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

• Published in: Geology (Boulder) 2000-03, Vol.28 (3), p.227-230
• Main Authors: MacLeod, Kenneth G, Smith, Roger M. H, Koch, Paul L, Ward, Peter D
• Format: Article
• Language: English
• Subjects: affinities; Africa; assemblages; biozones; bones; C-13/C-12; calcite; carbon; carbonates; chemostratigraphy; Chordata; diagenesis; Dicynodontia; Endangered & extinct species; extinction; isotope ratios; isotopes; Karoo Basin; Lower Triassic; Lystrosaurus; Mammalia; Mesozoic; O-18/O-16; oxygen; paleoecology; Paleontology; Paleozoic; Permian; Permian-Triassic boundary; Reptiles & amphibians; Reptilia; South Africa; Southern Africa; stable isotopes; stratigraphic boundary; Stratigraphy; Synapsida; Tetrapoda; Therapsida; Triassic; Upper Permian; Vertebrata
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/0091-7613(2000)28<227:TOMREA>2.0.CO;2

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.