Dr. Stephen R. Meyers
Assistant Professor
Paleoclimatology, Sedimentary Geochemisty, Stratigraphy, Geostatistics

Ph.D., Northwestern University, 2003

Download Curriculum Vitae

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UNC Chapel Hill, Winter 2007
(Photo © Gigi Cohen)

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The Astronomical Clock
Old Town Square, Prague, 2005
(Photo: S. Meyers)

THE BIOGEOCHEMISTRY OF ORGANIC MATTER BURIAL




(Figure from Meyers, Sageman and Lyons, 2005)

A major advance in paleoclimate analysis has been the recognition of linked biogeochemical cycles and the development of biogeochemical models for the Earth System, providing a valuable framework for the evaluation of geologic data and the testing of hypotheses. One of the major research questions that has been investigated with this approach pertains to the controls on atmospheric carbon dioxide over geologic time and its role as a forcing factor in climate change. Biogeochemical analysis of intervals of Earth History that record perturbations to the carbon cycle provides a unique opportunity to evaluate the linkage between carbon dioxide and climate. One such interval is the Cenomanian/Turonian Oceanic Anoxic Event II (OAE II), a time of enhanced organic matter burial and hypothesized atmospheric carbon dioxide drawdown.

This research project investigates the controls on organic matter burial during OAE II, and evaluates its impact on paleoclimate change, through an integration of biogeochemical modeling and data analysis (Meyers et al., 2001; Meyers et al., 2005;Meyers, submitted). This includes the development of proxy methods for assessment of paleo-production, organic matter remineralization and dilution flux (e.g., terrigenous clay delivery). Application of the methodology to the OAE II interval in the Cretaceous Western Interior Basin (USA) indicates that organic matter accumulation was controlled by changes in the depth of the sulfate reduction zone in the sediment, which is determined by the balance between metabolic demands within pore waters (i.e., consumption of oxygen and sulfate due to organic matter degradation), rates of hydrogen sulfide production (the presence of which excludes aerobic bioturbators, the principal agents of oxygen penetration in sediments), and rates of sulfide depletion (dominantly through formation of iron sulfides that are limited mainly by reactive iron supply). The two most significant results from this analysis of OAE II are: 1) reactive iron plays a critical role in controlling organic matter burial by modulating oxygen exposure time, and 2) the strong correlation between source rock development and intervals of transgression in the geologic record may reflect a confluence of biogeochemical processes within sediments without requiring fundamental changes in primary production levels or oceanographic conditions, such as prolonged periods of stable water column stratification.

The integrated biogeochemical and cyclostratigraphic methodology developed in this study is now being employed to investigate paleoenvironmental change and the controls on organic matter burial globally during OAE II. Future work will also investigate the relationship between reactive iron delivery and oxygen exposure time in modern sedimentary environments.

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