Symposium on conodont biostratigraphy

Abstract

Palaeobiogeography of four consecutive Early Permian (Cisuralian) stages is quantitatively analyzed based on a global database of brachiopods consisting of 9131 occurrences, 3003 species of 515 genera of brachiopods from 2757 localities all over the world. Our analyses reveal three distinct largely palaeolatitude-related palaeobiogeographical realms developed during the Cisuralian like the other stages of the Permian. Six distinct provinces are distinguished during the Asselian. The Asselian brachiopod faunas from Gondwanaland and its surrounding areas in general are not well differentiated at the provincial level and characterized an Indoralian province. A large transitional zone (Southern Transitional Zone, STZ) between the Palaeoequatorial and Gondwanan Realms and another distinct Austrazean province in the eastern margin of Gondwanaland were formed from Sakmarian, contemporaneous with the largest peak of the Late Palaeozoic Ice Age. In contrast to the STZ, the palaeogeographical stations in the northern temperate transitional zone are not differentiated before Kungurian; instead they are grouped with the stations in the palaeoequatorial region, thus collectively constituting a large asymmetrical Cathaysian province stretching from South China, Iran in the western Palaeotethys to the Mongolian continent in the north. The Northeast European province mainly consisting of the stations in the Ural Fold Belt and eastern and northeastern parts of the European Platform shows a closer palaeobiogeographical relationship with the Cathaysian province when the Ural seaway opened to the Palaeotethys in the southern end before the Kungurian, but became more distinguished during the Kungurian after the closure of the Ural seaway and showed a relationship with the faunas of the Boreal Realm and the Northern Transitional Zone (NTZ). The stations in Texas, western North America constitute a distinct Grandian province based on the high-diversity brachiopod faunas with abundant endemic taxa, and became distinguishable even at the realm level during the Kungurian. Three high-latitude provinces, the Verkolyman province with characteristic Boreal brachiopod faunas, the Paratinan province with some bipolar and cosmopolitan genera in South America, and the Austrazean province in eastern Australia and New Zealand, were present from the Sakmarian.Further Principal Co-Ordinate analysis (PCO) and Minimum Spanning Tree (MST) analysis suggest that palaeolatitude-related thermal gradient was the major controlling determinant for the Cisuralian provincialism and brachiopod distribution. In addition, geographic barriers and regional eustatic changes also played some roles in the brachiopod distribution and Cisuralian marine palaeobiogeography. The transition from an icehouse to greenhouse stage led to a steady increase in brachiopod diversity and provincialism during the Cisuralian and Guadalupian.