PERSPECTIVES FOR THE UTILIZATION OF GEOBOTANICAL GUIDES IN THE DETECTION OF SALT-DOME STRUCTURES

In a hot, dry climate the presence of salt-loving vegetation (halophytes) may serve as a supplementary indicator of the presence of a salt-dome structure. Deep-seated oily water apparently forces the highly saline waters to the surface, where vegetation indicators may take two forms: where drainage is poor, the halophytes will be found along the anticline itself, but where drainage is good, the salt-loving plants concentrate along the perimeter of the salt-dome structure, sometimes virtually outlining it. In addition, the presence of gigantic and deformed plants in the area may indicate a high bitumen content. However, the influence of the deep oily water on the salinity of overlying deposits, soil and ground water varies with geologic conditions, depth and chemical composition of the ground water, conditions for its ascendance and conditions determining soil formation. The authors caution against over-simplification, since not every halophytic association indicates a buried salt dome; the specie composition of the association and presence or absence of bitumen-indicating forms must also be considered. --A. Eustus.     

APPLICATION OF THE GEOBOTANICAL METHOD IN HYDROGEOLOGIC STUDIES OF DESERTS AND SEMIARID REGIONS

Plant associations in arid and semiarid regions serve as indicators not only of presence of ground water, but of its depth, relative salinity and seasonal variations. Plants such as phreatophytes may serve as direct water indicators, while Anabasis salsa, an indirect water indicator, is more indicative of geologic conditions, in this case clayey or argillaceous soils. An Anabasis salsa association in the Temirsk-Aktyubinska Ural region indicates that the ground water is located at considerable depth; in the northwestern Caspian area, however, this same association is often found in low wastelands forming localized impermeable horizons where ground water may be found at depths of 5 to 10 m. Some associations indicate the degree of salinity, rather than ground-water depth. Preparation of a ground-water resources map from such geobotanical data requires field work, during which associations around known wells, ponds or ground-water areas are analyzed to provide a criteria for the area as a whole. It has been found that data from field studies tally closely from that made from aerial photographs. Hence, after initial studies are made, prospecting of a given region may be carried out by aerial photographs. Variations in vegetation relative to depth and mineralization of ground water also may be used to forecast changes in the vegetation which would occur following construction of an irrigation system. --A. Eustus.     

Chemistry and pollution of natural waters in western Kenya

Selected water analyses from the literature and current research in western Kenya are tabulated and the relationships between critical water quality parameters described. The waters are chemically characterised with Na as the dominant cation and bicarbonate as the dominant anion and, while waters of obviously different sources are represented, the available chemical data point to a general classification of bicarbonate-Na-rich waters, even for the saline waters of Lake Magadi. Potassium and chloride are among the less abundandt constituents. The concentration level of nutrients (nitrate, phosphate and sulphate) is mostly lower than maxium permissible drinking water levels, and salinity is not yet a serious problem in water bodies that are exploited for domestic and industrial purposes. Fluoride levels are variable with the higher values occurring in waters in and around the Rift Valley. Limited analytical data for I in waters from the Eldoret, Kiambu and Nairobi areas indicate concentrations well above world average figures. Mean values of some key water quality indicators such as total dissolved solids, total suspended solids and heavy metals are well below the threshold for contaminated water. These values are however exceeded by several factors in saline waters of lakes and in some springs. Significant organic pollution is reflected by mean values of parameters such as biochemical oxygen demand and faecal coliforms. The present quality of most of the water bodies in this part of the country is considered to be adequate at present for domestic and other purposes, though a gradual decrease in quality is evident from the recent upsurge in industrial activities in the subregion.     

Origin of salinity in produced waters from the Palm Valley gas field,Northern Territory,Australia

