Timing of mammal-like reptile extinctions across the Permian-Triassic boundary in South Africa

The rate, timing, and pattern of change in different regions and paleoenvironments are critical for distinguishing among potential causes for the Permian-Triassic (P-T) extinction. Carbon isotopic stratigraphy can provide global chronostratigraphic control. We report a large δ¹³C excursion at the P-T boundary and no long-term Permian δ¹³C trends for samples from the interior of Pangea. Stratigraphic gaps between available samples limit the resolution of our δ¹³C curve, but the excursion is within a 15-m-thick zone of overlap between Permian and Triassic taxa. Sedimentological and taphonomic observations demonstrate that this 15 m interval does not represent geologically instantaneous deposition. Together these data support a rapid and globally synchronous P-T event, but suggest that it occurred over a geologically resolvable interval of time.