The exploitation of coal, petroleum and natural gas in northern Shaanxi not only promoted the rapid development of economy, but also brought about enormous pressure to fragile ecology and resulted to severe water poll...The exploitation of coal, petroleum and natural gas in northern Shaanxi not only promoted the rapid development of economy, but also brought about enormous pressure to fragile ecology and resulted to severe water pollution, water and soil loss, vegetation destruction and other ecological environmental problems, so many countermeasures were put forward according to these problems, such as greatly developing circular economy, conducting cleaner production in petroleum enterprises, continuously renewing mining technology and so on.展开更多
Objective At present,there is controversy regarding the existence of marine-terrestrial transitional facies that can act as a source of shale gas.This detailed study of CarboniferousPermian age geological data from th...Objective At present,there is controversy regarding the existence of marine-terrestrial transitional facies that can act as a source of shale gas.This detailed study of CarboniferousPermian age geological data from the northern Shaanxi area(China)provides new insight for this type of shale gas.In addition,a new deposition and accumulation pattern for this type of shale gas is established.Thus,the objectives of this study were to identify high quality gasbearing shale intervals in the lithological column of展开更多
Groundwater is of vital importance to many aspects of ecosystem services,especially in the central and northern Shaanxi Provence,China,-an area covered by loess deposits and short of water resources.We studied the sol...Groundwater is of vital importance to many aspects of ecosystem services,especially in the central and northern Shaanxi Provence,China,-an area covered by loess deposits and short of water resources.We studied the solute geochemistry and water quality of groundwater in this area to improve the understanding of hydrogeochemical processes in loess deposits area.The results showed that the average pH of groundwaters was 8.03±0.36(1 SD)with large ranges(324-83,379 mg/L)of the total dissolved solids(TDS).The cations and anions followed the order of Na^+>Ca^2+>Mg^2+>K^+>SiO2 and HCO3>Cl^->SO4^2->F^->NO3^-.Most groundwater samples show the HCO3^--Na^+-Ca^2+water type and a small number of samples the Na^+-Cl^-type.Irrigation water quality assessments showed that 40%of the groundwater has good water quality,42%moderate water quality,and 18%(the upper reaches of Wuding River and Wei River)poor water quality with very high salinity.About 40%of groundwater samples were not suitable for drinking due to the high TDS,fluoride,sulfide,and chloride.Gibbs plot and stoichiometry analysis showed that carbonate weathering is the main source of groundwater chemistry in central Shaanxi Province while evaporite dissolution dominates in northern Shaanxi Provence.The loess weathering significantly influences the dissolved solutes of groundwater in the Loess Plateau.The ion-exchange between Mg^2+and Ca^2+in groundwater and Na^+in clay minerals and the deposition of carbonate minerals increased Na^+but decreased the Ca^2+in groundwater.Our research results improve our understanding of hydrogeochemical processes that affect the solutes chemistry of groundwater in the loess area and provide essential data to the global groundwater database.展开更多
The Loess Plateau in northern Shaanxi Province of China covers Yulin,Yan'an,and Tongchuan cities mainly. The kind of physiognomy is complicated and various,including the transitional region of the sand and wind,th...The Loess Plateau in northern Shaanxi Province of China covers Yulin,Yan'an,and Tongchuan cities mainly. The kind of physiognomy is complicated and various,including the transitional region of the sand and wind,the hilly-gully fragile region,the pimple mound region from North to South. Large-scale land reclamation projects that are severely affecting these ecosystems have been implemented. In this paper,we reported an investigation to the changes in land use and ecosystem services on the Loess Plateau in northern Shaanxi Province from 1978 to 2000. We used three LANDSAT TM and/or ETM data sets to estimate the changes in the size of five land-cover/land-use categories,and we also used previously published value coefficients to estimate the changes in the value of ecosystem services delivered by each land category. Finally,we ranked the contribution of various ecosystem functions to the overall value of the ecosystem services. we have estimated that the annual value of the ecosystem services is 56.95 billon RMB yuan in the Loess Plateau in northern Shaanxi Province in 2000. In the region,from 1978 to 2000,the economic value of the fixing carbon was higher,the economic value of water conservation was the lowest,but the economic value of the NPP,fixing carbon,and supplying oxygen accounted for above ninety percent of the total value,obviously the vegetation created the biggest ecosystem service value. We can conclude that future land-use policy formulation should give precedence to the conservation of these ecosystems over uncontrolled reclamation,and that further land reclamation should be based on rigorous environmental impact analyses.展开更多
