ECO-ENVIRONMENT CHANGE AND SOIL EROSION PROCESS IN THE RECLAIMED FORESTLAND OF THE LOESS PLATEAU     

ZHA Xiao-chun  TANG Ke-li 《中国地理科学(英文版)》2003,13(3):232-237

1INTRODUCTIONSerioussoilerosionhasmadetheeco-environmentfragileintheLoessPlateau.InthemodernsoilerosionoftheLoessPlateau,theman-madeerosionwasthedominanterosionpattern (TANGetal.,1993a,1993b).Manyhumanactivitiesacceleratesoilerosion,butthemostinfluentialactivitiesaretodestroyforestandgrass,eventodestroyallvegetation.Reclamationbydestroyingforestlandandgrasslandartificiallycouldrapidlyincreasesoilerosionintensityinshorttimeandenlargeerosionspacegradually,evenchangeerosiondirectionandwor…  相似文献   

柴北缘西端冷湖盐场北山辉长岩地球化学及年代学研究   总被引：2，自引：0，他引：2       下载免费PDF全文

董增产  辜平阳  焦和  查显锋  陈锐明  张海迪 《地质科学》2014,49(4):1132-1149

柴北缘冷湖盐场北山镍铜矿区发育辉长岩和角闪辉长岩;属亚碱性岩石系列。球粒陨石、 原始地幔标准化曲线呈两组特征;但配分型式基本一致;反映其来自同一源区。稀土标准化曲线表现为弱右倾型;Eu基本无异常;说明斜长石分离结晶作用不明显。Rb、 Nb、 Zr、Cr等微量元素丰度及比值具有近似平行部分熔融的演化趋势。结合岩体Mg^#值和岩体固结指数（SI）高等特点;揭示原始岩浆具有幔源原生玄武岩浆特征;认为其成因与俯冲板片流体交代地幔楔源区的部分熔融有关;而且;Nb、 Zr、 Y元素丰度表明辉长岩源区为过渡型地幔。另外;两类岩体强烈亏损Nb、 Ta、 Zr、 Hf、 Ti等高场强元素（HFSE）;富集Ba、 Th、 U、 Pb等大离子亲石元素;反映明显的消减带和岛弧环境岩浆岩典型特征。LA-ICPMS锆石U-Pb测年结果表明辉长岩形成于254±3 Ma;结合该时期区域地质构造背景;认为柴北缘晚二叠世处于俯冲作用之下的岛弧构造环境;具有活动大陆边缘性质。  相似文献   

Source model of the 11th July 2004 Zhongba earthquake revealed from the joint inversion of InSAR and seismological data     

Don Helmberger 《地震学报(英文版)》2011,(2):207-220

We use interferometric synthetic aperture radar (InSAR) and broadband seismic waveform data to estimate a source model of the 11th July, 2004 M W 6.2 Zhongba earthquake, Tibet of China. This event occurred within the seismically active zone of southwestern Tibetan Plateau where the east-west extension of the upper crust is observed. Because of limitations in one pair of InSAR data available, there are trade-offs among centroid depth, rupture area and amount of slip. Available seismic data tightly constrain ...  相似文献   

Relocating ruptures of two M6 earthquakes in Zhongba, South-central Tibet in 2004 and 2005 with seismological and geodetic methods     

Feng Bao Yingjie Zha Zhenjie Wang Mengcheng National Geophysical Observatory  School of Earth  Space Sciences  University of Science  Technology of China  Hefei  China 《地震学报(英文版)》2011,(2):229-237

To better understand repeatability of strong earthquakes in previously ruptured zones during one seismogenic period, we studied the rupture zones of the doublet of M6 earthquakes in Zhongba region of southcentral Tibet, China, in 11 July 2004 and 7 April 2005, respectively. We focused on the overlapping degree of two strong quakes’ aftershock areas one week after the mainshocks by using the SQH station in China Seismic Network and a 68-stations temporary broadband seismic array, a part of the international ...  相似文献   

Extraordinary floods related to the climatic event at 4200 a BP on the Qishuihe River,middle reaches of the Yellow River,China   总被引：1，自引：0，他引：1  

