Beyond Tethys: An Examination of Molybdenum Isotopes in the Neuquén Basin Argentina as a Proxy for Global Ocean Redox

AL-SUWAIDI, A.; DICKSON, A.; JENKYNS, H.; HESSELBO, S.; DAMBORENEA, S.E.; MANCEÑIDO, M.O.; RICCARDI, A.C

Austin

Conferencia; SEPM Research Conference Oceanic Anoxic Events (OAEs); 2016

SEPM

The Toarcian, Early Jurassic, Oceanic Anoxic Event (T-OAE: ~183 Ma) was characterized by relatively high mid-latitude sea-surface temperatures (~6°Cwarmer than present), mass extinction, and the deposition of sediments rich inorganic carbon (black shales). The T-OAE correlates with emplacement of a large igneous province (Karroo-Ferrar) and is associated with a positive carbon-isotope excursion punctuated by a stepped negative carbon-isotope excursion, in bulk sedimentary organic matter and fossil wood, the later recording the atmospheric isotopic composition with values as low as -34?. The T-OAE has been extensively studied in Northern and Southern Europe, but whilst new studies from the Southern Hemisphere have provided chemostratigraphic evidence for the global expression of the event, studies, which have applied more novel geochemical proxies outside of the Tethyan realm, are limited. Here we present new high-resolution d98/95Mo data from the Neuquén Basin, Argentina, with values ranging from ~ -1?1?. The new molybdenum-isotope data reflect redox variability within the Neuquén Basin, associated with oxygenation of bottom water and potentially high inputs of volcanically derived sediments with ad98/95Mo closer or 0?. The new data also call into question the inference that the northern European seaways record global molybdenum-isotope fluctuations during the T-OAE.