The chemical composition and evolution of produced waters associated with gas production in the Palm Valley gas field, Northern Territory, has important implications for issues such as gas reserve calculations, reservoir management and saline water disposal. The occurrence of saline formation water in the Palm Valley field has been the subject of considerable debate. There were no occurrences of mobile water early in the development of the field and only after gas production had reduced the reservoir pressure, was saline formation water produced. Initially this was in small quantities but has increased dramatically with time, particularly after the initiation of compression in November 1996.The produced waters range from highly saline (up to 300,000 mg/L TDS), with unusual enrichments in Ca, Ba and Sr, to low salinity fluids that may represent condensate waters. The Sr isotopic compositions of the waters (⁸⁷Sr/⁸⁶Sr = 0.7041–0.7172) are also variable but do not correlate closely with major and trace element abundances. Although the extreme salinity suggests possible involvement of evaporite deposits lower in the stratigraphic sequence, the Sr isotopic composition of the high salinity waters suggests a more complex evolutionary history.The formation waters are chemically and isotopically heterogeneous and are not well mixed. The high salinity brines have Sr isotopic compositions and other geochemical characteristics more consistent with long-term residence within the reservoir rocks than with present-day derivation from a more distal pool of brines associated with evaporites. If the high salinity brines entered the reservoir during the Devonian uplift and were displaced by the reservoir gas into a stagnant pool, which has remained near the reservoir for the last 300–400 Ma, then the size of the brine pool is limited. At a minimum, it might be equivalent to the volume displaced by the reservoired gas.     

AN EXPERIMENT ON THE APPLICATIONS OF GEOBOTANICAL GUIDES IN DISTINGUISHING BETWEEN LITHOLOGICALLY SIMILAR STRATA OF DIFFERENT ORIGIN

This article will present the techniques and the various steps followed in the utilization of geobotanical indicators for geologic mapping of areas east of and adjacent to the Mugodzharskiye mountains. It was found that despite the apparent homogeneity of the plant cover on lithologically similar rocks, a geobotanical analysis reveals a number of fundamental differences. Even when the floristic composition of associations is the same, other differences are seen in quantitative ratios of species, in the occurrence of some species in the plant cover, and finally, in the development cycle of an association as a whole, or of its individual species. In many instances also considerable floristic differences are observed in the plant cover found on lithologically similar rocks. Differences in plant cover on lithologically similar formations result from the physical chemical properties of rocks, which in turn result from the origin of rocks, the conditions of their formation, and the depths of their occurrence. In utilizing geobotanical data for lithological,mapping, of great importance is the character of plants growing at the contacts of formations which emerge at the surface. The following regularly occurring characteristics were noted. a) Hydrophytes develop at the contacts of rocks of different lithologic composition when impermeable rocks underlie permeable and moderately permeable rocks (sandstone, marly sandstone). b) At the contact of rocks of a different lithologic composition, when water-impermeable rocks (clays) overlie water-permeable rocks (sand, sandstone, manly sandstone) vegetation quickly dries up because the overlying rocks are dry as a result of being separated from the ground water. c) A transitional zone of plants is observed at the contacts of lithologically similar rocks and makes possible the determination of the boundaries of these rocks. The boundaries may be very sharp if the lithologically similar rocks have a different type and amount of salinity. — M. Russell     

Tracing Chernobyl's Fallout

When the third angel blew his trumpet a great star flaming like a torch descended from the sky, falling upon the third part of the rivers and upon the sources of water. The star is called wormwood. The third part of the waters turned to wormwood, and great numbers of men died from drinking the waters because they had been poisoned.     

Hydrogeochemical processes in an arid region of Europe (Almeria,SE Spain)

In the Lower Andarax river basin 3 aquifer units have been defined, namely the Carbonate Aquifer, the Deep Aquifer and the Detrital Aquifer, which between them contain a wide variety of water types. Identification of hydrogeochemical processes has been performed by studying a series of ionic ratios, comprising the principal constituents together with B and Li (Cl vs SO₄, Cl vs Mg, Cl vs Li, B vs Li). Among the processes detected, the circulation of groundwaters with high concentrations of SO₄ was found to have significant effects. Moreover, in the coastal region, naturally occurring processes related to the flushing of saline waters from sediments of marine origin occur in conjunction with others, clearly of human origin, that are related to saltwater intrusion. A further factor is the entry, from overlying deposits, of waters with a high saline content; this salinity is related to the flushing of sediments of marine origin. The use of B and Li together enables waters in which salinity is related to seawater to be distinguished from others in which salinity is related to evaporitic layers or to thermal areas. The concentration of Li is directly related to water temperature, while that of B is greater in the most saline sectors, of gypsiferous and/or seawater origin.     

THE SALT BALANCE OF THE ARAL SEA

In the Aral Sea there exists an excess of influx of salts over loss by deposition, yet there has been no appreciable increase in the salinity of the sea since 1871 Loss of water by evaporation is less than influx by drainage, hence influx of ground water cannot explain it. A method for calculating the salt loss from interior basins by wind is described and analyzed mathematically. Only 0.05 percent of the salt carried in by river drainage is lost through the action of wind. Outflow of saline water by filtration through the sandy shores along the coasts is shown to be a factor explaining salt loss and the maintenance of salinity equilibium. --M. Russell.     

