Quaternary Lake Deposits of Nam Co, Tibet, with a Discussion of the Connection of Nam Co with Ring Co-Jiuru Co

Shorelines are widespread and lake deposits and lake geomorphology are welldeveloped on the northern Tibetan Plateau. Through field observations of lacustrine deposits of NamCo-the highest and largest Quaternary lake in Tibet, the authors found four-step shore terracescomposed of sands and clays with well-developed horizontal bedding and 3-12 m, 15-22 m, 25-30 m and35-45 m higher than the lake surface respectively, lacustrine deposits resting on the bedrocks and60-150 m higher than the lake surface, and up to approx 50 levees composed of oblate lakeshoregravels. Moreover they found lacustrine and lakeshore deposits making up the terraces and levees onthe bottoms of wide dividing valleys connecting Nam Co with the Rencoyuema, Rencogongma and Jiuru Conorthwest of Nam Co (the valley bottoms are 20 m, 90 m and 60 m higher than the above-mentionedthree lakes) and on slopes north of it, i.e. terraces II and III of Nam Co. Thus they confirm thatNam Co and Ring Co-Jiuru Co had connected with each other several times, i.e. formed a unified largelake several times, rather than had been different lakes connected only by river channels. Fromindications such as the distribution of the highest shoreline and lake deposits and geomorphology,the authors conclude that the total area of the old large lakes on the northern Tibetan Plateau is afew times larger than that of the modern lakes and that the last-stage old large lakes formed inthe interglacial interval of the last glaciation.

Progress and Prospects of Salt Lake Research in China

China has unique salt lake resources, and they are distributed in the east of Eurasian salt lake subzone of the Northern Hemisphere Salt Lake Zone, mainly concentrated in the regions with modern mean annual precipitation lower than 500 mm. This paper preliminarily reviews the progress made in salt lake research in China for the past 60 years. In the research of Paleoclimate and paleoenvironment from salt lake sediments, a series of salts have been proposed to be indicators of paleoclimate, and have been well accepted by scholars. The chloride-sulfate depositional regions of the west Qaidam and the east Tarim have been revealed to be the drought center of China since the Quaternary, and more than 6 spreading stages of arid climate （salt forming） have been identified. Five pan-lake periods with highstands have been proved to exist during the late Quaternary on the Tibetan Plateau. In mineral resource prospecting and theories of the forming of salt deposits： the atlas （1：2500000） of hydrochemical zoning of salt lakes on the Tibetan Plateau has been compiled for the first time, revealing the zonal distribution and transition from carbonate type to chloride type from south to north and presenting corresponding mineral assemblages for different type of salt lakes; several large continental salt deposits have been discovered and the theory of continental potash deposition has been developed, including the salt deposition in deep basins surrounded by high mountains, the mineral deposition from multistage evolution through chains of moderate or shallow lakes with multilevels, the origin of potassium rich brines in gravel layers, and the forming of potassium deposits through the inheriting from ancient salt deposits, thus establishing the framework of ＂Continental Potash Deposition Theory＂; several new types of Mg-borate deposits have been discovered, including the ulexite and pinnoite bed in Da Qaidam Lake, Qinghai, the pinnoite and kurnakovite bed in Chagcam Caka, Tibet, the kurnakovite bed in Lake Nyer, and the corresponding model of borate deposition from the cooling and dissolution of boron rich brines was proposed based on principles of geology, physics and chemistry. The anti-floatation-cold crystallization method developed independently has improved the capacity of KCI production to 3 million tons per year for the Qarham, serving the famous brand of potash fertilizer products. One 1.2 million ton K-sulfate production line, the biggest in the world, has been built in Lop Nor, and K-sulfate of about 1.6 million tons was produced in 2015. Supported by the new technology, i.e. brine preparation in winter-cooling-solarization-isolation-lithium deposition from salt gradient solar pond＂ the highest lithium production base at Zabuye Lake （4421 m）, Tibet, has been established, which is the first lithium production base in China that reaches the year production of 5000 tons of lithium carbonate. The concept of Salt lake agriculture （Salt land agriculture） has been established based on the mass growth of Dunaliella and other bacillus-algae and the occurrence of various halophytes in saltmarsh and salt saline-alkali lands, finding a new way to increase arable lands and develop related green industry in salt rich environments. Finally this paper presents some new thoughts for the further research and development on salt science, and the further progress in salt science and technology will facilitate the maturing of the interdisciplinary science ＂Salinology＂.

