Missing molluscs: Field testing taphonomic loss in the Mesozoic through early large-scale aragonite dissolution

Research Article| March 01, 2003 Missing molluscs: Field testing taphonomic loss in the Mesozoic through early large-scale aragonite dissolution Paul Wright; Paul Wright 1Department of Earth Sciences, Cardiff University, Cardiff CF10 3YE, UK Search for other works by this author on: GSW Google Scholar Lesley Cherns; Lesley Cherns 1Department of Earth Sciences, Cardiff University, Cardiff CF10 3YE, UK Search for other works by this author on: GSW Google Scholar Peter Hodges Peter Hodges 2Department of Geology, National Museum of Wales, Cardiff CF10 3NP, UK Search for other works by this author on: GSW Google Scholar Author and Article Information Paul Wright 1Department of Earth Sciences, Cardiff University, Cardiff CF10 3YE, UK Lesley Cherns 1Department of Earth Sciences, Cardiff University, Cardiff CF10 3YE, UK Peter Hodges 2Department of Geology, National Museum of Wales, Cardiff CF10 3NP, UK Publisher: Geological Society of America Received: 23 Jun 2002 Revision Received: 02 Nov 2002 Accepted: 08 Nov 2002 First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2003) 31 (3): 211–214. https://doi.org/10.1130/0091-7613(2003)031<0211:MMFTTL>2.0.CO;2 Article history Received: 23 Jun 2002 Revision Received: 02 Nov 2002 Accepted: 08 Nov 2002 First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Paul Wright, Lesley Cherns, Peter Hodges; Missing molluscs: Field testing taphonomic loss in the Mesozoic through early large-scale aragonite dissolution. Geology 2003;; 31 (3): 211–214. doi: https://doi.org/10.1130/0091-7613(2003)031<0211:MMFTTL>2.0.CO;2 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 As a field test for Cherns and Wright's previously published hypothesis based on Paleozoic faunas—that the paucity of certain molluscan groups in the fossil record may be largely a taphonomic, not ecologic, effect—a typical Mesozoic molluscan-dominated fauna is compared with its early-silicified (lagerstätten) equivalent from a similar depositional setting. A Lower Jurassic offshore carbonate ramp facies in South Wales comprises alternating thin limestones and organic-rich shales; the former are largely diagenetic and carry marine isotopic signatures. Their typical fauna is mainly well preserved, calcitic and bimineralic (calcite + aragonite), epifaunal and semiinfaunal bivalves. Evidence of aragonitic shells is normally restricted to molds, common in inner ramp settings in high-energy skeletal grainstones, but mostly poorly preserved and restricted to deep-burrowing bivalves in offshore deposits. However, locally, early silicification in offshore facies has preserved much more diverse faunas with abundant, formerly aragonitic, molluscs, including many more infaunal burrowers. It appears that major aragonite dissolution normally distorted both apparent diversity (65% decrease in bivalve diversity) and the trophic structure of the offshore facies, providing aragonite that probably sourced the diagenetic carbonates. We suggest that aragonitic shells were selectively dissolved in the upper sediment column in lower-energy settings, where high organic contents favored microbial decay and acidity; such early dissolution was absent from the higher-energy facies that originally had low organic contents. Taphonomic loss through early skeletal aragonite dissolution was an equally important process in Mesozoic offshore shelf environments, and although still leaving depleted molluscan-dominated faunas, resulted in a massive distortion of diversity. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.