Origin of brine in the Kangan gasfield: isotopic and hydrogeochemical approaches

The Kangan Permo-Triassic brine aquifer and the overlying gas reservoir in the southern Iran are located in Kangan and Dalan Formations, consisting dominantly of limestone, dolomite, and to a lesser extent, shale and anhydrite. The gasfield, 2,900 m in depth and is exploited by 36 wells, some of which produce high salinity water. The produced water gradually changed from fresh to saline, causing severe corrosion in the pipelines and well head facilities. The present research aims to identify the origin of this saline water (brine), as a vital step to manage saline water issues. The major and minor ions, as well as δ²H, δ¹⁸O and δ³⁷Cl isotopes were measured in the Kangan aquifer water and/or the saline produced waters. The potential processes causing salinity can be halite dissolution, membrane filtration, and evaporation of water. The potential sources of water may be meteoric, present or paleo-seawater. The Na/Cl and I/Cl ratios versus Cl^? concentration preclude halite dissolution. Concentrations of Cl, Na, and total dissolved solid were compared with Br concentration, indicating that the evaporated ancient seawater trapped in the structure is the cause of salinization. δ¹⁸O isotope enrichment in the Kangan aquifer water is due to both seawater evaporation and interaction with carbonate rocks. The δ³⁷Cl isotope content also supports the idea of evaporated ancient seawater as the origin of salinity. Membrane filtration is rejected as a possible source of salinity based on the hydrochemistry data, the δ¹⁸O value, and incapability of this process to dramatically enhance salinity up to the observed value of 330,000 mg/L. The overlaying impermeable formations, high pressure in the gas reservoir, and the presence of a cap rock above the Kangan gasfield, all prevent the downward flow of meteoric and Persian Gulf waters into the Kangan aquifer. The evaporated ancient seawater is autochthonous, because the Kangan brine aquifer was formed by entrapment of brine seawater during the deposition of carbonates, gypsum, and minor clastic rocks in a lagoon and sabkha environment. The reliability of determining the source of salinity in a deep complicated inaccessible high-pressure aquifer can be improved by combining various methods of hydrochemistry, isotope, hydrodynamics, hydrogeology and geological settings.     

Origin of salinity of deep groundwater in crystalline rocks

Deep groundwater in fractured crystalline basement has been reported from deep mines and from scientific deep wells. Highly saline brines have been described from several km depth in the continental basement of the Canadian, Fennoscandian and Ukrainian shields and elsewhere in the world. The origin of salinity is unknown and many different possibilities have been presented. We compare the compositional evolution of deep waters in the Black Forest basement, SW Germany, with those of other deep crystalline waters, and use halogen systematics (e.g. Cl/Br ratios) and other parameters of the waters to deduce the origin of their salinity. In the Black Forest the composition of deep thermal waters results from chemical interaction of surface water with the rock matrix (mainly weathering of plagioclase and mica) and from mixing of the reacted water with stagnant saline deep water. Here we show by Na/TDS-and Cl/TDS-investigations, by molality-ratios of the Na and Cl concentrations, and by Cl/Br systematics that these deep saline waters have a marine origin. The Cl/Br ratios in deep crystalline waters are very close to normal marine ratios (Cl/Br = 288 ppm basis). In contrast, Cl/Br ratios of other possible sources of salinity show distinctly different Cl/Br ratios: water derived from dissolved Tertiary halite deposits of the rift valley is in the order of Cl/Br = 2400 and water from dissolved Muschelkalk halite deposits has values of about Cl/Br = 9900. Leaching experiments on crystalline rocks, on the other hand, show that the average Cl/Br ratio of crystalline rocks is far below Cl/Br = 100.     

