Lacustrine tempestite and its geological significance in the Cenozoic study of the Qaidam Basin

During the Cenozoic a typical lacustrine tempestite deposition was developed in the Lulehe and Xichagou sections of the Qaidam Basin. The sedimentary structures of these two sections above are examined here in detail, which consist of storm erosion, storm tear, storm wave and rapid storm-generated sedimentary structures after storm processes, such as groove casts, scour structures, cutoff structures, hummocky cross-stratification (HCS), parallel bedding and graded bedding. On the basis of these sedimentary characteristics and the vertical facies sedimentary sequence, the causes of the sedimentary succession are analyzed and a Cenozoic sedimentary model of the Qaidam Basin containing shallow proximal, transitional and deep distal tempestites is established. According to the tempestite scale and HCS wavelength, the Cenozoic storm was obviously more intense in the basin’s Upper Ganchaigou formation than that in the Lower Youshashan formation. This variation indicates that a paleoclimatic transition largely corresponded with the second uplift of the whole Qinghai-Tibet Plateau. The discovery of a Cenozoic tempestite in the Qaidam Basin is significant in the paleogeographic, paleoclimate and paleostructural fields, which provides a new insight in further study of the Qinghai-Tibet Plateau uplift.