Paper No. 11-13
Presentation Time: 11:00 AM
ARE OAES ACTUALLY CBES? EVIDENCE OF MARINE ANOXIA THROUGH THE EYES OF A NOVEL METAL ISOTOPE
THEM II, Theodore R.1, GILL, Benjamin C.2, CARUTHERS, Andrew H.3, GRÖCKE, Darren R.4, MARROQUÍN, Selva M.2, TRABUCHO-ALEXANDRE, João P.5 and OWENS, Jeremy D.6, (1)Department of Geology and Environmental Geosciences, College of Charleston, Charleston, SC 29424, (2)Department of Geosciences, Virginia Polytechnic Institute and State University, 4044 Derring Hall, Blacksburg, VA 24061, (3)Department of Geological and Environmental Sciences, Western Michigan University, 1903 W. Michigan Ave, Kalamazoo, MI 49008-5241, (4)Department of Earth Sciences, University of Durham, Science Labs, Durham, DH1 3LE, United Kingdom, (5)Institute of Earth Sciences, Utrecht University, Budapestlaan 4, Utrecht, 3584 CD, Netherlands, (6)Department of Earth, Ocean, and Atmospheric Sciences, Florida State University, National High Magnetic Field Laboratory, Tallahassee, FL 32306
The development of widespread anoxia in the oceans during past intervals of environmental deterioration is generally accepted as one of the main drivers of biotic crises. Many traditional proxies such as carbon isotopes, trace metal enrichments, and the deposition of organic matter-rich sediments have been utilized to demarcate the timing of increased anoxia. However, recent research has suggested that a novel geochemical proxy can fingerprint the timing and duration of deoxygenation associated with these events. The Early Jurassic Toarcian Oceanic Anoxic Event (OAE) is associated with perturbations to multiple elemental systems, deposition of organic matter-rich sediments, and a marine mass extinction. These changes have been linked to the emplacement of the Karoo-Ferrar large igneous province and associated biogeochemical feedbacks within the Earth system.
We will present a multi-proxy dataset of novel and traditional geochemical proxies across the T-OAE from eastern Panthalassa. Iron speciation data are used to constrain local water column redox that suggests anoxic and euxinic (anoxic and sulfidic water column) conditions. Thallium isotopes, a new and novel proxy, are utilized to determine the onset of widespread deoxygenation. Redox-sensitive trace metal contents are used to track the marine reservoir of the respective element. These combined data suggest that widespread deoxygenation initiated ~600 kyr before the traditional T-OAE interval at Pliensbachian/Toarcian boundary. A decrease in the trace metal inventory of the oceans is associated with the traditional T-OAE interval and related to the expansion of euxinia. These data are generally consistent with a Cretaceous OAE (Cenomanian/Turonian Boundary Event) but the timescales are vastly different. Thus, the use of novel and traditional geochemical proxies suggests that the traditional OAE interval is better defined as a carbon burial event (CBE) or oceanic euxinic event (OEE).
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