The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help recon...The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abundant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identification of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.展开更多
This study identified soft-sediment deformation structures (SSDS) of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation stru...This study identified soft-sediment deformation structures (SSDS) of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.展开更多
Sediments of the western part of the Valjevo-Mionica basin (Serbia) were examined both geochemically and mineralogically to explain, on the basis of their sedimentologicai characteristics, the causes of changes in t...Sediments of the western part of the Valjevo-Mionica basin (Serbia) were examined both geochemically and mineralogically to explain, on the basis of their sedimentologicai characteristics, the causes of changes in their qualitative and quantitative composition. A total of 62 samples obtained from the drillhole at depths up to 400 m was investigated. Using correlation of the obtained data, six geochemical zones were defined, two of which being specially distinguished by their mineralogical, geochemical and sedimentological characteristics. The first one, upper zone A, consists of banded marlstones interbedded with clay and oil shales and is characterized by presence of analcite and searlesite. These minerals and very high contents of Na20 indicate sedimentation in alkaline conditions with increased salinity in arid climate. That provided pronounced water stratification, as well as higher bioproductivity in the basin and sedimentary organic matter preservation. Therefore, the zone A sediments are characterized by high organic matter contents of the type which provides good potential for production of liquid hydrocarbons. Another specific zone, zone F, contains sediments with very high MgO, K2O and Li concentrations. Their geochemical correlation, as well as almost complete absence of illite in this zone, indicates the presence of interstratified clay mineral type illite-saponite (lithium-bearing Mg-smectite).展开更多
1 Introduction The Qarhan Playa of Qaidam Basin is located at the northeastern QinghaiTibetan Plateau(QTP),in which thick lacustrine and evaporate sediments deposited since the late Pleistocene(Chen et al.,1985,1986)....1 Introduction The Qarhan Playa of Qaidam Basin is located at the northeastern QinghaiTibetan Plateau(QTP),in which thick lacustrine and evaporate sediments deposited since the late Pleistocene(Chen et al.,1985,1986).As surrounded by capacious Gobi and yardang fields and suffered strong westerly-northwesterly wind,abundant aeolian materials were trapped in these sediment sequences in the展开更多
This paper aims to investigate the present situation and transfer mechanisms of microplastics in lacustrine sediments in the Qinghai-Tibet Plateau.The study surveyed the average abundance of microplastics in sediments...This paper aims to investigate the present situation and transfer mechanisms of microplastics in lacustrine sediments in the Qinghai-Tibet Plateau.The study surveyed the average abundance of microplastics in sediments.The abundance of microplastics in sediments of lakes from the Qinghai-Tibet Plateau is 17.22-2643.65 items/kg DW and 0-60.63 items/kg DW based on the data of the Qinghai Lake and the Siying Co Basin.The microplastic abundance in sediments from small and medium lakes is very high compared to that in other areas in the world.Like microplastics in other lakes of the world,those in the lakes in the Qinghai-Tibet Plateau mainly include organic polymers PA,PET,PE,and PP and are primarily in the shape of fibers and fragments.The microplastic pollution of lacustrine sediments in the Qinghai-Tibet Plateau is affected by natural changes and by human activities,and the concentration of microplastics in lacustrine ecosystems gradually increases through food chains.Furthermore,the paper suggests the relevant administrative departments of the Qinghai-Tibet Plateau strengthen waste management while developing tourism and pay much attention to the impacts of microplastics in water environments.This study provides a reference for preventing and controlling microplastic contamination in the Qinghai-Tibet Plateau.展开更多
Pearl River Mouth Basin undergoes complex tectonic evolution processes and forms lacustrine,transitional and marine sediments.Drilling shows that there exist large petroleum reserves in the hydrocarbon-rich sags of Pe...Pearl River Mouth Basin undergoes complex tectonic evolution processes and forms lacustrine,transitional and marine sediments.Drilling shows that there exist large petroleum reserves in the hydrocarbon-rich sags of Pearl River Mouth Basin,South China Sea.To reduce the risk,the exploration,structural and sedimentary characteristics of the hydrocarbon-rich sags should be identified and described.Drilling,seismic,and microfossil data are integrated to interpret the structural and sedimentary evolution of the hydrocarbon-rich sags in Pearl River Mouth Basin.By analyzing the tectonic and sedimentary evolutionary characteristics,three conclusions may be drawn:1、The present regional tectonic characteristics of the PRMB are formed by mutual interactions of the Eurasian Plate,Pacific Plate,Philippine Plate and Indian