Compilation of widespread, Cretaceous OAE2 black shale horizons documented in wells from the Gulf of Mexico, Caribbean, and Atlantic passive margins



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Oceanic anoxic events are periods in Earth’s history when oceans were depleted in dissolved oxygen and characterized by deposition of organic-rich, and black, marine sediments. Variations in δ13C are known to correlate with the presence of trace metals related to emplacement of large igneous provinces (LIPs). OAEs are now recognized to provide widespread source rocks for hydrocarbon generation. OAE2 event coincided with high sea level and was response to LIP event in the Caribbean region. This Caribbean LIP event provided the driving force for organic carbon deposition. I have compiled thickness of OAE2 black shales on the Gulf of Mexico, Caribbean and Atlantic passive margins using published well data. Gulf of Mexico black shale can vary in thickness from 45 to 150m with average TOC values in the range from 1% to 4.6%. OAE2 black shale horizons for the Caribbean region can vary in thickness from 37 to 550m with low TOC value of 0.07%. South American Atlantic basins contain black shale that varies in thickness from 11 to 610m with TOC values ranging from 1% to 36%. African Atlantic margins black shale varies in thickness from 100 to 700m with TOC values ranging from 10% to 30%.