2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 41-7
Presentation Time: 9:00 AM-5:30 PM


BORRELLI, C.1, GABITOV, R.I.2, MESSENGER, S. R.3, NGUYEN, A.N.4, TORRES, M.E.5 and KESSLER, J.D.1, (1)Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, (2)Department of Geosciences, Mississippi State University, Mississippi State, MS 39762-5448, (3)Robert M. Walker Laboratory for Space Science, Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, Houston, TX 77058, (4)Robert M. Walker Laboratory for Space Science, Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center, Houston, TX 77058; JETS, Jacobs, NASA Johnson Space Center, Houston, TX 77058, (5)College of Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331-5503, cborrelli@ur.rochester.edu

Methane (CH4) is an important greenhouse gas, with a global warming potential much higher than carbon dioxide (CO2) on a short time scale. Even if the residence time of CH4 in the atmosphere is relatively short (tens of years), one of the products of CH4 oxidation is CO2, a greenhouse gas with a much longer residence time in the atmosphere (tens to hundreds of years). CH4 has been proposed as one of the trigger mechanisms for rapid global climate change today and in the geological past. With regards to the geological past, numerous studies proposed the benthic foraminiferal carbon isotope ratio (δ13C) as a tool to reconstruct the impact of marine CH4 on rapid climate changes; however, the investigation of modern benthic foraminiferal δ13C have produced inconclusive results.

CH4 has a distinctive hydrogen isotope (δD) and δ13C signature compared to seawater, and sulfate reduction, often coupled to CH4 anaerobic oxidation in sediments, changes the sulfur isotope signature (δ34S) of the remaining sulfate in porewater. Therefore, we hypothesize that the δD and δ34S signature of infaunal benthic foraminiferal species can provide a complementary approach to δ13C to study CH4dynamics in sedimentary environments.

Here, we present the preliminary results obtained analyzing Uvigerina peregrina δD and δ34S from three different locations at Hydrate Ridge, offshore Oregon. Unfortunately, the lack of chemical data related to the moment of foraminiferal calcification makes it difficult to build a robust relationship among the U. peregrina stable isotopes and the CH4 fluxes at the sampling sites. However, our results look very promising, as each site is characterized by a different δD and δ34S signature. We emphasize that this study represents the first step in the development of new proxies (δD and δ34S), which may complement the more traditional benthic foraminiferal δ13C values, to reconstruct marine CH4 fluxes in the geological past.