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Nitrogen isotope and trace metal analyses from the Mingolsheim core (Germany): Evidence for redox variations across the Triassic‐Jurassic boundary
Author(s) -
Quan Tracy M.,
van de Schootbrugge Bas,
Field M. Paul,
Rosenthal Yair,
Falkowski Paul G.
Publication year - 2008
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2007gb002981
Subject(s) - extinction event , geology , isotopes of nitrogen , trace element , total organic carbon , phanerozoic , denitrification , isotopes of carbon , redox , water column , trace metal , paleontology , environmental chemistry , nitrogen , structural basin , oceanography , metal , geochemistry , chemistry , cenozoic , inorganic chemistry , biological dispersal , population , demography , organic chemistry , sociology
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 15 N values and low concentrations of redox‐sensitive elements, characteristic of an oxic environment with significant terrestrial input. The Early Jurassic features enrichment in δ 15 N 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.