Distribution of Mid-Cretaceous Orbitolinids in Tibet and ItsPaleobiogeographic ImplicationsWAN Xiaoqiao, WU Yianhua and LI Guobiao (China Universityof Geosciences, Beijing 100083, China)Orbitolinids is a kind of large foraminifera. It occurredfrequently during the late Barremian to Cenomanian of theCretaceous and is distributed worldwide, especially in theshallow marine belts surrounding the Tethys Ocean. Itsdistribution in Tibet is limited to the Lhasa Block and some partsof the Qiangtang Basin. On both sides of this area, the