Formation of lithified micritic laminae in modern marine stromatolites (Bahamas); the role of sulfur cycling

Abstract

Other| December 01, 1998 Formation of lithified micritic laminae in modern marine stromatolites (Bahamas); the role of sulfur cycling Pieter T. Visscher; Pieter T. Visscher University of Connecticut, Department of Marine Sciences, Groton, CT, United States Search for other works by this author on: GSW Google Scholar R. Pamela Reid; R. Pamela Reid Search for other works by this author on: GSW Google Scholar Brad M. Bebout; Brad M. Bebout Search for other works by this author on: GSW Google Scholar Shelley E. Hoeft; Shelley E. Hoeft Search for other works by this author on: GSW Google Scholar Ian G. Macintyre; Ian G. Macintyre Search for other works by this author on: GSW Google Scholar John A. Thompson John A. Thompson Search for other works by this author on: GSW Google Scholar American Mineralogist (1998) 83 (11-12_Part_2): 1482–1493. https://doi.org/10.2138/am-1998-11-1236 Article history first online: 02 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 Pieter T. Visscher, R. Pamela Reid, Brad M. Bebout, Shelley E. Hoeft, Ian G. Macintyre, John A. Thompson; Formation of lithified micritic laminae in modern marine stromatolites (Bahamas); the role of sulfur cycling. American Mineralogist 1998;; 83 (11-12_Part_2): 1482–1493. doi: https://doi.org/10.2138/am-1998-11-1236 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 SocietyAmerican Mineralogist Search Advanced Search Abstract Microbial mats on the surfaces of modern, marine stromatolites at Highborne Cay, Bahamas, were investigated to assess the role of microbial processes in stromatolite formation. The Highborne Cay stromatolitic mats contain Schizothix as the dominant cyanobacterium and show millimeter-scale lamination: Some layers in the mat are soft (unlithified), whereas other layers are crusty (lithified). Lithified layers within the mats correspond to micritic horizons composed of thin (20-50 mu m) micritic crusts, which commonly overlie truncated, micritized carbonate sand grains. These features are identical to lithified laminae in the underlying stromatolite; the micritic crusts are similar in thickness to micritic laminae in many ancient stromatolites. Biogeochemical parameters in a representative stromatolitic mat from Highborne Cay were measured to identify the role of bacteria in precipitation and dissolution of CaCO 3 . Depth distributions of O 2 , HS (super -) , and pH were determined with microelectrode measurements in the field. Oxygen profiles were used to calculate photosynthesis and aerobic respiration. Sulfate reduction was determined using 35 SO 4 (super 2-) and sulfide oxidation potential was measured in homogenized samples. Our results indicate that cyanobacterial photosynthesis, sulfate reduction, and anaerobic sulfide oxidation in stromatolitic mats at Highborne Cay are responsible for CaCO 3 precipitation, whereas aerobic respiration and aerobic sulfide oxidation cause CaCO 3 dissolution. A close coupling of photosynthesis and aerobic respiration in the uppermost few millimeters of the mats results in no, or very little, net lithification. Sulfur cycling, on the other hand, shows a close correlation with the formation of lithified micritic layers. Photosynthesis, combined with sulfate reduction and sulfide oxidation results in net lithification. Sulfate reduction rates are high in the uppermost lithified layer and, on a diel basis, consume 33-38% of the CO 2 fixed by the cyanobacteria. In addition, this lithified layer contains a significant population of sulfide-oxidizing bacteria and shows a high sulfide oxidation potential. These findings argue that photosynthesis coupled to sulfate reduction and sulfide oxidation is more important than photosynthesis coupled to aerobic respiration in the formation of lithified micritic laminae in Highborne Cay stromatolites. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.