The northeastern Qinghai-Tibetan Plateau(QTP) of China is located at the triple junction of the Asian winter and summer monsoons and the westerlies, where paleoclimatic evolution has an important scientific significan...The northeastern Qinghai-Tibetan Plateau(QTP) of China is located at the triple junction of the Asian winter and summer monsoons and the westerlies, where paleoclimatic evolution has an important scientific significance for recognizing the spatial-temporal pattern of Asian monsoons in the past and predicting environmental change in the future. Nevertheless, the framework of the Holocene moisture variation and related mechanisms remain controversial, owing to complex hydroclimatic conditions triggered by the landform of the large mountain-arid basin. Here, we employed geochemical proxies from typical aeolian sand-palaeosol sequences in the Gonghe Basin, northeastern QTP, together with Optically Stimulated Luminescence(OSL) dating, to reconstruct the pattern of effective moisture variation and associated mechanisms in this region. Our results indicate that the regional effective moisture was at its lowest until 9–8 ka, and approached a maximum during 8–4/3 ka of the middle Holocene. Afterwards, the climate became relatively dry in general, but with a transient humid interval around 2–1 ka. Our geochemical evidence indicates that the dry early Holocene probably can be attributed to a strong winter monsoon forced by remnant ice sheet, combined with the high evaporation caused by solar insolation. Also, shifts of humid-dry are closely linked to the Asian summer monsoonal strength and therefore the balance of evaporation-precipitation in the middle and late Holocene. Thus, the pattern of the Holocene effective moisture variation is characterized as the ‘monsoon model’ in a closed intermontane arid and semi-arid basin near the western Asian monsoonal limit.展开更多
Influenced by neo-tectonic movement, the Sanhu area of China's Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quaternary...Influenced by neo-tectonic movement, the Sanhu area of China's Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quaternary aqueously deposited aeolian sandstones in the Qigequan Formation of the Sanhu area. Here we report the sedimentary petrology and geochemistry data of these deposits that constrain their depositional history. Evidence for aeolian influence during deposition includes: sorting and roundness, pure quartz sand with single mode grain size distribution and few suspension materials,very fine sand grain size distribution indicating sorting by saltation and suspension transport, dish-shaped and crescentshaped pits in grain surfaces indicating aeolian transport and chemical composition similar to that observed in active or recent dune deposits, namely enrichment in Si O_2, Na_2 O, and Mg O relative to the sand dam sediment in the lakeshore.Identification of these aqueously deposited aeolian sandstones expands the range of sedimentary deposit types found in the Sanhu area and improves understanding of its paleoclimatic history.展开更多
Desert-oasis ecotones are boundary areas between oases and desert ecosystems.Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes,especially aeolian transport ...Desert-oasis ecotones are boundary areas between oases and desert ecosystems.Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes,especially aeolian transport and deposition.Previous studies on aeolian sediment deposition have focused primarily on a single land surface type or a single engineering approach.Few studies have considered deposition in a multi-layer oasis protective system.A complete oasis protective system consists of an outer bare sand area,a sand barrier zone,a shrub and herbaceous plant zone,and a farmland shelter zone.This study used sedimentary analysis to quantify grain-size characteristics in samples from the four land surfaces under different types of weather conditions in the Gelintan oasis of the Tengger Desert,the fourth largest desert in China.The results showed that aeolian sediment deposition decreased from the outer bare sand area through the oasis protective system and into the interior.The four land surface types showed significant differences in deposition volume(P<0.05).Deposited sediment showed gradual decrease in dominant grain-size from sand to silt,but sediment deposited during dust weather contained a larger coarse-grained fraction.From the outer desert to the inner oasis,transport mechanisms shifted from saltation(sand)to suspension(silt and smaller)in non-dust weather.During dust weather,deposition primarily occurs from near-surface aeolian sand transport with saltation.Sediment sorting decreased from exterior to interior zones of the protective system while skewness and kurtosis showed no significant change(P<0.05).These results can help inform strategies for stabilizing and protecting desert-oasis ecotones in this region and other localities.展开更多