By dividing the diagenetic reservoir facies and studying its distribution,we can effectively evaluate reservoirs.Using an analytical method for mutual relationships among diagenesis of reservoirs,structural characteri...By dividing the diagenetic reservoir facies and studying its distribution,we can effectively evaluate reservoirs.Using an analytical method for mutual relationships among diagenesis of reservoirs,structural characteristics and the origin of types of sand,we classified the diagenetic reservoir of the Yanchang formation Chang-3 oil layer into different types and analyzed the factors controlling this high quality reservoir.The results show that:1) the catagenesis of the Chang-3 oil layer in the Fuxian region is complex and variable;2) mechanical compaction,pressure solutions and cementation of all kinds of authogenous minerals decreases porosity by 28.13% and 3) corrosion increases porosity by 3.39%.Cementation and corrosion of laumontite is a kind of catagenesis which makes this region different from other exploratory regions.The original amount and rate of corrosion of laumontite are the main factors for the increase in laumontite porosity.The Chang-3 oil layer developed four kinds of diagenetic reservoir facies,of which the weak compaction facies,i.e.,laumontite corrosion and overgrowth,of the original pore reservoir facies has the most promising diagenesis.Its distribution is controlled by a sedimentary facies zone and is widely developed in the original truncated tributary channel facies belt of the delta plain.The development of this high quality reservoir is controlled by the distribution of sedimentary sand bodies and secondarily-eroded porosity of laumontite in the Chang-3 oil layer of the Fuxian exploratory region.展开更多
Using the theory and method of the ecological footprint, and combining the changes of regional land use, resource environment, population, society and economy, this paper calculated the ecological footprint, ecologica...Using the theory and method of the ecological footprint, and combining the changes of regional land use, resource environment, population, society and economy, this paper calculated the ecological footprint, ecological carrying capacity and ecological surplus/loss in 1986-2002 on the Loess Plateau in northern Shaanxi Province. What is more, this paper has put forward the concept of ecological pressure index, set up ecological pressure index models, and ecological security grading systems, and the prediction models of different ecological footprints, ecological carrying capacity, ecological surplus and ecological safety change, and also has assessed the ecological footprint demands of 10,000 yuan GDP. The results of this study are as follows: (1) the ecological carrying capacity in northern Shaanxi shows a decreasing trend, the difference of reducing range is the fastest; (2) the ecological footprint appears an increasing trend; (3) ecological pressure index rose to 0.91 from 0.44 during 1986-2002 on the Loess Plateau of northern Shaanxi with an increase of 47%; and (4) the ecological security in the study area is in a critical state, and the ecological pressure index has been increasing rapidly.展开更多
There are large deltaic systems in the Triassic Yanchang Formation in the northern Shaanxi area of the Ordos Basin, and developed two sets of good source-reservoir-caprock assemblages and many sets of oil-beating beds...There are large deltaic systems in the Triassic Yanchang Formation in the northern Shaanxi area of the Ordos Basin, and developed two sets of good source-reservoir-caprock assemblages and many sets of oil-beating beds. Exploration experience demonstrates that the formation and distribution of the reservoir were controlled by the generative depression of the Yanchang Formation, and deltaic reservoir sand body is the material basis for large-scale oilfields. In addition, secondary laumontite in a low permeable area was dissolved and then a high permeable area was formed. The updip lithologic variety of reservoir sand bodies is favorable to the formation of subtle lithologic traps, and the deltaic reservoirs are characterized by large multi-beds of oil-generation and abundant hydrocarbon resources. In this paper, the petroleum geologic settings of the studied area are analyzed, and the accumulation characteristics and exploration methods of lithologic reservoirs are summarized. It is of theoretical significance for the study of the exploration theories of lithologic reservoirs, and also expedites the exploration steps of deltaic reservoirs in the northern Shaanxi area.展开更多
