Saline Lake Basin Research Articles

Quaternary evaporites of biogenic methane gas in the eastern Qaidam Basin, China

Biogenic methane is a variety of metabolites generated by methane bacteria, consuming a simple-nutrition organic substrate under anaerobic conditions. Due to the shallow depth at which it is generally produced, biogenic methane is easily released into the atmosphere, becoming a significant contributor to the greenhouse effect. However, if suitable collection methods are employed, biogenic methane can be gathered and used as a clean and efficient energy source. The Qaidam Basin is a large saline lake basin in the Tibetan Plateau, which is rich in biogenetic gas. During the Quaternary period, the area’s sedimentary center moved to the east of the Qaidam Basin. This resulted in the deposition of thick lacustrine sedimentary strata in the basin. Lacustrine mudstone is the primary source rock for biogenetic gas, and as a result, the gas is mostly found in the lacustrine strata of siltstone. In addition, evaporated lacustrine saline calcareous mudstone forms an effective covering layer for the gas. These lacustrine sedimentary strata provide both a favorable hydrocarbon accumulation environment and good preservation conditions for biogenic gas. As such, they could be converted into structural or lithologic gas reservoirs, through biogenic methane lateral migration with a suitable reservoir-cap configuration.

Genetic framework of Neogene–Quaternary basin closure process in central Turkey

Central Turkey represents the only orogenic plateau in the Mediterranean region. Also, the largest closed drainage basin and the largest intracontinental basin of Turkey, the Lake Tuz Basin, is located in this region. Results from a three-dimensional (3-D) computer modeling study of the Lake Tuz Basin indicate a southward-deepening freshwater lake basin with great depth in the Mio–Pliocene, which regressed toward the north during the Plio–Quaternary into the shallow saline lake basin it is today. The spatio-temporal variations of Neogene and Quaternary deposits reflect the main effects of internal forces (isostasy>volcanism>faulting) that were caused by lithospheric slab breakoff and subsequent asthenospheric upwelling under central Turkey. Climatic change played a relatively minor role during these periods and was closely associated with the results of internal forces.

Quantification and implica-tions of two types of soluble organic matter from brackish to saline lake source rocks

Two types of soluble organic matter, the free and adsorbed, were obtained and quantified from the brackish to saline lake source rocks. The adsorbed type was extracted with chloroform, solvent mixtures of methanol: acetone: chloroform (MAC) and CS2:N-methyl-2-pyrrolidinone (CS2/NMP). The total amounts of the two types of soluble organic matter from some immature source rocks are >830 mg/g TOC, more than 63% of the total organic matter in these samples. This result indicates that the majority of the organic matter in the immature source rocks in the brackish to saline lake basin is soluble, and is significant for study of petroleum formation and helpful for petroleum exploration in the brackish to saline lake basin.

Optical dating of tufa via in situ aeolian sand grains: a case example from the Southern High Plains, USA

Precipitated carbonates (commonly termed tufas or travertines) maybe of considerable utility for palaeoenvironmental reconstruction. Their potential, however, for such reconstruction is commonly limited by difficulties associated with their absolute age control. Attempts to date such deposits via uranium series techniques have been complicated by their chemically open behaviour. Here we describe an alternative approach to date tufa deposits associated with ephemeral saline lake basins from the Southern High Plains, USA. We have optically dated sand grains of a mixed aeolian/fluvial (spring fed) origin as the integrating dosimeter. We assume that the grains are fully resetting prior to their incorporation into the tufa deposits and employ a time-dependent disequilibrium dosimetric model to account for the build-up of uranium series daughter products. The approach was applied to a set of four samples with known stratigraphic association. We obtained stratigraphically sensible optical ages ranging from 78±8 to 56±4 ka. These data are consistent with existing palaeoenvironmental models of regional recharge.

Subdividing the Pleistocene using the Matuyama–Brunhes boundary (MBB): an Australasian perspective

The last major reversal of the Earth's magnetic field, the Matuyama–Brunhes boundary (MBB), dated at 0.78 Ma, is widely identified in Australian and New Zealand Pleistocene deposits. In New Zealand, the MBB is precisely located in shallow marine sediments of Wanganui Basin, where it corresponds with the base of the New Zealand Putikian Substage. A combination of marine biostratigraphy, sequence stratigraphy and tephrostratigraphy permit correlation from Wanganui Basin to other on-land sections and deep-sea cores. In Australia, the MBB is identified in many continental sequences, particularly saline lake basins. However, chemical weathering has resulted in variable Brunhes-age normal overprints that are sometimes difficult to remove. Australasian tektites are a potential lithostratigraphic marker just prior to the MBB, but have yet to be identified in the same on-land section as the MBB in Australia. Identification of reverse polarity magnetisation in weathered deposits, including soils, provides a minimum age of 0.78 Ma for these materials. A widespread arid shift in paleoclimate succeeded the MBB in Australia. Placement of the Lower–Middle Pleistocene boundary at the MBB would constitute the most recognisable chronostratigraphic marker in weathered continental deposits.

