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SUMMARY The Qinling Mountain range forms an important climate barrier between southern and northern China. Its western part, referred to as the West Qinling, constitutes a unit of northeastern Tibetan Plateau. The uplift history of Qinling during the Neogene is still a contentious issue. Magnetostratigraphic results from the 150-m-thick Xihe loess-soil sequence (NL-VI), located on the alluvial highlands surrounding an intermontane basin from the West Qinling, indicate 17 reverse and 17 normal magnetozones. They are correlative with the interval from chron C5n to chron C2Ar in the Geomagnetic Polarity Timescale. The age of the NL-VI section can thus be palaeomagnetically constrained to a period from 10.5 to 4.2 Ma. The middle portion of the section has been affected intermittently by surface erosion processes. As loess is sensitive to any erosion that may have been induced by substratum deformation and tectonic uplift, this sequence indicates that the intermontane basin-ridge pattern of the West Qinling had already been formed by 10.5 Ma, thus providing suitable topographic conditions for aeolian deposition. This timing is consistent with a significant deformation phase between ∼14 and 10 Ma reported for the Tibetan Plateau. Meanwhile, the complete preservation of the NL-VI loess-soil sequence precludes both intense deformation of the substrate and rapid uplift of the West Qinling between 10.5 and 4.2 Ma. Although the erosion-affected portion of the NL-VI section reflects some degree of tectonic instability from 8.3 to 6.9 Ma, the intensity must have been sufficiently weak to prevent the erosion of the aeolian deposits. These further suggest that the late Miocene growth of the Tibetan Plateau has not significantly affected the West Qinling. Thus, the studied NL-VI aeolian sequence provides not only independent evidence for the uplift history of the West Qinling within an accurate chronological framework, but also provides new insights into the tectonic changes on the northeastern Tibetan Plateau. [ABSTRACT FROM AUTHOR]

The East Asian summer monsoon affects precipitation and hence vegetation in the densely populated Northwest Pacific region, yet a long-standing controversy exists concerning the spatial and temporal dynamics of the Holocene Optimum (HO) in the East Asian Monsoon Region. Here we use a detailed 14,000-year record reconstructing vegetation variations from a strategically selected crater lake from Northeast China, as well as a compilation of previous paleoclimatic studies, to show that the HO began around 6,000 Cal a BP in Northeast China, significantly later than generally recognized. By comparing our paleoenvironmental data with Holocene vegetation records from other regions of East Asia, we identified a marked northward shift for the onset of the HO from ∼ 10 , 260 Cal a BP in South China to ∼ 6 , 000 Cal a BP in Northeast China. The gradual northward transgression of the vegetation change could be caused by both the temperature and precipitation changes in different regions. Finally, we fitted a regression model of the start of the HO period versus latitude, which allowed us to make predictions for the beginning of the HO at different geographical locations. This study reveals a strong relationship between latitude and the initiation of the HO, and provides a window towards better understanding the forcing of vegetation changes in the East Asian monsoon region. [ABSTRACT FROM AUTHOR]