大陆漂移、高原隆升与新生代亚-非-澳洲季风区和干旱区演化

亚-非-澳洲季风区和干旱区的面积约占这三大洲陆地总面积的60%以上.基于新生代以来亚-非-澳洲季风和干旱环境以及东半球海陆分布和青藏高原等地形显著变化的地质事实,利用全球海-气耦合模式开展新生代5个特征地质时期气候模拟试验,系统探讨了新生代亚-非-澳洲季风区和干旱区形成演化及其受大陆漂移和高原隆升的影响.结果表明,亚-非-澳洲季风区和干旱区形成的时间和原因明显不同.北非与南非季风在古新世中期已经存在,南亚次大陆季风在始新世印度大陆移入北半球热带后开始出现,而东亚和澳大利亚北部季风在中新世才建立.北非、南非、南亚和澳大利亚热带季风的建立是大陆漂移的位置和热带辐合带季节性迁移共同决定的,而青藏高原的位置和高度则是东亚季风建立的关键因素.北非、南非、亚洲和澳大利亚副热带干旱区的存在取决于大陆的位置和行星尺度副热带高压的控制,阿拉伯半岛和西亚干旱区的发展与区域尺度海陆变迁,特别是古特提斯海的退缩密切相关,而亚洲内陆中纬度干旱区的形成则是青藏高原隆升的结果.这一研究揭示了地球构造边界条件在地质时期区域气候环境形成演化中的重要作用.     

Cenozoic sedimentary records and geochronological constraints of differential uplift of the Qinghai-Tibet Plateau

Geological mapping data (1:250000) in the Qinghai-Tibet Plateau and its adjacent regions reveal the sediment sequences, distribution and tectonic evolution of the 92 Tertiary remnant basins. Southern Tibet and the Yecheng area in Xinjiang, located at southern and northwestern margins of the Qinghai-Tibet Plateau, respectively, were parts of the Neo-Tethys remnant sea in the Paleogene. In southern Tibet, both the subabyssal and abyssal sequences occur at the Gyangze, Saga, Guoyala, and Sangmai areas. The deep-water facies successions outcrop in the west, whereas the shallow-water facies sequences in the east, indicating the east to the west retreat of the Neo-Tethys Ocean. The retreat of the Neo-Tethys Ocean in the east was contributed to the earlier tectonic uplift of the eastern Qinghai-Tibet Plateau. The uplift process of the Plateau from the Late Cretaceous to Pliocene is described as follows: During the Late Cretaceous, tectonic uplift of the Qinghai-Tibet Plateau occurred in the northeastern part and the configuration of the Qinghai-Tibet Plateau was characterized by rise in the northeast and depression in the west. In the Paleocene-Eocene interval, the Tengchong-Baingoin and Kuyake-Golmud areas experienced local tectonic uplifting, the West Kunlun uplift zone broadened easterly, the Qilian uplift zone broadened southerly, and the Songpan-Garzê uplift zone shrank easterly. The Oligocene configuration of the Qinghai-Tibet Plateau was characterized by mountain chains rising along its margins and sedimentary basins in the central part because of tectonic uplifts of the Gangdisê and the Himalaya blocks. Meanwhile, the Kunlun-Altyn-Qilian uplift zones have also broadened southerly and northerly. In contrast, the great uplift zones of the Gangdisê, the Himalaya, the Karakorum, and the Kunlun blocks characterize the paleogeographic contours of the Qinghai-Tibet Plateau during the Miocene-Pliocene. Additionally, the thermochronological data on tectonic uplift events in southern Tibet, West Kunlun Mountains, Altyn Tagh, eastern Tibet, and western Sichuan all suggest that the most intense deformation occurred at 13-8 Ma and since 5 Ma, respectively, corresponding to two great uplift periods in Neogene. As a result, turnover of paleogeographic configuration of the Qinghai-Tibet Plateau occurred during the Neogene, experiencing a change from high contours in the east in the pre-Oligocene to high contours in the west at the end-Pliocene. The uplift of the Qinghai-Tibet Plateau during the Cenozoic was episodic, and the uplifts of various blocks within the Plateau were spatially and chronologically different.     

