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Chronology of Holocene lacustrine sediments in Co Ngoin, central Tibetan Plateau

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Science China Earth Sciences 2006年第9期49卷 991-1001页

作者： WU Yanhong1, WANG Sumin1& HOU Xinhua1,3 1. Key Laboratory of Lake Sedimentation and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China 2. Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 10085, China 3. Graduate University of Chinese Academy of Sciences, Beijing 100039, China 1. Key Laboratory of Lake Sedimentation and Environment Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China 2. Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 10085 China 3. Graduate University of Chinese Academy of Sciences Beijing 100039 China

Chronology is the basis for using lacustrine sediments to reconstruct the history of en-vironmental change. Radioactive-nuclides such as 14C, 210Pb and 137Cs dating are mainly used to establish the chronology for recent several ten thousand years. Because of being mixed with “dead carbon”, the measured 14C age is always older than the actual age which is recognized as “reservoir effect”. Cs is a kind of active metal element, and easy to migrate vertically in the sediment that leads to the error of the time marker. 210Pb dating should make sure to select CIC model or CRS model. On the Tibetan Plateau, most of the lakes are alkaline closed lake where Cs is more moveable in the sediment and the reservoir effect caused by “dead carbon” on 14C dating is stronger. Based on the analysis on results of 14C, 210Pb and 137Cs of the lacustrine sediments from Co Ngoin, central Tibetan Plateau, we use the simple regression method to re-calculate the 14C calendar ages, and establish the time sequence for cores CE-1 and CE-2 with result of 210Pb CRS model for the upper 35 cm and re-calculated 14C calendar age for sediments bellow 35 cm. Since 1400 cal. a BP, sedimentation inter-rupted for more than 1000 years. According to this time sequence, variations of environmental proxies confidently reflect the major climatic events in Holocene.

关键词： 14C, 210Pb and 137Cs, chronology, lacustrine sediments, climatic event, Co Ngoin, central Tibetan Plateau.

Environmental characteristics of Mid-Holocene recorded by lacustrine sediments from Lake Daihai, north environment sensitive zone, China

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Science China Earth Sciences 2006年第9期49卷 968-981页

作者： SUN Qianli1,2, ZHOU Jie1, SHEN Ji3, CHEN Peng1,2, WU Feng1,2 & XIE Xiuping1,2 1. State Key Lab of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710075, China 2. Graduate University of Chinese Academy of Sciences, Beijing 100039, China 3. Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China 1. State Key Lab of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an 710075 China 2. Graduate University of Chinese Academy of Sciences Beijing 100039 China 3. Nanjing Institute of Geography and Limnology Chinese Academy of Sciences Nanjing 210008 China

Climate proxies, such as total organic carbon and nitrogen (TOC, TN), carbonate content (CaCO3), grain-size and pollen of the sediment core retrieved from enclosed Lake Daihai which lies in the north China environment sensitive zone are analyzed to reconstruct the environment evolution of the area based on high-resolution radiocarbon chronology. The results reveal that the TOC and TN contents of the sediments correlate well with pollen percentage and pollen flux variations during the Holocene, and both reach their peak values simultaneously at 6.7―3.5 ka BP (calendar age, 7.6―3.6 ka BP). Since 6.7 ka BP, both the CaCO3 and organic matter contents of the core have simultaneous variations, and their high values also occur during 6.7―3.5 ka BP. While during 9.0―6.7 ka BP (calendar age, 10―7.6 ka BP) relatively lower level of organic matter content and pollen flux corre- spond to the higher level of carbonate content. The above relations suggest that during 6.7―3.5 ka BP, the productivity and effective precipitation were greatly improved in the lake drainage area, and this would probably strengthen the hydrodynamic conditions, enhancing organic matter, pollen and carbonate inputs from terrestrial sources. Such processes would account for the enrichment of both organic matter and carbonate in the sediments. While during 9.0―6.7 ka BP, the lower level of or- ganic matter, pollen flux but high carbonate content show depressed productivity and declined vege- tation coverage. The higher carbonate content at this stage would have probably resulted from the higher evaporation ratio of the lake water under relatively drier climate conditions. Therefore, it is in- ferred that during 6.7―3.5 ka BP, the climate was more humid with abundant rainfalls and vegetation was more flourishing in the Lake Daihai area. This can be seen as Holocene Climate Optimum (HCO). As a result, this has evident discrepancies with the traditional notion that the HCO occurs at Early Holocene or early Mid

