Clara Blättler, D.Phil.

Education: University of Oxford, DPhil., Earth Sciences
Institution: Princeton University (laboratory of John Higgins)

SCOL Project: Ca and Mg Isotopic Indicators in Ancient Carbonates

This proposal introduces two new geochemical tools to the search for evidence of the earliest life on Earth and the environments it may have inhabited. The tools for this research will be the stable isotope ratios of calcium and magnesium, which are major components of limestone and dolomite rocks and hold promise as proxies for recording early microbial activity and marine conditions. Substantial work on both modern analogue environments and theoretical considerations suggests that this approach can introduce valuable new dimensions to long-debated problems on the chemical composition of seawater during the early evolution of life and the biogenicity of minerals in the ancient (> 2.5 billion year old) rock record. This work is directed at answering two major questions: 1) did the earliest oceans resemble modern soda lakes, rather than the sodium-chloride-rich oceans of today, and 2) can the presence of microbial activity be identified through a characteristic isotope signal in ancient sedimentary deposits.