The Ordovician Northern Shaanxi Salt Basin(ONSSB), located in the east–central Ordos Basin, western North China Craton(NCC), is one of the largest marine salt basins yet discovered in China. A huge amount of halite d...The Ordovician Northern Shaanxi Salt Basin(ONSSB), located in the east–central Ordos Basin, western North China Craton(NCC), is one of the largest marine salt basins yet discovered in China. A huge amount of halite deposited in the Mid-Ordovician Majiagou Formation, and potashcontaining indication and local thin layer of potash seam were discovered in O2 m65(6 th submember, 5 th member of the Majiagou Formation). This makes ONSSB a rare Ordovician potash-containing basin in the world, and brings new hope for prospecting marine solid potash in this basin. However, several primary scientific problems, such as the coupling relationship between ONSSB and the continent nucleus, how the high-precision basement fold controls the ONSSB, and how the basement faults and relief control ONSSB, are still unclear due to the limitations of the knowledge about the basement of the Ordos Basin. This has become a barrier for understanding the potash-forming regularity in the continental nucleus(CN) area in marine salt basin in China. Up to now, the material accumulation has provided ripe conditions for the answers to these questions. Latest zircon U-Pb ages for the basement samples beneath the Ordos Basin reveal that there exists a continental nucleus(Yi-Meng CN) beneath the northern Ordos Basin. And this brings light into the fact that the ONSSB lies not overlying on the YiMeng CN but to south Yi-Meng CN. Both do not have superimposed relationship in space. And borehole penetrating into the basement reached Palaeoproterozoic meta-sedimentary rocks, which suggests the ONSSB is situated in the accretion belt of Yi-Meng CN during geological history. Basement relief beneath the ONSSB area revealed by seismic tomography and aeromagnetic anomaly confirms the existence of basement uplift and faults, which provides tectonic setting for sedimentary center migration of the ONSSB. Comparative research with various data sources indicates that the expanding strata in the ONSSB adopted the shape of the basement folds. We found that the orientations of the potash sags showed high correlation with those of several basement and sedimentary cover faults in the ONSSB. The secondary depressions are also controlled by the faults. Comparative research between all the global salt basins and continental nuclei distribution suggests that distribution of the former is controlled by the latter, and almost all the salt basins developed in or at the margin of the continental nucleus area. The nature of the tectonic basement exerts a key controlling effect on potash basin formation. And on this basis we analyzed in detail the geological conditions of salt-forming and potash-forming in the ONSSB.展开更多
[Objective] The research aimed to study change characteristics and formation cause of summer precipitation abnormality in Loess Plateau of northern Shaanxi Province. [Method] Based on summer precipitation data at 15 o...[Objective] The research aimed to study change characteristics and formation cause of summer precipitation abnormality in Loess Plateau of northern Shaanxi Province. [Method] Based on summer precipitation data at 15 observation stations in Loess Plateau of northern Shaanxi Province and NCEP/NCAR dataset from 1961 to 2008, change characteristics of summer precipitation in the region were investigated by using linear trend estimation and composite analysis. [Result] Summer rainfall had decrease trend in most parts of northern Shaanxi Province, but had increase trend in western and southern regions. The interannual and interdecadal variations were obvious. It had a large amount of precipitation from the mid-1970s to the mid-1990s, while summer rainfall had decrease trend after the mid-1990s and increase trend in recent years. In wet years, it was a large positive anomaly zone from western Ural Mountains to northern Lake Baikal at middle and high latitudes, indicating that there was a blocking high over the Ural Mountains, while it was negative anomaly zone from northern Okhotsk Sea to Lake Baikal. From Northwest Pacific Ocean to Bohai Sea Bay and North China, it was a wide range of significant positive anomaly zone, which was favorable for Western Pacific subtropical high extending westward and northward. The analysis in dry years showed opposite circulation configuration. It was "-, +, -" wave train distribution in middle and high latitudes and positive anomaly zone along the Sea of Okhotsk. Western Pacific subtropical high was also by south and east. Major water vapor was from southeast direction in wet years, and abundant water vapor caused more summer rainfall in northern Shaanxi. In dry years, water vapor was from westerly turning southerly flow. It was weaker and by east. [Conclusion] The research provided reference for reasonable utilization of summer precipitation in the zone.展开更多
Lacustrine turbidite of Chang-7 Member in the studied area consists of siltstone and fine sandstone with respect to grain size,which is feldspathic lithic sandstone,syrosem arkose and arkose with respect to mineral co...Lacustrine turbidite of Chang-7 Member in the studied area consists of siltstone and fine sandstone with respect to grain size,which is feldspathic lithic sandstone,syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology,sedimentary structure,sedimentary sequence and well logs,to recognize turbidite. During the paleogeographic evolution of Chang-7 Member,lake basin and deep lake are both at their maximum extent during Chang-73 stage,resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity,connectivity and more thickness,from stages of Chang-73,Chang-72 and Chang-71 ,which can be favorable reservoir in deep-water.展开更多
