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Surface soil samples collected over a high spatial resolution in eastern China were analyzed for carbon Isotope composition (δ13C) of total organic carbon (TOC) and higher plant-derived long-chain n-alkanes, with the latter reported as weighted mean values. The two sets of δ13C values are significantly correlated and show similar trends in spatial variation. The spatial distribution of δ13C shows less negative values in the mid-latitudes between 31°N and 40°N and more negative ones at higher and lower latitudes. This is consistent with previously reported carbon isotope data from surface soil phytoliths in the same region and suggests that the mid-latitude area provides relatively favorable growing conditions for C4 plants. Furthermore, δ13C values of both TOC and long-chain n-alkanes from 12 surface soil samples collected from a small grassland in north China displayed similar carbon isotope values and the difference between paired δ13C of a soil samples remains relatively constant. Our data demonstrate that in eastern China, soil δ13C composition of both TOC and long-chain n-alkanes is effective indicators of C3/C4 ratios of the prevailing vegetation. This work suggests that -22% and -32% are good estimated end members for the weighted mean δ13C values of long-chain n-alkanes (C27, C29 and C31 n-alkanes) from soils under dominant C4 or C3 vegetation, allowing us to reconstruct paleovegetation trends. [ABSTRACT FROM AUTHOR]

After Wenchuan Ms8.O earthquake, the surface fractures have been investigated in Beichuan City and Yingxiu Town. It was found that the Beichuan-Yingxiu earthquake fracture zone trends northeastward, dipping to northwest. The earthquake fracture zone is mainly characterized by thrust faulting with small amounts of strike-slip movement, and demonstrating various complexities for different areas. The phenomena related to dextral strike-slip displacement are found in Beichuan City and those related to left-lateral strike-slip movement in Yingxiu Town. The compressive shortening of the two surface fracture zones in Beichuan City is 2.8-3.9 m and the left-lateral strike-slip displacement of the surface fractures in Yingxiu Town is 0.52 m. [ABSTRACT FROM AUTHOR]

The paleoenvironment indicated by the geochronology, major oxides-SiO2, Al2O3 and TOFE (Fe2O3 + FeO), and CIA (Chemical Index of Alteration) value of the red earth and brown-yellow silt primarily characterized by the Linjiang stratigraphic section, based on the geological investigation of Late Quaternary along the river banks of northeastern part of China's Guangdong Province, south to the Nanling Mountains, allow us to hypothesize that the red earth on the first terrace in northeastern part of Guangdong belongs to reticulated red clay developed in a hot-wet environment of the last interglacial period (132-73 ka BP), similar to the monsoon environment in the northern margin of modern tropical zone, while the overlying brown-yellow silt layer mainly accumulated in a monsoon environment of warm temperate zone in the last glacial period (73--11 ka BP), with the aeolian sand LJ3 representing an extreme period of worsening climate. Such a hypothesis corresponds well with predecessors' research on the paleoenvironment indicated by abundant fossils in both south and east to the Nanling Mountains. Hence, it follows that the bioclimatic zone did experience a large and rapid vicissitude in northeastern part of China's Guangdong Province, and even in the full extent of the region south to the Nanling Mountains from the last interglacial period to the last glacial period, with the red earth being replaced by the brown-yellow silty sediment, and even maybe with the Ailuropoda-Stegodon Fauna being replaced by the Penghu Fauna. This study may provide an important geological demonstration for the environmental response to global change in China's low latitudes on a 10 ka scale. [ABSTRACT FROM AUTHOR]