Geochemical and grain size analysis on the DQ (Dongqi) profile from Gonghe Basin, northeastern Qinghai-Tibetan Plateau, indi- cates that regional climate has experienced several cold-dry and warm-wet cycles since th...Geochemical and grain size analysis on the DQ (Dongqi) profile from Gonghe Basin, northeastern Qinghai-Tibetan Plateau, indi- cates that regional climate has experienced several cold-dry and warm-wet cycles since the last glacial maximum (LGM). The cold and dry climate dominated the region before 15.82 cal. ka B.E due to stronger winter monsoon and weaker summer monsoon, but the climate was relatively cold and wetter prior to 21 cal. ka B.E. In 15.824.5 cal. ka B.E, summer monsoon strength in- creased and winter monsoon tended to be weaker, implying an obvious warm climate. Specifically, the relatively cold and dry condition appeared in 14.7-13.7 cal. ka B.E and 12.14.5 cal. ka B.R, respectively, while relatively warm and wet in 13.~12.1 cal. ka B.E. The winter and summer monsoonal strength presents frequent fluctuations in the Holocene and relatively warm and wet conditions emerged in 9.5~.0 cal. ka B.E due to stronger summer monsoon. From 7.0 to 5.1 cal. ka B.E, the cycle of cold-dry and warm-wet climate corresponds to frequent fluctuations of winter and summer monsoons. The climate becomes warm and wet in 5.1 2.7 cal. ka B.E, accompanying increased summer monsoon, but it tends to be cold and dry since 2.7 cal. ka B.R due to en- hanced winter monsoonal strength. In addition, the evolution of regional winter and summer monsoons is coincident with warm and cold records from the polar ice core. In other words, climatic change in the Gonghe Basin can be considered as a regional re- sponse to global climate change.展开更多
Based upon cruise observations broadly covering the tropical North Pacific during July-November 2017,together with data obtained from the World Ocean Circulation Experiment Hydrographic Program,this study examined the...Based upon cruise observations broadly covering the tropical North Pacific during July-November 2017,together with data obtained from the World Ocean Circulation Experiment Hydrographic Program,this study examined the distribution of dissolved inorganic nitrogen(DIN,nitrate(NO_(3)^(-))+nitrite(NO_(2)^(-))),dissolved inorganic phosphorus(DIP)and related N^(*)(nitrogen-anomaly,N^(*)=N-16P+2.9,where N and P are the concentrations of DIN(>1.0μmol/L)and DIP(>0.1μmol/L)),used as an index of N2fixation,in the upper 1000 m of the water column.Nutrient concentrations displayed distinct spatial variability in the upper ocean but became relatively constant at a depth of 1000 m:they were high at low latitudes and in the eastern region,with an obvious nutricline at~150 m(DIN,~32.0μmol/L;DIP,~2.4μmol/L)and then generally increased with depth;they decreased markedly(DIN,~1.2μmol/L;DIP,~0.1μmol/L;at~150 m)at high latitudes and in the western region,where a nutricline was not apparent.The N^(*)index showed significant meridional and zonal variation,with the most negative values located at low latitudes and in the eastern region(~10°N,~150°-170°E),while becoming positive towards the northwest(the north of~18°N,~160°E westward).A N^(*)concentration larger than 2.0μmol/L which often used as an indicator of N2fixation,was observed between 155°E and 165°E;N^(*)values were 2.0μmol/L to6.0μmol/L at~15°-28°N,i.e.,much higher than those in the southern sector(0-2.0μmol/L at~5°-10°N).Zonally,N^(*)decreased gradually from west(-2.0μmol/L to 4.0μmol/L,~145°-165°E)to east(-2.0μmol/L to-8.0μmol/L,~155°W)along~10°N,which was consistent with the distribution of Trichodesmium abundance and N2fixation rates.Furthermore,since such region was also supplied with aeolian deposition,high N^(*)was probably not only induced by N2fixation but also influenced by iron and/or nitrogen deposition.展开更多
Thick loess is deposited on the platform in the piedmont zone of Muling-Xingkai Plain(Muxing Plain),but the genesis of the Muxing loess is still unclear.The aims of this study are to analyze the grain size characteris...Thick loess is deposited on the platform in the piedmont zone of Muling-Xingkai Plain(Muxing Plain),but the genesis of the Muxing loess is still unclear.The aims of this study are to analyze the grain size characteristics of Muxing loess collected from the cores of a typical borehole(ZK1)in the piedmont zone of Muxing Plain,and to verify its genesis.The Muxing loess is mainly composed of the particles with diameter less than 50μm,with an average content of 92.48%.The coarse silt particles with diameter of 10-50μm are the basic composition of aeolian sediments,and their average content is 44.34% for the Muxing loess,which is the mode class among the particles with different diameters.The grain size parameters and frequency curves are similar to those of the typical aeolian sediments.The distribution characteristic of the Muxing loess in the C-M scatter diagram is consistent with that of the Xi Feng loess.In addition,the discriminant analysis shows the Muxing loess mostly consists of aeolian sediments.Therefore,it can be concluded that the Muxing loess mainly resulted from aeolian deposition based on the grain size characteristics.Muxing Plain is dominated by the monsoon climate,and the wind-blown dusts are gradually deposited after being transported over long distances.展开更多