Chun Chang Huang  Jiangli Pang  Xiaochun Zha  Hongxia Su  Yaofeng Jia 《Quaternary Science Reviews》2011,30(3-4):460-468

Palaeo-hydrological study was carried out in the Qishuihe River valley in the middle reaches of the Yellow River. Several bedsets of flood slackwater deposit were identified in the Holocene loess-soil sequences on the riverbanks. They were differentiated from aeolian loess and soils by the parallel and waving beddings and the distinctive stratigraphic breaks separating individual palaeoflood events. Chronology of the flood events was established by OSL dating, checked by archaeological identification of the anthropogenic remains retrieved from the sequences. The results show that successive floods occurred between 4300 and 4000 a BP in association with the abrupt climatic event of 4200 a BP. These overbank floods had the riverbank settlement inundated repeatedly. Another series of extraordinary floods occurred between 3200 and 3000 a BP when monsoonal climate shifted from the mid-Holocene Climatic Optimum toward late Holocene dry conditions. The climatic event of 4200 a BP and the climatic decline at 3100 a BP were believed to be characterized by droughts previously. This work provides solid evidence that both severe droughts and extreme floods were parts of the climatic variability during abrupt climatic event and climatic decline in the semi-arid to sub-humid zones over the world.  相似文献   

河南渑池县仰韶村遗址不同土层微形态特征研究     

查理思  吴克宁  黎卓轩  兰文哲 《热带地理》2023,43(1):125-134

仰韶文化时期气候环境与古人类活动是如何变化？大部分变化信息尽管从宏观视野中消失,但却保存在土壤微形态中。故文章采用土壤微形态学方法,对仰韶村遗址一处含有文化层区域进行多点采样,通过比较古土壤、文化层和表土层土壤微形态特点差异,研究了气候变化及古人类活动对土壤微形态的影响,为探究仰韶文化时期的古人类活动遗迹和古农业发展状况提供依据。结果显示：1）古土壤层中具有明确边界的铁质垒结形成物,粗粒质多分解细小颗粒,呈现堆积状,细粒质多为微晶b-垒结,细粒质与粗粒质相对分布主要呈现包膜状和桥接状,孔隙壁附着锰质胶膜。2）文化层中粗粒质多分解细小颗粒,呈现堆积状,细粒质呈现出多种b-垒结,细粒质与粗粒质空间关系也呈现多样化。孔隙壁附着腐殖质,孔道内填充炭屑。3）表土层中土壤形成物主要为继承性钙质形成物和钙质新生体,还可识别淀积黏粒体,土壤垒结回归单一,孔隙呈现出堆集性不规则非稳定态。研究发现：1）古土壤层主要受暖湿气候影响,脱硅富铁铝化作用明显,次生矿物以赤铁矿为主。古人类开始居住活动,促进了土壤发育,淀积黏化作用明显,黏粒胶膜发育充分。2）文化层主要受到古人类活动影响,古人类活动强度增强,土壤形成...  相似文献   

Sedimentary fill history of the Huicheng Basin in the West Qinling Mountains and associated constraints on Mesozoic intracontinental tectonic evolution   总被引：2，自引：0，他引：2  

LI Wei  DONG YunPeng  GUO AnLin  LIU XiaoMing  LIU YiQun  ZHA XianFeng  ZHANG KuaiLe 《中国科学:地球科学(英文版)》2013,56(10):1639-1653

