Geological Environments in China and Global Change

Abstract

A large variety of geological evidence are presented and summarized here to address the links between the geological environments in China and global environmental changes in the Cenozoic era. Environmental indicators (coal beds, salt and gypsum deposits, palaeo-vegetation remains etc.) from the presently monsoonal regions provide the first terrestrial evidences of the inceptions of the Southeast Asian summer monsoon, the Southwest Asian summer monsoon and the Northwest Asian winter monsoon. The Palaeocenc and the Eocene environmental pattern in China was dominated by roughly zonal climates resulted from the planetary wind system. The decrease in the aridity for the southeastern country in the Oligocene indicates the inception of the southeast summer monsoon. Conspicuous changes have occurred for the Miocene when the originally arid south-western part of the country became much more humid, indicating the initiation of the south-west summer monsoon. The south-east summer monsoon was also significantly strengthened at the same time. The geographic location of the arid region in northern China was further close to the present-day one, suggesting that the Himalayans and the Tibetan Plateau may have began to uplift. These were also more or less synchronous with the rapid growth of the Antarctic ice-sheet. Another drastic change occurred around the latest Miocene when extensive aeolian dust began to deposit in the northern China, indicating the emergence of the north-east winter monsoon andan increase in the continental aridity in central Asia. Since then, a stepwise increase of continental aridity in northern China was observed for the last 2.5 Ma as shown by the loess-palaeosol sequences.