Basing on the limiting factor method and Composite Index method,for the northern China crop-pasture band,the authors established the system of evaluation index,and abstracted the dominant factor,then through applying ...Basing on the limiting factor method and Composite Index method,for the northern China crop-pasture band,the authors established the system of evaluation index,and abstracted the dominant factor,then through applying expert grade and weighing way the suitability of grids are evaluated,the results showed that:without the input of a large number of cash,most of the area was not suitable for farming,and more appropriate area for farming was only 8.45% of total area,mainly located in the southeast and southwest of the study area,followed by the study area in the northeast,areas that was not suitable for farming mainly in the middle of the east,large areas of central and western regions.展开更多
The composition,provenance,and genetic mechanism of sediment on different sedimentary units of the East China Sea(ECS)shelf are essential for understanding the depositional dynamics environment in the ECS.The sediment...The composition,provenance,and genetic mechanism of sediment on different sedimentary units of the East China Sea(ECS)shelf are essential for understanding the depositional dynamics environment in the ECS.The sediments in the northern ECS shelf are distributed in a ring-shaped distribution centered on the southwestern Cheju Island Mud.From the inside to the outside,the grain size goes from fine to coarse.Aside from the“grain size effect”,hydrodynamic sorting and mineral composition are important restrictions on the content of rare earth elements(REEs).Based on the grain size,REEs,and clay mineral composition of 300 surface sediments,as well as the sedimentary genesis,the northern ECS shelf is divided into three geochemical zones:southwestern Cheju Island Mud Area(ZoneⅠ),Changjiang Shoal Sand Ridges(ZoneⅡ-1),Sand Ridges of the East China Sea shelf(ZoneⅡ-2).The northern ECS shelf is mostly impacted by Chinese mainland rivers(the Changjiang River and Huanghe River),and the provenance and transport mechanism of sediments of different grain sizes is diverse.The bulk sediments come primarily from the Changjiang River,with some material from the Huanghe River carried by the Yellow Sea Coastal Current and the North Jiangsu Coastal Current,and less from Korean rivers.Among them,surface sediments in the southwestern Cheju Island Mud Area(ZoneⅠ)come mostly from the Changjiang River and partly from the Huanghe River.It was formed by the counterclockwise rotating cold eddies in the northern ECS shelf,which caused the sedimentation and accumulation of the fine-grained sediments of the Changjiang River and the Huanghe River.The Changjiang Shoal Sand Ridges(ZoneⅡ-1)were developed during the early-middle Holocene sea-level highstand.It is the modern tidal sand ridge sediment formed by intense hydrodynamic action under the influence of the Yellow Sea Coastal Current,North Jiangsu Coastal Current,and Changjiang Diluted Water.The surface sediments mainly originate from the Changjiang River and Huanghe River,with the Changjiang River dominating,and the Korean River(Hanjiang River)influencing just a few stations.Sand Ridges of the East China Sea shelf(ZoneⅡ-2)are the relict sediments of the paleo-Changjiang River created by sea invasion at the end of the Last Deglaciation in the Epipleistocene.The clay mineral composition of the surface sediments in the study area is just dominated by the Changjiang River,with the North Jiangsu Coastal Current and the Changjiang Diluted Water as the main transporting currents.展开更多
The diffuse attenuation coefficient for downwelling irradiance(Kd(λ)) is an important parameter for ocean studies.Based on the optical profile data measured during three cruises in the northern South China Sea in aut...The diffuse attenuation coefficient for downwelling irradiance(Kd(λ)) is an important parameter for ocean studies.Based on the optical profile data measured during three cruises in the northern South China Sea in autumn from 2003 to 2005,variations in the Kd(λ) spectra were analyzed.The variability of Kd(λ) shows much distinct features in both magnitude and spectra pattern,it is much higher in coastal waters than that of open oceanic waters;and the blue-to-green(443/555) ratio of Kd(λ) tends to increase with chlorophyll a concentration([Chl-a]) from open ocean to coastal waters.These characteristics can be explained most by the increase of aw+p(443)/aw+p(555) with [Chl-a].In short waveband,the relation between Kd(λ)-Kw(λ) and [Chl-a] can be well described by a power law function,indicating the large contribution of phytoplankton to the variations in Kd(λ).As for the spectral model of the diffuse attenuation coefficient,there are good linear relationships between Kd(490) and Kd(λ) in other wavelengths with own slope and intercept of a linear functions in the spectral range 412-555 nm.Kd(490) is well correlated with the spectral ratio of remote sensing reflectance;and should enough measurement data are given,this empirical algorithm would be used in the Kd(λ) retrieval from ocean color satellite data.The variation in Kd(λ) provides much useful information for us to study the bio-optical property in the northern South China Sea.展开更多
The correlation of ambient noise with wind speed,and the depth dependence of ambient noise are both investigated,where the ocean noise data were recorded by a vertical line array in the northern South China Sea.It is ...The correlation of ambient noise with wind speed,and the depth dependence of ambient noise are both investigated,where the ocean noise data were recorded by a vertical line array in the northern South China Sea.It is shown that the correlation coefficients increase with increasing hydrophone depth during typhoon periods when the frequency≥250 Hz,which opposes the generally accepted knowledge that the correlation coefficients of noise level and wind speed decrease with increasing depth during non-typhoon periods.Particularly at frequencies of 250 Hz,315 Hz and 400 Hz,the correlation coefficients increase by more than 0.05 at depths ranging from 155 m to 875 m.At the three frequencies,the average noise levels also increase with increasing depth during typhoon periods.It is suggested that these differences are attributed to the wind-generated noise in shallow waters and the effect of"downslope enhancement"to sound propagation.During typhoon periods,the surf breaking and surf beat upon the shores and reefs are strengthened,and the source levels are increased.The wind-generated noise in shallow waters interacts with the downslope sea floor,with the noise-depth distribution changed by a"downslope enhancement"effect promoting noise propagation.展开更多
We examined the influences of the wind fi eld and wave-current interaction(WCI)on the numerical simulation results of typhoon-induced wind waves in the northern East China Sea(NECS)using the coupled Simulating Waves N...We examined the influences of the wind fi eld and wave-current interaction(WCI)on the numerical simulation results of typhoon-induced wind waves in the northern East China Sea(NECS)using the coupled Simulating Waves Nearshore+Advanced Circulation(SWAN+ADCIRC)model.The simulations were performed during two typhoon events(Lekima and Muifa),and two widely used reanalysis wind fields,the Climate Forecast System Version 2(CFSv2)from the National Centers for Environmental Prediction(NCEP)and the fifth-generation European Centre for Medium-Range Weather Forecasts(ECMWF)Reanalysis(ERA5),were compared.The results indicate that the ERA5 and CFSv2 wind fields both reliably reproduced the wind variations measured by in-situ buoys,and the accuracy of the winds from ERA5 were generally better than those from CFSv2 because CFSv2 tended to overestimate the wind speed and the simulated significant wave height(SWH),particularly the peak SWH.The WCI effects between the two wind field simulations were similar;these effects enhanced the SWH throughout the nearshore NECS during both typhoons but suppressed the SWH on the right side of the Typhoon Muifa track in the deep and off shore sea areas.In summary,variations in the water depth and current propagation direction dominate the modulation of wave height.展开更多
The clay minearals are composed of illite, chlorite, kaolinite, montmorillonite and mixed-layer minerals in the submarine sediments of the northern South China Sea. Three types of clay mineral zone can be recognized o...The clay minearals are composed of illite, chlorite, kaolinite, montmorillonite and mixed-layer minerals in the submarine sediments of the northern South China Sea. Three types of clay mineral zone can be recognized on the basis of the distributive regularity of clay minerals, submarine relief, hydrodynamic conditions and depositional characteristics in this region. Apart from the northern mainland source, kaolinites carried from the Philippines volcanic arc in the east and Malaysia in the south are also assumed to be one of the sources of the clay minerals in the deep sea. The increase of chlorites to the abyssal direction in the west of 116° E might be associated with the residual chlorites carried from the ancient Zhujiang River during the glacial period and the conversion of kaolinite into chlorite submarine volcanoes appear to be one of the sources of the increment of montmorillonite and chlorite around the Huangyan Island. From the distribution pattern of clay minerals in the whole area, it is known that the types of clay mineral assemblage in the study area are mainly controlled by climate and rock types of the source are-展开更多
