scholarly journals Does large igneous province volcanism always perturb the mercury cycle? Comparing the records of Oceanic Anoxic Event 2 and the end-Cretaceous to other Mesozoic events

2018 ◽  
Vol 318 (8) ◽  
pp. 799-860 ◽  
Author(s):  
Lawrence M.E. Percival ◽  
Hugh C. Jenkyns ◽  
Tamsin A. Mather ◽  
Alexander J. Dickson ◽  
Sietske J. Batenburg ◽  
...  
Keyword(s):  
Large Igneous Province ◽  
Oceanic Anoxic Event ◽  
Igneous Province ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Mercury Cycle

scholarly journals Regional chronostratigraphic synthesis of the Cenomanian-Turonian Oceanic Anoxic Event 2 (OAE2) interval, Western Interior Basin (USA): New Re-Os chemostratigraphy and 40Ar/39Ar geochronology

2020 ◽  
Author(s):  
Matthew M. Jones ◽  
Bradley B. Sageman ◽  
David Selby ◽  
Brian R. Jicha ◽  
Brad S. Singer ◽  
...  
Keyword(s):  
Stable Carbon Isotope ◽  
Rapid Onset ◽  
Large Igneous Province ◽  
Oceanic Anoxic Event ◽  
The North ◽  
Marine Carbonate ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Western Interior Basin ◽  
Astronomical Tuning

Fluctuations in depositional conditions during the onset of severe climate events in Earth history predispose stratigraphic archives to hiatuses, often hindering complete reconstructions of paleoclimate events and their triggers. Several studies have proposed that a hiatus of unknown duration exists at the base of Oceanic Anoxic Event 2 (OAE2) in the North American Western Interior Basin at the base Turonian global boundary stratotype section and point (GSSP) in Pueblo, Colorado, which potentially influences integrated radioisotopic, biostratigraphic, and astrochronologic age models of the Cenomanian-Turonian boundary interval. To quantify the duration of this hiatus, refine the chronology of OAE2, and assess marine geochemical perturbations associated with the onset of the event, we present new 40Ar/39Ar dates from regional bentonites along with a new proximal-distal chemostratigraphic transect of the epeiric Western Interior Basin (WIB), including initial osmium isotope (Osi) and stable carbon isotope (δ13C) data. The new 40Ar/39Ar age determinations confirm and further constrain previous estimates of Cenomanian-Turonian boundary timing. Further, the regional chemostratigraphic synthesis demonstrates the conformity of the OAE2 successions correlated to Pueblo, shows that the duration of the lag between the onset of the Osi and δ13C excursions is ∼60 k.y., and thus constrains the magnitude of the pre-OAE2 hiatus in Pueblo to less than this value. The new astronomically tuned, conformable Osi record across the onset of OAE2 captures a geologically rapid onset of large igneous province volcanism, consistent with other records, such that the addition of CO2 to the ocean-atmosphere system may have driven changes in marine carbonate chemistry. Additionally, the refined chronostratigraphy of OAE2 and the Cenomanian-Turonian boundary in the central WIB improves correlation with other records, such as those in the Eagle Ford Group, Texas. The correlations highlight that discrepancies among OAE2 age models from globally distributed sections commonly stem from differing definitions of the event and uncertainties associated with astronomical tuning, in addition to stratigraphic preservation.

scholarly journals Uranium isotope evidence for two episodes of deoxygenation during Oceanic Anoxic Event 2

2018 ◽  
Vol 115 (12) ◽  
pp. 2918-2923 ◽  
Author(s):  
Matthew O. Clarkson ◽  
Claudine H. Stirling ◽  
Hugh C. Jenkyns ◽  
Alexander J. Dickson ◽  
Don Porcelli ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Large Igneous Province ◽  
Global Ocean ◽  
Uranium Isotopes ◽  
Carbonate Sediments ◽  
Cold Event ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event ◽  
Isotope Evidence

Oceanic Anoxic Event 2 (OAE 2), occurring ∼94 million years ago, was one of the most extreme carbon cycle and climatic perturbations of the Phanerozoic Eon. It was typified by a rapid rise in atmospheric CO2, global warming, and marine anoxia, leading to the widespread devastation of marine ecosystems. However, the precise timing and extent to which oceanic anoxic conditions expanded during OAE 2 remains unresolved. We present a record of global ocean redox changes during OAE 2 using a combined geochemical and carbon cycle modeling approach. We utilize a continuous, high-resolution record of uranium isotopes in pelagic and platform carbonate sediments to quantify the global extent of seafloor anoxia during OAE 2. This dataset is then compared with a dynamic model of the coupled global carbon, phosphorus, and uranium cycles to test hypotheses for OAE 2 initiation. This unique approach highlights an intra-OAE complexity that has previously been underconstrained, characterized by two expansions of anoxia separated by an episode of globally significant reoxygenation coincident with the “Plenus Cold Event.” Each anoxic expansion event was likely driven by rapid atmospheric CO2injections from multiphase Large Igneous Province activity.

NORTH CAROLINA SHELF SHOWS EVIDENCE OF INCREASED TERRIGENOUS FLUX DURING THE CENOMANIAN-TURONIAN OCEANIC ANOXIC EVENT 2

2020 ◽  
Author(s):  
Christopher Lowery ◽  
◽  
Jean M. Self-Trail ◽  
Craig Barrie ◽  
Kate Gilbreath ◽  
...  
Keyword(s):  
North Carolina ◽  
Oceanic Anoxic Event ◽  
Oceanic Anoxic Event 2 ◽  
Anoxic Event
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