End-Permian Biotic Disturbances: Floral Changes From the Permian Through Middle Triassic of Pakistan

Hermann, E., Hochuli, P. A., Bucher, H., Brühwiler, Hautmann, M., Ware, D., and G. Roohi. In Press. Terrestrial ecosystems on North Gondwana following the end-Permian mass extinction. Gondwana Research (2011). doi:10.1016/j.gr.2011.01.008
 Abstract - The impact of the end-Permian mass extinction on terrestrial ecosystems is still highly controversial. Here, new high-resolution palynological data from biostratigraphically well-dated Upper Permian to Middle Triassic successions of the Salt Range and Surghar Range (Pakistan) are presented. Our results reveal seven successive floral phases between the Late Permian and the Middle Triassic. At the onset of the Mesozoic, the flora is characterised by high abundances of lycopods associated with pteridosperms and conifers. This association prevails up to the middle Smithian and is followed by a prominent spore spike similar to the global spore spike reported from the Permian-Triassic boundary. Like that of the end-Permian, the middle Smithian spore spike is associated with a negative isotope excursion and is succeeded by a major marine faunal extinction event in the late Smithian. The recurrent patterns observed at the Permian-Triassic boundary and in the middle–upper Smithian suggest a common cause such as massive ejections of volcanic gases. The increasing abundance of conifers still associated with common lycopods in the Spathian suggests fading volcanically induced environmental perturbations and stabilisation of terrestrial ecosystems ca. 2.1 My after the end-Permian event.