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GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 22, GB2014, doi:10.1029/2007GB002981, 2008

Nitrogen isotope and trace metal analyses from the Mingolsheim core (Germany): Evidence for redox variations across the Triassic-Jurassic boundary

Tracy M. Quan

Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey, USA


Bas van de Schootbrugge

Institute of Geosciences, Johann Wolfgang Goethe University Frankfurt, Frankfurt, Germany


M. Paul Field

Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey, USA


Yair Rosenthal

Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey, USA


Paul G. Falkowski

Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, New Jersey, USA
Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, New Jersey, USA


Abstract

The Triassic-Jurassic (T-J) boundary was one of the largest but least understood mass extinction events in the Phanerozoic. We measured bulk organic nitrogen and carbon isotopes and trace metal concentrations from a core near Mingolsheim (Germany) to infer paleoenvironmental conditions associated with this event. Poorly fossiliferous claystones across the boundary have relatively low δ 15N values and low concentrations of redox-sensitive elements, characteristic of an oxic environment with significant terrestrial input. The Early Jurassic features enrichment in δ 15N coincident with high redox-sensitive element concentrations, indicating an increase in water column denitrification and decreased oxygen concentrations. These redox state variations are concordant with shifts in abundance and species composition in terrestrial and marine microflora. We propose that the mass extinction at the T-J boundary was caused by a series of events resulting in a long period of stratification, deep-water hypoxia, and denitrification in this region of the Tethys Ocean basin.

Received 21 March 2007; accepted 18 January 2008; published 10 May 2008.

Keywords: T-J boundary; nitrogen; isotopes; redox environments.

Index Terms: 1041 Geochemistry: Stable isotope geochemistry (0454, 4870); 4912 Paleoceanography: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805); 1065 Geochemistry: Major and trace element geochemistry; 4924 Paleoceanography: Geochemical tracers.

Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 2848136 bytes)

Citation: Quan, T. M., B. van de Schootbrugge, M. P. Field, Y. Rosenthal, and P. G. Falkowski (2008), Nitrogen isotope and trace metal analyses from the Mingolsheim core (Germany): Evidence for redox variations across the Triassic-Jurassic boundary, Global Biogeochem. Cycles, 22, GB2014, doi:10.1029/2007GB002981.