Soil erosion in northern Shaanxi region has been greatly affected by human activities. On the one hand, newly occurred soil and water loss has been observed due to accelerated soil erosion caused by irrational human e...Soil erosion in northern Shaanxi region has been greatly affected by human activities. On the one hand, newly occurred soil and water loss has been observed due to accelerated soil erosion caused by irrational human economic activities such as excessive reclamation, mining, etc.. On the other hand, great economic, social and ecological benefits have been brought into play due to vast amount of sediment trapping in watershed management as a result of adoption of engineering measures like silt arrester and horizontal terracing and of biological measures like afforestation and grass planting.展开更多
In order to explore subsistence patterns in northern Shaanxi Province around 4,000 yr BP,28 human and 24 animal bones from the Shengedaliang site were sampled for stable carbon and nitrogen isotope ratio analysis.The ...In order to explore subsistence patterns in northern Shaanxi Province around 4,000 yr BP,28 human and 24 animal bones from the Shengedaliang site were sampled for stable carbon and nitrogen isotope ratio analysis.The results show that most people primarily subsisted on C_4 resources,e.g.millet and millet-related animal products,despite the fact that there was some intake of C_3 plants by some individuals.Stable nitrogen isotope values indicate that there were differences in meat consumption between individuals at the site.Pigs were mainly foddered with millet and millet byproducts,as well as some cattle,according to their highδ^(13)C values.However,most cattle and the sheep/goats consumed wild C_3 plants at Shengedaliang.Our above findings indicates that subsistence patterns in northern Shaanxi around 4,000 yr BP were characterized by millet farming,while the grassland animal husbandry,e.g.cattle and sheep/goats raising,displayed very little contribution to local economy.The intensive millet farming in northern Shaanxi provided enough food for population growth,ensured the accumulation of wealth,and consequently accelerated social differentiation and complexity.展开更多
文摘The exploitation of coal, petroleum and natural gas in northern Shaanxi not only promoted the rapid development of economy, but also brought about enormous pressure to fragile ecology and resulted to severe water pollution, water and soil loss, vegetation destruction and other ecological environmental problems, so many countermeasures were put forward according to these problems, such as greatly developing circular economy, conducting cleaner production in petroleum enterprises, continuously renewing mining technology and so on.
基金funded by the Geological Survey Project of China Geological Survey(No.1212011085516)Geological Survey Level 2 Project(No.121201103000150011)Basic Research Professional Expenses of CAGS(No. YYWF201609)
文摘Objective At present,there is controversy regarding the existence of marine-terrestrial transitional facies that can act as a source of shale gas.This detailed study of CarboniferousPermian age geological data from the northern Shaanxi area(China)provides new insight for this type of shale gas.In addition,a new deposition and accumulation pattern for this type of shale gas is established.Thus,the objectives of this study were to identify high quality gasbearing shale intervals in the lithological column of
基金financially supported by the Shaanxi Science Fund for Distinguished Young Scholars(2020JC030)the CAS"Light of West China"Program(XAB2018A02)+1 种基金the National Natural Science Foundation of China(41673128)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40020200)。
文摘Groundwater is of vital importance to many aspects of ecosystem services,especially in the central and northern Shaanxi Provence,China,-an area covered by loess deposits and short of water resources.We studied the solute geochemistry and water quality of groundwater in this area to improve the understanding of hydrogeochemical processes in loess deposits area.The results showed that the average pH of groundwaters was 8.03±0.36(1 SD)with large ranges(324-83,379 mg/L)of the total dissolved solids(TDS).The cations and anions followed the order of Na^+>Ca^2+>Mg^2+>K^+>SiO2 and HCO3>Cl^->SO4^2->F^->NO3^-.Most groundwater samples show the HCO3^--Na^+-Ca^2+water type and a small number of samples the Na^+-Cl^-type.Irrigation water quality assessments showed that 40%of the groundwater has good water quality,42%moderate water quality,and 18%(the upper reaches of Wuding River and Wei River)poor water quality with very high salinity.About 40%of groundwater samples were not suitable for drinking due to the high TDS,fluoride,sulfide,and chloride.Gibbs plot and stoichiometry analysis showed that carbonate weathering is the main source of groundwater chemistry in central Shaanxi Province while evaporite dissolution dominates in northern Shaanxi Provence.The loess weathering significantly influences the dissolved solutes of groundwater in the Loess Plateau.The ion-exchange between Mg^2+and Ca^2+in groundwater and Na^+in clay minerals and the deposition of carbonate minerals increased Na^+but decreased the Ca^2+in groundwater.Our research results improve our understanding of hydrogeochemical processes that affect the solutes chemistry of groundwater in the loess area and provide essential data to the global groundwater database.
