nai

Project Progress

My group has primarily focused on the problem of environmental evolution during the Archean-Proterozoic boundary, with the major contribution being the article in Geochemistry Geophysis Geosystems in 2001. This article generated considerable interest among people interested in mantle evolution (see Sleep’s Nature News and Views article) as well as in the evolution of the atmospheric composition.

Ellen Herman (MS Student) has received some support from the Pennsylvania State Astrobiology Research Center (PSARC) to develop a numerical model of the microbial mat. The model is used to evaluate how microbial mats may have differed during Archean and Proterozoic times, when the overlying water may have been O₂ poor and/or sulfide rich. Her thesis is now completed and will be published soon.

Andy Kurtz’s (postdoc) work on Ge/Si ratios in Precambrian cherts is being written up presently. The goal of this research was to determine the intensity of chemical weathering through geologic time and the relative influences of riverine and hydrothermal sources of Ge (and by proxy, Si) in the Precambrian.

I have collaborated with my Task 5 colleagues on the Snowball Earth problem. Modeling of the paleoceanography of the Neoproterozoic is under way. I have also collaborated with Bill Seyfried (U. Minn.) on the response of seafloor hydrothermal systems to depressurization during sea-level lowstands. That work is under revision for Nature.

We have done a bit of fieldwork. I participated in the first Western Australia field trip and collected samples through the Paleoproterozoic diamictite (Snowball Earth 1) interval. Jay Kaufman (U. Md.) is in possession of those samples, and will be running C-isotope analyses shortly. Mike Moreland, Master’s student, and I have collected samples from Green Lake, NY, anticipating that this could be a site for intensive study as an analog for Precambrian planktonic ecosystems.

Finally, in collaboration with colleagues from a variety of institutions, we have published a paper on CO₂ levels just following the Cretaceous Tertiary mass extinction (Beerling et al., 2002, PNAS 99, 7844-7847) based on modeling (my part) and fossil leaf stomatal density.