Timing and patterns of the Great Ordovician Biodiversification Event and Late Ordovician mass extinction: Perspectives from South China

The early Paleozoic sediments document two major biological events: the Great Ordovician Biodiversification Event (GOBE) and Late Ordovician mass extinction (LOME). Many investigations have focused on taxonomic richness patterns during these major diversification and extinction events, providing insights into their timings and potential causes. However, the coarse temporal resolutions used in previous investigations hampered their ability to document fine-scale patterns. To address these issues, we employed CONOP analysis to data collected from a large suite of southern Chinese stratigraphic successions to construct a high-resolution (temporal resolution of ~21.0 Kyr) regional chronostratigraphy and document species richness dynamics during the middle-late Cambrian to early Silurian interval. Our results showed that the GOBE began in the early Tremadocian and ended at the Dapingian-Darriwilian boundary and consisted of two major radiation phases. The main pulse of GOBE, which lasted from the late Floian to the earliest Darriwilian, exhibited a species richness increase with elevated origination and extinction rates. Major marine groups showed no significant diachroneity during the GOBE, with most presenting richness peaks in this event's main pulse of the GOBE. Plankton demonstrated a significant diversification from the late Cambrian to the GOBE climax and subsequently dominated the marine realm in South China. Marine life experienced two extinction events in the Late Ordovician, the Katian extinction and Hirnantian extinction, which resulted in a regional species loss of ~67%.