The Continuous Cenozoic Sedimentary Sequence of the Weihe Basin (central China) and Its Implications for Asian Monsoon Evolution

Continuous high-resolution sedimentary sequences are fundamental to understanding Cenozoic climate evolution. The Weihe Basin in central China preserves a complete >7000-meter thick fluvial-lacustrine sedimentary record from the Eocene to Pleistocene and Holocene, making it a unique archive for revealing the long-term evolution of the Asian monsoon climate. The Weihe Basin is a graben basin that, due to the extension and compression of the Qinling orogenic belt and the Ordos block, has undergone episodic continuous subsidence since ~50 Ma, accommodating fluvial-lacustrine sediments and developing strata of Eocene, early Oligocene, middle to late Miocene, Pliocene, Pleistocene, and Holocene, thus providing an excellent record for understanding Cenozoic climatic and environmental evolution. Located within the Asian monsoon domain and featuring a moderate catchment area, the Weihe Basin acts as a “rain gauge” for recording long-term changes in monsoon precipitation. Since the spring of 2009, our research team from Nanjing University has conducted comprehensive and continuous studies on the geomorphology, sediments, stratigraphy, and paleomonsoon climate of the Weihe Basin. Based on sediment characteristics, mammalian fossil assemblages, high-precision apatite fission-track dates, detrital zircon U-Pb ages, and high-density magnetostratigraphic analyses, a reliable chronological framework for the Cenozoic sedimentary sequence of the Weihe Basin has been built. Using multiple paleoclimatic proxies, our study demonstrates that the Weihe Basin experienced a warm, semi-humid to semi-arid climate during the Paleogene, a cool, semi-humid to semi-arid climate during the Neogene, a dry and cold climate during the Quaternary, as well as orbital-scale monsoon climate variability during these intervals. These findings reveal the response of long-term Asian monsoon evolution to high-latitude temperature and low-latitude hydrological processes, providing scientific evidence for understanding the evolution and driving mechanisms of the Asian monsoon, as well as its future trends under increased atmospheric CO2 and global warming. This report presents new insights based on field sedimentary observations and studies in geochronology, sedimentology, stratigraphy, geochemistry, and paleoclimatology.