Paleoclimate evolution of the Middle Triassic Guanling Formation from South China and its significance for the preservation of the Luoping biota

The Middle Triassic is regarded as an important period of biotic recovery after the end-Permian mass extinction, of which the Middle Triassic Luoping biota represents a full recovery of marine ecosystem. However, the research on the relationship between biotic recovery and environmental evolution in the Middle Triassic remains poorly understood. To investigate this issue, microfacies analysis and multiple geochemical proxies (Al, Ti, Th, Sc, and ∑REY) of an Anisian (Middle Triassic) succession (the Member II of the Guanling Formation, Leniduo section, South China) yielding the Luoping biota are carried out. Five sedimentary facies are identified through field investigation and microfacies analysis: open platform, restricted platform, tidal flat, shoal and intra-platform depression. According to the changes of multiple geochemical proxies, this section can be divided into five stages. A sudden facies transition from open platform to intra-platform depression, and high contents of Al, Ti, Sc, Th, and ∑REY in stage IV indicate a rapid sea-level rise and detrital input increase, coinciding with the preservation of the Luoping biota. This evidence suggest that enhanced continental weathering caused by global warming, global sea level rise, and frequent regional volcanic activities promoted the death and preservation of the Luoping biota.