Conodontophorid biodiversification during the Ordovician in South China

摘要

Analysis of the Ordovician conodontophorid diversity pattern for South China using normalized and total diversity measures reveals that diversity peaks occurred in the mid-Tremadocian, mid-late Floian, early Dapingian and mid-Darriwilian periods. The conodontophorids radiated during the Floian, maintaining relatively high diversity into the early part of the Middle Ordovician until a significant diversity decrease occurred in the late Dapingian. A relatively low diversity level prevailed in the Late Ordovician. Three diversification intervals based on origination, extinction and turnover rates have been identified i.e. (1) Tremadocian to mid-late Floian, (2) early Dapingian and (3) late Dapingian to early Darriwilian. Diversity curves for conodontophorids, brachiopods, graptolites, acritarchs and trilobites from South China are comparable during the Early Ordovician, although differences are apparent in the Middle and Late Ordovician. In South China, conodontophorid diversity reacted primarily to sea-level changes during the Early and Middle Ordovician, when the peak of this biodiversification generally coincided with a transgression. Climate changes - especially the global cooling that occurred during the Late Ordovician glaciation - and sea-water chemistry were also important controlling factors. □Biodiversification, conodonts, Ordovician, South China.