Uranium exploration breakthrough was extremely rare in an aeolian depositional system.In order to know the complicate characteristics of oxidation associated closely with uranium mineralization in the aeolian depositi...Uranium exploration breakthrough was extremely rare in an aeolian depositional system.In order to know the complicate characteristics of oxidation associated closely with uranium mineralization in the aeolian depositional system,petrology and mineralogy markers of the oxidation and its genetic mechanisms are identified and illustrated by fieldwork,thin section analysis and scanning electron microscopy test,based on 2 field outcrops in Zhenyuan County in the southwest of the Tianhuan depression in the Ordos Basin and the core of 2 wells in the north and south of Ordos Basin.The results showed:the typical macroscopic indicator of primary oxidation was the red fine sediments in the aeolian interdune with a thickness of 10-50 cm,and the microscopic characteristics of primary oxidation were the minerals such as hematite,ilmenite,and the irony matrix rich in fine-grained dolomite and biotite;the phreatic oxidation was manifested as the red sandstone with limonite horizontal layer with a thickness of 1-4 cm and a width of 60 cm-1 m,and the circular limonite nodules with a diameter of 3-7 cm,in which there was intergranular limonite cement;the interlayer oxidation was characterized by lenticular tongue and tapered red sandstone with a length of 1-10 m and a width of 10 cm-5m,in which detrital particles are coated with hematite and hematite was distributed inside the rhombus dolomite.The paleoclimate of the sedimentary period,the water-table movement and the pore and permeability conditions of the sand body were the key factors for the formation of different oxidation types in the aeolian depositional system.展开更多
基金This study was supported by the Strategic Priority Research Program of Chinese Academy of Sciences, Pan-Third Pole Environment Study for a Green Silk Road (Grant No. XDA 2009000001)the National Natural Science Foundation of China (Grants No. 41977393 and 41671204)
文摘The northeastern Qinghai-Tibetan Plateau(QTP) of China is located at the triple junction of the Asian winter and summer monsoons and the westerlies, where paleoclimatic evolution has an important scientific significance for recognizing the spatial-temporal pattern of Asian monsoons in the past and predicting environmental change in the future. Nevertheless, the framework of the Holocene moisture variation and related mechanisms remain controversial, owing to complex hydroclimatic conditions triggered by the landform of the large mountain-arid basin. Here, we employed geochemical proxies from typical aeolian sand-palaeosol sequences in the Gonghe Basin, northeastern QTP, together with Optically Stimulated Luminescence(OSL) dating, to reconstruct the pattern of effective moisture variation and associated mechanisms in this region. Our results indicate that the regional effective moisture was at its lowest until 9–8 ka, and approached a maximum during 8–4/3 ka of the middle Holocene. Afterwards, the climate became relatively dry in general, but with a transient humid interval around 2–1 ka. Our geochemical evidence indicates that the dry early Holocene probably can be attributed to a strong winter monsoon forced by remnant ice sheet, combined with the high evaporation caused by solar insolation. Also, shifts of humid-dry are closely linked to the Asian summer monsoonal strength and therefore the balance of evaporation-precipitation in the middle and late Holocene. Thus, the pattern of the Holocene effective moisture variation is characterized as the ‘monsoon model’ in a closed intermontane arid and semi-arid basin near the western Asian monsoonal limit.
基金funding support from the Qinghai Oilfield Company of the China National Petroleum Corporation
文摘Influenced by neo-tectonic movement, the Sanhu area of China's Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quaternary aqueously deposited aeolian sandstones in the Qigequan Formation of the Sanhu area. Here we report the sedimentary petrology and geochemistry data of these deposits that constrain their depositional history. Evidence for aeolian influence during deposition includes: sorting and roundness, pure quartz sand with single mode grain size distribution and few suspension materials,very fine sand grain size distribution indicating sorting by saltation and suspension transport, dish-shaped and crescentshaped pits in grain surfaces indicating aeolian transport and chemical composition similar to that observed in active or recent dune deposits, namely enrichment in Si O_2, Na_2 O, and Mg O relative to the sand dam sediment in the lakeshore.Identification of these aqueously deposited aeolian sandstones expands the range of sedimentary deposit types found in the Sanhu area and improves understanding of its paleoclimatic history.
