Early diagenetic celestite replacement of demosponges in Upper Cretaceous (Campanian–Maastrichtian) chalk, Stevns, Denmark

Research Article| April 01, 2009 Early diagenetic celestite replacement of demosponges in Upper Cretaceous (Campanian–Maastrichtian) chalk, Stevns, Denmark H.B. Madsen; H.B. Madsen 1Geological Survey of Denmark and Greenland, Copenhagen 1350-DK, Denmark Search for other works by this author on: GSW Google Scholar L. Stemmerik L. Stemmerik 2Department of Geography and Geology, University of Copenhagen, Copenhagen 1350-DK, Denmark Search for other works by this author on: GSW Google Scholar Author and Article Information H.B. Madsen 1Geological Survey of Denmark and Greenland, Copenhagen 1350-DK, Denmark L. Stemmerik 2Department of Geography and Geology, University of Copenhagen, Copenhagen 1350-DK, Denmark Publisher: Geological Society of America Received: 13 Jun 2008 Revision Received: 13 Nov 2008 Accepted: 16 Nov 2008 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2009 Geological Society of America Geology (2009) 37 (4): 355–358. https://doi.org/10.1130/G25254A.1 Article history Received: 13 Jun 2008 Revision Received: 13 Nov 2008 Accepted: 16 Nov 2008 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation H.B. Madsen, L. Stemmerik; Early diagenetic celestite replacement of demosponges in Upper Cretaceous (Campanian–Maastrichtian) chalk, Stevns, Denmark. Geology 2009;; 37 (4): 355–358. doi: https://doi.org/10.1130/G25254A.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 Celestite nodules with subordinate amounts of chalcedony are common in Upper Cretaceous chalk in two cores drilled at Stevns, Denmark. The nodules occur throughout the cores, indicating that the environmental conditions that led to their formation were an integral part of the biogeochemical cycle in the chalk sea. Petrographic evidence indicates that the celestite nodules were formed by replacement of lithistid demosponges in localized reduced environments prior to sediment compaction and chert formation. The 87Sr/86Sr values of the celestite nodules indicate that the Sr is mainly sourced from seawater and the δ34S values indicate activity of sulfate-reducing bacteria. This unusual occurrence of celestite is interpreted as a result of rapid burial of the sponges and following decomposition of the organic tissue by sulfate-reducing and sulfide-oxidizing bacteria, forming an anoxic microenvironment. The decomposition produced hydrogen sulfide, which was oxidized to sulfate by sulfide-oxidizing bacteria, resulting in decreasing pH. Strontium precipitated as celestite in dysoxic microenvironments and at the anoxic-dysoxic interface within the sponge. The crystallization of celestite apparently created an Sr gradient that drove Sr into the site of crystallization. This geochemical environment in dead demosponges represents an unknown celestite-forming process. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.