三山岛海底金矿突涌水优势渗流通道与来源研究

在对巷道导水裂隙详细调查量测的基础上, 通过对导水裂隙产状的归纳总结, 结合涌水水样的温度、矿化度及氢、氧同位素的动态监测结果, 分析了三山岛金矿两个矿区的渗流优势方位以及矿坑水与地表水体的连通性。研究表明:西山矿区的渗流优势方位与最大水平地应力平行, 而新立矿区的渗流优势方位与最大水平地应力近于垂直; 西山矿区存在海水、基岩咸水和第四系淡水的稳定补给, 新立矿区的咸水和淡水补给量不断减小, 海水补给量不断增大; 新构造断裂对矿区渗流优势方位的控制作用大于采动裂隙, 使得西山矿坑与地表水体存在良好的连通性, 也控制着海水补给矿坑的方式; 而新立矿仅在采动裂隙的影响下与海水、咸水和淡水存在较弱的连通性。     

唐古拉山侏罗系沉积的若干特征及沉积盆地背景条件的探讨

对于唐古拉山侏罗系沉积类型的不同认识由来已久,然而无论是将其视为地槽型沉积,还是地台型沉积,均难以令人满意地解释该区侏罗纪沉积的特点和性质。 作者在野外工作和室内研究的基础上,从地球化学因素、古生态分析、沉积岩沉积构造和矿物结构成熟度等综合考虑,对该区侏罗纪沉积的特点和性质提出下列证据: （1）含盐度值一般均低于广海的平均盐度值。 （2）发育了海相一半咸水相一陆相的双壳类动物群序列,并以半咸水双壳类属占优势。 （3）沉积构造多为浅水成因的小型波痕,交错层理沉积组合。 （4）沉积岩粒度分析表现了近岸环境的概率曲线特征。 （5）沉积岩矿物结构,成熟度较高,未见海相成因的粒级层理。 结论是唐古拉山区侏罗系应为近岸局限海环境下的沉积产物,在海退时期还发育了滨岸湖相沉积。 根据羌塘地区侏罗纪沉积相空间展布的特点,可以认为唐古拉山区侏罗系仅仅是大西洋型大陆边缘沉积的一个组成部分,是陆架大幅度坳陷所承受的巨厚陆源碎屑沉积,整个羌塘地区侏罗纪沉积在空间上的演替关系及其巨大厚度可借助于大西洋型大陆边缘特有的大陆堤前展沉积模式得到较好的解释。     

Geochemistry of deep formation waters in the Canning Basin,Western Australia,and their relationship to Zn‐Pb mineralization

The Canning Basin contains several Mississippi Valley‐type Zn‐Pb sulphide prospects and deposits in Devonian carbonate reef complexes on the northern edge of the Fitzroy Trough, and in Ordovician and Silurian marine sequences on the northern margin of the Willara Sub‐basin. This study uses the ionic composition and 5D, δ¹⁸O, δ³⁴S, ⁸⁷Sr/⁸⁶Sr isotopic data on present‐day deep formation waters to determine their origin and possible relationship to the Zn‐Pb mineralizing palaeofluids.

The present‐day Canning Basin formation waters have salinity ranging from typically less than 5000 mg/L up to 250 000 mg/L locally. The brines are mixtures of highly saline water, formed by seawater which evaporated beyond halite saturation (bittern water), with meteoric water ranging in salinity from low (<5000 mg/L) to hypersaline water (up to about 50 000 mg/L) formed by re‐solution of halite and calcium sulphate minerals. The original marine chemical composition of the bittern‐dominated brines was changed to that of a Na‐Ca‐Cl water by addition of Ca and removal of Mg and SO₄, initially by bacterial sulphate reduction and later by dolomitization of carbonate. Other reactions with terrigenous components of the sediment have provided additional Ca and Sr, including a small proportion of ⁸⁷Sr‐rich material. The δ³⁴S values of the bittern‐containing waters are within the range over which marine sulphate has fluctuated from the Ordovician to the Holocene, although one of the hypersaline waters has a value of +6.8%, indicating SO₄ of non‐marine origin. The pH of the bittern‐containing waters is low (about 5) and they contain significant concentrations of dissolved Fe (up to 120 mg/L).

The Canning Basin bitterns appear similar in origin and chemical composition to highly saline marine brines in the Mississippi Salt Dome Basin, USA, which are known to be either metal or sulphide‐rich depending on the organic content of the host rock. In the Canning Basin, mixing of the bittern water with the various types of meteoric water has resulted in decreases in salinity, Na, Ca, Mg, K, Sr, Li and Fe, and increases in HCO₃, SO₄ and pH.

Mixing of the bitterns with other types of metalliferous fluids and/or with sulphate‐containing hypersaline meteoric waters formed from the same marine evaporite sequence should produce ore‐precipitating fluids which are relatively hot and saline, and the resulting ore deposit should be of high grade and contain abundant sulphate minerals. In the southern Canning Basin, this type of mixing and the corresponding style of ore deposit is evident in the evaporite‐associated areas of Zn‐Pb mineralization near the Admiral Bay Fault. If the bitterns mix with low salinity HCO₃‐waters in near‐surface environments, then the ore‐precipitating fluids should have relatively low salinities and carbonate minerals would precipitate during later stages of mixing. In the Lennard Shelf, the present‐day formation waters, the style of the Zn‐Pb deposits, and range of salinity and temperature of the ore‐forming palaeofluids are consistent with this type of mixing.     

