Geochronological study on the sanjiaochengzi fossil locality: Age constraints on a Late Jurassic flora of western Liaoning, Northeast china

Some fossil plants, previously identified as angiosperm species, have been reported from the “Jiulongshan”/Haifanggou Formation at the Sanjiaochengzi fossil locality in Huludao City, western Liaoning, Northeast China. However, the precise ages of these fossil plants remain uncertain. To address this issue, we conducted LA-ICP-MS zircon U-Pb dating on two tuffaceous interlayer samples from the fossil-bearing horizon of this section. The resulting ages of 159.9 ± 0.5 Ma and 160.1 ± 0.5 Ma constrain the depositional age of the fossil-bearing horizon to the Late Jurassic (Oxfordian stage). By integrating these chronological results with regional stratigraphic correlations, we determine that the fossil-bearing horizon of the Sanjiaochengzi section belongs to the lower part of the Tiaojishan Formation.