Microfacies Analysis of Mixed Siliciclastic-Carbonate Deposits in the Early-Middle Ordovician Meitan Formation in the Upper Yangtze Platform in SW China: Implications for Sea-Level Changes during the GOBE

During the Early-Middle Ordovician, Upper Yangtze Platform experienced extensive development of a distinctive set mixed siliciclastic-carbonate deposits known as Meitan Formation. To conduct comprehensive study relationship between sedimentation and sea-level changes, Hailong section, situated at southwest margin in SW China, was selected area due to its typical sedimentary sequence. This section effectively compared with sections other regions. Clustering analysis point-count groups from Honghuayuan Formations revealed nine microfacies that developed during this period. Such diverse range provides evidence frequent changes throughout Specifically, two rises were identified early TS.2b TS.3b, event occurring globally. Furthermore, four falls observed late TS.2b, TS.2c, TS.3a, TS.3b periods. The fall globally significant. From TS.2c onwards, distinct variations among Platform, North Baltoscandia, Australia, America emerged alterations paleogeographic pattern. By comparing curves diversity chitinozoans, acritarchs, brachiopods, it became evident environmental played crucial role Great Ordovician Biodiversification Event (GOBE), especially Floian. rising sea level increased detrital materials fostered habitats, prompting organisms adapt varying environments. In general, levels favored brachiopod diversity, while falling enhanced planktonic chitinous acritarch species. shedding new light on biodiversification region, offers fresh perspective subject analysis.