The Neogene Terrestrial Chronostratigraphic Sequence of China

Abstract

Seven terrestrial chronostratigraphic units, namely the Xiejian, Shanwangian, Tunggurian, Bahean, Baodean, Gaozhuangian, and Mazegouan stages, are recognized for the Chinese Neogene based on updated large and small mammalian faunas. In the past, the positions of the Chinese mammalian faunas in the chronological chart and their correlations to European faunas were determined mainly by the evolutionary levels of mammals because of the lack of accurate absolute ages. However, during the last three decades, great progress has been made in Chinese Neogene terrestrial stratigraphic studies. Most of the classic regions have been revisited, such as the Yushe and Baode areas in Shanxi, the Lantian area in Shaanxi, and the Tunggur area in Inner Mongolia. New discoveries have been made in well-exposed fossiliferous regions, such as Tongxin in Ningxia, central Inner Mongolia, the northern Junggar Basin in Xinjiang, the Linxia Basin in Gansu, and the Qaidam Basin in Qinghai. Magnetostratigraphic work has also been conducted in several regions. Despite this, large gaps still exist between China and its European and North American counterparts in terms of the accumulation of fossils as well as such basic tasks as the documentation of fossil occurrences and their biostratigraphic contexts. However, land mammal ages for China have now been better constrained by data from new localities and new taxa. The significance of these new data is that they are improving our understanding of mammal turnovers and boundary calibrations. The faunal components are thought to be stable throughout each chronostratigraphic unit, without large changes occurring. For each unit, series of species or genera are regarded as characteristic forms on the basis of correlation with the European taxa. Generally, the chronostratigraphic units deal with the first appearance datum of mammals at the generic level. Some of these genera are immigrants, and their entry into China often marks the beginning of a unit. The exact correlations between the Chinese and European mammalian ages based on more accurate dating will increase our ability to recognize mammal migrations between China and Europe. Asia acted as a faunal dispersal centre for Europe during the Neogene, and the great majority of the exchanges were migrations from Asia into Europe. China was one of the main dispersal centres of the Neogene. In recent years, the Chinese Neogene mammal ages have become more accurate with the introduction of magnetostratigraphy, which has enabled ages to be calibrated and well dated at their boundaries. The increasing number of palaeomagnetic measurements has enabled a good calibration to be made for the correlation of Chinese Neogene mammalian faunas with their European and North American counterparts. A new Neogene chronostratigraphic framework is proposed, one that is more consistent with the reality of the state of research and conditions in China. This will provide a foundation for the establishment of a formal Chinese Neogene terrestrial chronostratigraphic system. Given that China possesses well-developed Neogene terrestrial strata that are richly endowed with fossil mammals, such a system should play a role in the establishment of an Asian Neogene terrestrial scheme in the future.KeywordsChronostratigraphic unitStageMammal ageMagnetostratigraphyNeogeneChina