First High-Precision U–pb Age for the Early Jurassic Beipiao Formation (ne China): Implications for Source Rock Deposition and the Toarcian Hyperthermal Event

The Beipiao Formation in western Liaoning, northeastern China, represents one of the most important Early Jurassic organic-rich successions and is widely regarded as a potential source rock for hydrocarbons. However, the absence of robust radiometric age constraints has long-hindered its accurate stratigraphic correlation, in turn corresponding source-rock evaluation, and regional paleoenvironmental reconstruction. In this study, zircon U–Pb isotopic dating of a well-preserved volcanic ash layer interbedded within the lower coal-bearing interval of the Beipiao Formation yields a weighted mean age of 187.04 ± 0.98 Ma, providing the first reliable absolute age for this formation. The new age solidly constrains the main depositional interval of the Beipiao Formation to the Pliensbachian–Toarcian, consistent with existing but poorly constrained biostratigraphic evidence. Our refined chronology suggests that the distinctive thick organic-rich mudstones in the upper Beipiao Formation were most likely coeval with the well-known early Toarcian hyperthermal event (Jenkyns Event, ~183 Ma). Our study provides a fundamental stratigraphic framework for future assessments of the Beipiao Formation on hydrocarbon generation potential and regional response of continental lacustrine systems to the Early Jurassic climatic perturbation.