A tale of two Tweefonteins: What physical correlation, geochronology, magnetic polarity stratigraphy, and palynology reveal about the end-Permian terrestrial extinction paradigm in South Africa

Abstract The contact between the Daptocephalus to Lystrosaurus declivis (previously Lystrosaurus) Assemblage Zones (AZs) described from continental deposits of Karoo Basin was commonly interpreted represent an extinction crisis associated with end-Permian mass-extinction event at ca. 251.901 ± 0.024 Ma. This terrestrial model is based on several sections in Eastern Cape and Free State Provinces South Africa. Here, new stratigraphic paleontologic data are presented for Province, geochronologic magnetostratigraphic context, wherein lithologic biologic changes assessed over a physically correlated stratigraphy exceeding 4.5 km distance. Spatial variation lithofacies demonstrates gradational nature lithostratigraphic boundaries depositional trends. pattern mimicked by distribution vertebrates assigned L. AZs where diagnostic taxa each co-occur as lateral equivalents landscapes dominated Glossopteris flora. High-precision U-Pb zircon (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) age results indicate maximum Changhsingian dates that can be used approximate tie points our framework, which supported magnetic polarity stratigraphy. coeval pre- post-extinction vertebrate AZ did not replace stratigraphically, biotic turnover likely absent, reevaluation required utilization these biozones here globally. Based set, we propose multidisciplinary approach correlate classic Upper Permian localities Province localities, their time-transgressive nature.