The results of the determination of the age of zircon grains from tuffites of the Leskovo Unit of the UndaDaya Basin, Eastern Transbaikalia, are presented for the first time. The age of the youngest population of zircon grains is 145.8 3.8 Ma, approximately corresponding to the JurassicCretaceous boundary and indicating the Early Cretaceous age of most of the Leskovo Unit. Given that the similar taxonomic composition of ostracods from the middle part of the Leskovo Unit and the ValanginianLower Hauterivian Dabeigou Formation of northeastern China, our UPb age from the lower part of the Leskovo Unit allows confident correlations of these lithostratons.
