Conundrums of Wapadsberg Pass and other locales in the Karoo Basin, South Africa: The death knell of the end-Permian vertebrate-extinction model

Over the past 30 years, the vertebrate-fossil record of the Karoo Basin, South Africa, has served as a model for the coeval response of terrestrial ecosystems with the end-Permian marine extinction event. This model presumes a vertebrate-assemblage turnover involving the replacement of synapsids and other tetrapods with diagnostic taxa of the Lystrosaurus declivis Assemblage Zone in the Palingkloof Member, Balfour Formation, and is based on collections from a small number of Eastern Cape and southernmost Free State province localities. Although there are previous tests of the Karoo Basin extinction model at the classic Free State and Eastern Cape province localities, this contribution further tests the current vertebrate extinction model with a multidisciplinary dataset from the classic localities in and around Wapadsberg Pass in the Eastern Cape Province. We present an expanded lithostratigraphic framework, encompassing ∼800 m of measured and correlated sections, extending over an ∼6 km distance northward from the New Wapadsberg Pass locality. To this we add U-Pb chemical abrasion−isotope dilution−thermal ionization mass spectrometry dates from three beds yielding detrital zircons; details on magnetic polarity stratigraphy information from 11 sites in sedimentary strata above an Early Jurassic Karoo sill and related rock magnetic data; and stable δ13C and δ18O data from calcite-cemented pedogenic nodules from paleosols, supplementing previously published data and augmenting prior interpretations. We demonstrate that previously reported high-resolution biostratigraphic schemes are not stratigraphically constrained to the intervals to which they were assigned. These stratigraphic subunits cannot be correlated across the study area over a distance of <2 km. The stratigraphic frameworks established at both the Wapadsberg and the adjacent Lootsberg Pass localities reveal a complicated sedimentary montage in the stratigraphic record of the Balfour and Katberg formations, complicating high-resolution comparison. We conclude from our independent, and a posteriori, tests that the prevailing Karoo Basin vertebrate-extinction paradigm violates fundamental biostratigraphic principles and that the terrestrial end-Permian mass extinction model on which it is based should be abandoned in the Karoo Basin and globally.