关键词： Lake Daihai, Mid-Holocene, lacustrine sediments, environmental characteristics.

lacustrine SEDIMENTS—AN INDICATOR OF HISTORICAL CLIMATIC VARIATION——THE CASE OF QINGHAI LAKE AND DAIHAI LAKE

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Chinese Science Bulletin 1991年第16期36卷 1364-1368页

作者：王苏民李建仁 Nanjing Institute of Geography and Limnology Academia Sinica Nanjing 210008 PRC

lacustrine sediments, especially those of the closed lakes in semi-arid and arid areas, preserve abundant information and hence the lakes serve as an indicator of climatic and environmental changes, characterized by its continuity, sensitivity and high resolution. Now the studies on lake environmental changes on different time scales have become an important basis for establishing global climatic model. In order to study the characteristics of

关键词： lacustrine sediments climatic variation quasi-periodicity.

Scale-Dependent Nature of Porosity and Pore Size Distribution in lacustrine Shales: An Investigation by BIB-SEM and X-Ray CT Methods

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Journal of Earth Science 2019年第4期30卷 823-833页

作者： Junqian Li Pengfei Zhang Shuangfang Lu Chen Chen Haitao Xue Siyuan Wang Wenbiao Li School of Geosciences China University of Petroleum (East China)

Due to heterogeneous pore distributions within shales,petrophysical properties of shales determined by scanning electron microscopy(SEM) and X-ray computed tomography(CT) methods strongly depend on the observed domain size(analysis scale). In this paper,the influence of the analysis scale on areal and bulk porosities and pore size distribution(PSD) for lacustrine shales from the Dongying sag of Bohai Bay Basin,China were investigated using broad ion beam(BIB)-SEM and X-ray CT *** BIB-SEM cross-sections with high imaging resolution(10 nm/pixel) and a large field of view(>1 mm2)mainly describe the 2 D nanoscale pore system in the two shales(samples F41#-2 and Y556#-1),while CTbased 3 D reconstructions with resolutions of 0.42(F41#-1) and 0.5 μm/pixel(H172#-1) reflect the 3 D submicron pore system. The results indicate that the areal(bulk) porosity exhibits a multiple power-law distribution with increasing analysis area(volume),which can be used to extrapolate the porosity of a given area(volume). Based on SEM and CT investigations,the sizes of the minimum representative elementary areas(REAs) and volumes(REVs) were determined respectively,which are closely associated with the heterogeneousness of the pore system. Minimum REAs are proposed to be 2.93×10~4(F41#-2) and 0.91×10~4μm2(Y556#-1),and minimum REVs are 0.016(F41#-1) and 0.027 mm^3(H172#-1). As the analyzed areas(volumes) are larger than the minimum REA(REV),obtained 2 D(3 D) PSDs are comparable to each other and can be considered to reflect the shale PSD. These results provide insights into the porosity and PSD characterization of shales by SEM and X-ray CT methods.

关键词： lacustrine shale porosity pore size distribution BIB-SEM X-ray CT

Characterization of a lacustrine Shale Reservoir and the Evolution of its Nanopores: A Case Study of the Upper Cretaceous Qingshankou Formation in the Songliao Basin, Northeastern China

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Acta Geologica Sinica(English Edition) 2020年第2期94卷 337-351页

作者： ZHANG Xu LIU Chenglin LI Bing WU Linqiang GUI Herong WANG Ziling ZHANG Zhihui LIANG Dexiu State Key Laboratory of Petroleum Resource and Prospecting China University of PetroleumBeijing 102249China College of Geosciences China University of Petroleum.Beijing 102249China National Engineering Research Center of Coal Mine Water Hazard Controlling(Suzhou University) SuzhouAnhui234000China Geological Exploration Technology Institute of Anhui Province Hefei 230031China Development and Research Center China Geological SurveyBeijing 100037China

