Salt Lake Sediments Research Articles

New progress of lake sediments and environmental changes research in China

Environmental change recorded by lake sediments is one of the important branches of the past global changes study. The new progress of lake sediments and environmental changes in China since the late 1980s has been comprehensively discussed. The highlights emphasized are Asian paleomonsoon migration reflected by lake level fluctuation, uplift of the Qinghai-Xizang Plateau recorded by lacustrine sediments, saltlake sediments and environmental evolution, lake response to the natural-human interaction and modern lake biogeochemical process. Meanwhile important suggestions for the lake sediments and environmental research in the future are proposed, which include studies on the quantitative relationship between lake environment proxies and climate factors, high-resolution evolutionary sequence and spatial differentiation of environments, modern lake dynamic process and environment, Quaternary Chinese lake database and global changes.

Geochemistry of rare elements in waters and sediments of alkaline lakes in the Sasykkul depression, East Pamirs

The saline lakes (Tuzkul, Chukurkul, Sasykkul Lakes) of the Sasykkul depression located in the semidesert part of the Pamirs provide a prominent example of the evaporative concentration of alkaline waters in a closed basin under arid climate conditions. Chemical evolution of the lake waters has resulted in the development of residual Na–Cl–CO 3–SO 4 and Na–Cl–CO 3 brines. The contents of a number of rare elements were determined in waters and sediments of the Sasykkul depression lakes. Speciation modelling suggests that the main aqueous species of Ag are chloride complexes, Cu, Pb, Zn, Mn are carbonate complexes, Be, Bi, Nb are hydroxocomplexes, Mo, W, As, V are oxyanions. It was established that the salt lake sediments are significantly enriched in B, Ba, Mo, W, U, Th. High contents of trace elements are considered to be due to chemical weathering of rocks within the catchment basin, significant contribution from thermal springs derived from the residual fluids associated with acid igneous and volcanic rocks, and following evapoconcentration in a closed basin. The processes of evaporative concentration, solution complexation, chemical precipitation, and water-sediment interaction lead to the partitioning of trace metals in the salt sediments.

Acyclic isoprenoids – molecular indicators of archaeal activity in contemporary and ancient Chinese saline/hypersaline environments

Acyclic isoprenoid hydrocarbons are found to be the predominant components in the organic matter extracted from sedimentary cores and oils of various hypersaline settings, including Tertiary Janghan salt lake basin, Cretaceous Taian salt lake basin, and Triassic, Permian and Cambrian Yangtze evaporitic marine platform. Inland saline lake basins are characterized by tremendous predominance of phytane (iC20) ranging up to 15% of the total extract. While the evaporitic marine sediments are unique for their complete series of super-long-chain acyclic isoprenoids, up to C40. These isoprenoids possess head-to-head, tail-to-tail or regular linkages and generally are indicators of the significant contribution from various archaea (archaebacteria), i.e. halophiles, methanogens and acidothermophiles. According to the great discrepancy of distribution and composition of isoprenoids, these modern and Cenozoic inland salt lake sediments are likely dominated by halophilic archaea, while the studied Mesozoic and Paleozoic evaporitic marine sediments are predominantly distinguished by methanogens and acidothermophiles. Concentration of chlorine salt is more directly proportional to the abundance of phytane than sulfate. Reduced species of sulfur, sulfide, S0 and organic sulfur compounds (OSC), however, may have played a key role in the preservation and formation of the highly abundant phytane observed in the inland salt lake basins.

Enzymological classification of salt lakes in Romania

Sediments of 56 salt lakes from Romania were studied enzymologically. The following 7 enzymatic and nonenzymatic catalytic activities have been measured: phosphatase, H2O2-splitting in nonautoclaved (catalase) and autoclaved samples, TTC reduction in nonautoclaved (dehydrogenase) and autoclaved samples, without or with glucose addition. A formula is proposed for the evaluation of the enzymatic potential of salt lake sediments or other habitats. A hierarchy of the studied lakes has been established on the basis of the enzymatic potential of their sediments expressed as enzymatic indicator.

Sedimentary characteristtxcs of zk91-2 core and climate-environment evolution of Zabuye Lake, Tibet Plateau