Plate.During the Paleocene to early Eocene and late Eocene and early Oligocene,the PRMB is at the rifting stage.During the late Oligocene,the PRMB was at the rifting-depression transitional stage.After the Oligocene,the PRMB is at the depression stage.2、Tectonic conditions control the sedimentation process in the hydrocarbon-rich sags.During the lacustrine sedimentation stage,synsedimentary faults and intense faulting control the sedimentation.During the transitional sedimentation stage,weak fault activity influences the deposition process in the hydrocarbon-rich sags.During the marine sedimentation stage,weak fault activity and depression activity control the deposition process in the hydrocarbon-rich sags.3、Tectonic evolution affects the deposition process.The lacustrine,transitional and marine sedimentation corresponds to different tectonic conditions.The lacustrine sedimentation is formed under fault activity during the rifting stage.The transitional sedimentation is formed under weak fault activity during the late rifting stage.The marine sedimentation is formed under weak fault activity and depression activity during the rifting-depression and depression stages.4、The half graben is beneficial for the formation of lacustrine source rocks,which is responsible for the hydrocarbon-rich sag.Therefore the half graben mode contributes to the hydrocarbon-rich sags.展开更多
Sequences of wave-enhanced sediment-gravity flows(WESGFs) have been widely recognized in the marine shelf environment. In this study, we show observations of WESGF deposits in lacustrine settings using well core and t...Sequences of wave-enhanced sediment-gravity flows(WESGFs) have been widely recognized in the marine shelf environment. In this study, we show observations of WESGF deposits in lacustrine settings using well core and thin section data from the Paleogene in the Jiyang sub-basin, Bohai Bay basin, eastern China. The findings of this study include the following: 1) the sequence of WESGFs in the lacustrine basin is similar to that of marine; it consists of three units, MF1 unit: siltstone with basal erosion surface, MF2 unit: silt-streaked claystone, and MF3 unit: silty-mudstone; and 2) prodelta sand sheets are found in the lacustrine WESGF sequence and are classified as the MFd unit: clay-streaked siltstone. However, because the system size and variability in hydrodynamic conditions are different between the lacustrine and marine basins, lacustrine WESGFs do appear to have three distinguishable features: 1) the sediment grain size and sand content are slightly higher than those of the marine WESGFs; 2) lacustrine WESGFs may contain prodelta sediments or sedimentary sequences of other types of gravity flows, such as hyperpycnal flows; and 3) the scale of the sedimentary structures for lacustrine WESGFs is smaller. The WESGFs found in the continental lacustrine basin provide a new model for sediment dispersal processes in lake environments and may be helpful to explain and predict the distribution of sandy reservoirs for oil and gas exploration.展开更多
The mid-Pleistocene climate transition (MPT) has been widely reported in worldwide geological events. As a key issue of the Quaternary geology, it has attracted much attention from the paleoclimate community. MPT re...The mid-Pleistocene climate transition (MPT) has been widely reported in worldwide geological events. As a key issue of the Quaternary geology, it has attracted much attention from the paleoclimate community. MPT refers to a period lasting for several hundreds of thousand years, during which the dominant climate periodicity gradually extended from 41 kyr to 100 kyr (Ruddiman et al., 1989),展开更多
Although extensive studies have been performed on nitrogen isotopes in lake sediments,understanding the complexity of the δ~15N variation related to past environmental and climatic conditions still remains unclear.Su...Although extensive studies have been performed on nitrogen isotopes in lake sediments,understanding the complexity of the δ~15N variation related to past environmental and climatic conditions still remains unclear.Supported by multi-proxy records including litho-units,organic carbon isotopes,ration of total organic carbon and total nitrogen,organic matter content,bulk dry density,the accumulation rate of organic matter,median grain size,magnetic susceptibility,and Rb/Sr and Ca/Mg ratios obtained from a sedimentary sequence in a small lake(i.e.,Dahu Swamp) in the eastern Nanling Mountains in South China,we deduce that variation in the δ15N values results primarily from the sources of organic matter,which are significantly influenced by climatic conditions over the past ~16 000 years.A low(or high) lake level resulting from dry(or wet) conditions would lead to more(or fewer) vascular plant remains in the sediments and stronger(or weaker) denitrification associated with hypolimnetic anoxia,resulting in lower(or higher) δ15N values.In addition,dry(or wet) conditions would favor weakened(or strengthened) biogeochemical activity in the catchment,which could result in less(or more) external input of15N-enriched OM,thus leading to decreased(or increased) δ15N values.Our results indicate that the lake sediment δ15N record in the Nanling Mountains has the potential to provide valuable insight into past East Asian monsoon climatedriven environmental changes.展开更多
