Basinward nitrogen limitation demonstrates role of terrestrial nitrogen and redox control of δ15N in a Late Devonian black shale

Abstract

Research Article| October 01, 2013 Basinward nitrogen limitation demonstrates role of terrestrial nitrogen and redox control of δ15N in a Late Devonian black shale Michael L. Tuite, Jr.; Michael L. Tuite, Jr. Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA Search for other works by this author on: GSW Google Scholar Stephen A. Macko Stephen A. Macko Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Michael L. Tuite, Jr. Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA Stephen A. Macko Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22904, USA Publisher: Geological Society of America Received: 05 Mar 2013 Revision Received: 01 Jun 2013 Accepted: 03 Jun 2013 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2013 Geological Society of America Geology (2013) 41 (10): 1079–1082. https://doi.org/10.1130/G34549.1 Article history Received: 05 Mar 2013 Revision Received: 01 Jun 2013 Accepted: 03 Jun 2013 First Online: 09 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 Michael L. Tuite, Stephen A. Macko; Basinward nitrogen limitation demonstrates role of terrestrial nitrogen and redox control of δ15N in a Late Devonian black shale. Geology 2013;; 41 (10): 1079–1082. doi: https://doi.org/10.1130/G34549.1 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 depleted nitrogen isotope values observed in Devonian black shales have been ascribed to the dominant role of marine diazotrophic N fixation in providing new reactive N for the productivity that generated the organic matter preserved in these organic-rich facies. However, the emergence of substantial terrestrial ecosystems in the Middle to Late Devonian introduced an additional source of reactive N to shallow epicontinental seas. We examined three sites along a deepening transect of the Late Devonian Appalachian Basin (eastern United States) employing element ratios of C, N, and P, degree of pyritization, and stable isotope analyses of C, N, and S, in order to determine whether basinward changes in N biogeochemistry and δ15N reflect the dominant source of new reactive N. High degrees of pyritization and depleted δ34S indicate a persistently dysoxic to euxinic water column. Sediment N/P rises basinward, indicating that P was relatively more abundant than N in the water column with increasing distance from the shore. Nitrogen isotope values, however, are very consistently ∼0‰ at all three sites despite the evidence of distally increasing N limitation, suggesting that terrestrially derived reactive N was an important source of reactive N and that marine N fixation was not sufficient to address the stoichiometric deficit. Depleted δ15N values in these black shales do not provide a reliable record of diazotrophy; rather, they are a product of the reducing state of the water column and underlying sediments. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.