基金the National Natural Science Foundation of China(40771019)the National Natural Science Foundation of Shaanxi Province,China(2007D16).
文摘The Loess Plateau in northern Shaanxi Province of China covers Yulin,Yan'an,and Tongchuan cities mainly. The kind of physiognomy is complicated and various,including the transitional region of the sand and wind,the hilly-gully fragile region,the pimple mound region from North to South. Large-scale land reclamation projects that are severely affecting these ecosystems have been implemented. In this paper,we reported an investigation to the changes in land use and ecosystem services on the Loess Plateau in northern Shaanxi Province from 1978 to 2000. We used three LANDSAT TM and/or ETM data sets to estimate the changes in the size of five land-cover/land-use categories,and we also used previously published value coefficients to estimate the changes in the value of ecosystem services delivered by each land category. Finally,we ranked the contribution of various ecosystem functions to the overall value of the ecosystem services. we have estimated that the annual value of the ecosystem services is 56.95 billon RMB yuan in the Loess Plateau in northern Shaanxi Province in 2000. In the region,from 1978 to 2000,the economic value of the fixing carbon was higher,the economic value of water conservation was the lowest,but the economic value of the NPP,fixing carbon,and supplying oxygen accounted for above ninety percent of the total value,obviously the vegetation created the biggest ecosystem service value. We can conclude that future land-use policy formulation should give precedence to the conservation of these ecosystems over uncontrolled reclamation,and that further land reclamation should be based on rigorous environmental impact analyses.
文摘By dividing the diagenetic reservoir facies and studying its distribution,we can effectively evaluate reservoirs.Using an analytical method for mutual relationships among diagenesis of reservoirs,structural characteristics and the origin of types of sand,we classified the diagenetic reservoir of the Yanchang formation Chang-3 oil layer into different types and analyzed the factors controlling this high quality reservoir.The results show that:1) the catagenesis of the Chang-3 oil layer in the Fuxian region is complex and variable;2) mechanical compaction,pressure solutions and cementation of all kinds of authogenous minerals decreases porosity by 28.13% and 3) corrosion increases porosity by 3.39%.Cementation and corrosion of laumontite is a kind of catagenesis which makes this region different from other exploratory regions.The original amount and rate of corrosion of laumontite are the main factors for the increase in laumontite porosity.The Chang-3 oil layer developed four kinds of diagenetic reservoir facies,of which the weak compaction facies,i.e.,laumontite corrosion and overgrowth,of the original pore reservoir facies has the most promising diagenesis.Its distribution is controlled by a sedimentary facies zone and is widely developed in the original truncated tributary channel facies belt of the delta plain.The development of this high quality reservoir is controlled by the distribution of sedimentary sand bodies and secondarily-eroded porosity of laumontite in the Chang-3 oil layer of the Fuxian exploratory region.