The mechanism of formation of lacustrine deposits within stable orogenic belts and their potential for shale oil and gas exploration are frontier themes of challenge in the fields of sedimentology and petroleum explor...The mechanism of formation of lacustrine deposits within stable orogenic belts and their potential for shale oil and gas exploration are frontier themes of challenge in the fields of sedimentology and petroleum exploration. Orogenic belts witness strong tectonic activities and normally cannot host stable lacustrine basins and deep shale formations. Therefore, basins in orogenic belts are considered to have no potential to form shale hydrocarbon reservoirs. Here we investigate the Luanping Basin located in the Yanshan orogenic belt where previous studies regarded rivers and fan deltas as the major main Mesozoic deposits. Based on detailed field exploration and scientific drilling, we report the finding of a large number of lacustrine shale continental deep-water deposits in the Mesozoic strata. Our finding of the occurrence of active shale oil and gas also in this basin also subvert the previous perceptions.We report SHRIMP zircon U-Pb age that define the bottom boundary of the target interval as 127.6 ± 1.7 Ma belonging to the early Cretaceous strata. Tectonics and climate are considered to be the main factors that controlled the deep-water sedimentation during this period. The drill cores revealed evidence of shale gas and the TOC of shale is 0.33%–3.60%, with an average value of 1.39% and Ro is 0.84%–1.21%, with an average value of 1.002%. The brittleness index of shale is between 52.7% and 100%. After vertical well fracturing, the daily gas production is more than 1000 m^(3). Our findings show that the basin has considerable potential for shale oil and gas. The geological resources of the shale gas in the Xiguayuan Fm. are estimated as 1110.12 × 10^(8) m^(3), with shale oil geological resources of 3340.152 × 10^(4) t. Our findings indicate that the Yanshan orogenic belt has potential exploration prospect. This work not only redefines the Luanping Basin as a rift deep-water Mesozoic Lake Basin, but also rules out the previous notion that the basin is dominated by shallow water sediments. The discovery of shale oil and gas also provides an important reference for subsequent petroleum exploration and development in this basin. Our study shows that shale oil and gas reservoirs can be found in the lacustrine basins of orogenic belts which were strongly influenced by volcanism. These results have significant implications for the sedimentology and oil exploration in the Qinling and Xingmeng Orogenic Belts of China, as well as those in other terranes of the world including the New England Orogenic Belt in Australia.展开更多
Uranium(U)provides especially useful information for reconstructing paleoredox conditions due to its unique geochemical properties and behavior in supergene environments.The proxy potential under suboxic-oxic
This paper examines the relationship among organic geochemical proxies (TOC, C/N ratio and ~13C) and pollen assemblages in Zhuye Lake sediments since the Late Glacial. Results show that the reaction extent of organi...This paper examines the relationship among organic geochemical proxies (TOC, C/N ratio and ~13C) and pollen assemblages in Zhuye Lake sediments since the Late Glacial. Results show that the reaction extent of organic geochemical proxies and pollen as- semblages to environment changes are different. Organic geochemical proxies are sensitive to overall environmental change, while pollen assemblages indicate detailed information of environmental change. For the entire sedimentary section (except the sand layer fi'om the bottom of the section), when values of TOC, C/N ratio and total pollen concentrations are high, 813C values are low, and vice versa. The different responses of organic geochemical proxies and pollen records in Zhuye Lake are mainly due to their different sensitivity and diverse influencing factors in different environmental conditions.展开更多
In the present work,15400 yr old geochemical records of a core from the subalpine Daping swamp are presented with the aim to examine the relationship between the chemical weathering and the climatic changes in the reg...In the present work,15400 yr old geochemical records of a core from the subalpine Daping swamp are presented with the aim to examine the relationship between the chemical weathering and the climatic changes in the region of the western Nanling Mountains,China.The climate of the study region was deeply controlled by the East Asian summer monsoon.The results indicate that,in the past 15400 yrs,the values of chemical index of alteration(CIA)ranged from 73.9%to 88.2%(mean:85.3%),suggested a medium and high intensity of chemical weathering.The local exogenous clastic materials,which were derived from the weathered residues,played a key role in contributing towards the sediments.Since the climate-induced chemical weathering exerted strong influences on the geochemical features of weathered residues,the geochemical characteristics of the sediments were deeply impacted by climatic conditions.Wetter and warmer conditions would favor increased chemical weathering,resulting in more leaching of soluble and mobile elements(e.g.,Ba and Sr)and leaving the resistant and immobile elements(e.g.,Al and Ti)enriched in the weathered residues.These materials were then eroded and transported into the lake,and led to the sediments characterized by the characteristic of having depleted soluble elements.In contrast,dry and cold conditions would result in an opposite trend.In this sense,the geochemical records can serve as proxies to indicate changes of chemical weathering intensity,which were closely related to the evolution of summer monsoon.展开更多
