Formation of iron sulfide nodules during anaerobic oxidation of methane

Bart E. van Dongen, Andrew P. Roberts, Stefan Schouten, Wei Teh Jiang, Fabio Florindo, Richard D. Pancost

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Abstract

The biomarker compositions of iron sulfide nodules (ISNs; upper Pliocene Valle Ricca section near Rome, Italy) that contain the ferrimagnetic mineral greigite (Fe3S4) were examined. In addition to the presence of specific terrestrial and marine biomarkers, consistent with formation in coastal marine sediments, these ISNs contain compounds thought to originate from sulfate reducing bacteria (SRB). These compounds include a variety of low-molecular-weight and branched alkanols and several non-isoprenoidal dialkyl glycerol diethers (DGDs). In addition, archaeal biomarkers, including archaeol, macrocyclic isoprenoidal DGDs and isoprenoidal glycerol dialkyl glycerol tetraethers are also present. Both SRB and archaeal lipid δ13C values are depleted in 13C (δ13C values are typically less than -50‰), which suggests that the SRB and archaea consumed 13C depleted methane. These biomarker and isotopic signatures are similar to those found in cold seeps and marine sediments where anaerobic oxidation of methane (AOM) occurs with sulfate serving as the terminal electron acceptor. Association of AOM with formation of greigite-containing ISNs could provide an explanation for documented remagnetization of the Valle Ricca sediments. Upward migration of methane, subsequent AOM and associated authigenic greigite formation are widespread processes in the geological record that have considerable potential to compromise paleomagnetic records.

Original languageEnglish
Pages (from-to)5155-5167
Number of pages13
JournalGeochimica et Cosmochimica Acta
Volume71
Issue number21
DOIs
Publication statusPublished - 2007 Nov 1

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

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    van Dongen, B. E., Roberts, A. P., Schouten, S., Jiang, W. T., Florindo, F., & Pancost, R. D. (2007). Formation of iron sulfide nodules during anaerobic oxidation of methane. Geochimica et Cosmochimica Acta, 71(21), 5155-5167. https://doi.org/10.1016/j.gca.2007.08.019