The Songliao Basin is one of the most important petroliferous basins in northern China. With a recent gradual decline in conventional oil production in the basin, the exploration and development of unconventional resources are becoming increasingly urgent. The Qingshankou Formation consists of typical Upper Cretaceous continental strata, and represents a promising and practical replacement resource for shale oil in the Songliao Basin. Previous studies have shown that low-mature to mature Qingshankou shale mainly preserves type Ⅰ and type Ⅱ1 organic matter, with relatively high total organic carbon(TOC) content. It is estimated that there is a great potential to explore for shale oil resources in the Qingshankou Formation in this basin. However, not enough systematic research has been conducted on pore characteristics and their main controlling factors in this lacustrine shale reservoir. In this study, 19 Qingshankou shales from two wells drilled in the study area were tested and analyzed for mineral composition, pore distribution and feature evolution using Xray diffraction(XRD), scanning electron microscopy(SEM), low-pressure nitrogen gas adsorption(N2-GA), and thermal simulation experiments. The XRD results show that clay, quartz, and feldspar are the dominant mineral constituents of Qingshankou shale. The clay minerals are mostly illite/smectite mixed layers with a mean content of 83.5%, followed by illite, chlorite, and kaolinite. There are abundant deposits of clay-rich shale in the Qingshankou Formation in the study area, within which many mineral and organic matter pores were observed using SEM. Mineral pores contribute the most to shale porosity;specifically, clay mineral pores and carbonate pores comprise most of the mineral pores in the shale. Among the three types of organic matter pores, type B is more dominant the other two. Pores with diameters greater than 10 nm supply the main pore volume;most are half-open slits and wedge-shaped pores. The total por

关键词： lacustrine shale pore structure pore evolution Upper Cretaceous Songliao Basin

Palaeoenvironmental setting of lacustrine stromatolites in the Miocene Wudaoliang Group, northern Tibetan Plateau

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Journal of Palaeogeography 2019年第3期8卷 270-284页

作者： Ling-Qi Zeng Hai-Sheng Yi Guo-Qing Xia Klaus Simon Christine Heim Gernot Arp Institute of Sedimentary Geology Chengdu University of Technology Chengdu 610059 Sichuan Province China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu 610059 Sichuan Province China Geoscie nee Center Georg-August-Universitat Gottingen GoldschmidtstraBe 3 37077 Gottingen Germany

lacustrine stromatolites were widespread in the Miocene Wudaoliang Group(stromatolites of the Wudaoliang Group), northern Tibetan Plateau;but only at one location nearby the Wudaoliang Town, they occurred intensively in thick, laterally traceable beds(Wudaoliang stromatolites). Although deposited in lacustrine environment, the lack of fossils in these rocks hampers determining whether the stromatolites formed in freshwater or saline *** address this problem, and in an attempt to identify criteria to distinguish differences of freshwater and saline conditions, we studied the laminae microfabrics, stable carbon and oxygen isotope ratios, rare earth element patterns and biomarkers of the stromatolites. These stromatolites can be divided into fenestral stromatolites and agglutinated stromatolites. The fabric of fenestral stromatolites is formed by microcrystalline carbonate enclosing spar-cemented, angular crystal traces. Essentially, this fabric is interpreted as pseudomorph after former formed evaporite crystals. Faecal pel ets identical to that of the present-day brine shrimp Artemia, lack of other eukaryotic fossils,and stable isotopic signals point to a shal ow, evaporation-dominated hypersaline lake setting. Covariation of carbon and oxygen isotopes indicates hydrological y closed conditions of the Miocene lake on northern Tibetan ***, if compared to other lacustrine carbonates of the Wudaoliang Group, the high δ13 C values of the investigated Wudaoliang stromatolites reveal an additional photosynthetic effect during the deposition of the ***, although no direct evidence is available from field observations and microfabrics, a positive europium anomaly of Wudaoliang stromatolites indicates that a palaeo-hydrothermal inflow system had existed in the outcrop *** new results favour a hypersaline lake setting subject to hot spring inflow for the Wudaoliang stromatolites, in contrast to earlier interpretations suggesti

关键词： lacustrine stromatolites Miocene Wudaoliang Group Hypersaline lake Hydrothermal Northern Tibetan plateau

Some contributions to mechanical behaviors of lacustrine deposit in Bogota, Colombia

