), valine (val), and phenylalanine (phe), by reverse-phase liquid chromatography.

The activation energy (Ea), frequency factor (A), and forward rate constant (k1) of the Arrhenius equation are determined from the racemization of specific amino acids over time. The Arrhenius parameters, combined with racemization data and independent age estimates of fossil Succinea shells, are used to solve for temperature in geologic samples.

Succinea recovered from a loess sequence in western Germany, located around the town of Nussloch, has been chosen for amino acid paleothermometry calculations. Samples were collected from the Nussloch loess -- paleosol sequence in the summer of 2001. The sequence spans from greater than 130,000 years to the present, is dated by luminescence and radiocarbon methods, and has abundant published proxy paleoclimate data for comparison.

Temperatures calculated for the bracketed time interval representing the last glacial maximum (25 - 20ka) averaged -5.3°C± 6.8°C using aspartic acid racemization data. Arrhenius parameters for aspartic acid racemization were the best constrained and provide temperature estimates consistent with previously published data. Paleotemperatures calculated for other bracketed intervals of time within the Succinea shells from Nussloch dated within the last 150,000 years exhibited values similar to previously published data with acceptable error.

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