Collaborative Research: Integrated Late Devonian Earth evolution: Diverse perspectives on ocean-climate-biosphere interaction from Laurentia and Gondwana

The Devonian Period (419 to 359 million years ago) witnessed some of the most important transformations leading to the habitable planet that we have today. Plants and vertebrate animals first colonized the land surface, oxygen levels rose in the oceans and atmosphere, and the planet cooled significantly. There were also a series of mass extinctions related to a temporary loss of oxygen in the shallow oceans.

The funded work seeks to understand the timing, causes, and consequences of these Devonian mass extinctions, and how they can be identified in rocks deposited across North America, as well as in Bolivia and Western Australia. Ultimately, this study will provide a new integrated framework of ocean oxygen loss across time and space through the Devonian extinctions, improving our understanding of how our planet came to resemble to modern world.

This project also supports two early-career faculty members of mixed-race and African ancestry, expands field geology opportunities for high school students, supports numerous undergraduate and graduate students and a postdoc, and will disseminate results to non-technical audiences in English and in Spanish.

The Late Devonian is a unique interval in Earth history during which the proliferation of land plants triggered a cascade of Earth system perturbations, including atmospheric CO2 drawdown and O2 rise, climate cooling, eutrophication and widespread development of anoxia in epeiric seas, and ultimately, a series of mass extinctions that fundamentally altered the trajectory of Earth’s biosphere. This proposal seeks to link key Late Devonian global events in a new genetic framework that ties a refined temporal record of anoxic expansion in epeiric seas across Laurentia and Gondwana directly to the extinction events, determines the effect of epeiric sea anoxia on the global carbon cycle, and then links these records to global carbonate-based isotopic curves.

Specifically, this work proposes to: 1) develop a new, integrated geologic framework that ties Late Devonian mass extinctions to the epeiric black shale successions of North and South America using a combination of conodont biostratigraphy, Re-Os geochronology, and redox geochemistry; 2) use these data to refine the open access Macrostrat database for the Late Devonian with the goal of estimating global carbon burial, CO2 drawdown, and O2 buildup; and 3) generate a new uranium and carbon isotope record through Late Devonian carbonates of Western Australia, which will provide a quantitative record of global ocean anoxia and carbon burial.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.