基金National Natural Science Foundation of China, No.40371003 Ministry of Education of China, No.01158 Master Research Project of Shaanxi Normal University
文摘Using the theory and method of the ecological footprint, and combining the changes of regional land use, resource environment, population, society and economy, this paper calculated the ecological footprint, ecological carrying capacity and ecological surplus/loss in 1986-2002 on the Loess Plateau in northern Shaanxi Province. What is more, this paper has put forward the concept of ecological pressure index, set up ecological pressure index models, and ecological security grading systems, and the prediction models of different ecological footprints, ecological carrying capacity, ecological surplus and ecological safety change, and also has assessed the ecological footprint demands of 10,000 yuan GDP. The results of this study are as follows: (1) the ecological carrying capacity in northern Shaanxi shows a decreasing trend, the difference of reducing range is the fastest; (2) the ecological footprint appears an increasing trend; (3) ecological pressure index rose to 0.91 from 0.44 during 1986-2002 on the Loess Plateau of northern Shaanxi with an increase of 47%; and (4) the ecological security in the study area is in a critical state, and the ecological pressure index has been increasing rapidly.
文摘There are large deltaic systems in the Triassic Yanchang Formation in the northern Shaanxi area of the Ordos Basin, and developed two sets of good source-reservoir-caprock assemblages and many sets of oil-beating beds. Exploration experience demonstrates that the formation and distribution of the reservoir were controlled by the generative depression of the Yanchang Formation, and deltaic reservoir sand body is the material basis for large-scale oilfields. In addition, secondary laumontite in a low permeable area was dissolved and then a high permeable area was formed. The updip lithologic variety of reservoir sand bodies is favorable to the formation of subtle lithologic traps, and the deltaic reservoirs are characterized by large multi-beds of oil-generation and abundant hydrocarbon resources. In this paper, the petroleum geologic settings of the studied area are analyzed, and the accumulation characteristics and exploration methods of lithologic reservoirs are summarized. It is of theoretical significance for the study of the exploration theories of lithologic reservoirs, and also expedites the exploration steps of deltaic reservoirs in the northern Shaanxi area.
基金financially supported by the National Key R&D Program of China (grant No. 2017YFC0602806)the National Basic Research Program of China (973 program, grant No. 2011CB403001)
文摘The Ordovician Northern Shaanxi Salt Basin(ONSSB), located in the east–central Ordos Basin, western North China Craton(NCC), is one of the largest marine salt basins yet discovered in China. A huge amount of halite deposited in the Mid-Ordovician Majiagou Formation, and potashcontaining indication and local thin layer of potash seam were discovered in O2 m65(6 th submember, 5 th member of the Majiagou Formation). This makes ONSSB a rare Ordovician potash-containing basin in the world, and brings new hope for prospecting marine solid potash in this basin. However, several primary scientific problems, such as the coupling relationship between ONSSB and the continent nucleus, how the high-precision basement fold controls the ONSSB, and how the basement faults and relief control ONSSB, are still unclear due to the limitations of the knowledge about the basement of the Ordos Basin. This has become a barrier for understanding the potash-forming regularity in the continental nucleus(CN) area in marine salt basin in China. Up to now, the material accumulation has provided ripe conditions for the answers to these questions. Latest zircon U-Pb ages for the basement samples beneath the Ordos Basin reveal that there exists a continental nucleus(Yi-Meng CN) beneath the northern Ordos Basin. And this brings light into the fact that the ONSSB lies not overlying on the YiMeng CN but to south Yi-Meng CN. Both do not have superimposed relationship in space. And borehole penetrating into the basement reached Palaeoproterozoic meta-sedimentary rocks, which suggests the ONSSB is situated in the accretion belt of Yi-Meng CN during geological history. Basement relief beneath the ONSSB area revealed by seismic tomography and aeromagnetic anomaly confirms the existence of basement uplift and faults, which provides tectonic setting for sedimentary center migration of the ONSSB. Comparative research with various data sources indicates that the expanding strata in the ONSSB adopted the shape of the basement folds. We found that the orientations of the potash sags showed high correlation with those of several basement and sedimentary cover faults in the ONSSB. The secondary depressions are also controlled by the faults. Comparative research between all the global salt basins and continental nuclei distribution suggests that distribution of the former is controlled by the latter, and almost all the salt basins developed in or at the margin of the continental nucleus area. The nature of the tectonic basement exerts a key controlling effect on potash basin formation. And on this basis we analyzed in detail the geological conditions of salt-forming and potash-forming in the ONSSB.