This paper takes the sediments of Dianchi Lake as the research object.The results show that the total phosphorus content in the sediments of Dianchi Lake is relatively high,and the spatial variation is large,ranging f...This paper takes the sediments of Dianchi Lake as the research object.The results show that the total phosphorus content in the sediments of Dianchi Lake is relatively high,and the spatial variation is large,ranging from 1,193.94 to 4,629.25 mg/kg.The spatial distribution characteristics of total phosphorus in the sediments of Dianchi Lake have obvious regional differences.The average content of total phosphorus in the sediments of Dianchi Lake is 2,184.39(+579.09 mg/kg),and the TP(Total Phosphorus)content in the areas over 60%of the lake is higher than 2,000 mg/kg,which is in heavily flat.By analyzing the distribution of phosphorus forms in surface sediments of different areas of Dianchi Lake,it can be concluded that the difference is significant.The relationship between the phosphorus contents of different forms is HCl-P>NaOH-rP>NaOH-nrP>Res-P>BD-P.Through summarizing the characteristics of different phosphorus distribution in the sediments of Dianchi Lake,this paper concludes that the sustained release of endogenous phosphorus load will be an important factor to delay the ecological health recovery time of Dianchi Lake and offset the effect of exogenous treatment.展开更多
The Nenjiang Formation was continuously cored in the SK-1 borehole(China Cretaceous Continental Scientific Drilling Project-SongKe1well).Over 95.7%recovery rate,the obtained continuous core is 827.6 m in length,coveri...The Nenjiang Formation was continuously cored in the SK-1 borehole(China Cretaceous Continental Scientific Drilling Project-SongKe1well).Over 95.7%recovery rate,the obtained continuous core is 827.6 m in length,covering the geological age ranges from late Santonian to middle Campanian.This is the most complete and continuous sedimentary deposits in the Songliao basin till now.Here we systematically presented the lithological results of the observation of the cores in 2--5 cm thickness scale at the drilling spot,and the analysis on lithofacies and sedimentary sequence,cyclic stratigraphy.13 types of sedimentary rocks deposited mainly in lacustrine,delta and fluvial environments were found in the Nenjiang Fromation,and they were subdivided into 19 microfacies including dolomite,marl,argillaceous limestone,turbidite,mudstone of still water,volcanic ash,channel-lag deposit,point bar,natural levee,crevasse splay,crevasse channel,floodplain,flood lake,distributary mouth bar,subaqueous distributary channels,subaqueous natural levee,subaqueous inter-distributary bay,distal bar and adjacent shore sand bar.The whole sedimentary column is composed of 630 sixth-order depositional cycles in the meter-scale,which can be further organized in 148 fifth-order depositional cycles,38 fourth-order depositional cycles and 5 third-order depositional cycles.Meticulous depiction(centimeter level)of the whole Formation provides an approach to study its sedimentary process with high precision.The centimeter-scale description of the sequent core presented some previously unidentified dolomite and volcanic ash layers.The cyclostratigraphy of the Nenjiang Formation was controlled by Milankovitch cycled,which is helpful to discover the climatic changes of the late Santonian to the middle Campanian in Songliao Basin.In addition,the detailed description of the sequent section is significant for the upcoming oil and gas exploration in the Songliao Basin if regarding the new type of oil/gas systems.展开更多
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 ...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.展开更多
基金the National Institute of Natural Hazards,Ministry of Emergency Management of China(ZDJ2019-21)the National Natural Science Foundation of China(Nos.41872227 and 41602221).
文摘The traces left by earthquakes in lacustrine sediments are studied to determine the occurrence of ancient earthquakes by identifying seismically induced soft-sediment deformation structures(SSDS).Dating can help reconstruct the relative frequency of earthquakes.Identifying seismically induced seismites,which carry abundant seismic information from numerous SSDS,is both critical and challenging.Studying the deformation mechanism of SSDS and learning about the common criteria of seismically induced SSDS improve the identification of earthquake triggers.With better research into SSDS,seismic events can be effectively captured,and temporal constraints can be carried out by 14C dating and optically stimulated luminescence(OSL)dating to identify and date the occurrence of ancient earthquakes.The present contribution primarily addresses the meaning and mechanism of SSDS and their relationship with earthquake magnitude as well as the common criteria of the SSDS induced by earthquakes.
