中国科学院南京地质古生物研究所机构知识库

Ecological shifts from C-3 to C-4 vegetation took place in many parts of the world around 7.5-5 Ma in response to global climate change. Previous evidences from pollen, paleosol isotope, and faunal have suggested that the expansion of C-4 vegetation also occurred in the central Chinese Loess Plateau (CLP) at 7.4 Ma, which, however, is incompatible with palaeoclimate evidence from the CLP of cold and dry conditions during the late Miocene. In this study, stable oxygen (delta O-18) and carbon (delta C-13) isotope ratios preserved in tooth enamel from hipparionine were analyzed to elucidate the late Miocene (similar to 7.4 Ma) palaeoecology of the central CLP. The enamel delta C-13 values indicated a diet comprised entirely of C-3 plants, consistent with the C-3 steppe inferred from the faunal composition for the western district of the Neogene palaeozoogeographical boundary of Northern China. The delta O-18 values were indicative of a mild continental climate with Late Miocene seasonality that is not as pronounced as the modern steppe environment of Mongolia. The local landscape was most likely dominated by C-3 steppe which belonged to the western district of the Neogene palaeozoogeographical boundary of Northern China. Comparison of results presented here and with published records from other localities in this region such as the Linxia Basin, Yushe and central Inner Mongolia suggests a veer of the East Asian summer monsoon (EASM) since 7.5 Ma.