Abstract

The stratigraphy and biotas of the major late Permian⁴ and early Triassic sequences in the British Isles, and major changes in the composition of fossil assemblages, are examined against the framework of contemporary regional paleogeography. A faunal and floral “explosion” accompanied the formation of the epicontinental Zechstein and Bakevellia seas and was followed by a progressive impoverishment of the biota as those seas dwindled and dried up. Fossils are extremely rare in the latest Permian and the earliest Triassic deposits but reappear in moderate numbers in the later part of the Early Trias, following a minor phase of earth movements and a marine incursion into the North Sea area. Progressive changes in the composition of the late Permian marine assemblages, the virtual absence of fossils throughout a red-bed sequence in which the system boundary is arbitrarily located and the establishment of non-marine biotas during the late Scythian and Anisian are seen as a response to changing environmental conditions. The biostratigraphical record around the Permian-Triassic boundary in the British Isles is thus incomplete and there are few fossil groups common to the deposits of both systems. The authors regard the incomplete biostratigraphical record in the late Permian and early Triassic of Britain as yielding no particularly dramatic evidence of extinction of biotas and do not support theories involving “catastrophism”.