基金financially supported by the National Natural Science Foundation of China (41702372)the Open Fund of State Key Laboratory of Earthquake Dynamics (LED2017B03)
文摘This study identified soft-sediment deformation structures (SSDS) of seismic origin from lacustrine sediments in the late Quaternary paleo-dammed lake at Tashkorgan, northeastern Pamir. The observed deformation structures include sand dykes, liquefied diapir and convolute structures, gravity induced SSDS, and thixotropic pillar and tabular structures. We conducted a preliminary study on the morphology, formation and trigger mechanisms of pillar and tabular structures formed by liquefaction of underlying coarse sand and thixotropy of the upper silty clay. The regional tectonic setting and distribution of lacustrine strata indicate that the most probable trigger for the SSDS in lacustrine sediments was seismic activity, with an approximate earthquake magnitude of M〉6.0; the potential seismogenic fault is the southern part of the Kongur normal fault extensional system. AMS ^4C dating results indicate that the SSDS were formed by seismic events occurring between 26050±100 yrBP and 22710±80 yrBP, implying intense fault activity in this region during the late Pleistocene. This study provides new evidence for understanding tectonic activity and regional geodynamics in western China.
基金the Central Laboratory of NIS-Naftagas,Novi Sad for Rock-Eval determinations and the Ministry of Science and Environmental Protection of the Government of the Republic of Serbia for supporting this research
文摘Sediments of the western part of the Valjevo-Mionica basin (Serbia) were examined both geochemically and mineralogically to explain, on the basis of their sedimentologicai characteristics, the causes of changes in their qualitative and quantitative composition. A total of 62 samples obtained from the drillhole at depths up to 400 m was investigated. Using correlation of the obtained data, six geochemical zones were defined, two of which being specially distinguished by their mineralogical, geochemical and sedimentological characteristics. The first one, upper zone A, consists of banded marlstones interbedded with clay and oil shales and is characterized by presence of analcite and searlesite. These minerals and very high contents of Na20 indicate sedimentation in alkaline conditions with increased salinity in arid climate. That provided pronounced water stratification, as well as higher bioproductivity in the basin and sedimentary organic matter preservation. Therefore, the zone A sediments are characterized by high organic matter contents of the type which provides good potential for production of liquid hydrocarbons. Another specific zone, zone F, contains sediments with very high MgO, K2O and Li concentrations. Their geochemical correlation, as well as almost complete absence of illite in this zone, indicates the presence of interstratified clay mineral type illite-saponite (lithium-bearing Mg-smectite).
文摘1 Introduction The Qarhan Playa of Qaidam Basin is located at the northeastern QinghaiTibetan Plateau(QTP),in which thick lacustrine and evaporate sediments deposited since the late Pleistocene(Chen et al.,1985,1986).As surrounded by capacious Gobi and yardang fields and suffered strong westerly-northwesterly wind,abundant aeolian materials were trapped in these sediment sequences in the
基金funded by the survey projects initiated by the Ministry of Natural Resources of the People’s Republic of China(DD20189220,DD20211317,DD20211398,1212011220224,and 121201011000150022)the project of the 2015 Natural Science Basic Research Plan of Shaanxi Province(2015JM4129)+1 种基金the project of 2016 Fundamental Research Funds for the Central Universities(open fund,310829161128)the project of 2021 Fundamental Research Funds for the Central Universities(open fund).
文摘This paper aims to investigate the present situation and transfer mechanisms of microplastics in lacustrine sediments in the Qinghai-Tibet Plateau.The study surveyed the average abundance of microplastics in sediments.The abundance of microplastics in sediments of lakes from the Qinghai-Tibet Plateau is 17.22-2643.65 items/kg DW and 0-60.63 items/kg DW based on the data of the Qinghai Lake and the Siying Co Basin.The microplastic abundance in sediments from small and medium lakes is very high compared to that in other areas in the world.Like microplastics in other lakes of the world,those in the lakes in the Qinghai-Tibet Plateau mainly include organic polymers PA,PET,PE,and PP and are primarily in the shape of fibers and fragments.The microplastic pollution of lacustrine sediments in the Qinghai-Tibet Plateau is affected by natural changes and by human activities,and the concentration of microplastics in lacustrine ecosystems gradually increases through food chains.Furthermore,the paper suggests the relevant administrative departments of the Qinghai-Tibet Plateau strengthen waste management while developing tourism and pay much attention to the impacts of microplastics in water environments.This study provides a reference for preventing and controlling microplastic contamination in the Qinghai-Tibet Plateau.
