Ann Bauer, Ph.D.

Education: Massachusetts Institute of Technology, Ph.D., Geology
Institution: Yale University (laboratory of Alan Rooney)

SCOL Project: Dynamics of the Lomagundi-Jatuli Excursion and Implications for Early Life

The Great Oxidation Event was an irreversible increase in the presence of oxygen in the Earth’s atmosphere during the early Paleoproterozoic (approximately 2.3 billion years ago) and was a critical transition in the lead-up to the evolution of macroscopic life. The Lomagundi-Jatuli event, the largest and longest-lived positive carbon isotope excursion in Earth history, followed the Great Oxidation Event and may have lasted as long as 260 million years. These carbon isotope signals indicate high amounts of primary productivity in the oceans, which would result in an increase in the degree of carbon burial. The substantial amount of carbon burial required to generate this long-lived carbon isotope excursion would result in large-scale oxygen production and thus may be expected to coincide with dramatic changes in chemical weathering and nutrient fluxes to the oceans, ultimately providing an ideal environment for evolving eukaryotes.

Determining the tempo of the Lomagundi-Jatuli event and deciphering the resultant impact on global redox conditions and biological processes is critical for efforts to unravel the evolution of complex life. However, despite decades of investigation, the temporal framework for the Lomagundi-Jatuli event is extremely limited. As a result, major questions remain unanswered regarding the duration and synchroneity of the carbon isotope excursion: was it a single long-lived excursion or were there numerous events of varying magnitude, and what mechanisms and processes could generate such an enormous disturbance to the global carbon cycle?

Testing hypotheses surrounding the timing and rates of evolutionary innovation and the interplay between changing geochemical cycles and biological processes is reliant on gaining absolute age constraints for the Lomagundi-Jatuli event. We propose to generate absolute age constraints using the Re-Os sedimentary rock geochronometer on carefully selected samples from North America and Africa. These new age constraints from globally distributed sections for this critical interval in the lead-up to the evolution of eukaryotic life will yield an improved understanding of the interplay between chemical weathering, ocean redox chemistry, biogeochemical cycles and the evolution of aerobes in the Paleoproterozoic.