基金Supported by National Science and Technology Support Plan Project,China ( 2007BAC03A01)
文摘[Objective] The research aimed to study change characteristics and formation cause of summer precipitation abnormality in Loess Plateau of northern Shaanxi Province. [Method] Based on summer precipitation data at 15 observation stations in Loess Plateau of northern Shaanxi Province and NCEP/NCAR dataset from 1961 to 2008, change characteristics of summer precipitation in the region were investigated by using linear trend estimation and composite analysis. [Result] Summer rainfall had decrease trend in most parts of northern Shaanxi Province, but had increase trend in western and southern regions. The interannual and interdecadal variations were obvious. It had a large amount of precipitation from the mid-1970s to the mid-1990s, while summer rainfall had decrease trend after the mid-1990s and increase trend in recent years. In wet years, it was a large positive anomaly zone from western Ural Mountains to northern Lake Baikal at middle and high latitudes, indicating that there was a blocking high over the Ural Mountains, while it was negative anomaly zone from northern Okhotsk Sea to Lake Baikal. From Northwest Pacific Ocean to Bohai Sea Bay and North China, it was a wide range of significant positive anomaly zone, which was favorable for Western Pacific subtropical high extending westward and northward. The analysis in dry years showed opposite circulation configuration. It was "-, +, -" wave train distribution in middle and high latitudes and positive anomaly zone along the Sea of Okhotsk. Western Pacific subtropical high was also by south and east. Major water vapor was from southeast direction in wet years, and abundant water vapor caused more summer rainfall in northern Shaanxi. In dry years, water vapor was from westerly turning southerly flow. It was weaker and by east. [Conclusion] The research provided reference for reasonable utilization of summer precipitation in the zone.
文摘Lacustrine turbidite of Chang-7 Member in the studied area consists of siltstone and fine sandstone with respect to grain size,which is feldspathic lithic sandstone,syrosem arkose and arkose with respect to mineral constitution affected by provenance. There are such apparent signatures as lithology,sedimentary structure,sedimentary sequence and well logs,to recognize turbidite. During the paleogeographic evolution of Chang-7 Member,lake basin and deep lake are both at their maximum extent during Chang-73 stage,resulting in the deposition of Zhangjiatan shale with widespread extent and of turbidite with fragmental-like. Deep lake line is gradually moving toward lake center and turbidite sand bodies are gradually turning better with better lateral continuity,connectivity and more thickness,from stages of Chang-73,Chang-72 and Chang-71 ,which can be favorable reservoir in deep-water.
文摘Soil erosion in northern Shaanxi region has been greatly affected by human activities. On the one hand, newly occurred soil and water loss has been observed due to accelerated soil erosion caused by irrational human economic activities such as excessive reclamation, mining, etc.. On the other hand, great economic, social and ecological benefits have been brought into play due to vast amount of sediment trapping in watershed management as a result of adoption of engineering measures like silt arrester and horizontal terracing and of biological measures like afforestation and grass planting.
基金supported by the Knowledge Innovation Fund of the Chinese Academy of Social Sciencesthe National Natural Science Foundation of China(Grant Nos.41373018&41471167)
文摘In order to explore subsistence patterns in northern Shaanxi Province around 4,000 yr BP,28 human and 24 animal bones from the Shengedaliang site were sampled for stable carbon and nitrogen isotope ratio analysis.The results show that most people primarily subsisted on C_4 resources,e.g.millet and millet-related animal products,despite the fact that there was some intake of C_3 plants by some individuals.Stable nitrogen isotope values indicate that there were differences in meat consumption between individuals at the site.Pigs were mainly foddered with millet and millet byproducts,as well as some cattle,according to their highδ^(13)C values.However,most cattle and the sheep/goats consumed wild C_3 plants at Shengedaliang.Our above findings indicates that subsistence patterns in northern Shaanxi around 4,000 yr BP were characterized by millet farming,while the grassland animal husbandry,e.g.cattle and sheep/goats raising,displayed very little contribution to local economy.The intensive millet farming in northern Shaanxi provided enough food for population growth,ensured the accumulation of wealth,and consequently accelerated social differentiation and complexity.