基金the National Natural Science Foundation of China(No.41702135)the Yangtze Youth Fund(No.2015qq33),the 13th“Five-year”plan of the Ministry of Science and Technology of China(No.2016ZX05037-002)National Science and Technology Major Project(NO.2016ZX05015-006).
文摘Pearl River Mouth Basin undergoes complex tectonic evolution processes and forms lacustrine,transitional and marine sediments.Drilling shows that there exist large petroleum reserves in the hydrocarbon-rich sags of Pearl River Mouth Basin,South China Sea.To reduce the risk,the exploration,structural and sedimentary characteristics of the hydrocarbon-rich sags should be identified and described.Drilling,seismic,and microfossil data are integrated to interpret the structural and sedimentary evolution of the hydrocarbon-rich sags in Pearl River Mouth Basin.By analyzing the tectonic and sedimentary evolutionary characteristics,three conclusions may be drawn:1、The present regional tectonic characteristics of the PRMB are formed by mutual interactions of the Eurasian Plate,Pacific Plate,Philippine Plate and Indian Plate.During the Paleocene to early Eocene and late Eocene and early Oligocene,the PRMB is at the rifting stage.During the late Oligocene,the PRMB was at the rifting-depression transitional stage.After the Oligocene,the PRMB is at the depression stage.2、Tectonic conditions control the sedimentation process in the hydrocarbon-rich sags.During the lacustrine sedimentation stage,synsedimentary faults and intense faulting control the sedimentation.During the transitional sedimentation stage,weak fault activity influences the deposition process in the hydrocarbon-rich sags.During the marine sedimentation stage,weak fault activity and depression activity control the deposition process in the hydrocarbon-rich sags.3、Tectonic evolution affects the deposition process.The lacustrine,transitional and marine sedimentation corresponds to different tectonic conditions.The lacustrine sedimentation is formed under fault activity during the rifting stage.The transitional sedimentation is formed under weak fault activity during the late rifting stage.The marine sedimentation is formed under weak fault activity and depression activity during the rifting-depression and depression stages.4、The half graben is beneficial for the formation of lacustrine source rocks,which is responsible for the hydrocarbon-rich sag.Therefore the half graben mode contributes to the hydrocarbon-rich sags.
基金support by the National Nature Science Foundation of China (General Program) Grant No. 41572134National Program on Key Basic Research Project of China (973 Program) Grant No. 2014CB239102
文摘Sequences of wave-enhanced sediment-gravity flows(WESGFs) have been widely recognized in the marine shelf environment. In this study, we show observations of WESGF deposits in lacustrine settings using well core and thin section data from the Paleogene in the Jiyang sub-basin, Bohai Bay basin, eastern China. The findings of this study include the following: 1) the sequence of WESGFs in the lacustrine basin is similar to that of marine; it consists of three units, MF1 unit: siltstone with basal erosion surface, MF2 unit: silt-streaked claystone, and MF3 unit: silty-mudstone; and 2) prodelta sand sheets are found in the lacustrine WESGF sequence and are classified as the MFd unit: clay-streaked siltstone. However, because the system size and variability in hydrodynamic conditions are different between the lacustrine and marine basins, lacustrine WESGFs do appear to have three distinguishable features: 1) the sediment grain size and sand content are slightly higher than those of the marine WESGFs; 2) lacustrine WESGFs may contain prodelta sediments or sedimentary sequences of other types of gravity flows, such as hyperpycnal flows; and 3) the scale of the sedimentary structures for lacustrine WESGFs is smaller. The WESGFs found in the continental lacustrine basin provide a new model for sediment dispersal processes in lake environments and may be helpful to explain and predict the distribution of sandy reservoirs for oil and gas exploration.
