Climate and geological factors explaining chemical composition of the natural water in northern Xinjiang watersheds, China

Climate and geological factors explaining chemical composition of the natural water in northern Xinjiang watersheds, China

Abstracts / Quaternary International 279-280 (2012) 462–565 Our present study primarily focuses on the problems and differences of horizons, profile t...

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Abstracts / Quaternary International 279-280 (2012) 462–565

Our present study primarily focuses on the problems and differences of horizons, profile texture and geochronology between the best developed, thickest and most widely distributed variegated clays with the age of 1.0 to 0.8 Ma BP in the coastal South China and the typical reticulate red clays in the Yangtse River valley and the southwestern hill areas of China. Moreover, we suggest that some important scientific problems during this period, which is a sharp change stage of tectonic and climatic condition in both marine and continent, such as the pedogenises laws of variegated clays and reticulate red clays, the development-evolution intensity and laws of the weathering, and their signification to indicate the geological and climatic evolution in southern parts of China, will be awaited to research further. TRACKING FOR CLIMATE AND PARENT ROCKS FROM RARE EARTH ELEMENTS IN TOPSOILS ALONG THE EASTERN PART OF CHINA Zhaoyu Zhu. Key Laboratory of Marginal Sea Geology, Guangzhou, China E-mail address: [email protected]

The analysis results of rare earth elements (REEs) in fifty topsoil samples collected along the eastern part of China from Heilongjiang province to Hainan province indicate that the contents of rare earth elements in topsoils from the eastern part of China are much higher than those in China as well as in the World; it is characterized by LREE-enrichment and HREEdepletion with negative d Eu and positive d Ce; noticeable positive? Ce values have been found in the soils from south subtropics and tropics with hot-humid climate and intense weathering process; the plot of Ce/Eu against Eu/Sm is proved to be useful to distinguish different parent rocks of topsoil. This study suggests that the distribution characteristic can be used as a tracer for parent rock of soils, but not an good index for climatic zone;? Ce value can be used as an index of hot-humid climate. However, it is currently not well known how the factors such as sedimentary origin, source area and local climate affect the distribution of rare earth elements. More data would be necessary to answer this question. GEOCHEMICAL COMPOSITIONS OF SOLUBLE SALTS IN AEOLIAN SANDS FROM DESERTS OF NORTHERN CHINA: IMPLICATIONS FOR REGIONAL RESPONSE ON LOCAL HYDROLOGY AND CLIMATE Bingqi Zhu. Institute of Geology & Geophysics, Chinese Academy, China E-mail address: [email protected]

Two large sandy seas in northern China, the Taklamakan and the Badanjilin Desert, were investigated for a geochemical variation of the soluble salts in dune sand, with the aim to explore factors influencing the composition and distribution of inorganic salt in aeolian sand and their environmental implications. The total salt contents range 0.141.32&, with pH value 8.4-9.6, indicating a low degree of salt accumulation and alkaline desert conditions in aeolian sand. Sodium chloride and bicarbonate are the dominant salts. High interregional homogenization and small local difference on the chemical compositions and distributional patterns of salt occur in the two deserts. Variations of salt contents display a clearly relationship with the latitudes and longitudes of sampling sites, as well as the grain size compositions of aeolian samples, but are weakly linked with local hydrologies. It suggests a great influence of the regional hydro-thermal conditions of climate and local windblown process on dune salt. Based on the Waliguan database, two relative salt contributions from dry and wet atmospheric depositions are evaluated conservatively. It reveals a high contribution from regional dry deposition. Cases about variations of soluble salts in several Quaternary sedimentary sequences with lacustrine and aeolian deposits interbedded in the two deserts are also studied. The results indicate the soluble salts of sediments in desert environment may be a latent proxy in revealing local hydrological variations and climate change during the late Quaternary. THE CONTINENTAL CHEMICAL WEATHERING OF THE TAKLAMAKAN DESERT, NORTHWESTERN CHINA: EVIDENCE FROM THE MAJORELEMENT COMPOSITIONS OF AEOLIAN SEDIMENTS Bingqi Zhu. Institute of Geology & Geophysics, Chinese Academy, China E-mail address: [email protected]

