Biosignatures link microorganisms to iron mineralization in a paleoaquifer

Abstract

Research Article| August 01, 2012 Biosignatures link microorganisms to iron mineralization in a paleoaquifer Karrie A. Weber; Karrie A. Weber * 1School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA2Department of Earth and Atmospheric Sciences, University of Nebraska, Lincoln, Nebraska 68583, USA *E-mail: kweber2@unl.edu. Search for other works by this author on: GSW Google Scholar Trisha L. Spanbauer; Trisha L. Spanbauer 1School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588, USA †Current address: Department of Earth and Atmospheric Sciences, University of Nebraska, Lincoln, Nebraska 68583, USA. Search for other works by this author on: GSW Google Scholar David Wacey; David Wacey 3Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Crawley, WA 6009, Australia4School of Earth and Environment, University of Western Australia, Crawley, WA 6009, Australia Search for other works by this author on: GSW Google Scholar Matthew R. Kilburn; Matthew R. Kilburn 3Centre for Microscopy, Characterisation and Analysis, University of Western Australia, Crawley, WA 6009, Australia Search for other works by this author on: GSW Google Scholar David B. Loope; David B. Loope 2Department of Earth and Atmospheric Sciences, University of Nebraska, Lincoln, Nebraska 68583, USA Search for other works by this author on: GSW Google Scholar Richard M. Kettler Richard M. Kettler 2Department of Earth and Atmospheric Sciences, University of Nebraska, Lincoln, Nebraska 68583, USA Search for other works by this author on: GSW Google Scholar Geology (2012) 40 (8): 747–750. https://doi.org/10.1130/G33062.1 Article history received: 28 Nov 2011 rev-recd: 08 Mar 2012 accepted: 12 Mar 2012 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Karrie A. Weber, Trisha L. Spanbauer, David Wacey, Matthew R. Kilburn, David B. Loope, Richard M. Kettler; Biosignatures link microorganisms to iron mineralization in a paleoaquifer. Geology 2012;; 40 (8): 747–750. doi: https://doi.org/10.1130/G33062.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Concretions, preferentially cemented masses within sediments and sedimentary rocks, are records of sediment diagenesis and tracers of pore water chemistry. For over a century, rinded spheroidal structures that exhibit an Fe(III) oxide–rich exterior and Fe-poor core have been described as oxidation products of Fe(II) carbonate concretions. However, mechanisms governing Fe(III) oxide precipitation within these structures remain an enigma. Here we present chemical and morphological evidence of microbial biosignatures in association with Fe(III) oxides in the Fe(III) oxide–rich rind of spheroidal concretions collected from the Jurassic Navajo Sandstone (southwest United States), implicating a microbial role in Fe biomineralization. The amount of total organic carbon in the exterior Fe(III) oxides exceeded measured values in the friable interior. The mean δ13C value of organic carbon from the Fe(III) oxide–cemented exterior, δ13C of −20.55‰, is consistent with a biogenic signature from autotrophic bacteria. Scanning electron micrographs reveal microstructures consistent with bacterial size and morphology, including a twisted-stalk morphotype that resembled an Fe(II)-oxidizing microorganism, Gallionella sp. Nanoscale associations of Fe, O, C, and N with bacterial morphotypes demonstrate microorganisms associated with Fe(III) oxides. Together these results indicate that autotrophic microorganisms were present during Fe(III) oxide precipitation and present microbial catalysis as a mechanism of Fe(III) oxide concretion formation. Microbial biosignatures in rinded Fe(III) oxide–rich concretions within an exhumed, Quaternary aquifer has broad implications for detection of life within the geological record on Earth as well as other Fe-rich rocky planets such as Mars, where both Fe(II) carbonate and Fe(III) oxide–rich concretions have been identified. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.