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第4期11卷 837-849页

作者： Bernardo Caicedo Cristhian Mendoza Arcesio Lizcano Fernando Lopez-Caballero Department of Civil and Environmental Engineering Universidad de Los AndesBogotaColombia Department of Civil Engineering Universidad Nacional de Colombia Sede ManizalesManizalesColombia SRK Consulting VancouverCanada Laboratoire MSS-Mat CNRS UMR8579CentraleSupelecParis-Saclay UniversityFrance

This paper presents the mechanical behaviors of the lacustrine deposit,a representative soil in Bogota,***,the physical characterization of the deposit is performed via laboratory tests (grain size distribution,scanning electron microscopy,Atterberg limits and water content).This characterization intends to explain the special characteristics of the mechanical behaviors of this ***,various triaxial tests are carried out with controlled loading path,strain rate change,relaxation,extensile stress,and cyclic *** test results reveal the shape of the yield curve for Bogotá soil (in a natural state),and also show that an increasing effect of the strain rate depends on the liquid *** effect is also preserved with extensile stresses (which are poorly studied in soil mechanics).Finally,other effects,such as the loss of structure in the reconstituted samples and the effect of shear modulus at low strains,are studied for Bogota soil.

关键词： Cyclic triaxial tests Triaxial compression test Time-dependent response lacustrine soils Soil compressibility Yield curve

The Sedimentation and Formation Mechanism of lacustrine Endogenic Debris Flow

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Acta Geologica Sinica(English Edition) 1992年第2期66卷 119-140,220-221页

作者： Wang Deping Institute of Geology, Shengli Petroleum Administration, Dongying, Shandong Liu Linqun Institute of Geology Shengli Petroleum Administration Dongying Shandong

The debris flow formed by mass transportation of lacustrine deltaic sediments is quite unique comparedwith subaerial one, and is called 'endogenic debris flow' in this paper. The major diagnostic features ofendogenic debris flow sediments are muddy rip-ups, sandy lumps, randomly distributed carbonaceous plantleaves and rhyotaxitic structure. However, such debris flow can not be completely generalized by the conclu-sion that larger granules are supported by cohesive strength of the matrix. The fact that sediments can betransported in plastic state is considered to be related with two different functions of combined clay-water ma-terials: serving as a matrix in texture and as an adhesive between grains. This paper also discusses the originand sediment types of endogenic debris flow as well as the general concepts of matrix and debris flow. From the viewpoint of 'true debris flow', this paper attempts to generalize and illustrate the basic featuresand variation of endogenic debris flow sediments on the basis of the Bingham (Coulomb-viscosity) model.

关键词： debris lacustrine sedimentary Bingham adhesive texture granules viscosity bedding gentle

Environmental records of lacustrine sediments in different time scales:Sediment grain size as an example

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Science China Earth Sciences 2004年第10期47卷 954-960页

作者： CHEN Jing’an1, WAN Guojiang1, David Dian Zhang2, ZHANG Feng1 & HUANG Ronggui1 1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China 2. Department of Geography and Geology, University of Hong Kong, Pokfulam Road, Hong Kong, China 1. State Key Laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences 550002 Guiyang China 2. Department of Geography and Geology University of Hong Kong Pokfulam Road Hong Kong China

Sediment grain size is a conventional proxy of climatic changes. Larger sediment grain size is often interpreted to indicate dry climate during lower lake level while smaller sedi- ment grain size implies wet climate during higher lake level. Through detailed study on sediment grain sizes in Lake Erhai and Lake Chenghai, this paper reveals the different indication signifi- cances of sediment grain sizes in different time scales, different resolution investigations. For long time-scale and low resolution (102a or 103a) studies, larger sediment grain size indicates lower lake level, smaller lake area and drier climate while smaller sediment grain size indicates higher lake level, larger lake area and wetter climate. For short time-scale and high resolution (a or 10a) studies, larger sediment grain size reflects more rainfall and wetter climate while smaller sediment grain size reflects less rainfall and drier climate. Environmental information revealed by lacustrine sediment records is often different in different time scales because of the variance of sedimentation resolution, sampling resolution and dating precision. Therefore, paleoclimate im- plications of environmental proxies in long time-scale and low resolution investigations could not be mechanically applied to short time-scale and high resolution studies. Only after synthetically analyzing the influence manner and extent of all factors on the sediment records in different time scales, can credible conclusions be obtained.

关键词： lacustrine sediment, environmental record, grain size, time scale.