Using the fuzzy clustering as the principal method, eight water masses in the northern South China Sea (NSCS) are distinguished. They are Alongshore Diluted Water Mass (F), Nearshore Mixed Water Mass (M), Warm Surface...Using the fuzzy clustering as the principal method, eight water masses in the northern South China Sea (NSCS) are distinguished. They are Alongshore Diluted Water Mass (F), Nearshore Mixed Water Mass (M), Warm Surface Water Mass(WS), Surface Water Mass(S), Surface-Subsurface Mixed Water Mass(SU), Subsurface Water Mass (U), Subsurface-Intermediate Water Mass (UI) and Intermediate Water Mass (1). A synthertic study is made on the formations, basic properties and modified characters of each water mass and the regularities of their disributions and growth and decline variations . They may be classified into three types; the type of runoff-diluted water (F). the type of shallow sea-modified water (M, WS. S. and SU) and the type of deep sea-oceanic water (U, UI, and I).展开更多
The average upper mantle P wave velocity structure and lateral heterogeneity in the northern part of China and Mongolia are investigated by waveform inversion of broadband body waveform data recorded by CDSN and digit...The average upper mantle P wave velocity structure and lateral heterogeneity in the northern part of China and Mongolia are investigated by waveform inversion of broadband body waveform data recorded by CDSN and digital stations around China. The average model has a low P wave velocity lid (about 7.8~8.0 km·s -1 ) with thickness about 60 km, and two discontinuities with velocity jumps of 0.29 km·s -1 and 0.55 km·s -1 at depth of 410 km and 665 km respectively. In the Jungger basin, the P wave velocity of uppermost mantle is about 7.7 km·s -1 . The lid thickness (90~100 km) and velocity gradient (average gradient is greater than 0.005 5/s) are large. At the depth of 140 km the P wave velocity reaches to 8.2 km·s -1 . Near in Baikal, the lid is about 30 km thick with average P wave velocity of 8.00~8.05 km·s -1 .展开更多
-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of t...-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indicate that the monsoon wind is stronger in the summer and weaker in the winter than the normal by 1-1. 5 m/s during the events, and this anomaly will cause a decrease of the sea level by 7-11 cm . Changes of the wind field, therefore, is mainly responsible for a large negative anomalies of the sea level and SST there during the ENSO events.展开更多
In the Inner Mongolia axis and Jiaoliao anteclise along the northern margin of the North China Platform.it has been found that the strata formerly considered as Archaean and Proterozoic are in fact an ophiolite suites...In the Inner Mongolia axis and Jiaoliao anteclise along the northern margin of the North China Platform.it has been found that the strata formerly considered as Archaean and Proterozoic are in fact an ophiolite suitesimilar to the Early Palaeozoic Ondor Sum Group in the Northern Geosyncline region of China. The stratahave been named in northern Liaoning as the Qinghezhen Group. The emphasis of this paper is on the discus-sion of the simall shelly fossils found in the siliceous rocks in the upper part of the Qinghezhen Group. Thisophiolite suite stretches in an E-W direction for about 1000 km along the northern margin of the North ChinaPlatform. in which 15 fossil localities with stable stratigraphic horizons have been discovered. In this paper. 4types. 7 genera (including 5 new ones) and 10 species (including 8 new ones and 1 new subspecies) aredescribed, which are collectively referred to as the Qinghezhen Fauna. The characteristics of these fossils are:shell form simple. the maximum length not exceeding 4 mm. with obvious shell wall and wall ornaments. TheQinghezhen Fauna is comparable in shell structure of some genera and species with the Meishucun Fauna inSouth China, but differs from the latter in having only monotonous fossil groups developed in a distinctly va-ried ecological environment. The two faunas may belong to the same evolutionary stage of the Early Cambrianbut have developed parallelly in different regions. The existence of the Qinghezhen Fauna represents an impor-tant biological event in the Early Cambrian in the Northern Geosyncline region of China. The discovery of theQinghezhen Fauna will bring new knowledge and profound influence to a series of problems on basic geologyand mineral deposit prospecting such as the Cambrian faunas. biogeographical povincialism in China and thegeotectonic features of the northern margin of the North China Platform.展开更多