基金financially supported by the Geological Investigation Project of China Geological Survey(No.12120113006200)
文摘The mid-Pleistocene climate transition (MPT) has been widely reported in worldwide geological events. As a key issue of the Quaternary geology, it has attracted much attention from the paleoclimate community. MPT refers to a period lasting for several hundreds of thousand years, during which the dominant climate periodicity gradually extended from 41 kyr to 100 kyr (Ruddiman et al., 1989),
基金Supported by the National Natural Science Foundation of China(Nos.41071137,40671189)the Research Program of Higher Education Institution in Guangdong Province for High-level Talents,and the Natural Science Foundation of Guangdong Province(Nos.S2011010003413,8151063101000044)
文摘Although extensive studies have been performed on nitrogen isotopes in lake sediments,understanding the complexity of the δ~15N variation related to past environmental and climatic conditions still remains unclear.Supported by multi-proxy records including litho-units,organic carbon isotopes,ration of total organic carbon and total nitrogen,organic matter content,bulk dry density,the accumulation rate of organic matter,median grain size,magnetic susceptibility,and Rb/Sr and Ca/Mg ratios obtained from a sedimentary sequence in a small lake(i.e.,Dahu Swamp) in the eastern Nanling Mountains in South China,we deduce that variation in the δ15N values results primarily from the sources of organic matter,which are significantly influenced by climatic conditions over the past ~16 000 years.A low(or high) lake level resulting from dry(or wet) conditions would lead to more(or fewer) vascular plant remains in the sediments and stronger(or weaker) denitrification associated with hypolimnetic anoxia,resulting in lower(or higher) δ15N values.In addition,dry(or wet) conditions would favor weakened(or strengthened) biogeochemical activity in the catchment,which could result in less(or more) external input of15N-enriched OM,thus leading to decreased(or increased) δ15N values.Our results indicate that the lake sediment δ15N record in the Nanling Mountains has the potential to provide valuable insight into past East Asian monsoon climatedriven environmental changes.
基金In the process of writing this paper,we received the financial support of the National Science and Technology Major Project(Grant No.2017ZX05009-002)the support from Wuxi Branch of SINOPEC Petroleum Exploration&Production Research Institute。
文摘The mechanism of formation of lacustrine deposits within stable orogenic belts and their potential for shale oil and gas exploration are frontier themes of challenge in the fields of sedimentology and petroleum exploration. Orogenic belts witness strong tectonic activities and normally cannot host stable lacustrine basins and deep shale formations. Therefore, basins in orogenic belts are considered to have no potential to form shale hydrocarbon reservoirs. Here we investigate the Luanping Basin located in the Yanshan orogenic belt where previous studies regarded rivers and fan deltas as the major main Mesozoic deposits. Based on detailed field exploration and scientific drilling, we report the finding of a large number of lacustrine shale continental deep-water deposits in the Mesozoic strata. Our finding of the occurrence of active shale oil and gas also in this basin also subvert the previous perceptions.We report SHRIMP zircon U-Pb age that define the bottom boundary of the target interval as 127.6 ± 1.7 Ma belonging to the early Cretaceous strata. Tectonics and climate are considered to be the main factors that controlled the deep-water sedimentation during this period. The drill cores revealed evidence of shale gas and the TOC of shale is 0.33%–3.60%, with an average value of 1.39% and Ro is 0.84%–1.21%, with an average value of 1.002%. The brittleness index of shale is between 52.7% and 100%. After vertical well fracturing, the daily gas production is more than 1000 m^(3). Our findings show that the basin has considerable potential for shale oil and gas. The geological resources of the shale gas in the Xiguayuan Fm. are estimated as 1110.12 × 10^(8) m^(3), with shale oil geological resources of 3340.152 × 10^(4) t. Our findings indicate that the Yanshan orogenic belt has potential exploration prospect. This work not only redefines the Luanping Basin as a rift deep-water Mesozoic Lake Basin, but also rules out the previous notion that the basin is dominated by shallow water sediments. The discovery of shale oil and gas also provides an important reference for subsequent petroleum exploration and development in this basin. Our study shows that shale oil and gas reservoirs can be found in the lacustrine basins of orogenic belts which were strongly influenced by volcanism. These results have significant implications for the sedimentology and oil exploration in the Qinling and Xingmeng Orogenic Belts of China, as well as those in other terranes of the world including the New England Orogenic Belt in Australia.
文摘Uranium(U)provides especially useful information for reconstructing paleoredox conditions due to its unique geochemical properties and behavior in supergene environments.The proxy potential under suboxic-oxic
基金supported by the National Natural Science Foundation of China(Grant Nos.41371009 and 41001116)the Fundamental Research Fund for the Central Universities(Grant Nos.lzujbky-2013-127 and lzujbky-2013-129)
文摘This paper examines the relationship among organic geochemical proxies (TOC, C/N ratio and ~13C) and pollen assemblages in Zhuye Lake sediments since the Late Glacial. Results show that the reaction extent of organic geochemical proxies and pollen as- semblages to environment changes are different. Organic geochemical proxies are sensitive to overall environmental change, while pollen assemblages indicate detailed information of environmental change. For the entire sedimentary section (except the sand layer fi'om the bottom of the section), when values of TOC, C/N ratio and total pollen concentrations are high, 813C values are low, and vice versa. The different responses of organic geochemical proxies and pollen records in Zhuye Lake are mainly due to their different sensitivity and diverse influencing factors in different environmental conditions.