Evolution of the monsoon and dry climate in East Asia during late Cenozoic: A review

Climate in Eastern Asia is composed of monsoon climate in the east,arid and semi-arid climate in the north and west,and the cold and dry climate of Qinghai-Tibetan Plateau in the southwest.The underlying causes for the evolution of East Asian climate during late Cenozoic have long been investigated and debated,particularly with regards to the role played by the Qinghai-Tibetan Plateau uplift and the global cooling.In this paper,we reviewed major research developments in this area,and summarized the important results.Based on a synthesis of data,we propose that the Qinghai-Tibetan Plateau uplift alone cannot fully explain the formation of monsoon and arid climates in Eastern Asia during the past 22–25 Ma.Other factors such as the global ice volume and high-latitude temperature changes have also played a vital role.Moreover,atmospheric CO2changes may have modulated the monsoon and dry climate changes by affecting the location of the inter-tropical convergence zone(ITCZ),which controls the monsoon precipitation zone and the track of the East Asian winter monsoon during late Cenozoic.The integration of high-resolution geological record and numerical paleoclimate modeling could make new contributions to understanding the climate evolution and variation in eastern Asia in future studies.It could facilitate the investigation of the regional differences in East Asian environmental changes and the asynchronous nature between the uplift of Qinghai-Tibetan Plateau and their climatic effects.These would be the keys to understanding underlying driving forces for the evolution of the East Asian climate.     

Geochemistry of Cenozoic volcanic rocks in Tengchong,SW China: relationship with the uplift of the Tibetan Plateau

There are wide spread Cenozoic volcanic rocks in Tengchong (CVRT), Yunnan province, SW China. These rocks comprise three rock types: basalt, andesite (dominant type) and dacite. Most samples are sub‐alkaline, and among the sub‐alkaline rocks, most are high‐K calc‐alkaline. These rocks have a SiO₂ range of 49.1 wt.% to 66.9 wt.%. TiO₂ contents are not high and have a variation of 0.7 wt.%–1.6 wt.%. Trace element concentrations and element ratios (such as Nb/U, Ce/Pb, Nb/La, etc.) of these rocks have a large variation. ⁸⁷Sr/⁸⁶Sr values fall in the range of 0.7057–0.7093 and ¹⁴³Nd/¹⁴⁴Nd values change from 0.5120 to 0.5125. ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb, and ²⁰⁸Pb/²⁰⁴Pb ratios are in the range of 17.936–19.039, 15.614–15.810, and 38.894–39.735, respectively. These geochemical characteristics of CVRT make them resemble island‐arc volcanic rocks. We suggest that the magmas were generated in the lithospheric mantle that had already been metasomatized by previous subduction processes. By the study of the uplift history of the Tibetan Plateau, we found that the beginning of the geotectonic processes to the eruption of CVRT was coeval with one uplift event. Therefore, we propose that the uplift of the Tibetan Plateau caused collapse of the collisional orogeny in Tengchong, which further triggered the generation and eruption of the CVRT magmas.     

Eolian evidence from the Chinese Loess Plateau: the onset of the Late Cenozoic Great Glaciation in the Northern Hemisphere and Qinghai-Xizang Plateau uplift forcing

On the basis of a newly-constructed record of magnetic susceptibility (SUS) and the depositional rate change of eolian loess-red clay sequences in the last 7.2 Ma BP from the hea Plateau, together with a cornperison of a record of °¹⁸O values from the equatorial East Pacific Ocean and eolian Quartz flux variations fmm the North Pacific Ocean, the evolutiomuy process of the Late Cenozoic Great Glaciation in the Northern Hemisphere can be divided into three stages: the arrival stage around 7.2–3.4 Ma BP, the initial stage at about 3.4—2.6 Ma BP, and the Great Ice Age since 2.6 Ma BP. The evolution of the East Asian monsoon is characterized by paid winter and summer monsoons, and it is basically composed of the initial stage of weak winter and summer monsoons, the transitional stage of simultaneous increase in intensity of winter and summer monsoons, and the prevailing stage of strong winter and week summer monsoons, or weak winter and strong summer monsoons. The Late Cenowic global tectonic uplift, paaicdarly the Qinghai-Xizang Plateau uplift and the associated CO₂ concentration variation, controls the dng processes of the onset of Great Glaciation and the long-term changes of East Asian monsoom climate in the Northern Hemisphere to a large extent. The accelerating uplift of the Qinghai-Xizang Plateau between 3.4 and 2.6 Ma BP provided an important driving force to global climiatic change. Project supported by the foundation of Chinese Academy of Sciences (Grant No. KZ951-A1-402), the State Science and Technology Committee (Grant No. 95-pre-40)and the Chinese Nature Science Foundation (Grant No. 49672140)     

Geochemistry and Sr-Nd-Pb isotopic characteristics of the Mugouriwang Cenozoic volcanic rocks from Tibetan Plateau:Constraints on mantle source of the underplated basic magma

