Xunhua Basin is one of the inter-mountainous basins distributed in northeastern margin of the Cenozoic Tibetan Plateau. Based on the vertebrate fossils found at the upper part of the section and characters of the magnetozones,the magnetostratigraphy of the Xigou Section can correlate well with the geomagnetic polarity timescale (CK95), which suggests a depositional age of ～14.6 Ma to ～5.0 Ma. On the basis of the analysis of the sedimentary faceis at the Xigou Section,the authors are convinced that the Xunhua basin shrinked gradually during ～14.6 to 5.0 Ma. One huge thick conglomerate layer (～20 m thickness) appeared firstly at ～7.3 Ma and was considered to be caused by rapid uplift of the surrounded mountains, which was almost coinstantaneous with rapid uplift of the Tibetan Plateau at ～8.0 Ma, implying the synchronous uplift of Tibetan Plateau.