基金sponsored as a sub-project of the National Key Research and Development Program of China-Desertification Land Management and Sand Industry Technology Research and Development and Demonstration in Inner Mongolia Desertification Area,named Key Techniques and Demonstration of Sand Damage Control in Oasis and Saline-alkali Lake(2016YFC0501003)a sub-project of the National Key Research and Development Program of Study on Restoration and Protection of Typical Fragile Ecology,named Study and Demonstration of Sand-fixing and Wind-breaking Techniques of Cyperus Esculentus L.in North Wind-blown Sand Region(2019YFC0507600)。
文摘Desert-oasis ecotones are boundary areas between oases and desert ecosystems.Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes,especially aeolian transport and deposition.Previous studies on aeolian sediment deposition have focused primarily on a single land surface type or a single engineering approach.Few studies have considered deposition in a multi-layer oasis protective system.A complete oasis protective system consists of an outer bare sand area,a sand barrier zone,a shrub and herbaceous plant zone,and a farmland shelter zone.This study used sedimentary analysis to quantify grain-size characteristics in samples from the four land surfaces under different types of weather conditions in the Gelintan oasis of the Tengger Desert,the fourth largest desert in China.The results showed that aeolian sediment deposition decreased from the outer bare sand area through the oasis protective system and into the interior.The four land surface types showed significant differences in deposition volume(P<0.05).Deposited sediment showed gradual decrease in dominant grain-size from sand to silt,but sediment deposited during dust weather contained a larger coarse-grained fraction.From the outer desert to the inner oasis,transport mechanisms shifted from saltation(sand)to suspension(silt and smaller)in non-dust weather.During dust weather,deposition primarily occurs from near-surface aeolian sand transport with saltation.Sediment sorting decreased from exterior to interior zones of the protective system while skewness and kurtosis showed no significant change(P<0.05).These results can help inform strategies for stabilizing and protecting desert-oasis ecotones in this region and other localities.
基金funded by National Natural Science Foundation of China (Nos. 40971005 and 41271215)
文摘Geochemical and grain size analysis on the DQ (Dongqi) profile from Gonghe Basin, northeastern Qinghai-Tibetan Plateau, indi- cates that regional climate has experienced several cold-dry and warm-wet cycles since the last glacial maximum (LGM). The cold and dry climate dominated the region before 15.82 cal. ka B.E due to stronger winter monsoon and weaker summer monsoon, but the climate was relatively cold and wetter prior to 21 cal. ka B.E. In 15.824.5 cal. ka B.E, summer monsoon strength in- creased and winter monsoon tended to be weaker, implying an obvious warm climate. Specifically, the relatively cold and dry condition appeared in 14.7-13.7 cal. ka B.E and 12.14.5 cal. ka B.R, respectively, while relatively warm and wet in 13.~12.1 cal. ka B.E. The winter and summer monsoonal strength presents frequent fluctuations in the Holocene and relatively warm and wet conditions emerged in 9.5~.0 cal. ka B.E due to stronger summer monsoon. From 7.0 to 5.1 cal. ka B.E, the cycle of cold-dry and warm-wet climate corresponds to frequent fluctuations of winter and summer monsoons. The climate becomes warm and wet in 5.1 2.7 cal. ka B.E, accompanying increased summer monsoon, but it tends to be cold and dry since 2.7 cal. ka B.R due to en- hanced winter monsoonal strength. In addition, the evolution of regional winter and summer monsoons is coincident with warm and cold records from the polar ice core. In other words, climatic change in the Gonghe Basin can be considered as a regional re- sponse to global climate change.
