New evidence for Cretaceous age of the feathered dinosaurs of Liaoning: zircon U-Pb SHRIMP dating of the Yixian Formation in Sihetun, northeast China

We present the first report of U-Pb SHRIMP dating of zircons from three tuffs interbedded within the “feathered dinosaur”-bearing deposits in western Liaoning, China. One is a sample from the Bed 6 tuff (LX-SHT-12) of the Yixian Formation in Sihetun, for which our zircon U-Pb SHRIMP analyses gave a Cretaceous age (124.7 ± 2.7 Ma), in agreement with a previously published sanidine 40Ar/39Ar age (124.60 ± 0.25 Ma). The other two are from the Bed 1 tuff (LX-HBJ-1) and Bed 8 tuff (LX-HBJ-6) of the Yixian Formation in Huangbanjigou; the former gave an age of 124.9 ± 1.7 Ma, the latter an age of 122.8 ± 1.6 Ma. The three consistent ages indicate that the Yixian Formation was deposited in the Early Cretaceous within a very short time period (ca. 2 Ma).