Lower Miocene gypsum palaeokarst in the Madrid Basin (central Spain): dissolution diagenesis, morphological relics and karst end‐products

Abstract The Miocene sedimentary record of the Madrid Basin displays several examples of palaeokarstic surfaces sculpted within evaporite formations. One of these palaeokarstic surfaces represents the boundary between two main lithostratigraphic units, the Miocene Lower and Intermediate units of the Madrid Basin. The palaeokarst formed in lacustrine gypsum deposits of Aragonian age and corresponds to a surface palaeokarst (epikarst), further buried by terrigenous deposits of the overlying unit. Karst features are recognized up to 5·5 m beneath the gypsum surface. Exokarst and endokarst zones are distinguished by the spatial distribution of solution features, i.e. karren, dolines, pits, conduits and caves, and collapse breccias, sedimentary fills and alteration of the original gypsum across the karst profiles. The development of the gypsum palaeokarst began after drying out of a saline lake basin, as supported by recognition of root tubes, later converted to cylindrical and funnel‐shaped pits, at the top of the karstic profiles. The existence of a shallow water table along with low hydraulic gradients was the main factor controlling the karst evolution, and explains the limited depth reached by both exokarst and endokarst features. Synsedimentary fill of the karst system by roughly laminated to massive clay mudstone with subordinate carbonate and clastic gypsum reflects a punctuated sedimentation regime probably related to episodic heavy rainfalls typical of arid to semi‐arid climates. Duration of karstification is of the order of several thousands of years, which is consistent with previous statements that gypsum karstification can develop rapidly over geologically short time periods.

Role of ground water in geomorphology, geology, and paleoclimate of the Southern High Plains, USA.

Study of ground water in the Southern High Plains is central to an understanding of the geomorphology, deposition of economic minerals, and climate change record in the area. Ground water has controlled the course of the Canadian and Pecos rivers that isolated the Southern High Plains from the Great Plains and has contributed significantly to the continuing retreat of the westward escarpment. Evaporative and dissolution processes are responsible for current plateau topography and the development of the signature 20,000 small playa basins and 40 to 50 large saline lake basins in the area. In conjunction with eolian processes, ground water transport controls the mineralogy of commercially valuable mineral deposits and sets up the distribution of fine efflorescent salts that adversely affect water quality. As the water table rises and retreats, lunette and tufa formation provides valuable paleoclimate data for the Southern High Plains. In all these cases, an understanding of ground water processes contributes valuable information to a broad range of geological topics, well beyond traditional interest in water supply and environmental issues.

Biogeochemistry of silica in Devils Lake: implications for diatom preservation

Diatom-salinity records from sediment cores have been used to construct climate records of saline-lake basins. In many cases, this has been done without thorough understanding of the preservation potential of the diatoms in the sediments through time. The purpose of this study was to determine the biogeochemistry of silica in Devils Lake and evaluate the potential effects of silica cycling on diatom preservation. During the period of record, 1867–1999, lake levels have fluctuated from 427 m above sea level in 1940 to 441.1 m above sea level in 1999. The biogeochemistry of silica in Devils Lake is dominated by internal cycling. During the early 1990s when lake levels were relatively high, about 94% of the biogenic silica (BSi) produced in Devils Lake was recycled in the water column before burial. About 42% of the BSi that was incorporated in bottom sediments was dissolved and diffused back into the lake, and the remaining 58% was buried. Therefore, the BSi accumulation rate was about 3% of the BSi assimilation rate. Generally, the results obtained from this study are similar to those obtained from studies of the biogeochemistry of silica in large oligotrophic lakes and the open ocean where most of the BSi produced is recycled in surface water. During the mid 1960s when lake levels were relatively low, BSi assimilation and water-column dissolution rates were much higher than when lake levels were high. The BSi assimilation rate was as much as three times higher during low lake levels. Even with the much higher BSi assimilation rate, the BSi accumulation rate was about three times lower because the BSi water-column dissolution rate was more than 99% of the BSi assimilation rate compared to 94% during high lake levels. Variations in the biogeochemistry of silica with lake level have important implications for paleolimnologic studies. Increased BSi water-column dissolution during decreasing lake levels may alter the diatom-salinity record by selectively removing the less resistant diatoms. Also, BSi accumulation may be proportional to the amount of silica input from tributary sources. Therefore, BSi accumulation chronologies from sediment cores may be effective records of tributary inflow.

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.

Eolian transport, saline lake basins, and groundwater solutes

Eolian processes associated with saline lakes are shown to be important in determining solute concentration in groundwater in arid and semiarid areas. Steady state mass balance analyses of chloride in the groundwater at Double Lakes, a saline lake basin in the southern High Plains of Texas, United States, suggest that approximately 4.5 × 105 kg of chloride is removed from the relatively small (4.7 km2) basin floor each year by deflation. This mass enters the groundwater down the wind gradient from the lake, degrading the water quality. The estimates of mass transport were independently determined by evaluation of solutes in the unsaturated zone and by solute mass balance calculations of groundwater flux. Transport of salts from the lake was confirmed over a short term (2 years) by strategically placed dust collectors. Results consistent with those at Double Lake were obtained from dune surfaces collected upwind and downwind from a sabkha near the city of Abu Dhabi in the United Arab Emirates. The eolian transport process provides an explanation of the degraded groundwater quality associated with the 30–40 saline lake basins on the southern half of the southern High Plains of Texas and New Mexico and in many other arid and semiarid areas.

