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The palynomorph assemblage of lake sediments younger than 51.9 kaBP from Wulagai Gobi in Inner Mongolia was analyzed to reconstruct the vegetation and climate. From 51.9 to 30.6 kaBP, the vegetation was arid to semi-arid grassland with only slight changes. According to the palynomorphs, trees and shrubs were very rare. The large number and diversity of algae indicate the presence of a lake. Quantitative climatic conditions were reconstructed using the Best Analogues Method. The results indicate that the annual mean temperature was higher than that at present. The combination of temperature and annual precipitation suggests a change in the climate from cool dry to warm dry and then cool humid. Our results show that the annual precipitation values were mostly higher than that at present but were lower than 400 mm. It infers that the study area was already within the arid to semi-arid regions but with a stronger influence of the summer monsoon during 51.9 to 30.6 kaBP than at present. With slight differences mainly in time scale, the changing trend of the annual temperature curve is consistent with the other climatic records from Antarctica, Greenland, Hulu Cave (East China), and the Tibetan Plateau during the last glacial period. From 30.6 kaBP to present, very few palynomorphs were detected in the samples. Hence, no information about the vegetation and climate could be extracted. Combined with other studies during Late Pleistocene, we presume that the reason for the lack of pollen during this period was caused by an abrupt temperature fall after 30.6 kaBP or that the lacustrine conditions were unsuitable for pollen deposition. It was probably incurred by the oxidation on land prior to deposition. But for those samples only with algae, it might be caused by the fact that algae could finish their life history in a very short time in a seasonal lake. [ABSTRACT FROM AUTHOR]

The detailed magnetic susceptibility anisotropy study on the sediments of two sections, which are located in the lake-center and the lakeshore of the Huangqihai Lake, Inner Mongolia, revealed their hydrodynamics and sedimentary environment changes in the recent 2000 years. The results show that the sediments of two sections both display normal depositional magnetic fabrics, of which the minimum susceptibility axes ( K3) are oriented perpendicular to the bedding plane and the maximum magnetic susceptibility axes ( K1) lie parallel with the bedding plane. In addition, the lakeshore presents higher magnetic anisotropy degree ( P), magnetic foliation ( F) and current factor ( Fs) than the lake-center, showing that the lakeshore has higher flow velocity. For the west Huangqihai Lake (HQW) section in the lake-center, the magnetic matrix grain degree ( Q) and the inclination of the minimum susceptibility axes sharply increased and decreased, respectively, at a depth of about 10 cm, 24 cm, 45 cm and 74 cm, which indicate abnormal depositional events with strong kinetic energy. Through comparative analysis, the HQW section can be divided into three stages from top to bottom. The upper stage was a stable depositional environment with strong hydrodynamic energy and low water level, which shows relatively higher Fs value and the Q value varies similarly with P and F. The middle stage was a stable depositional environment with high water level and low hydrodynamic energy, intermitted with high-energy abnormal events, which shows relatively lower Fs and the Q value was negatively correlated with P and F. The lower stage was an unstable depositional environment with low hydrodynamic energy and high water level, which shows relatively lower P, F, and Fs value. [ABSTRACT FROM AUTHOR]