Fike, David A. and Orphan, Victoria J. (2009) High resolution SIMS-based sulfide δ^(34)S: A new tool for characterizing microbial activity in a variety of depositional environments. Geochimica et Cosmochimica Acta, 73 (13, S). A375. ISSN 0016-7037. http://resolver.caltech.edu/CaltechAUTHORS:20140723-162327430
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The sulfur isotopic compositions of sedimentary sulfates and sulfides are useful for understanding modern microbial ecology and for reconstructing paleoenvironmental conditions associated with the deposition of ancient sediments. In many modern microbially-dominated sedimentary environments, such as microbial mats, or methane seeps, the redox gradients can be steep with the transition from oxic to sulfidic condition over the space of mm to cm. In these environments, it is frequently difficult (either for logistical reasons or sample volume requirements) to sample at a sufficiently high resolution to capture the geochemical and microbiological details associated with these redox transitions. We build upon earlier work  to demonstrate the ability to capture aqueous sulfide as silver sulfide, which can then be analyzed using a Cameca NanoSIMS 50L or 7F/Geo for its isotopic composition at a spatial resolution down to ~ 1 - 50 um. This allows for the construction of 2D isotopic datasets that document vertical isotope gradients as well as lateral heterogeneity . Here we present the application of this sulfide capture technique to three different modern environments: (1) microbial mats from Guerrero Negro, Baja California Sur, Mexico; (2) the chemocline of meromictic Lake Mahoney, British Columbia, Canada; and (3) methane seep-associated marine sediments offshore Costa Rica. Coherent variations up to 20 permil in δ34S are observed over ranges as small as 1 mm at all depths examined. These data highlight the additional ecological information that can be extracted from high resolution isotopic data, which may improve our understanding of the activity of the microbial ecosystems driving biogeochemical cycling in these systems.
|Additional Information:||Copyright © 2009 Elsevier.|
|Official Citation:||Goldschmidt Abstracts 2009 – F, Geochimica et Cosmochimica Acta, Volume 73, Issue 13, Supplement, June 2009, Pages A348-A405, ISSN 0016-7037, http://dx.doi.org/10.1016/j.gca.2009.05.005. (http://www.sciencedirect.com/science/article/pii/S0016703709002579)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||George Porter|
|Deposited On:||24 Jul 2014 15:50|
|Last Modified:||09 Jan 2016 04:02|
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