CENOZOIC STRATIGRAPHY IN DANGHE AREA, GANSU PROVINCE, AND UPLIFT OF TIBETAN PLATEAU

The Danghe area, located in the western most part of the Gansu Province, is southerly bordered by the Tibetan Plateau. It is one of the classic areas in the Asian Paleogene biostratigraphy. Early in the 1930s Bohlin explored this area and collected plenty of mammalian fossils. However, he did not further subdivide the strata he surveyed, nor did he name the strata or give clear indication of the fossil levels. The main reason of his hesitation was the extremely complex tectonic structure of the area (Bohlin, 1937, 1942, 1945, 1946, 1960). Since the 1950s the Danghe strata have been variously assigned to formations founded in the Yumen Basin more than 200 km to the northeast, such as Huoshaogou, Baiyanghe, Shulehe formations and Yumen Gravels. However, no detailed lithologic comparison between the Danghe area and Yumen Basin has ever been carried out. Furthermore, the stratigraphic position of Bohlin's fossils has never been satisfactorily clarified. Since the 1990s when the Tibetan Plateau became an area of intense studies, the Danghe area has gained worldwide attention among geologists. Tectonic and paleomagnetic study has been conducted there. Unfortunately, all these endeavors were based on outdated or wrong stratigraphic data (Wang, 1997; Guo and Xiang, 1998; Gilder at al., 2001, Van de Woerd et al., 2001).\;In 1999 and 2001, a joint team of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (IVPP), the Cultural Relic Archaeology Institute of Gansu and the Gansu Provincial Museum made geologic survey of the Danghe area. As a result, a number of stratigraphic problems were clarified based primarily on new interpretation of the rock sequences and the newly found mammalian fossils.\;