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Pseudofossils in relict methane seep carbonates resemble endemic microbial consortia

Bailey, Jake V. and Raub, Timothy D. and Meckler, A. Nele and Harrison, Benjamin K. and Raub, Theresa M. D. and Green, Abigail M. and Orphan, Victoria J. (2010) Pseudofossils in relict methane seep carbonates resemble endemic microbial consortia. Palaeogeography, Palaeoclimatology, Palaeoecology, 285 (1-2). pp. 131-142. ISSN 0031-0182.

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Pleistocene-age methane seep carbonates from the Eel River Basin, California contain aggregate-like structures composed of tightly-packed hollow spheres that morphologically resemble syntrophic archaeal–bacterial consortia known to catalyze the anaerobic oxidation of methane (AOM). Tetragonal microstructures also present in the carbonates resemble seep-endemic Methanosarcinales cell clusters. Despite morphological similarities to the seep-endemic microbes that likely mediated the authigenesis of Eel River Basin carbonates and sulfides, detailed petrographic, SEM, and magnetic microscopic imaging, remanence rock magnetism, laser Raman, and energy dispersive X-ray spectroscopy, suggest that these microstructures are not microfossils, but rather mineral structures that result from the diagenetic alteration of euhedral Fe-sulfide framboids. Electron microscopy shows that during diagenesis, reaction rims composed of Fe oxide form around framboid microcrystalites. Subsequent dissolution of greigite or pyrite crystals leaves behind hollow cell-like casings (external molds) — a transformation that occurs on timescales of ~100 kyr or less. Despite their superficial resemblance to morphologically-distinctive extant microbes in local sediments, the presence of acellular precursor grains, as well as of partially-altered transitional forms, complicate the interpretation of these and other framboidal microstructures that have been reported from the rock record.

Item Type:Article
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URLURL TypeDescription
Raub, Timothy D.0000-0002-7471-0246
Orphan, Victoria J.0000-0002-5374-6178
Additional Information:© 2009 Elsevier B.V. Received 26 April 2009; revised 1 October 2009; accepted 3 November 2009. Available online 10 November 2009. We thank George Rossman and Liz Boyd for technical guidance and support during Raman spectrum collection, Ray Lee for carbon isotope analyses, Frank Corsetti for helpful discussions and two anonymous reviewers for comments that greatly improved this manuscript. We also thank Joe Kirschvink and Jess Adkins for supporting major instrumentation used in our analyses. Funding for this work was provided by the NASA Astrobiology Institute (Grant award # 3903-CIT-NASA.A76A) as part of the Penn State Astrobiology Research Center (PSARC) and grants from the Gordon and Betty Moore Foundation (to VJO), a research scholarship from the German Research Foundation (to ANM), and the Agouron Institute Geobiology Postdoctoral Fellowship (to JVB). Magnetic microscopy was supported by a Human Frontiers Science Program grant (RGP0028/2007-C) and rock-magnetic analysis was supported by NASA Exobiology grant (NNX07AK12G) to J.L. Kirschvink. Collection of samples in the Eel River Basin was supported by the NOAA-National Underseas Research Program (UAF 05-0132).
Funding AgencyGrant Number
Gordon and Betty Moore FoundationUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)UNSPECIFIED
Agouron InstituteUNSPECIFIED
Human Frontiers Science ProgramRGP0028/2007-C
National Oceanic and Atmospheric Administration (NOAA)UAF 05-0132
Subject Keywords:Framboids; Greigite; Pyrite; AOM; Sulfate-reducing bacteria; Archaea
Issue or Number:1-2
Record Number:CaltechAUTHORS:20100302-113604574
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Official Citation:Jake V. Bailey, Timothy D. Raub, A. Nele Meckler, Benjamin K. Harrison, Theresa M.D. Raub, Abigail M. Green, Victoria J. Orphan, Pseudofossils in relict methane seep carbonates resemble endemic microbial consortia, Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 285, Issues 1-2, 1 January 2010, Pages 131-142, ISSN 0031-0182, DOI: 10.1016/j.palaeo.2009.11.002.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17627
Deposited By: Tony Diaz
Deposited On:12 Mar 2010 17:17
Last Modified:09 Mar 2020 13:19

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