Based essentially on research results of calcareous nannofossils, combined with some other microfossil da-ta and several secondary depositional breaks, this paper discusses the criteria of division and comparison of t...Based essentially on research results of calcareous nannofossils, combined with some other microfossil da-ta and several secondary depositional breaks, this paper discusses the criteria of division and comparison of themiddle and late Tertiary marine sediments, palaeogeographical and palaeoenvironmental evolution andpalaeoclimates on the northern continental margin of the South China Sea, comprising the Tainan basin, PearlRiver Mouth basin. Southeast Hainan basin and Beibu Gulf basin. Study shows that the upper Oligocene toPliocene strata in the whole area consist essentially of marine sediments except in the Beibu Gulf basin. Theyinclude littoral. neritic and deltaic sediments as well as carbonate rock-bioherm limestone. The sea advancedfrom southeast to northwest. During the transgression there appeared three culminations coinciding to thestages of deposition of nannofossil zones NN4-5, NN11 and 13-15.展开更多
Influenced by the seasonally reversed monsoons, water exchange through straits, and topography, the shelf and slope circulation in the northern South China Sea(NSCS) is complex and changeable. The typical current syst...Influenced by the seasonally reversed monsoons, water exchange through straits, and topography, the shelf and slope circulation in the northern South China Sea(NSCS) is complex and changeable. The typical current system in the NSCS consists of the slope current, South China Sea warm current(SCSWC), coastal current, and associated upwelling(in summer) and downwelling(in winter). This paper reviews recent advances in the study of NSCS shelf and slope circulation since the 1990 s,and summarizes the roles of Kuroshio intrusion, the monsoons, topography, and the buoyancy effect of the Pearl River plume in the shelf and slope current system of the NSCS. We also point out some potential scientific issues that require further study, such as the dynamic connection between the internal basin and shelf areas of the NSCS, the persistence of the SCSWC in winter, the temporo-spatial characteristics of downwelling during winter in the NSCS, and its material and energy transport.展开更多
Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of ...Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of the upper crust is 150–300°C lower than that of the lower crust, and the viscous coefficient of the upper crust is 2–3 orders of magnitude larger than that of the lower crust. It reveals that the upper crust is characterized by brittle deformation while the lower crust by ductile deformation. A channel of lower-viscosity should be formed between the upper and lower crust when the lithosphere is scattered and spreads out toward ocean from northwest to southeast along the northern margin of South China Sea. And, a brittle deformation takes place in the upper part of the lithosphere while a ductile deformation takes place in the lower part of the lithosphere due to different viscous coefficients and temperature. The layered deformation leads the faulted blocks to rotate along the faulting and the marginal grabens to appear in the northern margin of South China Sea in Cenozoic tectonic expansion.展开更多
基金Support by National Natural Science Foundation of China(30590384,30900197)~~
文摘Basing on the limiting factor method and Composite Index method,for the northern China crop-pasture band,the authors established the system of evaluation index,and abstracted the dominant factor,then through applying expert grade and weighing way the suitability of grids are evaluated,the results showed that:without the input of a large number of cash,most of the area was not suitable for farming,and more appropriate area for farming was only 8.45% of total area,mainly located in the southeast and southwest of the study area,followed by the study area in the northeast,areas that was not suitable for farming mainly in the middle of the east,large areas of central and western regions.