The Mugouriwang Cenozoic volcanic rocks exposed in the north Qiangtang Block of Tibetan Plateau are mainly composed of basalt and andesitic-basalt,both characterized by the lower SiO2 (51%―54%),high refractory elements (i.e. Mg,Cr,Ni) as well as the moderate enrichment in light rare earth elements (LREE) relative to a slight depleted in Eu and high strength field elements (HFSE,i.e. Nb,Ta,Ti). Be-sides,the fairly low Sm/Yb value (3.07―4.35) could signify that the rocks should be derived directly from partial melting of the spinel lherzolite at the upper part of the asthenosphere. These rocks have radiogenic Sr and Pb (87Sr/86Sr = 0.705339 to 0.705667; 208Pb/204Pb = 38.8192 to 38.8937; 207Pb/204Pb = 15.6093 to 15.6245; 206Pb/204Pb = 18.6246 to 18.6383),and non-radiogenic Nd (143Nd/144Nd = 0.512604 to 0.512639; εNd = 0.02 to -0.66) in agreement with those values of the BSE mantle reservoir. The DUPAL anomaly of the rocks can be evidently attested by the △8/4Pb = 66.82 to 74.53 ,△7/4Pb = 9.88 to 11.42,△Sr>50,implying that the Mugouriwang volcanic rock is likely to be generated by partial melting of a Gondwana-bearing asthenospheric mantle ever matasomatised by the fluid from subduction zone. Depending on the previous study on the high-K calc-alkaline intermediate-felsic volcanics in the study area,this paper proposed that the fluids derived from the subducted Lhasa Block metasomatised the asthenosphere beneath the Qiangtang Block,and induced its partial melting,and then the melt under-plated the thickened Qiangtang lithosphere and caused the generation of the Cenozoic adakite-like felsic magmas in the Qiangtang region.     

Cenozoic tectonic and sedimentary evolution of southern Qaidam Basin,NE Tibetan Plateau and its implication for the rejuvenation of Eastern Kunlun Mountains

The Eastern Kunlun Mountains play an important role in the growth and eastward extrusion of the Tibetan Plateau. Tectonic and sedimentary study of the Cenozoic Qaidam Basin, especially the southern part, provides key evidence for understanding their evolution. Here we present evidence including isopach maps, seismic sections and sedimentary analysis of single well to illustrate the sedimentary development of the basin and the structural features of its southern margin. The Qaidam Basin extended across Qiman Tagh-Eastern Kunlun Mountains in the early Cenozoic and withdrew northward at ca. 35.5 Ma, and then buckled as an EW striking elliptical depression since ca. 14.9 Ma, with the main depocenter migrating eastward. Our results support the view that the Kumukol and Hoh Xil basins joined the Qaidam Basin in the early Cenozoic time and we propose the Eastern Kunlun Mountains uplifted in the mid-Miocene.     

Primary study on pattern of general circulation of atmosphere before uplift of the Tibetan Plateau in eastern Asia

The Tibetan Plateau is a key factor for the pattern of the general circulation of the atmosphere (GCA) in eastern Asia. The pattern of the GCA after the uplift of the plateau is well known, while the pattern of the GCA before the uplift of the plateau is lack of direct evidences. Based on the knowability of desert, a section recording wind directions across the Cretaceous northern hemisphere mid-low latitude desert belt is measured and the pattern of the GCA in the Cretaceous is revealed. The result shows that the eastern Asia was really controlled by the planetary circulation before the uplift of the plateau, i.e. westerlies in the north and northeast trades in the south. The convert belt between westerlies and trades had drifted northwards and southwards. The possibility of existence of paleo-monsoon is also dealt with and a possibly imposed paleo-monsoon is suggested.     

Fission track dating of the Cenozoic uplift in Mabian area, southern Sichuan Province, China

The apparent ages of samples are obtained from fission track dating of apatite samples collected from the fault zones in Mabian area, southern Sichuan Province. In addition, thermal history is simulated from the obtained data by applying AFT Solve Program, to acquire the thermal evolution history of the samples. The result shows that tectonically the Mabian area was relatively stable between 25 and 3 Ma, compared to the inner parts and other marginal areas of the Tibetan Plateau. The studied area had little response to the rapid uplift events that occurred for several times in the Tibetan Plateau during 25-3 Ma. The latest thermal event related to the activity of the Lidian fault zone (about 8 Ma ) is later than that of the Ebian fault zone (18-15 Ma ) to the west, indicating to some extent that the evolution of fault activity in the Mabian area has migrated from west to east. The latest extensive tectonic uplift occurred since about 3 Ma. As compared with the Xianshuihe fault zone, the Mabian area is closer to the east- ern margin of the plateau, while the time of fast cooling event in this area is later than that in the southeast segment of the Xianshuihe fault zone (3.6-3.46 Ma ). It appears to support the assumption of episodic uplift and stepwise outward extension of the eastern boundary of the Tibetan Plateau in late Cenozoic.     

