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The first record of the Early Toarcian Oceanic Anoxic Event (c. 183 Ma) from the Southern Hemisphere is described from the Neuquén Basin, Argentina, identified chemostratigraphically on the basis of a relative increase in marine organic carbon and a characteristic negative carbon-isotope excursion (δ13Corg) in bulk rock and fossil wood. The negative excursion of -6 in bulk organic carbon (falling to -31.3‰) crosses the boundary of the tenuicostatum-hoelderi Andean ammonite Zones, equivalent to the tenuicostatum-falciferum/serpentinum zones of Europe. These data indicate that the Early Toarcian Oceanic Anoxic Event was a global phenomenon. [ABSTRACT FROM AUTHOR]