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

The rate, tinting, and pattern of change in different regions and paleoenvi ronments are critical for distinguishing among potential causes for the Per mian-Triassic (P-T) extinction. Carbon isotopic stratigraphy can provide gl obal chronostratigraphic control. We report a large delta(13)C excursion at the P-T boundary and no long-term Permian delta(13)C trends for samples fr om the interior of Pangea, Stratigraphic gaps between available samples Lim it the resolution of our delta(13)C curve, but the excursion is within a 15 -m-thick zone of overlap between Permian and Triassic taxa. Sedimentologica l and taphonomic observations demonstrate that this 15 m interval does not represent geologically instantaneous deposition, Together these data suppor t a rapid and globally synchronous P-T event, but suggest that it occurred over a geologically resolvable interval of time.