Sources of elevated salinity in the Mississippi River Alluvial Aquifer, south-central Louisiana, USA

Salinization is a process impacting groundwater quality and availability across much of southern Louisiana, USA. However, a broad divergence of opinion exists regarding the causes of this elevated salinity: updip-migrating marine waters from the Gulf of Mexico, saline fluids migrating up fault planes, movement of water from salt domes, and/or remnant seawater from the last major marine transgression. The Mississippi River Alluvial Aquifer (MRAA) in south-central Louisiana is recharged by the Mississippi River, and there are discharge zones to the west and east. Recharge waters from the Mississippi River are fresh, but Cl⁻ levels in the western portions of the aquifer are as high as 1000 mg/L. The aquifer is an important source of water for several municipalities and industries, but prior to this study the source(s) of the elevated salinity or whether the salinization can be remediated had not been determined.The low Br/Cl ratios in the groundwaters are consistent with a saline endmember produced by subsurface dissolution of salt domes, not a marine source. The H and O isotopic systematics of the aquifer waters indicate meteoric sources for the H₂O, not marine waters or diagenetically-altered deep brines. The westward salinization of aquifer water represents a broad regional process, instead of contamination by point sources. Mapping of spatial variations in salinity has permitted the identification of specific salt domes whose subsurface dissolution is producing waters of elevated salinity in the aquifer. These include the Bayou Choctaw and St. Gabriel domes, and possibly the Bayou Blue dome. Salinization is a natural, on-going process, and the potential for remediation or control is slight, if not non-existent.     

中国西北地区第四纪盐湖沉积中钙质超微化石的发现及其古环境意义

报导了中国西北地区的甘肃、青海、新疆等地陆相第四纪盐湖沉积中发现的钙质超微化石,它们主要是：Ｇｅｐｈｙｒｏｃａｐｓａｏｃｅａｎｉｃａ,Ｃｏｃｏｌｉｔｈｕｓｐｅｌａｇｉｃｕｓ,Ｃａｌｃｉｄｉｓｃｕｓｌｅｐｔｏｐｏｒｕｓ,Ｃ．ｍａｃｉｎｔｙｒｅｉ,Ｒｅｔｉｃｕｌｏｆｅｎｅｓｔｒａｍｉｎｕｔｕｌａ等。上述钙质超微化石群具有以下特征：（１）化石丰度中等,属、种分异度低,化石保存差;（２）赋存化石的层位均为富含石膏盐层的微咸水咸水的沉积物,或为盐湖沉积;（３）产出化石地点远距该地质时期时的古海岸线。它们与古海域既无通道相连,亦非残留海。中国西北地区盐湖沉积中钙质超微化石的发现说明了中国东部地区第三纪沙河街组某些层位中的钙质超微化石不能作为“海相生物”的标志,否定了这些化石层位与“海侵”或“海泛”的关联。     

察尔汗盐湖物质来源的研究

柴达木盆地察尔汗盐湖是一个以氯化物为主的盐湖,然而今天补给该盐湖的水是碳酸盐和硫酸盐型的。所以,该盐湖的物质来源问题是研究其成因的根本问题,也一直是中外学者感兴趣。同时又感到非常棘手的问题,他们提出了各种假说。本文综合了六化学、岩相古地理、Sr和Br的地球化学、古生态、同位素和构造方面的资料,对前人提出的各种假说逐一进行了论证,最后的结论是,察尔汗盐湖的盐类物质有三个来原:通过河流补给的地表化学风化淋滤物质、通过断层补给的油田水和柴达木古湖的遗留物质。否定了海水来源和第三纪含盐系风化淋滤来源的假说。 中更新世末,察尔汗湖从柴达木古湖中完全蚀立出来,并继承了部分从古湖遗留下来的盐类物质。在察尔汗湖蚀立过程中和独立后早期,构造运动比较强烈,通过断层补给的油田水较多,后来随着构造运动的减弱,油田水补给量逐渐减少,而地丧化学风化淋滤物质的补给一直是比较稳定的。     

