STRATIGRAPHY AND LAGENIDE FORAMINIFERAL EXTINCTION IN THE PERMIAN-TRIASSIC BOUNDARY INTERVAL, WESTERN TETHYS (TURKEY AND ITALY)

Lagenide foraminiferal diversity across the Permian-Triassic boundary has been investigated at four sections in western Tethys: the Taskent and Demirtas localities in the Aladag and Antalya nappes of the Central Taurides (Turkey); and the Tesero and Bulla localities in the western Dolomites of the Southern Alps (Italy). Lagenides are diverse and abundant in upper Permian (Changxingian) strata at the Turkish localities. Most failed to survive the end-Permian mass extinction, however, and the majority of last occurrences fall within the uppermost 0.5 m of the Permian. The Permian-Triassic boundary in the Taurides is an erosional unconformity associated with an indeterminate but probably minor lacuna. Lagenides are relatively less abundant and diverse in upper Permian rocks in the Italian sections, where the main pulse of extinction occurs within a depositionally continuous interval of the Tesero Member (Werfen Formation). The lagenide extinction level at the Bulla section falls within a few cm of the P-T boundary, which is identified on the appearance of Hindeodus parvus, 1.3 m above the base of the Tesero Member. The stratigraphic position of the lagenide extinction level relative to the P-T boundary is less clear at the Tesero locality because the local appearance of H. parvus is anomalously high. If the P-T boundary at the Tesero section corresponds with the appearance of Isarcicella changxingensis, as suggested by Perri and Farabegoli, then it again falls 1.3 m above the base of the Tesero Member and within a few cm of the lagenide extinction horizon. Basal Triassic (Griesbachian) strata in the Central Taurides are planar stromatolites that probably accreted as disaster forms in the immediate aftermath of the end-Permian mass extinction. Basal Triassic strata at the Bulla locality in Italy appear stromatolitic in the field, but definitive microbial textures cannot be identified petrographically because of recrystallization.