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The paleoenvironment and paleoclimate of Asia dramatically changed during the late Cenozoic, such as enhanced Central Asian aridification and East Asian monsoon development. The uplift of the Tibetan Plateau in the late Cenozoic is considered one of the major drivers forcing the Asian paleoenvironmental changes. However, the complex interaction between tectonic and climate change is still unclear. This is largely due to 1) the combined effect of aridification of the continent by global cooling, oceanic closure and uplift of the plateau, and 2) the lack of temporally and spatially matching tectonic and climatic records in a critical zone. The Xining Basin lies in the transitional zone between the arid Asian interior and the East Asian monsoon region. Here, we present detailed paleomagnetic analysis of a fluvial-lacustrine sequence in the Xining Basin and the first record of clay mineralogy and elemental geochemistry. High-resolution paleomagnetism revealed 16 normal and 16 reversed zones that correlate well with chrons 3n to 5Ar.1r of the Geomagnetic Polarity Time Scale, constraining the section to ~12.7–4.8 Ma. The changes in lithofacies from floodplain to braided river at ~8.6 Ma with predominantly southerly paleocurrent directions occur simultaneously with an increase in the sedimentation rates, representing a rapid uplift in the eastern Qilian Shan to the north. Geochemical provenance proxies (Th/Sc, Zr/Sc and Cr/Zr) in the <2 μm fraction show a significant provenance change at ~8.8 Ma. Silicate-based weathering indexes (CIA, CIW and PIA) displayed coeval changes with provenance but discrepant changes with regional climate. Since the clay mineralogy exhibit significant change at ~7.8 Ma uncorrelated with modifications in provenance, it can be employed to reveal regional climate change. The rise in illite, and associated decrease in the sum of smectite and illite/smectite mixed-layers reflect gradual and slow aridification since ~12.7 Ma with intensified drying since ~7.8 Ma until approaching the modern climate status. Our results, together with other regional climatic and tectonic records, clearly illustrate that accelerated uplift of the northeastern TP since ~8-9 Ma has mainly modulated the regional erosion, weathering, transportation and sedimentation, and amplified the global cooling and drying trend towards the regional climate of modern conditions. Our study suggests that in the tectonically active northeastern TP, a comprehensive mineralogical and geochemical investigation of the fine-grained fraction of the basin sediments could retrieve the interactions between tectonics and climate behind the complex change in exhumed lithology and sedimentary routing systems. [ABSTRACT FROM AUTHOR]

The modern Qaidam Basin (QB) is one of the highest and driest deserts on Earth and an important dust source in Asia. However, a large paleolake existed in the 150,000 km2 large basin during most of the Cenozoic. How and why this paleolake system collapsed is crucial for understanding of the dramatic drying processes in central Asia. We present a comprehensive assessment of a large data set of new oxygen isotope and grain size data and published proxy records from a drill core in the western QB spanning the period from ~2.7 to near present, based on statistical, wavelet and recurrence quantification analyses. Moreover, we compare the QB paleolake evolution with East Asian summer monsoon (EASM) records in the nearby Chinese Loess Plateau. The results indicate a similar evolution pattern of the lake system in the western QB and the EASM system until ~1.2 Ma, indicating a larger scale forcing of solar insolation change on both systems. A decoupling between the two systems was noticed after ~1.2 Ma, under which drier intervals in the QB were synchronous with stronger EASM. We suggest that the congruence of decreasing amplitude of obliquity and eccentricity minima at ~1.2 Ma facilitated ice sheet expansion which disturbed the response of both systems to solar insolation, and eventually led to their decoupling. At ~0.9 to 0.8 Ma, synchronous minimum states in obliquity amplitude and eccentricity, and the meantime prominent reduction in CO2 concentration, presumably forced continuously growing ice sheets. The resulting cooling may have reached a critical temperature that caused a negative water balance in the regional water cycle of the QB, leading to the collapse of Qaidam paleolake since ~0.6 Ma. [ABSTRACT FROM AUTHOR]