基金The Eastern Pacific Environment Monitoring and Protection Project under contract No.DY135-E2-5-02the Global Change and Air-Sea Interaction Project+1 种基金the National Natural Science Foundation of China under contract No.42103077the Natural Science Foundation of Fujian Province of China under contract No.2020J05077。
文摘Based upon cruise observations broadly covering the tropical North Pacific during July-November 2017,together with data obtained from the World Ocean Circulation Experiment Hydrographic Program,this study examined the distribution of dissolved inorganic nitrogen(DIN,nitrate(NO_(3)^(-))+nitrite(NO_(2)^(-))),dissolved inorganic phosphorus(DIP)and related N^(*)(nitrogen-anomaly,N^(*)=N-16P+2.9,where N and P are the concentrations of DIN(>1.0μmol/L)and DIP(>0.1μmol/L)),used as an index of N2fixation,in the upper 1000 m of the water column.Nutrient concentrations displayed distinct spatial variability in the upper ocean but became relatively constant at a depth of 1000 m:they were high at low latitudes and in the eastern region,with an obvious nutricline at~150 m(DIN,~32.0μmol/L;DIP,~2.4μmol/L)and then generally increased with depth;they decreased markedly(DIN,~1.2μmol/L;DIP,~0.1μmol/L;at~150 m)at high latitudes and in the western region,where a nutricline was not apparent.The N^(*)index showed significant meridional and zonal variation,with the most negative values located at low latitudes and in the eastern region(~10°N,~150°-170°E),while becoming positive towards the northwest(the north of~18°N,~160°E westward).A N^(*)concentration larger than 2.0μmol/L which often used as an indicator of N2fixation,was observed between 155°E and 165°E;N^(*)values were 2.0μmol/L to6.0μmol/L at~15°-28°N,i.e.,much higher than those in the southern sector(0-2.0μmol/L at~5°-10°N).Zonally,N^(*)decreased gradually from west(-2.0μmol/L to 4.0μmol/L,~145°-165°E)to east(-2.0μmol/L to-8.0μmol/L,~155°W)along~10°N,which was consistent with the distribution of Trichodesmium abundance and N2fixation rates.Furthermore,since such region was also supplied with aeolian deposition,high N^(*)was probably not only induced by N2fixation but also influenced by iron and/or nitrogen deposition.
基金This study was financially supported by the China Geological Survey’s project(No.DD20160311)National Natural Science Foundation of China(No.41602268).
文摘Thick loess is deposited on the platform in the piedmont zone of Muling-Xingkai Plain(Muxing Plain),but the genesis of the Muxing loess is still unclear.The aims of this study are to analyze the grain size characteristics of Muxing loess collected from the cores of a typical borehole(ZK1)in the piedmont zone of Muxing Plain,and to verify its genesis.The Muxing loess is mainly composed of the particles with diameter less than 50μm,with an average content of 92.48%.The coarse silt particles with diameter of 10-50μm are the basic composition of aeolian sediments,and their average content is 44.34% for the Muxing loess,which is the mode class among the particles with different diameters.The grain size parameters and frequency curves are similar to those of the typical aeolian sediments.The distribution characteristic of the Muxing loess in the C-M scatter diagram is consistent with that of the Xi Feng loess.In addition,the discriminant analysis shows the Muxing loess mostly consists of aeolian sediments.Therefore,it can be concluded that the Muxing loess mainly resulted from aeolian deposition based on the grain size characteristics.Muxing Plain is dominated by the monsoon climate,and the wind-blown dusts are gradually deposited after being transported over long distances.
基金supported by the National Key Research and Development Program of China (No.2018YFC0604202)from the Ministry of Science and Technology of China and the International Geosciences Program (No.IGCP675)
文摘Uranium exploration breakthrough was extremely rare in an aeolian depositional system.In order to know the complicate characteristics of oxidation associated closely with uranium mineralization in the aeolian depositional system,petrology and mineralogy markers of the oxidation and its genetic mechanisms are identified and illustrated by fieldwork,thin section analysis and scanning electron microscopy test,based on 2 field outcrops in Zhenyuan County in the southwest of the Tianhuan depression in the Ordos Basin and the core of 2 wells in the north and south of Ordos Basin.The results showed:the typical macroscopic indicator of primary oxidation was the red fine sediments in the aeolian interdune with a thickness of 10-50 cm,and the microscopic characteristics of primary oxidation were the minerals such as hematite,ilmenite,and the irony matrix rich in fine-grained dolomite and biotite;the phreatic oxidation was manifested as the red sandstone with limonite horizontal layer with a thickness of 1-4 cm and a width of 60 cm-1 m,and the circular limonite nodules with a diameter of 3-7 cm,in which there was intergranular limonite cement;the interlayer oxidation was characterized by lenticular tongue and tapered red sandstone with a length of 1-10 m and a width of 10 cm-5m,in which detrital particles are coated with hematite and hematite was distributed inside the rhombus dolomite.The paleoclimate of the sedimentary period,the water-table movement and the pore and permeability conditions of the sand body were the key factors for the formation of different oxidation types in the aeolian depositional system.