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Based on the analysis of major-element compositions of sediments from the Taklamakan Desert, this paper examined the chemical weathering process of aeolian sediments in the hyper-arid area. The distributions of major elements are basically similar to the average composition of upper continental crust (UCC), but show a clear enrichment of CaO and depletion of Na2O and K2O relative to the unweathered UCC, confirming that chemical weathering is in token of the enrichment of carbonates and the decomposition of sodium and potassium silicates. The index of chemical alteration (CIA) are relatively lower and correlate negatively with the content of Na2O, implying that the degree of chemical weathering is still weaker and mainly controlled by the erosion of sodium feldspars. The ACN-K model demonstrates that the detrial sediments from the Taklamakan Desert have a high homogeneity in the trend of chemical weathering and still in the early stage of the continental chemical weathering process. They are weathered not only less than sands and soil in many other Chinese deserts, but also less than detrital sediments in many other countries, indicating a low mineralogical maturity in the Taklamakan Desert. The aeolian sediments of different ages have similar CIA values, suggesting that the degree of chemical weathering is consistent in the Taklamakan Desert while the aeolian processes are dominant. CLIMATE AND GEOLOGICAL FACTORS EXPLAINING CHEMICAL COMPOSITION OF THE NATURAL WATER IN NORTHERN XINJIANG WATERSHEDS, CHINA Bingqi Zhu. Institute of Geology & Geophysics, Chinese Academy, China E-mail address: [email protected]

Located in northern Xinjiang of China, watersheds of Yili, Zhungarer and Erlqis are characterized by geological, climatic and hydrological diversity. In this paper, an analytical study of hydrochemistry of natural waters based on 48 sampling sites is carried out, and which, as well as climatic and geological conditions are used to access the weathering and geochemical processes of these three watersheds. Results show the natural waters are neutral to alkaline in nature. The total dissolved solid (TDS) varies over two orders of magnitude with a medium TDS of 580 mg/l. Wide spatial variations are observed both in the dissolved solids and water chemical types. Generally, four hydrochemical facies are identified and Ca2+, HCO3- and SO42- dominate the major ion composition. The river chemistry in the wet zones (AMP > 200 mm) is mainly controlled by Ca- and Na-rock weathering induced by precipitation, due to the abundance of carbonate rocks and relatively wet climate. Evaporation and dissolution of evaporites dominate in the plain areas owing to arid conditions. Correlation analysis of the chemical parameters suggests that most ions have additional sources. The stoichiometric calculations of major-ion composition indicate that the carbonate weathering is the primary source of the major ions to these waters, followed by silicate weathering and evaporate dissolution. Variation and distribution of water chemistry show great relationships with the regional geological setting and hydro-thermal conditions, revealing the chemistry of the natural waters markedly depends on the underlying geology as well as the climate. Contributions from atmospheric precipitation and regional geology to the tributary chemistry are evaluated roughly in range of 2-39% (average 13%) and 59-98% (average 86%), respectively, implying the highly effective control of regional geology on stream chemistry than that of atmospheric input. LAKE SEDIMENT RECORDS OF HUMAN ACTIVITY IN MID-LATE HOLOCENE AT MIANCHENG AREA, JIANGHAN PLAIN Yuxin Zhu. Nanjing Institute of Geography and Limnology,Chine, China E-mail address: [email protected]

Jianghan Plain, a very famous plain for its abundant products and riverlake cross landscape, is the place where Yunmenze palaeolake existed. The Miancheng area is the sedimentation center of Jianhan Plain with lowering topography. Human activities on this area were comparatively late in history. A 56.18-m-core was collected in Miancheng of Jianghan Plain in Oct. 1992. According to the sediment lithology, cultural remnants, 14C chronology and human-derived environmental proxies, e.g. pollen, frequency magnetic susceptibility and chemical element phosphorous, the temporal sequences of human activities in Miancheng area since the midlate Holocence and its relation with palaeoenvironment are discussed in