基金Under the auspices of the National Natural Science Foundation of China(No.41971101,41571187,41071137)。
文摘In the present work,15400 yr old geochemical records of a core from the subalpine Daping swamp are presented with the aim to examine the relationship between the chemical weathering and the climatic changes in the region of the western Nanling Mountains,China.The climate of the study region was deeply controlled by the East Asian summer monsoon.The results indicate that,in the past 15400 yrs,the values of chemical index of alteration(CIA)ranged from 73.9%to 88.2%(mean:85.3%),suggested a medium and high intensity of chemical weathering.The local exogenous clastic materials,which were derived from the weathered residues,played a key role in contributing towards the sediments.Since the climate-induced chemical weathering exerted strong influences on the geochemical features of weathered residues,the geochemical characteristics of the sediments were deeply impacted by climatic conditions.Wetter and warmer conditions would favor increased chemical weathering,resulting in more leaching of soluble and mobile elements(e.g.,Ba and Sr)and leaving the resistant and immobile elements(e.g.,Al and Ti)enriched in the weathered residues.These materials were then eroded and transported into the lake,and led to the sediments characterized by the characteristic of having depleted soluble elements.In contrast,dry and cold conditions would result in an opposite trend.In this sense,the geochemical records can serve as proxies to indicate changes of chemical weathering intensity,which were closely related to the evolution of summer monsoon.
文摘This paper takes the sediments of Dianchi Lake as the research object.The results show that the total phosphorus content in the sediments of Dianchi Lake is relatively high,and the spatial variation is large,ranging from 1,193.94 to 4,629.25 mg/kg.The spatial distribution characteristics of total phosphorus in the sediments of Dianchi Lake have obvious regional differences.The average content of total phosphorus in the sediments of Dianchi Lake is 2,184.39(+579.09 mg/kg),and the TP(Total Phosphorus)content in the areas over 60%of the lake is higher than 2,000 mg/kg,which is in heavily flat.By analyzing the distribution of phosphorus forms in surface sediments of different areas of Dianchi Lake,it can be concluded that the difference is significant.The relationship between the phosphorus contents of different forms is HCl-P>NaOH-rP>NaOH-nrP>Res-P>BD-P.Through summarizing the characteristics of different phosphorus distribution in the sediments of Dianchi Lake,this paper concludes that the sustained release of endogenous phosphorus load will be an important factor to delay the ecological health recovery time of Dianchi Lake and offset the effect of exogenous treatment.
基金Supported by projects of the National Key R&D Program of China(No.2019YFC0605402)National Natural Science Foundation of China(No.41790453)
文摘The Nenjiang Formation was continuously cored in the SK-1 borehole(China Cretaceous Continental Scientific Drilling Project-SongKe1well).Over 95.7%recovery rate,the obtained continuous core is 827.6 m in length,covering the geological age ranges from late Santonian to middle Campanian.This is the most complete and continuous sedimentary deposits in the Songliao basin till now.Here we systematically presented the lithological results of the observation of the cores in 2--5 cm thickness scale at the drilling spot,and the analysis on lithofacies and sedimentary sequence,cyclic stratigraphy.13 types of sedimentary rocks deposited mainly in lacustrine,delta and fluvial environments were found in the Nenjiang Fromation,and they were subdivided into 19 microfacies including dolomite,marl,argillaceous limestone,turbidite,mudstone of still water,volcanic ash,channel-lag deposit,point bar,natural levee,crevasse splay,crevasse channel,floodplain,flood lake,distributary mouth bar,subaqueous distributary channels,subaqueous natural levee,subaqueous inter-distributary bay,distal bar and adjacent shore sand bar.The whole sedimentary column is composed of 630 sixth-order depositional cycles in the meter-scale,which can be further organized in 148 fifth-order depositional cycles,38 fourth-order depositional cycles and 5 third-order depositional cycles.Meticulous depiction(centimeter level)of the whole Formation provides an approach to study its sedimentary process with high precision.The centimeter-scale description of the sequent core presented some previously unidentified dolomite and volcanic ash layers.The cyclostratigraphy of the Nenjiang Formation was controlled by Milankovitch cycled,which is helpful to discover the climatic changes of the late Santonian to the middle Campanian in Songliao Basin.In addition,the detailed description of the sequent section is significant for the upcoming oil and gas exploration in the Songliao Basin if regarding the new type of oil/gas systems.
基金supported by the Knowledge Innovation Project of the Chinese Academy of Sciences(Grant No.KZCX2-105)the National Natural Science Foundation of China(Grant Nos.403030140 and 49894170).
文摘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.