Abruptness of the end-Permian mass extinction as determined from biostratigraphic and cyclostratigraphic analyses of European western Tethyan sections

The Permian-Triassic (P-Tr) boundary is marked by the most severe mass extinction in the geologic record, but the time interval over which the extinctions occurred has been a subject of much debate. Published biostratigraphic data from P-Tr boundary sections in the southern Alps, Italy, were used to test the effects of sampling and species abundance on the record of the latest Permian extinction. The results for foraminiferal taxa match simulations for abrupt extinctions; the extinction level is close to the base of the Tesero horizon of the Werfen Formation. Using biostratigraphic estimates of sedimentation rates, we constrain the extinction interval to <10 k.y. High-resolution cyclostratigraphy on a 10⁴ yr scale across the P-Tr boundary in a core from the Carnic Alps (Austria) shows significant cycles in the ratio ∼40:10:4.7:2.3 m, identified with Milankovitch cycles of ∼412:100:40:20 k.y. (eccentricity 1 and 2, obliquity, and precession). Cycle analysis indicates continuity of deposition across the P-Tr boundary, and an average accumulation rate of ∼10 cm/k.y. The results define the dramatic faunal shift across the boundary within an interval of <8 k.y., and the accompanying sharp negative global carbon isotope shift within <30 k.y., suggesting a catastrophic cause.