<p>The first record of the Early Toarcian Oceanic Anoxic Event (<em>c</em>. 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 (δ<sup>13</sup>C<sub>org</sub>) in bulk rock and fossil wood. The negative excursion of −6‰ in bulk organic carbon (falling to −31.3‰) crosses the boundary
of the <em>tenuicostatum</em>–<em>hoelderi</em> Andean ammonite Zones, equivalent to the <em>tenuicostatum</em>–<em>falciferum</em>/<em>serpentinum</em> zones of Europe. These data indicate that the Early Toarcian Oceanic Anoxic Event was a global phenomenon.
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