"OAE 3" – regional Atlantic organic carbon burial during the Coniacian–Santonian

摘要

The Coniacian–Santonian time interval is the inferred time of oceanic anoxicevent 3 (OAE 3), the last of the Cretaceous OAEs. A detailed look on thetemporal and spatial distribution of organic-rich deposits attributed to OAE3 suggests that black shale occurrences are restricted to the equatorial tomid-latitudinal Atlantic and adjacent basins, shelves and epicontinentalseas like parts of the Caribbean, the Maracaibo Basin and the WesternInterior Basin, and are largely absent in the Tethys, the North Atlantic,the southern South Atlantic, and the Pacific. Here, oxic bottom watersprevailed as indicated by the widespread occurrence of red deep-marine CORBs(Cretaceous Oceanic Red Beds). Widespread CORB sedimentation started duringthe Turonian after Oceanic Anoxic Event 2 (OAE 2) except in the Atlanticrealm where organic-rich strata continue up to the Santonian. The temporaldistribution of black shales attributed to OAE 3 indicates that organic-richstrata do not define a single and distinct short-time event, but aredistributed over a longer time span and occur in different basins duringdifferent times. This suggests intermittent and regional anoxic conditionsfrom the Coniacian to the Santonian. A comparison of time-correlatedhigh-resolution δ13C curves for this interval indicates severalminor positive excursions of up to 0.5‰, probably as a result of massiveorganic carbon burial cycles in the Atlantic. Regional wind-inducedupwelling and restricted deep basins may have contributed to the developmentof anoxia during a time interval of widespread oxic conditions, thushighlighting the regional character of inferred OAE 3 as regional Atlanticevent(s).