Human impact recorded in the sediment of Honghu Lake, Hubei, China

Vertical profiles of the total organic carbon （TOC）, total nitrogen （TN）, phosphorus, susceptibilities, elements and partical size were analyzed in a short ^137Cs-dated sediment core collected from Honghu Lake, China. The average sedimentation rate was 1.55 mm/a. The results indicated that trophic status of Honghu Lake in the historical period had experienced three stages. Before 1840 the lake was characterized with lower productivity, TOC was less than 9.92 g/kg; TN was 0.902 to 1.24 g/kg. During about 1840-1950, population increased quickly, there was an obvious change in TOC with an average of 13.0 g/kg. Since 1950, human impacts have accelerated the lake eutrophication and nutrients enriched in the sediment with TOC of 21.7 to 93.1 g/kg, TN of 1.77 to 8.78 g/kg. The heavy metal concentration profiles presented similar distribution trends except Pb .and Mn. The results from elements analyses indicated that Honghu Lake had not been polluted by heavy metals except lead.

Geological characteristics and genesis of subbottom pinnoite deposit of Da Qaidam salt lake in Qaidam Basin

Da Qaidam salt lake is known for its both liquid and solid boron resource.Data from previous investigation of the Da Qaidam salt lake provided a comparable framework for this study that focused on investigating the section beneath the bottom of the perennial salt lake,including the timing,

Origin of boron in the Damxung Co Salt Lake(central Tibet):Evidence from boron geochemistry and isotopes

The origin of boron in boron-rich salt lakes in the Tibetan Plateau has long been the subject of debate.The Damzung Co Salt Lake in central Tibet has high boron concentrations(B=276–313 mg/L)and is an ideal site for

Chronostratigraphy and Stratigraphic Classification of the Cretaceous of the Songliao Basin

Isotopic ages of synsedimentary clay minerals were directly determined with the ultrasonicscattering-settlement separation-K-Ar dilution technique. The apparent age of black mudstoneis 123 Ma for the Quantou Formation, 111.9-89.0 Ma for the Qingshankou Formation and77.6-76.8 Ma for the upper part of the Nenjiang Formation. The Rb-Sr isochrone age of themuddy limestone-mudstone sequence of the lower part of the Nenjiang Formation is 81 Ma andthat of the muddy evaporite of the middle part of the Quantou Formation is 122.2 Ma. On thebasis of the above isotopic ages, the authors propose a modified scheme of stratigraphic classifi-cation of the Cretaceous of the Songliao basin.

The Discovery of the Quaternary Calcareous Nannofossils in the Deposits of Interior Saline Lakes from Northwestern China and its Paleoenvironmental Significance

A certain number of calcareous nannofos-sils were recovered in samples from the Qua-ternary deposits of interior saline lakes ofmore than ten localities in provinces of Qing-hai, Gansu and Xinjiang of China. They aremainly the Quaternary taxa, such

Evolution of an Eocene–Oligocene Saline Lake Depositional System and Its Controlling Factors, Jianghan Basin, China

The Upper Eocene–Lower Oligocene Qianjiang Formation of the Jianghan Basin in central China consists of a 4700-m-thick lacustrine succession, containing 1800 m of halite deposits. The maximum thickness of the formation is 4700 m, and includes 1800 m of halite. We have identified eight third-order depositional sequences based on pinch-out and onlap stratigraphic patterns in 2-D and 3-D seismic data and well logs. The basin evolved from a deep to shallow under-filled lake during the Eocene–Oligocene interval. The main rock types are dark mudstones, halite, and siltstone/sandstone in the depocenter, and alternating mudstone and gypsum in shallower areas. The vertical succession indicates a strong sedimentary cyclicity. Depositional facies indicate the presence of two lake system types. Halite developed in a saline lake system, whereas clastic sediments were deposited in freshwater lake systems. The alternating sediment types indicate that the basin cycled repeatedly between saline and freshwater lake systems. This cyclicity was caused by availability of accommodation space that was controlled by a combination of climate change, tectonic subsidence and sediment supply; notably, the highest frequency cycles occurred at Milankovitch timescales controlled by the Earth＇s orbital variations. The cyclic halite plays an important role in generating and preserving oil in the Qianjiang Formation of the Qianjiang depression.