Abstract

Shallow-water carbonate sediments are one of the most important geologic sinks of CO2 emitted from Earth’s interior and a widely used archive of Earth’s chemical and climate history. Some of the main limitations in interpreting the chemistry of ancient carbonate sediments include the potential for post-depositional diagenetic alteration and uncertainties in how to relate chemical changes in shallow-water environments to the global carbon cycle. In this talk I will discuss my labs efforts – using measurements of the stable isotopes of calcium, magnesium, and lithium – to disentangle the effects of diagenesis and local processes in ancient shallow-water marine carbonates in order to more accurately reconstruct the chemical composition of seawater in the geologic past. I will argue that our results are inconsistent with the commonly-used approach of using stratigraphic excursions in carbon and other geochemical proxies in shallow-water marine carbonate sediments as quantitative indicators of global isotopic mass balance.