FUSULINID DIVERSITY PATTERN AND THE CONTEMPORANEOUS SEA LEVEL CHANGE OF THE YUNNAN-GUIZHOU-GUANGXI BASIN DURING EARLY AND MIDDLE PERMIAN, SOUTH CHINA

The study of the diversification process of shallow sea benthos as well as their coupling relationship with sea-level fluctuation is important because it reveals the effect of global environmental changes on biological evolution and it can be used to discover the synergetic evolution pattern between the biota and environment during geological time. This paper analyzes the diversification progress of fusulinid fauna from the Yunnan-Guizhou-Guangxi Basin during Early to Middle Permian in detail. We also compared such progress with the relative contemporaneous sea-level fluctuation, in order to discuss the relationship between the diversification of fusulinid and sea-level fluctuation. Results show that during the stages from Asselian to Sakmarian of Early Permian, the relative sea-level of the Yunnan-Guizhou-Guangxi basin changed quite slowly. And the specific number of fusulinids increased rapidly while the generic diversity was rather low. During the stages from Kungurian to Middle Permian, the relative sea-level of the Yunnan-Guizhou-Guangxi Basin changed quickly and frequently. And the genera of fusulinid turned over rapidly, while the specific diversity was low. In the uppermost Middle Permian, the sea-level of the Yunnan-Guizhou-Guangxi Basin saw a rapid decrease to the minimum seen in the Permian. A rapid decrease in all biota is seen in the rock record at this time, showing an apparent extinction event. Fusilinid diversification has been shown to benefit from slow sea-level rise. While rapid and frequent fluctuations lead to turn over of the fusulinids, and very low levels are difficult environments for fusulinid reproduction. Thus, the observed rapid drop in sea-level is a strong indicator that this marked the extinction of fusulinids. The diversification progress of the species and genus agrees well with the third-order sea level fluctuation, as well as other benthos in the shallow sea. The coupling relationship between the sea level fluctuation and the benthos in the shallow sea are ubiquitous, and provided a concrete manifestation of synergetic evolution pattern between the biota and environment during geological time.