基金The National Natural Science Foundation of China under contract Nos 42276084 and 42176078the Special survey items of the China Geological Survey under contract Nos DD20190205 and DD20221710。
文摘The composition,provenance,and genetic mechanism of sediment on different sedimentary units of the East China Sea(ECS)shelf are essential for understanding the depositional dynamics environment in the ECS.The sediments in the northern ECS shelf are distributed in a ring-shaped distribution centered on the southwestern Cheju Island Mud.From the inside to the outside,the grain size goes from fine to coarse.Aside from the“grain size effect”,hydrodynamic sorting and mineral composition are important restrictions on the content of rare earth elements(REEs).Based on the grain size,REEs,and clay mineral composition of 300 surface sediments,as well as the sedimentary genesis,the northern ECS shelf is divided into three geochemical zones:southwestern Cheju Island Mud Area(ZoneⅠ),Changjiang Shoal Sand Ridges(ZoneⅡ-1),Sand Ridges of the East China Sea shelf(ZoneⅡ-2).The northern ECS shelf is mostly impacted by Chinese mainland rivers(the Changjiang River and Huanghe River),and the provenance and transport mechanism of sediments of different grain sizes is diverse.The bulk sediments come primarily from the Changjiang River,with some material from the Huanghe River carried by the Yellow Sea Coastal Current and the North Jiangsu Coastal Current,and less from Korean rivers.Among them,surface sediments in the southwestern Cheju Island Mud Area(ZoneⅠ)come mostly from the Changjiang River and partly from the Huanghe River.It was formed by the counterclockwise rotating cold eddies in the northern ECS shelf,which caused the sedimentation and accumulation of the fine-grained sediments of the Changjiang River and the Huanghe River.The Changjiang Shoal Sand Ridges(ZoneⅡ-1)were developed during the early-middle Holocene sea-level highstand.It is the modern tidal sand ridge sediment formed by intense hydrodynamic action under the influence of the Yellow Sea Coastal Current,North Jiangsu Coastal Current,and Changjiang Diluted Water.The surface sediments mainly originate from the Changjiang River and Huanghe River,with the Changjiang River dominating,and the Korean River(Hanjiang River)influencing just a few stations.Sand Ridges of the East China Sea shelf(ZoneⅡ-2)are the relict sediments of the paleo-Changjiang River created by sea invasion at the end of the Last Deglaciation in the Epipleistocene.The clay mineral composition of the surface sediments in the study area is just dominated by the Changjiang River,with the North Jiangsu Coastal Current and the Changjiang Diluted Water as the main transporting currents.
基金Supported by the Chinese Academy of Sciences (No. KZCX2-YW-215)the National Natural Science Foundation of China (No. 40476019)the Project of Knowledge Innovation of South China Sea Institute of Oceanology (No. LYQY200701)
文摘The diffuse attenuation coefficient for downwelling irradiance(Kd(λ)) is an important parameter for ocean studies.Based on the optical profile data measured during three cruises in the northern South China Sea in autumn from 2003 to 2005,variations in the Kd(λ) spectra were analyzed.The variability of Kd(λ) shows much distinct features in both magnitude and spectra pattern,it is much higher in coastal waters than that of open oceanic waters;and the blue-to-green(443/555) ratio of Kd(λ) tends to increase with chlorophyll a concentration([Chl-a]) from open ocean to coastal waters.These characteristics can be explained most by the increase of aw+p(443)/aw+p(555) with [Chl-a].In short waveband,the relation between Kd(λ)-Kw(λ) and [Chl-a] can be well described by a power law function,indicating the large contribution of phytoplankton to the variations in Kd(λ).As for the spectral model of the diffuse attenuation coefficient,there are good linear relationships between Kd(490) and Kd(λ) in other wavelengths with own slope and intercept of a linear functions in the spectral range 412-555 nm.Kd(490) is well correlated with the spectral ratio of remote sensing reflectance;and should enough measurement data are given,this empirical algorithm would be used in the Kd(λ) retrieval from ocean color satellite data.The variation in Kd(λ) provides much useful information for us to study the bio-optical property in the northern South China Sea.
