Effect of ambient Mg/Ca ratio on Mg fractionation in calcareous marine invertebrates: A record of the oceanic Mg/Ca ratio over the Phanerozoic

Research Article| November 01, 2004 Effect of ambient Mg/Ca ratio on Mg fractionation in calcareous marine invertebrates: A record of the oceanic Mg/Ca ratio over the Phanerozoic Justin B. Ries Justin B. Ries 1Morton K. Blaustein Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Justin B. Ries 1Morton K. Blaustein Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, Maryland 21218, USA Publisher: Geological Society of America Received: 21 May 2004 Revision Received: 27 Jul 2004 Accepted: 03 Aug 2004 First Online: 03 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (11): 981–984. https://doi.org/10.1130/G20851.1 Article history Received: 21 May 2004 Revision Received: 27 Jul 2004 Accepted: 03 Aug 2004 First Online: 03 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 Justin B. Ries; Effect of ambient Mg/Ca ratio on Mg fractionation in calcareous marine invertebrates: A record of the oceanic Mg/Ca ratio over the Phanerozoic. Geology 2004;; 32 (11): 981–984. doi: https://doi.org/10.1130/G20851.1 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 The Mg/Ca ratio of seawater has changed significantly over the Phanerozoic, primarily as a function of the rate of ocean-crust production. Echinoids, crabs, shrimps, and calcareous serpulid worms grown in artificial seawaters encompassing the range of Mg/Ca ratios that existed throughout the Phanerozoic exhibit a direct nonlinear relationship between skeletal and ambient Mg/Ca. Specimens grown in seawater with the lowest Mg/Ca (∼1) changed their mineralogy to low-Mg calcite (<4 mol% MgCO3), suggesting that these high-Mg calcareous organisms would have produced low-Mg calcite in the Cretaceous, when oceanic Mg/Ca was lowest (∼1). These results support the empirical evidence that the skeletal chemistry of calcareous organisms has varied significantly over the Phanerozoic as a function of the Mg/Ca of seawater, and that the Mg/Ca of unaltered fossils of such organisms may be a record of oceanic Mg/Ca throughout the Phanerozoic. Mg fractionation algorithms, which relate skeletal Mg/Ca, seawater Mg/Ca, and temperature, were derived from these and other experiments. They can be used to estimate paleoceanic Mg/ Ca ratios and temperatures from fossil skeletal Mg/Ca of the organisms evaluated. Pale oceanic Mg/Ca ratios, recalculated by using the echinoderm Mg fractionation algorithm from published fossil echinoid Mg/Ca, crinoid Mg/Ca, and paleotemperature data, are consistent with other estimates and models of oceanic Mg/Ca over the Phanerozoic. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.