New chronostratigraphic constraints on the Yixian Formation with implications for the Jehol Biota

摘要: Abstract The fossils of the Cretaceous Jehol Biota exhibit excellent preservation and extraordinary diversity. Terrestrial fossils, including plants, insects, dinosaurs, birds, mammals freshwater invertebrates have been discovered from Dabeigou, Yixian Jiufotang Formations (and correlative strata) in Central East Asia. Significant specimens recovered Formation Inner Mongolia, Hebei Province, western Liaoning Province NE China. is generally divided (from bottom to top) into Lujiatun Unit, Lower Lava Jianshangou Upper Dawangzhangzi Unit Jingangshan Unit. However, previously reported age data obtained through a range methods applied different units do not consistently integrate with Yixian's commonly accepted stratigraphic interpretation. Here we summarize previous for recalibrate 40Ar/39Ar ages by using new interpretations same standard (i.e. FCs = 28.294). We also present high-precision 125.8 ± 1.0 Ma 126.0 ± 0.8 Ma two basaltic samples unit uncertain age. re-calibrated published indicate that was deposited contemporaneously widely column therefore requires reinterpretation. Our study provides significant clues reconstructing sedimentary environment fossil-rich deposits allows constrain evolutionary rates early mammals, primitive birds feathered dinosaurs.