贵阳市区地表/地下水化学与锶同位素研究

贵阳市及邻近地区地表和地下水的化学与Sr同位素组成变化反映了典型喀斯特地区地表/地下水文系统的水-岩反应和城市污染特征:水体中的化学溶解物质主要来源于碳酸盐岩(石灰岩和白云岩)的风化作用和膏岩层的溶解,其次为人为污染物的输入;污染物以K⁺,Na⁺,Cl^-,SO^2-₄,NO^-₃为主,枯水期因大气降水补给小而受人为活动影响较大;丰水期和枯水期地表/地下水的化学组成变化说明地表/地下水交换活跃,地下水环境容易受到人为活动影响。     

Geochemistry and origin of saline groundwaters in the Fennoscandian Shield

Chemical and isotopic analyses of water from drill holes and mines throughout the Fennoscandian Shield show that distinct layers of groundwater are present. An upper layer of fresh groundwater is underlain by several sharply differentiated saline layers, which may differ in salinity, relative abundance of solutes, and O, H, Sr and S isotope signature. Saline groundwater can be classified into four major groups based on geochemistry and presumed origin. Brackish and saline waters from 50–200 m depth in coastal areas around the Baltic Sea exhibit distinct marine chemical and isotopic fingerprints, modified by reactions with host rocks. These waters represent relict Holocene seawater. Inland, three types of saline groundwater are observed: an uppermost layer of brackish and saline water from 300–900 m depth; saline water and brines from 1000–2000 m depth; and superdeep brines which have been observed to a depth of at least 11 km in the drill hole on the Kola Peninsula, U.S.S.R. Electrical and seismic studies in shield areas suggest that such brines are commonly present at even greater depths. The salinity of all inland groundwaters is attributed predominantly to water-rock interaction. The main solutes are Cl, Ca, Na and Mg in varying proportions, depending on the host rock lithology. The abundance of dissolved gases increases with depth but varies from site to site. The main gas components are N₂, CH₄ (up to 87 vol.%) and locally H₂. The δ¹³C value for methane is highly variable (−25 to −46%), and it is suggested that hydrothermal or metamorphic gases trapped within the surrounding rocks are the most obvious source of CH₄. The uppermost saline water has meteoric oxygen-hydrogen isotopic compositions, whereas values from deeper water plot above the meteoric water line, indicating considerably longer mean residence time and effective low temperature equilibration with host rocks. Geochemical and isotopic results from some localities demonstrate that the upper saline water cannot have been formed through simple mixing between fresh water and deep brines but rather is of independent origin. The source of water itself has not been satisfactorily verified although superdeep brines at least may contain a significant proportion of relict Precambrian hydrothermal or metamorphic fluids.     

青海湖全新世以来古环境参数的研究

作者根据青海湖水下近代沉积物岩芯中胖真星介(Ｅｕｃｙｐｒｉｓｉｎｆｌａｔａ)壳微量碳酸盐占δ_１８Ｏ、δ_１３Ｃ以及单体介壳的微量元素分析，重建了青海湖区冰后期以来的古气候环境演化序列，并在此基础上通过对全湖湖水水温、盐度、同位素以及现生胖真星介的δ_１８Ｏ和微量元素分析，定量地求取了１２０００ａＢ．Ｐ．以来各时段的古湖盐度、水位和水温变化数据。研究结果表明：古青海湖在全新世早期湖水含盐量在２０ｇ／Ｌ上下波动，进入大西洋期湖水盐度才波动下降，５Ｏ００—２５００ａＢ．Ｐ．年间湖水含盐量在５ｇ／Ｌ以下，此后湖水盐度才缓慢上升，达到今日的１４．１３４ｇ／Ｌ；全新世早期古青海湖处于浅湖环境其平均水位比现代低约８ｍ，全新世高湖面出现在６５００、５１００和３９００—３１００ａＢ．Ｐ．年间，水位比现今仅高１７—１８ｍ；全新世大暖期的时限为９３００—５３００ａＢ．Ｐ．，该时段古湖平均水温比现代高１．８℃。     

柴达木盆地大浪滩盐矿床基本特征及形成机理

大浪滩盐矿床已定名的24种盐类矿物中,钾镁盐矿物占13种。光卤石为其中主要钾矿物,已富集成钾矿层。本文在对盐矿物分布规律及沉积物地球化球研究的基础上,阐明了盐湖演化发展规律及钾矿层与其他盐矿物的形成机理。