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Short-term environmental change in a Jurassic lagoon deduced from geochemical trends in aragonite bivalve shells

2001; Geological Society of America; Volume: 113; Issue: 6 Linguagem: Inglês

10.1130/0016-7606(2001)113 2.0.co;2

1943-2674

James P. Hendry, William T. Perkins, Tristan Bane,

Geochemistry and Elemental Analysis

Research Article| June 01, 2001 Short-term environmental change in a Jurassic lagoon deduced from geochemical trends in aragonite bivalve shells James P. Hendry; James P. Hendry 1School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK Search for other works by this author on: GSW Google Scholar William T. Perkins; William T. Perkins 2Institute of Geography and Earth Sciences, University of Wales, Aberystwyth SY23 3DB, UK Search for other works by this author on: GSW Google Scholar Tristan Bane Tristan Bane 3School of Geosciences, Queen's University, Belfast BT7 1NN, UK Search for other works by this author on: GSW Google Scholar Author and Article Information James P. Hendry 1School of Earth and Environmental Sciences, University of Portsmouth, Burnaby Building, Burnaby Road, Portsmouth PO1 3QL, UK William T. Perkins 2Institute of Geography and Earth Sciences, University of Wales, Aberystwyth SY23 3DB, UK Tristan Bane 3School of Geosciences, Queen's University, Belfast BT7 1NN, UK Publisher: Geological Society of America Received: 15 Nov 1999 Revision Received: 11 Sep 2000 Accepted: 03 Oct 2000 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2001) 113 (6): 790–798. https://doi.org/10.1130/0016-7606(2001)113 2.0.CO;2 Article history Received: 15 Nov 1999 Revision Received: 11 Sep 2000 Accepted: 03 Oct 2000 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation James P. Hendry, William T. Perkins, Tristan Bane; Short-term environmental change in a Jurassic lagoon deduced from geochemical trends in aragonite bivalve shells. GSA Bulletin 2001;; 113 (6): 790–798. doi: https://doi.org/10.1130/0016-7606(2001)113 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 SocietyGSA Bulletin Search Advanced Search Abstract The Bathonian age Inverbrora Member of the Brora Coal Formation, northern Scotland, was deposited in a predominantly fresh- water coastal lagoon setting. However, two prominent shell beds within the mostly argillaceous succession have been interpreted as resulting from temporary inundation of marine water and establishment of brackish conditions. The ensuing lagoon hydrology and paleoenvironment were investigated by measuring stable isotopic (δ18O and δ13C) and trace element (Mg, Sr, Mn, Ba) variations within five exceptionally well preserved aragonite shells of the bivalve Isognomonmurchisoni. Transects were sampled across the visible growth banding with a resolution of 0.25−0.15 mm for stable isotopes, and 0.05 mm for trace elements. Oxygen and carbon isotope data define a broadly covariant trend (δ18O between +0.4‰ and −4.8‰ Peedee belemnite [PDB]; δ13C between +2.2‰ and −0.7‰ PDB) that supports a variably brackish-water setting with slight seasonal evaporation. Absolute trace element values vary from shell to shell but show consistent patterns of covariation. Profiles of Mg/Ca across shell layers display multiple sharp, episodic minima that are coincident with peaks in Sr/Ca and Ba/Ca. This is interpreted as documenting inundation of the restricted, brackish-water lagoon by relatively cooler seawater, leading to a temporary increase in metabolic activity of the bivalves. Less frequent minima in Mg/Ca, Sr/Ca, δ18O, and δ13C record fresh-water influx and dramatic salinity reduction in the lagoon. Bivalve metabolic efficiency was decreased, and in some cases breaks in shell growth occurred. This study shows that in hydrodynamically complex settings, trace element variation in bivalve shells can provide a detailed record of short-term environmental change. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.