Landscape perspectives on possible land use patterns for Early Pleistocene hominids in the Olduvai Basin, Tanzania

Abstract We present an ecologically derived model of the distribution of potential resources probably available to hominids among the landscapes that are, following Hay (1976), postulated to exist in the Olduvai Basin during lowermost Bed II times. On the basis of preliminary surveys of the resource structure of modern East African saline lake basins, the differential availability across the Olduvai Basin of potable water, fruit and edible rootstocks, refuge trees, scavengeable carcasses and stone/wood for tool manufacture, are hypothesized for a riparian corridor and stream-mouth dominated land system at two climate extremes. At both climate extremes, the stream-traversed Piedmont Alluvial Plain and slopes of the Crater Highlands to the east of the lake apparently would have provided the greatest availability and diversity of essential resources. In contrast, the Eastern Lacustrine Plain, to which current in situ archaeological evidence for hominid activities is restricted, was probably not as rich in resources. The resource distribution model suggests that hominid activities were concentrated in landscapes that have not been intensively studied. One of these, the Piedmont Alluvial Plain, is partially preserved in the geological record, and is predicted to contain a strong land use signature despite having experienced reworking of materials. This and other predictions of the model are amenable to testing through the landscape archaeological research being conducted on lowermost Bed II deposits, which also have a bearing on understanding the different land use strategies of contemporaneous hominid taxa.

Deposition of modern pollen and plant macroremains in a hypersaline prairie lake basin

Comparisons between current vegetation patterns and deposition of modern pollen and plant macroremains in a saline lake basin on the northern Great Plains are used to assess the value of plant remains as indicators of past local vegetation dynamics and lake-level changes. Results indicate that both modern pollen spectra and assemblages of plant macroremains reflect clearly the composition of the local vegetation, whereas plant macroremains best reflect lake size. Cactaceae pollen and seeds are confined to upland prairie deposits. Liguliflorae (Compositae) and Leguminosae pollen, Selaginella densa microspores, and Euphorbia and Cruciferae seeds are more abundant in prairie upland deposits than in shoreline or lacustrine environments. An abundance (> 50%) of Ruppia pollen distinguishes near-shore lake sediments, indicating that this taxon is a useful marker of shallow shoreline environments in saline lakes. Seeds of Chenopodiaceae, Erigeron, Cruciferae, and Cyperaceae, as well as Chara oogonia, are more abundant in near-shore lacustrine sediments than in the central lake area, suggesting that they too are indicators of shoreline proximity. These data are useful for paleobotanical reconstructions of past lake-level dynamics. Key words: saline lakes, Great Plains, pollen, paleobotany, paleohydrology, environmental reconstruction.

PHYSICS AND CHEMISTRY OF SALINE LAKES

本文根据近年来有关咸水湖的研究文献,介绍了咸水湖的概念、地理分布和湖盆的成因。进而从咸水湖的光学特性和热学特性两个方面阐述了湖泊的物理特性;从湖水盐度、蒸发和盐度、盐分来源,湖水的化学成分和类型以及盐湖的演化等方面说明咸水湖的化学特点;最后,从盐类沉积和古气候古环境关系的角度出发,指出咸水湖的古湖沼学研究在过去全球变化历史的重建中具有巨大的潜力,是全球研究体系中不可缺少的部分。;According to the recent research literatures on saline lakes, the conception of saline lake, geographical distribution and lake basin origin is introduced. The physical research realms of saline lake are illustrated from both optical properties (transparency, colour, turbidity, attenuation) and thermal characteristics, contemporaneously, the chemical features of saline lakes are mentioned from salinity, evaporation and salinity, salt sources,chemical composition and types of saline water and evolution of saline lakes. From the viewpoint of relationship between salty deposits and paleoclimate, it is evident that the paleolimnological studies of saline lakes show a great potantiality for reconstructing the history of past global change, an important part in global research system.

Recent carbonate sedimentation and brine evolution in the saline lake basins of the Cariboo Plateau, British Columbia, Canada

Recent carbonate sedimentation and brine evolution in the saline lake basins of the Cariboo Plateau, British Columbia, Canada

Geochemical characteristics of crude oils and source beds in different continental facies of four oil-bearing basins, China

Summary In order to correlate Chinese continental crude oils with their sources and, thus, the different depositional facies of the sources, the geochemical characteristics of crude oils and of extracts from related source rocks in four different types of continental facies were studied. The four types of facies were those of (1) inland and paralic freshwater to brackish lake basins, (2) saline lake basins, (3) inland swampy lake and swamp basins, and (4) terrestrial and marine intertonguing facies basins. Oils from these facies show both similarities and differences. Some specific biomarkers, such as the stereoisomers of onocerane, serratane and long chain acyclic polymethylalkanes which could be useful indicators of a palaeoenvironment, are also discussed. All the components were identified using mass spectrometry and a few retention index data: therefore, the identification of some compounds must be tentative.