Study of Lower–middle Triassic Conodont Biostratigraphy in the Clastic Facies of South China

The end-Permian mass extinction and diverse extreme climate and environmental conditions, which had jointly delayed the marine ecosystem reconstruction in the Triassic. To elucidate the co-evolutionary processes of organisms and environments and to facilitate precise stratigraphic correlation on a global scale during the Early–Middle Triassic, a high-resolution temporal framework is particularly important. In South China, there is a widespread and continuous development of diverse marine strata from the Lopingian to Middle Triassic, which yield a variety of fossil materials. This region is regarded as an ideal area for detailed biostratigraphic, biological, and environmental research. A considerable amount of research has been conducted on the conodont biostratigraphy in South China, yet most of the work has predominantly focused on carbonate facies, with less attention paid to the clastic facies. This study selected two clastic facies sections in the South China (the Bozhou and Datuguan sections) for the conodont biostratigraphy. The main achievements of this study are as follows: 1) For the first time, a total of 22 conodont species of six genera are identified, and ten conodont zones are established at the Bozhou section; 48 conodont species belonging to 16 genera are recognized, and 12 conodont zones are established at the Datuguan section. 2) Based on the conodont successions and lithostratigraphic correlation, the boundaries of the stages and substages of the Lower Triassic at the study sections were discussed and defined. 3) The occurrence of segminiplanate conodonts and their paleoclimatic implications in the Early Triassic at the study areas are explored. During relatively cooler periods of the Early Triassic, segminiplanate elements migrated toward the equatorial region four times and preferred a narrow mid-depth water environment, in addition to occupying the more oxygenated deep-water basin. This study enhanced the precision of stratigraphic division and correlation for the Late Permian to Middle Triassic in the study area, and provided an accurate timeframe for research on the geobiology and environment of this period.