Palaeoenvironment evolution and taphonomic controls on dinosaur burial in the Early–Middle Jurassic of Changdu Basin, eastern Xizang, China

The Jurassic greenhouse interval provides a key analogue for understanding terrestrial climate–environment dynamics under elevated CO2 conditions. The Changdu Basin (eastern Xizang) preserves a continuous Lower to Middle Jurassic lacustrine succession with abundant dinosaur fossils, offering a valuable archive for linking palaeoenvironmental evolution with vertebrate taphonomy. Here, we integrate sedimentological observations with multiple geochemical proxies from the Damala Mountain section to reconstruct palaeoclimate, hydrological conditions, and redox evolution, and to evaluate their role in controlling fossil burial. Results indicate that the succession was deposited in a lacustrine system comprising shore, shallow, semi-deep lacustrine, and alluvial fan facies. Palaeoclimate proxies suggest overall warm conditions with moderate chemical weathering, accompanied by a transition from relatively hot–arid to warm-humid conditions upward. Palaeosalinity proxies reveal predominantly brackish water conditions, while redox proxies indicate generally oxic environments with episodic dysoxia. Notably, intervals characterized by alluvial fan deposits coincide with pronounced fluctuations in palaeoclimate, salinity, redox proxies, and grain size, and host abundant dinosaur fossils. These results suggest that short-lived, high-energy depositional events exerted significant impacts on lacustrine environmental conditions. We propose that event-driven sedimentation, particularly debris-flow processes in alluvial fan systems, played a critical role in transporting, disarticulating, and burying vertebrate remains.