Mesoproterozoic carbon dioxide levels inferred from calcified cyanobacteria

Research Article| September 01, 2007 Mesoproterozoic carbon dioxide levels inferred from calcified cyanobacteria Linda C. Kah; Linda C. Kah 1Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, USA Search for other works by this author on: GSW Google Scholar Robert Riding Robert Riding 2School of Earth, Ocean, and Planetary Sciences, Cardiff University, Cardiff CF10 3YE, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Linda C. Kah 1Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, Tennessee 37996, USA Robert Riding 2School of Earth, Ocean, and Planetary Sciences, Cardiff University, Cardiff CF10 3YE, UK Publisher: Geological Society of America Received: 08 Jan 2007 Revision Received: 10 Apr 2007 Accepted: 12 Apr 2007 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 The Geological Society of America, Inc. Geology (2007) 35 (9): 799–802. https://doi.org/10.1130/G23680A.1 Article history Received: 08 Jan 2007 Revision Received: 10 Apr 2007 Accepted: 12 Apr 2007 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Linda C. Kah, Robert Riding; Mesoproterozoic carbon dioxide levels inferred from calcified cyanobacteria. Geology 2007;; 35 (9): 799–802. doi: https://doi.org/10.1130/G23680A.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 Filamentous and shrub-like carbonate fabrics produced by in vivo cyanobacterial sheath calcification in stromatolites of the ca. 1200 Ma Society Cliffs Formation, Baffin and Bylot Islands, Arctic Canada, are 400 m.y. older than previously reported examples. In vivo sheath calcification is promoted by carbon dioxide concentrating mechanisms (CCMs) and is a direct ecophysiological link to atmospheric CO2 concentration. CCMs are induced in present-day cyanobacteria under experimental conditions when pCO2 is below ∼0.36% (∼10 times present atmospheric level, PAL). Society Cliffs calcified cyanobacteria consequently imply pCO2 levels of <0.36% at ca. 1200 Ma. This inference is consistent with marine carbon isotope modeling that suggests pCO2 of 7–10 PAL in the late Mesoproterozoic. Combined, petro-graphic, experimental, and modeling results therefore suggest that Mesoproterozoic pCO2 concentrations were not substantially different from Phanerozoic values and were significantly less than previous estimates of up to 200 PAL. Assuming 10% lower solar luminosity in the late Mesoproterozoic, pCO2 levels of 10 PAL or less require the presence of additional greenhouse gases for maintenance of an ice-free Earth. At 10 PAL pCO2, methane concentrations of 100–200 ppm would have been sufficient to sustain warm Earth surface conditions. The low atmospheric oxygen and limited marine sulfate concentrations required to sustain atmospheric methane provide additional support for sulfur isotope models that suggest protracted oxygenation of Earth's Proterozoic biosphere. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.