基金The National Natural Science Foundation of China under contract No.41606116the Natural Science Foundation of Fujian Province of China under contract No.2016J01019the National Key R&D Program of China under contract No.2018YFC1405903。
文摘The correlation of ambient noise with wind speed,and the depth dependence of ambient noise are both investigated,where the ocean noise data were recorded by a vertical line array in the northern South China Sea.It is shown that the correlation coefficients increase with increasing hydrophone depth during typhoon periods when the frequency≥250 Hz,which opposes the generally accepted knowledge that the correlation coefficients of noise level and wind speed decrease with increasing depth during non-typhoon periods.Particularly at frequencies of 250 Hz,315 Hz and 400 Hz,the correlation coefficients increase by more than 0.05 at depths ranging from 155 m to 875 m.At the three frequencies,the average noise levels also increase with increasing depth during typhoon periods.It is suggested that these differences are attributed to the wind-generated noise in shallow waters and the effect of"downslope enhancement"to sound propagation.During typhoon periods,the surf breaking and surf beat upon the shores and reefs are strengthened,and the source levels are increased.The wind-generated noise in shallow waters interacts with the downslope sea floor,with the noise-depth distribution changed by a"downslope enhancement"effect promoting noise propagation.
基金Supported by the National Natural Science Foundation of China(Nos.U1706216,41976010,42006027,U1806227)the Natural Science Foundation of Shandong Province,China(No.ZR2016DQ16)+2 种基金the Key Deployment Project of Center for Ocean Mega-Science,Chinese Academy of Sciences(Nos.COMS2019J02,COMS2019J05)the Chinese Academy of Sciences Strategic Priority Project(Nos.XDA19060202,XDA19060502)the National Key Research and Development Program of China(No.2016YFC1402000)。
文摘We examined the influences of the wind fi eld and wave-current interaction(WCI)on the numerical simulation results of typhoon-induced wind waves in the northern East China Sea(NECS)using the coupled Simulating Waves Nearshore+Advanced Circulation(SWAN+ADCIRC)model.The simulations were performed during two typhoon events(Lekima and Muifa),and two widely used reanalysis wind fields,the Climate Forecast System Version 2(CFSv2)from the National Centers for Environmental Prediction(NCEP)and the fifth-generation European Centre for Medium-Range Weather Forecasts(ECMWF)Reanalysis(ERA5),were compared.The results indicate that the ERA5 and CFSv2 wind fields both reliably reproduced the wind variations measured by in-situ buoys,and the accuracy of the winds from ERA5 were generally better than those from CFSv2 because CFSv2 tended to overestimate the wind speed and the simulated significant wave height(SWH),particularly the peak SWH.The WCI effects between the two wind field simulations were similar;these effects enhanced the SWH throughout the nearshore NECS during both typhoons but suppressed the SWH on the right side of the Typhoon Muifa track in the deep and off shore sea areas.In summary,variations in the water depth and current propagation direction dominate the modulation of wave height.
