High-precision geochronology of the Early Cretaceous Jiufotang Formation: Temporal constraints on the late phase of the Jehol Biota

• High-precision U-Pb geochronology of the Jiufotang Formation. • Refined Jiufotang Formation age span to 124.44–112.25 Ma in western Liaoning. • Constrained late Jehol Biota to ∼124–121 Ma, shortening previous estimates. • Dated exceptional preserved fossil layers for cross-basin evolutionary comparison. The Lower Cretaceous Jiufotang Formation in western Liaoning, northeastern China, hosts exceptionally preserved fossils that represent the late phase of the Jehol Biota, a key Early Cretaceous terrestrial ecosystem. However, its temporal framework has remained poorly constrained. This study combines high-precision U-Pb geochronology, Bayesian age modeling, and cyclostratigraphy based on core data from the Yixian-Jiufotang succession to refine its chronology. The Yixian/Jiufotang formation boundary is dated to 124.44 ± 0.29 Ma, with the Jiufotang Formation deposited between 124.44 and 112.25 Ma, spanning 12.2 Myr from the Early Barremian to Early Albian. Sedimentation in the Jiufotang Formation was relatively stable at 8–16 cm/kyr, reflecting rift-related sustained subsidence and development of large lakes. Well preserved fossiliferous layers are precisely dated to 121.09+0.18/-0.75 Ma (Shangheshou, Chaoyang Basin) and 121.539 ± 0.085 Ma (Xiaotaizi, Jianchang Basin), constraining the late phase of the Jehol Biota to ∼124–121 Ma—∼1 Myr shorter than previous estimates. Additionally, widespread black shales in the Jiufotang Formation record enhanced organic carbon burial during the Aptian cold interval, indicating major carbon cycle perturbations. This refined chronostratigraphic framework improves the temporal calibration of the Jiufotang Formation and the late phase of the Jehol Biota.