2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 11
Presentation Time: 4:15 PM


GROVES, John R., Department of Earth Science, Univ of Northern Iowa, Cedar Falls, IA 50614-0335, RETTORI, Roberto, Dipartimento Scienze della Terra, Università degli Studi di Perugia, Piazza Università, Perugia, 06123, Italy, BOYCE, Matthew D., School of Geology & Geophysics, University of Oklahoma, Norman, OK 73019 and ALTINER, D., Department of Geological Engineering, Middle East Technical Univ, Ankara, Turkey, john.groves@uni.edu

The Permian–Triassic boundary, examined at two sections in the Southern Alps, occurs ~1.0 to 1.5 m above the base of the Tesero Oolite Member of the Werfen Formation in a depositionally continuous sequence of inner neritic carbonate strata. Lagenide foraminifers from below the boundary comprise 27 species in 15 genera plus additional unidentified elements, most of which became extinct during the end-Permian crisis. The only survivors were “Nodosaria” elabugae and unidentified species in Geinitzina and Nodosinelloides, with species in the latter two genera being short-term holdovers whose fate was evanescent. The end-Permian lagenide extinction level occurs a few decimeters below the biostratigraphically defined erathem boundary, just above the contact between the Bulla Member of the Bellerophon Formation and the overlying Tesero Oolite Member. Confidence intervals (> 96%) for the lagenide extinction at the two sections are 0.03 and 0.04 m thick. Plots of species' stratigraphic abundance versus their last observed occurrences below the estimated extinction intervals at both localities are consistent with abrupt extinction or gradual extinction lasting no more than the time required for 1 m of rock to accumulate. Blooms of the foraminiferal disaster taxa Rectocurnuspira kalhori and Earlandia sp. occurr in the extinction interval and continue well into the Dienerian part of the Mazzin Member of the Werfen Formation, consistent a protracted survival phase.