Paleoclimate change since the Miocene inferred from clay-mineral records of the Jiuquan Basin, NW China

Abstract Global cooling and the uplift of the Tibetan Plateau have long been considered the crucial controls of the climate change in inland Asia since the Cenozoic. However, which of these factors has played the leading role is unknown. To understand climate change and the controlling factors in inland Asia, here, we present new records of clay mineralogy and trace elements of clay fractions from the Neogene sedimentary sequence in the Jiuquan Basin of the northeastern Tibetan Plateau. The clay-mineral records reveal four stages of paleoclimate changes. From ca. 24 Ma to 17 Ma, the low total smectite and (smectite+I/S + kaolinite)/(illite+chlorite) and high illite contents suggest weak chemical weathering and hence arid climatic conditions. For ca. 17–14 Ma, the high total smectite and (total smectite + kaolinite)/(illite + chlorite) and low illite contents suggest strong chemical weathering, indicating a change in climate from cold and dry to warm and humid. There was no palygorskite during this warm and humid period. From ca. 14 Ma to 8 Ma, the low total smectite content, high illite content and the appearance of palygorskite indicate that the climate turned to cold and dry. Since 8 Ma, low total smectite as well as high illite and chlorite contents suggest a colder and drier period. The records of clay mineralogy illustrate that the Jiuquan Basin has experienced increasing aridity since ca. 14 Ma, synchronous with the inland Asian aridification. Given the synchroneity with the global cooling, we suggest that the climate evolution in the Jiuquan Basin from the late Oligocene to middle-late Miocene was mainly controlled by global climate change. Since the late Miocene, the uplift of the Tibetan Plateau and global cooling have significantly influenced the decreasing temperature and humidity of the Jiuquan Basin. The uplift of Tibetan Plateau may intensify the aridity by blocking moisture from reaching the Jiuquan Basin.