文摘The clay minearals are composed of illite, chlorite, kaolinite, montmorillonite and mixed-layer minerals in the submarine sediments of the northern South China Sea. Three types of clay mineral zone can be recognized on the basis of the distributive regularity of clay minerals, submarine relief, hydrodynamic conditions and depositional characteristics in this region. Apart from the northern mainland source, kaolinites carried from the Philippines volcanic arc in the east and Malaysia in the south are also assumed to be one of the sources of the clay minerals in the deep sea. The increase of chlorites to the abyssal direction in the west of 116° E might be associated with the residual chlorites carried from the ancient Zhujiang River during the glacial period and the conversion of kaolinite into chlorite submarine volcanoes appear to be one of the sources of the increment of montmorillonite and chlorite around the Huangyan Island. From the distribution pattern of clay minerals in the whole area, it is known that the types of clay mineral assemblage in the study area are mainly controlled by climate and rock types of the source are-
基金This project is supported by the National Natural Science Foundation of China.
文摘Using the fuzzy clustering as the principal method, eight water masses in the northern South China Sea (NSCS) are distinguished. They are Alongshore Diluted Water Mass (F), Nearshore Mixed Water Mass (M), Warm Surface Water Mass(WS), Surface Water Mass(S), Surface-Subsurface Mixed Water Mass(SU), Subsurface Water Mass (U), Subsurface-Intermediate Water Mass (UI) and Intermediate Water Mass (1). A synthertic study is made on the formations, basic properties and modified characters of each water mass and the regularities of their disributions and growth and decline variations . They may be classified into three types; the type of runoff-diluted water (F). the type of shallow sea-modified water (M, WS. S. and SU) and the type of deep sea-oceanic water (U, UI, and I).
文摘The average upper mantle P wave velocity structure and lateral heterogeneity in the northern part of China and Mongolia are investigated by waveform inversion of broadband body waveform data recorded by CDSN and digital stations around China. The average model has a low P wave velocity lid (about 7.8~8.0 km·s -1 ) with thickness about 60 km, and two discontinuities with velocity jumps of 0.29 km·s -1 and 0.55 km·s -1 at depth of 410 km and 665 km respectively. In the Jungger basin, the P wave velocity of uppermost mantle is about 7.7 km·s -1 . The lid thickness (90~100 km) and velocity gradient (average gradient is greater than 0.005 5/s) are large. At the depth of 140 km the P wave velocity reaches to 8.2 km·s -1 . Near in Baikal, the lid is about 30 km thick with average P wave velocity of 8.00~8.05 km·s -1 .
文摘-Variations of monsoon wind field in the sea area along the southeastern coast of China during the ENSO events and its influence on the sea level and sea surface temperature (SST) are explored mainly on the basis of the data of monthly mean wind at 850 hPa and five coastal stations during 1973-1987. The results from the analyses of the data and theoretical estimation show that the southwest wind anomalies appeared in the study area during the events, and northeast wind anomalies occurred in general before the events. With the coastline of the area being parallel basically to the direction of the wind, an Ekman transport will result in an accumulation of the water near the coast or a departure of the water from the coast. As a result , the sea level and SST there will be affected markedly. During the events, southwest wind will intensify in the summer, and northeast wind will weaken in the winter. Their total effect is that a large negative anomaly of the sea level and SST will occur. The estimations indicate that the monsoon wind is stronger in the summer and weaker in the winter than the normal by 1-1. 5 m/s during the events, and this anomaly will cause a decrease of the sea level by 7-11 cm . Changes of the wind field, therefore, is mainly responsible for a large negative anomalies of the sea level and SST there during the ENSO events.