扎布耶盐湖位于西藏高原腹地,1991年在其南部干盐滩中钻取了20m深湖相沉积,以5~10cm/个的密度进行高分辨率取样,详细探讨了沉积标志、矿物组合(尤其Mg、Ca、Li碳酸盐)、干旱与潮湿两种气候类型的元素组合等气候环境指标,推导了晚更新世以来该湖区湖面涨缩、水质咸谈及气温高低变化。;Zabuye saline lake is situated in the hinterland of Tibet Plateau. In 1991, a core of 20m was drilled up in the southern lake, and 5~10-cm-lorg sampler taken in succession. Valuable studies were performed on the climate-environmental indicator of sedimentary marks, mineral association, and element assemblage, etc. Sedimentary structure, size distribution, and organic materials etc. clearly revealed the fluctuation of water depth and air temperature, and it was consistent with the variation of content of dolomite and calcite. We have also paid special attention to Li-bearing carbonate, borate and mirabilite etc. which are sensitive to salinity and temperature of the lake water and exist commonly in salt lake sediments in Tibet Plateau. Cluster analysis of some elements (Ca, Mg, Sr, K, Na, B, Ba, Li, Fe, Mn, Cr, Co, Ni, V, Ci) in the sediments shows that they can be distinguished into twc parts:some elements (Ca, Mg, Sr, K, Na, B, Li, Ba) accumulate in the sediment during arid period an arid type, and the others concentrate in the sediments during humid period a humid type. It is found that the ratio of the arid type to the humid type is a better indicator of the climate for the sediments in geological era. The study shows that before 2.9×10⁴ a B-P., the old Zabuye Lake was deep and had a vast area, the climate then was cold and a little humid; during 2.9×10⁴~2.2×10⁴a B. P., the climate of the lake area turned warm and humid; from 2.O×10⁴ a B. P. onwards, the climate became dry and cold, the lake water dropped greatly and got salinized; but during 1.3×10⁴~1, 1×10⁴ a B, P., there existed a warm and humid period; from Holocene Epoch onwards, some soluble salt began to deposit, during 6000~4000 a B. P. 5 there was an obvious fluctuation to warm and humid; from then on, the climate was getting dryer and colder.

A Mössbauer spectroscopic study of salt lake sediments from Qaidam basin

Mossbauer spectroscopy, X-ray diffractometry and chemical fractionation have been used to study the clay smaples in sediments of Charhan playa and Qinghai lake. The spectral components of the Mossbauer spectra of the samples are attributed to Fe2+ ions in chlorite and siderite, Fe3+ ions in clay minerals and hematite, and partly in amorphous ferric hydroxides. The essential difference in the mineral composition of the sediments of both lakes is the presence of siderite in the samples of Char han playa, whereas it is absent in the samples of Qinghai lake. The fraction of the amorphous ferric hydroxides is higher in the sediments of Qinghai lake. Total Fe2+/Fe3+ ratios increase with sediment depth of Charhan playa, whereas these ratios are altogether smaller and run through a maximum at a certain depth for Qinghai lake.

Biological and sedimentary facies of Australian salt lakes

Four main types of salt lakes are recognized in Australian: (1) large playa lakes, (2) small closed lakes, or pans, (3) crater lakes, and (4) coastal lakes (not connected to the sea). Basically all have an NaCl chemistry. Biological and sedimentary facies characteristic of these salt lakes can be arranged into three basic groups which relate to particular phases in lake regimes. These phases are: (1) wet phases of ephemeral shallow lakes, (2) dry lakes, and (3) deep water lakes. All elements of the salt lake biota with fossilizable remains are discussed, with a detailed account of the (palaeo)ecological information they offer. Elements of the nonaquatic biota associated with salt lake sediments are also analysed. Sedimentary features of Australian salt lakes pertinent to palaeoecology are discussed in the context of their association with the biota, using numerous illustrations. The distribution of the biota on lake floors, for example, its concentration in particular areas of the lake, or its destruction during particular episodes such as lake filling and drying, is mentioned in the context of recognizing different facies. Three major lake regime phases are presented with emphasis on the biological and sedimentary facies which characterize them. The paper concludes with a brief discussion of the relevance of recognizing particular salt lake facies and changes in lake histories for the study of palaeoclimates and for mineral and oil exploration.

Peculiarities of salt lake sediments as potential source rocks in China

Hypersaline lake sediments are widely distributed in China and can be good sources for petroleum. The Palaeogene sediments of the Jianghan Basin in Eastern China are a typical example composed of salt lake evaporite-clastic facies in fault-subsided basins. Their organic matter is variable, but is dominated by Type II kerogen. The biological marker characteristics of core extracts and oils from the Jianghan Basin include: (i) low OEP values for n-alkanes and, occasionally, an even-odd predominance, (ii) a high concentration of phytane, (iii) a relatively high gammacerane/17α(H),21β(H)-hopane ratio and (iv) abundant, mainly nickel, porphyrins. Sample Guang-33 (K-33) is typical of the immature oils found in the Jianghan Basin. Geological and geochemical data both indicate that it was generated from source rocks in the maturity range R 0 0.45–0.55%. Its characteristics are similar to those of immature source rocks, with high concentrations of phytane, steranes, triterpanes and nickel porphyrins, and, for an oil, extremely low values for molecular parameters of maturity, such as C 29 20S/(20S + 20R) 14α(H),17α(H)-steranes, C 32 22S/(22S + 22R) 17α(H),21β(H)-hopanes and DPEP/(DPEP + Etio) porphyrins.