On the Lower Cretaceous in Yixian County of Jinzhou City, Western Liaoning, China

Traditionally, the lacustrine deposits in Yhdan County of Western Liaoning have been assigned to either the Dakangpu Bed of the Yixian Formation or the Jiufotang Formation. However, a Pb-206/U-238 age of 126.47 +/- 0.87 Ma is newly obtained from the sample (06051) of the lacustrine deposits in the Baitaigou fossil site of Potaizi village, Yixian County, indicating that the lacustrine deposits in Potaizi area are approximately equivalent to the Wumingshan volcanics of the Sihetun Bed of the Yixian Formation in Beipiao. From our new dating data have arisen some new problems: ere could we find the Jiufotang Formation in Yixian County? How widely distributed is the Jiufotang Formation in Western Liaoning? Could the traditionally named Jiufotang Formation somewhere in Western Liaoning be the synchronous deposits of other litho-units (e.g. the Yixian Formation) in different facies? Could some lacustrine deposits somewhere in Western Liaoning have been assigned to the Jiufotang Formation?