文摘In the Inner Mongolia axis and Jiaoliao anteclise along the northern margin of the North China Platform.it has been found that the strata formerly considered as Archaean and Proterozoic are in fact an ophiolite suitesimilar to the Early Palaeozoic Ondor Sum Group in the Northern Geosyncline region of China. The stratahave been named in northern Liaoning as the Qinghezhen Group. The emphasis of this paper is on the discus-sion of the simall shelly fossils found in the siliceous rocks in the upper part of the Qinghezhen Group. Thisophiolite suite stretches in an E-W direction for about 1000 km along the northern margin of the North ChinaPlatform. in which 15 fossil localities with stable stratigraphic horizons have been discovered. In this paper. 4types. 7 genera (including 5 new ones) and 10 species (including 8 new ones and 1 new subspecies) aredescribed, which are collectively referred to as the Qinghezhen Fauna. The characteristics of these fossils are:shell form simple. the maximum length not exceeding 4 mm. with obvious shell wall and wall ornaments. TheQinghezhen Fauna is comparable in shell structure of some genera and species with the Meishucun Fauna inSouth China, but differs from the latter in having only monotonous fossil groups developed in a distinctly va-ried ecological environment. The two faunas may belong to the same evolutionary stage of the Early Cambrianbut have developed parallelly in different regions. The existence of the Qinghezhen Fauna represents an impor-tant biological event in the Early Cambrian in the Northern Geosyncline region of China. The discovery of theQinghezhen Fauna will bring new knowledge and profound influence to a series of problems on basic geologyand mineral deposit prospecting such as the Cambrian faunas. biogeographical povincialism in China and thegeotectonic features of the northern margin of the North China Platform.
文摘Based essentially on research results of calcareous nannofossils, combined with some other microfossil da-ta and several secondary depositional breaks, this paper discusses the criteria of division and comparison of themiddle and late Tertiary marine sediments, palaeogeographical and palaeoenvironmental evolution andpalaeoclimates on the northern continental margin of the South China Sea, comprising the Tainan basin, PearlRiver Mouth basin. Southeast Hainan basin and Beibu Gulf basin. Study shows that the upper Oligocene toPliocene strata in the whole area consist essentially of marine sediments except in the Beibu Gulf basin. Theyinclude littoral. neritic and deltaic sediments as well as carbonate rock-bioherm limestone. The sea advancedfrom southeast to northwest. During the transgression there appeared three culminations coinciding to thestages of deposition of nannofossil zones NN4-5, NN11 and 13-15.
基金supported by the Frontier Science Research Project of Chinese Academy of Sciences (Grant No. QYZDJ-SSW-DQC022)the National Natural Science Foundation of China (Grant Nos. 41476012, 41406038 & 41576003)the Natural Science Foundation of Guangdong Province (Grant No. 2014A030313777)
文摘Influenced by the seasonally reversed monsoons, water exchange through straits, and topography, the shelf and slope circulation in the northern South China Sea(NSCS) is complex and changeable. The typical current system in the NSCS consists of the slope current, South China Sea warm current(SCSWC), coastal current, and associated upwelling(in summer) and downwelling(in winter). This paper reviews recent advances in the study of NSCS shelf and slope circulation since the 1990 s,and summarizes the roles of Kuroshio intrusion, the monsoons, topography, and the buoyancy effect of the Pearl River plume in the shelf and slope current system of the NSCS. We also point out some potential scientific issues that require further study, such as the dynamic connection between the internal basin and shelf areas of the NSCS, the persistence of the SCSWC in winter, the temporo-spatial characteristics of downwelling during winter in the NSCS, and its material and energy transport.
基金the National Natural Science Foundation of China (Grant Nos.49732005, 49733011) and the Chinese Academy of Sciences (Grant No. KZ951-A1-401). We wish to thank Prof. Xu Houze and Lu Yang for their contribution in gravitational model. The authors also than
文摘Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of the upper crust is 150–300°C lower than that of the lower crust, and the viscous coefficient of the upper crust is 2–3 orders of magnitude larger than that of the lower crust. It reveals that the upper crust is characterized by brittle deformation while the lower crust by ductile deformation. A channel of lower-viscosity should be formed between the upper and lower crust when the lithosphere is scattered and spreads out toward ocean from northwest to southeast along the northern margin of South China Sea. And, a brittle deformation takes place in the upper part of the lithosphere while a ductile deformation takes place in the lower part of the lithosphere due to different viscous coefficients and temperature. The layered deformation leads the faulted blocks to rotate along the faulting and the marginal grabens to appear in the northern margin of South China Sea in Cenozoic tectonic expansion.