Earth and Planetary Sciences ETDs

Publication Date

Summer 7-13-2020

Abstract

This dissertation presents a method of analyzing the triple oxygen isotope compositions of carbonates, presents an empirical calibration of the carbonate-water equilibrium fractionation line, presents a triple oxygen isotope equipped fluid-rock mixing model for carbonates to see-through diagenesis, and applies all these findings to ancient carbonate samples. Using modern carbonates and associate water, the following equations are calculated to describe equilibrium triple oxygen isotope fractionation of carbonates:

1000lnalpha18Occ-wt=2.84x106/T2-2.96 1),

Thetacc-wt=-1.39/T+0.5305 2).

Using these fractionation equations provides an extremely useful tool to determine whether a carbonate sample is altered or preserves its original isotopic composition. In samples that are altered, a fluid-rock mixing model is used to see-through the diagenesis. Applying these tools to ancient carbonate rocks shows that many samples thought to be pristine are altered and are confusing paleoenvironmental interpretations. This work shows that seawater temperature and isotopic composition is unchanged over the Phanerozoic, an important consideration when reconstruction paleoenvironments.

Degree Name

Earth and Planetary Sciences

Level of Degree

Doctoral

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Zachary Sharp

Second Committee Member

Maya Elrick

Third Committee Member

Peter Fawcett

Fourth Committee Member

Viorel Atudorei

Fifth Committee Member

Peter Swart

Project Sponsors

NSF GRFP DGE-1418062 and NSF EAR-1551226; PI – Zachary Sharp

Keywords

ancient seawater, oxygen fractionation, stable isotopes, paleoclimate

Document Type

Dissertation

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