Introduction to the Hezheng stratigraphic section: The Hezheng area is located at the intersection of the Qinghai-Tibet Plateau and the Loess Plateau. It has developed Cenozoic terrestrial sediments dating back about 30 million years. It is one of the largest sources of mammal fossils in the world. , represented by the late Oligocene giant rhinoceros fauna, the middle Miocene Eurasia fauna, the late Miocene three-toed horse fauna and the early Pleistocene equid fauna.