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Using a Novel Approach to Reconstruct Sulfur Cycling in Ancient Methane Seep Environments

Leanne Hancock
University of California, Riverside, Department of Earth Science, Riverside, CA, USA
[email protected]

Methane is an important greenhouse gas that has played a major role throughout Earth’s history, and methane seeps are an ideal natural laboratory in which to study the processes associated with methane release to the oceans. At seep sites, there are multitude of macrofauna that survive through use of microbial sulfide-oxidizing symbiotic partners, that allow them to survive in an otherwise uninhabitable environment. A study of marine methane is incomplete without concomitant analysis of sulfur species, which are more likely to be preserved in the carbonates forming in these systems. Pyrite is a major component in seeps, but pyrite formation is limited by the presence of reactive iron, and thus only captures the earliest burial processes. To fully track sulfur and its role in modulating methane release, a tracer of dissolved sulfate known as carbonate-associated sulfate is more useful. This study focuses on a modern and an ancient site of methane seepage, attempting to quantify the relationships between carbon in methane-derived carbonates and sulfur cycling by calibrating proxies in the modern to be used to understand past locations of hydrocarbon release. Quantifying sulfide availablity is crucial to understanding the distribution of macrofauna and the limitations on their ecosystems. Through the study of sulfur cycling in carbonates in modern and ancient seep environments, we will gain insight into not only the role of thiotrophy as a metabolic preference, but also the role of sulfur in the methane cycle through geologic history, which has played a major role in controlling Earth's climate.

AAPG Search and Discovery Article #90183©2013 AAPG Foundation 2013 Grants-in-Aid Projects