Earth and Planetary Sciences ETDs

Publication Date

Spring 5-1-2021


The secular chemical marine sediment trend showing an increase in δ18O over geologic time has traditionally been investigated using δ18O modelling of ancient ocean compositions, ocean surface temperatures, and sample diagenetic alteration. This study presents a triple oxygen isotope mass balance for the oceans using high precision δ18O and Δ'17O measurements of altered oceanic crust. The mass balance model predicts an ice-free seawater with δ18O = -0.29‰ and Δ’17O = -0.002‰ with steady state reached at approximately (0.5 to 1)×109 years. Modifications to the hydrothermal alteration and continental weathering fluxes to examine Archean ocean compositions predict seawater evolution slopes of λ = 0.524 and λ = 0.529, respectively. A model generated seawater of δ18O = -4.1‰ and Δ'17O = 0.014‰ predicts previously published Archean chert data precipitated in an ocean with 50 - 60°C surface temperatures and lost primary δ18O and Δ'17O signals from diagenetic alteration with low δ18O fluids.

Degree Name

Earth and Planetary Sciences

Level of Degree


Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Dr. Zachary Sharp

Second Committee Member

Dr. Adrian Brearley

Third Committee Member

Dr. Brandon Schmandt




Stable isotope geochemistry, mass balance model, Archean, altered oceanic crust, triple oxygen isotope

Document Type