Early Aptian algal bloom in a neritic proto-North Atlantic setting: Harbinger of global change related to OAE 1a?

Abstract

Research Article| November 01, 2012 Early Aptian algal bloom in a neritic proto–North Atlantic setting: Harbinger of global change related to OAE 1a? Stefan Huck; Stefan Huck † 1Geological Institute, ETH Zurich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland2Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, D-44801 Bochum, Germany †E-mail: huck@geowi.uni-hannover.de Search for other works by this author on: GSW Google Scholar Ulrich Heimhofer; Ulrich Heimhofer 3Institut für Geologie, Leibniz Universität Hannover, Callinstraße 30, D-30167 Hannover, Germany Search for other works by this author on: GSW Google Scholar Adrian Immenhauser Adrian Immenhauser 2Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, D-44801 Bochum, Germany Search for other works by this author on: GSW Google Scholar Author and Article Information Stefan Huck † 1Geological Institute, ETH Zurich, Sonneggstrasse 5, CH-8092 Zürich, Switzerland2Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, D-44801 Bochum, Germany Ulrich Heimhofer 3Institut für Geologie, Leibniz Universität Hannover, Callinstraße 30, D-30167 Hannover, Germany Adrian Immenhauser 2Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, D-44801 Bochum, Germany †E-mail: huck@geowi.uni-hannover.de Publisher: Geological Society of America Received: 10 Aug 2011 Revision Received: 21 Mar 2012 Accepted: 02 Apr 2012 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2012 Geological Society of America GSA Bulletin (2012) 124 (11-12): 1810–1825. https://doi.org/10.1130/B30587.1 Article history Received: 10 Aug 2011 Revision Received: 21 Mar 2012 Accepted: 02 Apr 2012 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Stefan Huck, Ulrich Heimhofer, Adrian Immenhauser; Early Aptian algal bloom in a neritic proto–North Atlantic setting: Harbinger of global change related to OAE 1a?. GSA Bulletin 2012;; 124 (11-12): 1810–1825. doi: https://doi.org/10.1130/B30587.1 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 SocietyGSA Bulletin Search Advanced Search Abstract Pervasive growth of microencrusters (Lithocodium/Bacinella) characterizes short-lived stratigraphic intervals in Lower Aptian shallow-water carbonate platform settings of the central and southern Tethys. Although a causal relationship between this peculiar shallow-water facies and the early Aptian oceanic anoxic event (OAE) 1a seems likely, the temporal and spatial distributions of Lithocodium and Bacinella mass occurrences in the rock record point to a rather complex pattern. Possible controls include various global and regional drivers expressed in environmental perturbation of neritic ecosystems. Microencruster blooms have hitherto been reported to occur at the onset and in the aftermath of OAE 1a, slightly pre- or postdating the deposition of dark organic-rich black shales in pelagic basins. This study presents evidence for a punctuated and well-expressed early Aptian bloom of the ulvophycean green algae Lithocodium aggregatum observed at the proto–North Atlantic margin, Lusitanian Basin, Portugal. Similar to southern and central Tethyan sections, a Lithocodium-dominated interval temporally replaces the rudist-dominated platform ecosystem. This Lithocodium-rich horizon is composed of oncoidal floatstones and boundstones, including a well-exposed biohermal level, and reaches a thickness of up to 6 m. High-resolution carbon-isotope stratigraphy shown here clearly argues for Lithocodium to represent a biotic harbinger of environmental change in the run-up of OAE 1a. Chemostratigraphy provides evidence that the subsequent carbonate platform breakdown in the proto–North Atlantic was coeval with an early Aptian carbonate platform drowning episode observed in the northern Tethys prior to OAE 1a. A regionally enhanced nutrient level and a relative sea-level rise are suggested to have triggered the transient mass occurrence of Lithocodium microencrusters, which also may have been influenced by elevated atmospheric CO2 concentrations related to the emplacement of the Ontong Java large igneous province. Upwelling water masses and enhanced terrigenous runoff due to increased weathering may have served as possible sources of the required nutrients, which tentatively diminished and finally interrupted the metazoan carbonate platform factory. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.