The Permian and the Lower Triassic Systems in Abadeh Region, Central Iran

Abstract

The continuous sequence of the Permian and the Lower Triassic Systems was fully examined paleontologically and sedimentologically in Abadeh region, Cenral Iran. Based on the correlation of the Permian in the Tethys province by means of fusulinid, ammonoid and conodont zonations together with brachiopod, coral and bryozoan fossils, it is concluded that the Upper Permian is reasonably classified into three stages, the Abadehian, the Dzhulfian, and the Dorashamian. Biostratigraphical and sedimentological study indicates a paraconformable relation between the Permian and Triassic, and the equivalent of the lower half of the Otoceras woodwardi zone is missing as judged from the conodont zones. The Dorashamian is older than the Griesbachian or Gangetian, and not the equivalent of the latter. The faunal change is related to not only local environmental change but universal causes. A remarkable attrition of species began in the Dzhulfian and reached a climax at the end of the Permian. Almost all the species had disappeared by the end of the Permian corresponding to the progressive shallowing and retreat of the sea. Rapid transgression and incoming of new organisms at the beginning of the Triassic is evident in the lithofacies and biofacies of the Lower Triassic.