Hi everyone,

Please join us for the Geodynamics Seminar in the Seismology Seminar Room (seismology 2nd floor) this coming Monday, November 18th at 2 pm. Our own Josh Murray will be presenting on ultramafic alteration and the cooling of Earth and Mars.

All the best,

Conor Bacon, Josh Murray, Collin Brandl, and Terry Plank

Title: Ultramafic alteration and the cooling of Earth and Mars

Abstract: Over geologic timescales Earth's climate has varied between periods of warm (ice-free) and cold (glacial). Understanding the drivers of these secular changes is integral to understanding the habitability of planets, feedbacks in the modern carbon cycle, and the evolution of life. By combining the tectonic history of the Paleozoic (541 Ma - 252 Ma) with a coupled model of mineral weathering and the carbon cycle, I show that glaciations can be initiated by enhanced organic carbon burial due to the emplacement and weathering of mafic and ultramafic rocks during ophiolite obduction. Specifically, the high-surface-area smectite clays formed as alteration products of these mafic and ultramafic rocks adsorb organic carbon, protecting the carbon from remineralization and locking it in the lithosphere. This mechanism for global cooling is corroborated by an interrogation of carbon isotope records and whole-rock geochemistry of shales. 

While Earth's climate has remained habitable for over 3 billion years, Mars' climate cooled catastrophically and irrecoverably. The same smectite clays I propose as drivers of Paleozoic cooling are the most abundant mineral on the Martian surface. In the second half of the talk I'll discuss recent work which reconciles Mars' climatic history with our understanding of its surface mineralogy, carbon isotopic composition, and estimated loss-to-space of CO2 through time. I show that a substantial reservoir of organic carbon, formed abiotically on early Mars and stored on clay surfaces, is consistent with the available constraints.

Bio: I started as a postdoc at Lamont in September. I use field observations, geochemistry, and computational methods to study how tectonic forces influence climate. I'm originally from Scarborough, England and came stateside for my bachelor's degree at Princeton and my PhD from MIT. Email is joshuam@ldeo: reach out to talk anytime!

Zoom link:

https://columbiauniversity.zoom.us/j/92780275650?pwd=BgfOzfYBkYE2iTUEKMkE2wJLoDI7Ul.1

For a complete view of the planned seminars this semester, please visit the calendar on the Geodynamics Seminar webpage.