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The last glacial–interglacial climate transition in East Asia was characterized by an intensified monsoon, but knowledge about hydrological responses at a regional scale during this transitional period is limited. Here we provide a novel lipid-based paleohydrological record for this period from the Dajiuhu peat deposit, central China. High water levels and persistent wet conditions during the Younger Dryas (12.5–11.6 ka) and the early Holocene (10.5–9.9 ka) were inferred on the basis of enrichments of sterenes, a group of unstable intermediate diagenetic products derived from biogenic sterols that are most likely preserved under a waterlogged peatland surface. These two wet intervals were accompanied by temperature decreases indicated by an increase in pollen abundance from cold favoring conifer trees and a decrease in total hardwood tree pollen. This cold and wet climate pattern, which is different from the concordant cold-dry pattern documented in north China, was probably caused by the regional influence of the western Pacific subtropical high on the residence time of the Meiyu rainband in the middle and lower reaches of the Yangtze River Valley. [ABSTRACT FROM AUTHOR]

Evaluating the pre-Jurassic marine source rocks in China has been difficult because these rocks are generally too high- or over-maturated for most traditional methods to work. As to the remaining parameter TOC (%), its lower limit for recognizing the carbonate source rocks in China has been in dispute. Nineteen Phanerozoic sections in the Middle-Upper Yangtze Platform and the Guizhou-Hunan-Guangxi Basin have been studied in search for a different approach to complementing the traditional evaluation method for these source rocks. We have applied a geobiological approach to tracing the organic carbon (OC) output and accumulation from the living stage (primary productivity) to the post-mortem deposited remains, and finally to the preserved burial organics. Four biological and geological parameters are employed to represent the OC of the three stages. A series of proxies of these parameters are discussed and integrated to establish a geobiological evaluation system independent of TOC and other traditional methods. Here we use the Guangyuan section in Sichuan as an example for the geobiological evaluation. Our results indicate that in the argillaceous rocks, the geobiological parameters show the qualified source rocks in accordance with high TOC values; but in the carbonates, the good source rocks delineated by the geobiological parameters have a wide range of TOC, from 0.03% to 1.59%, mostly <0.3%. We suggest that it is still premature to set TOC=0.3% or 0.5% as the lower limit for the pre-Jurassic carbonate source rocks in South China. [ABSTRACT FROM AUTHOR]

Abstract: Suspended particulate matter (SPM) was collected above and below the Three Gorges Dam (TGD) on the Yangtze River in May, July and December 2009, respectively, for a study of the spatial and temporal variation in glycerol dialkyl glycerol tetraethers (GDGTs) in the riverine system. The branched GDGTs (bGDGTs) were > 0.6ng/l and isoprenoid GDGTs (iGDGTs) > 0.3ng/l in most SPM samples in May and July, whereas, iGDGTs were on average about 10× more abundant than bGDGTs in December. The results suggest that the abundance of bGDGTs and iGDGTs in the Yangtze River at the TGD varied seasonally, which might be affected by soil runoff and in situ production. Despite these effects, the TEX86-inferred temperature derived from SPM reflected the measured river surface water temperature in the sampling months, suggesting that planktonic Thaumarchaeota might actively make iGDGTs in the river water near the TGD throughout the year. The bGDGT-derived CBT/MBT temperature from the SPM was not significantly different among the three seasons and the values together averaged 15.2±0.7°C, close to the annual mean air temperature (16.9°C) in the region near the TGD. However, the bGDGT-derived pHCBT values were close to the water pH and slightly higher than the pH of the local soil. These results suggest that the sources of bGDGTs in the river water are complicated and that bGDGTs may not solely derive from the local soil runoff. Nevertheless, our study highlights the potential of using TEX86 and MBT/CBT proxies for a better understanding of the source and mechanism of GDGT production in riverine systems increasingly affected by the construction of dams. [Copyright &y& Elsevier]

Abstract: A variety of phytoliths, together with prolific microcharcoal particles, sponge spicules and diatoms were extracted and identified in four cultural layers from an archeological site at Jinluojia, Macheng, Hubei Province, Central China. The warmth (Iw) and aridity (Iph) indices calculated from grass phytoliths reveal warm and wet periods during the West Zhou, early East Zhou, Tang and Song Dynasties whilst cool and dry periods occurred during the late East Zhou, Ming and Qing Dynasties. The paleoclimate conditions reconstructed on the basis of grass phytoliths extracted from archeological sediments are in agreement with those from natural sediments in the Middle Yangtze region. In contrast, the woody phytoliths show a positive correlation with microcharcoal particles, suggesting an anthropogenic contribution to the woody phytoliths from the use of woody plants for fuel during cooking and heating. Two episodes of the enhanced abundance of woody phytoliths and microcharcoal particles were found to occur at East Zhou Dynasty and from Ming and Qing Dynasties to the Present, proposed to be a consequence of the population expansion and/or the frequent wars. [Copyright &y& Elsevier]