COG3 Seminar - Mohammed Hashim (WHOI)

On the reliability and fragility of the carbonate paleoclimate archive

Sedimentary carbonate minerals represent a vast, continuous, and high-resolution archive of Earth history. Yet, these minerals are susceptible to post-depositional alterations (i.e., diagenesis) that can reset their primary geochemical signatures. During the first half of my talk, I will discuss the reliability of the carbonate record in reconstructing Earth’s deep history. I will particularly focus on the iodine redox proxy in dolomite and applying it in a quantitative manner to reconstruct the ocean oxygenation during the Precambrian. In the second half of the talk, I will focus on the fragility of the carbonate record and the susceptibility of carbonates to a wide range of diagenetic processes that are capable of altering and resetting their primary signals. I will specifically present on carbonate sediments from the Great Bahama Bank and our current effort to disentangle the various diagenetic processes they experience using mineralogic, elemental, textural, and petrographic data. I will show that although diagenesis of shallow-marine sediments in the Bahamas and its slope is extremely complicated, it is predictable and can thus be modeled and accounted for when using ancient carbonates.

About this series: The Chemical Oceanography, Geology, Geochemistry, and Geobiology Seminar [COG3] is a student-run seminar series. Topics include chemical oceanography, geology, geochemistry, and geobiology. Contact cog3_seminar_organizers@mit.edu for more information and Zoom password.