The Qinling Orogenic Belt is divided commonly by the Fengxian-Taibai strike-slip shear zone and the Huicheng Basin into the East and West Qinling mountains,which show significant geological differences after the Indosinian orogeny.The Fengxian-Taibai fault zone and the Meso-Cenozoic Huicheng Basin,situated at the boundary of the East and West Qinling,provide a natural laboratory for tectonic analysis and sedimentological study of intracontinental tectonic evolution of the Qinling Orogenic Belt.In order to explain the dynamic development of the Huicheng Basin and elucidate its post-orogenic tectonic evolution at the junction of the East and West Qinling,we studied the geometry and kinematics of fault zones between the blocks of West Qinling,as well as the sedimentary fill history of the Huicheng Basin.First,we found that after the collisional orogeny in the Late Triassic,post-orogenic extensional collapse occurred in the Early and Middle Jurassic within the Qinling Orogenic Belt,resulting in a series of rift basins.Second,in the Late Jurassic and Early Cretaceous,a NE-SW compressive stress field caused large-scale sinistral strike-slip faults in the Qinling Orogenic Belt,causing intracontinental escape tectonics at the junction of the East and West Qinling,including eastward finite escape of the East Qinling micro-plate and southwest lateral escape of the Bikou Terrane.Meanwhile,the strike-slip-related Early Cretaceous sedimentary basin was formed with a right-order echelon arrangement in sinistral shear zones along the southern margin of the Huicheng fault.Overall during the Mesozoic,the Huicheng Basin and surrounding areas experienced four tectonic evolutionary stages,including extensional rift basin development in the Early and Middle Jurassic,intense compressive uplift in the Late Jurassic,formation of a strike-slip extensional basin in the Early Cretaceous,and compressive uplift in the Late Cretaceous.  相似文献   

Extraction of internal wave amplitude from nautical X-Band radar observations     

查国震  林明森  申辉  何宜军  吕海滨 《中国海洋湖沼学报》2012,30(3):497-505

One of the most important parameters for oceanic internal waves (IWs) is their amplitude. We have developed a method to retrieve the IW amplitude from nautical X-Band radar images based on the KdV equation for continuous stratified finite depth system. We have also tested the method of measuring the amplitude of IWs from X-Band radar backscatter image sequences acquired on June 2009 in the northeastern South China Sea. The method was applied in several radar images. Experiments show that the retrieval amplitudes are consistent with the in-situ observational amplitudes of IWs by using the towed thermistor chain and conductivity-temperature-depth (CTD) profile. The uncertainty of the method is also discussed.  相似文献   

黄河上游靖远-景泰段全新世古洪水水文学   总被引：1，自引：0，他引：1  

胡贵明  黄春长  周亚利  庞奖励  查小春  郭永强 《吉林大学学报(地球科学版)》2015,45(6):1822-1832

对黄河上游靖远景泰段峡谷进行系统野外考察,在靖远县金坪村(JPC)发现典型的全新世古洪水滞流沉积物。通过光释光(OSL)测年和与黄河吉县段FJJ剖面进行地层对比,确定这期特大古洪水事件发生在 3 200~3 000 a B.P.,即全新世中期晚期气候恶化转折阶段,对应着我国历史上商末至西周早期。采用古洪水水文学方法恢复古洪水洪峰水位,并且采用比降-面积法计算这一期多次古洪水事件的洪峰流量为 16 110~17 740 m³/s。同时,根据野外调查获得 2012年7月31日黄河上游大洪水的洪痕高程,采用相同参数和方法恢复其洪峰流量,误差仅有 2.7%,表明在该河段对于古洪水水文恢复计算参数选取和计算结果是可靠的。  相似文献   

泾河中游全新世古洪水沉积学与水文学研究(英文)   总被引：1，自引：1，他引：0  

查小春  黄春长  庞奖励  李瑜琴 《地理学报(英文版)》2012,22(3):470-478

Palaeo-hydrological field investigation was carried out in the middle reaches of the Jinghe River. A set of palaeoflood slackwater deposit beds was identified in the Holocene loess-soil sequence in the riverbanks. The sediment samples were collected from the profile, and the particle-size distribution, magnetic susceptibility, loss-on-ignition were analyzed in laboratory. The analytical results showed that the palaeoflood slackwater deposits have re-corded extraordinary flood events in the Jinghe River valley. According to stratigraphic cor-relation and OSL dating, the palaeoflood events were dated to 4100-4000 a BP. The pa-laeoflood peak discharges were estimated to be 19,410-22,280 m3/s by using the hydro-logical model and checked by different approaches. These results have the flood data se-quence of the Jinghe River extended to 10,000-year time-scale. It provided significant data for hydraulic engineering and for mitigation of flood hazards in the Jinghe River drainage basin.  相似文献