Nd & Sr isotopes from the Mid Cenomanian Event (MCE) derived from the Eagle Ford Group, West Texas

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2020-09-29

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Ocean anoxic events (OAEs) occur during Earth’s greenhouse states and are defined as periods of anoxia within all oceans. While geochemical constraints of ocean anoxia such as rapid increases in seawater δ13Corg are well documented and understood, the biogeochemical triggers of these anoxic events remain enigmatic. It is theorized that the Ocean Anoxic Event 2 (OAE2; ca 94-85 Ma) was triggered by the emplacement of a large igneous province (LIP). Understanding the environmental conditions of the mid-Cenomanian event (MCE; 97ma) would contribute to a better understanding of OAE2. This study uses the reconstruction of the mid-Cenomanian cretaceous western interior seaway (KWIS) seawater ⁸⁷Sr/⁸⁶Sr and εNd from Shell’s Iona-1 research core to test the role of LIPs in triggering the MCE. The data indicates unusually high εNd values of -0.52 were derived from the emplacement of the CLIP (98.7 Ma) and carried northward into the KWIS by the migration of the equatorial Atlantic Tethyan water mass during the early Cenomanian (Serrano et.al. 2011; Eldrett et.al. 2017). This northward migration of ocean water mass with high nutrient content from volcanic input may be the trigger for the onset of ocean anoxia observed in the MCE.

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