Award: OCE-1821958

The chemistry of marine sediments stands as one of the central catalogs of climatic evolution and earth surface change on geological timescales.  Contributing to this library is the sulfur and oxygen isotopic composition of marine barite - a set of temporal records that anchor any interpretation of ocean chemistry over the last 125 million years. Barite, of course, stands as a proxy for marine sulfate, which itself serves as an energy source roughly 10 times larger than atmospheric oxygen (at present) and integrates across a wide range of biogeochemical processes and cycles, particularly C and Fe. Unlocking the unique history of sulfate would then serve as a powerful measure of oceanic/atmospheric change.

Much effort has been dedicated to opening the treasure chest that is marine barite. Most commonly the traditional sulfur and oxygen isotopic compositions of sulfate are measured and further modeled in an effort to extract paleoenvironmental information. What is required is a new, independent piece of information - we argue this comes in the form of 17O.

Through this work, we calibrated the compositon of the modern ocean and built a new, microbially informed model that placed new constraints on the activity of the sulfur cycle.  We next applied these lessons to the ~ 6 million year old evaporites of the Messinian Salinity Crisis to test the fidelity of this approach back in time.  Indeed, our work on the modern was validated.

 

Last Modified: 06/29/2020
Modified by: David T Johnston