Monazite age spectra in the Late Cenozoic strata of the Changjiang delta and its implication on the Changjiang run-through time

Uplift of the Tibetan Plateau, inversion of eastern and western geomorphology, eastward flowing of large rivers, and run-through of the Changjiang River exert great influence on sedimentation and environ-mental variations in the East China Sea. Provenance discrimination of Tibetan-Plateau-originated sediments in the river-mouth areas and marginal seas is key to figure out these issues.In the past, most studies of the run-through time of the Changjiang and the Yellow rivers focused on geomo…     

Pliocene cyprinids (Cypriniformes,Teleostei) from Kunlun Pass Basin,northeastern Tibetan Plateau and their bearings on development of water system and uplift of the area

Here described are the cyprinid fossils from the Pliocene Lower Member of Qiangtang Formation of the Kunlun Pass Basin,northeastern Tibetan Plateau,collected at a locality 4769 m above the sea level(asl).The materials consist of numerous disarticulated and incomplete bones as well as thousands of pharyngeal teeth,fin rays,and vertebrae.The fossils were referred to the genus Gymnocypris,lineage Schizothoracini,family Cyprinidae;the lineage Schizothoracini;and the family Cyprinidae respectively.The Schizothor...     

青藏高原腹地中新世从造山阶段向造高原阶段的转变及其动力学机制

通过对前人研究的综述,发现青藏高原新生代地质演化与高原东南缘构造演化密切相关.俯冲下插的印度地壳在藏南发生部分熔融并注入青藏高原中部地壳,这些塑性流变的地壳物质在高原东南缘先后沿两个通道流出高原内部：早期为印支通道,开放时间为35 Ma以前并持续到12 Ma;后期为川滇通道,开放时间为12 Ma至今.由于喜马拉雅东构造结与四川盆地之间强烈的挤压,印支通道不断变窄,并在12 Ma被关闭.两个通道的差异,通道的打开和关闭,造成高原中地壳物质流出速率在中新世发生明显变化,在23 Ma以来流出速率小于注入速率,在12 Ma流出速率最小,部分熔融的印度地壳物质不断滞留于高原地壳内部,使得地势相对平坦、面积巨大的青藏高原逐渐形成并分别向南和向北扩展.通过简单的力学分析,本文将高原腹地变形划分为两个阶段：大于35~23 Ma的造山阶段,受控于造山机制;23 Ma至今的造高原阶段,受控于造高原机制.     

Synoptic features and structures of some equatorial vortices over the South China Sea in the Malaysian region during the winter monsoon,December 1973

In December 1973, Peninsular Malaysia and Sarawak experienced a few periods of heavy rain caused by westward moving equatorial vortices from the South China Sea. In this report, the synoptic characteristies associated with the development and intersification of these vortices are shown. Structure of one of the disturbances was examined. Disturbances in the trades associated with lateral shear were found to be important for the genesis of the equatorial vortices. However, the intensification of these disturbances depended on the interaction with the cold monsoon surge.     

21世纪初青藏高原感热年代际增强对中国东部季风雨带关键区夏季降水年代际转折的影响

基于中国气象局提供的气象站点月值资料,NOAA、CMAP降水格点月值资料,NDVI卫星资料及再分析资料,利用统计方法分析了1961-2014年青藏高原感热与中国东部季风雨带关键区夏季降水的年代际变化,并根据热动力平衡方程结合CESM模式试验解释了21世纪初高原感热异常对关键区夏季降水的影响机理.结果表明：21世纪初,黄淮、江淮地区降水增加,而长江以南地区降水减少.同时,高原感热也发生年代际增强,当春季感热增强后,大气热能上传导致夏季高原近地面产生气旋性环流异常,大气辐合;高层产生反气旋性环流异常,大气辐散.黄淮、江淮地区在对流层中低层受异常偏南风控制,高层受高原上空的大尺度反气旋环流影响产生异常偏北风.此外,高原感热增强通过影响黄淮、江淮地区产生暖平流输送和非绝热加热正异常,该区域产生异常的上升运动,降水量增加.长江以南地区在对流层中低层存在一个异常的反气性环流,有来自海洋的冷平流输送,同时大气非绝热加热在该地区为负异常,产生异常的下沉运动,降水量减少.模式敏感性试验的结果证实了当高原感热发生年代际增强,黄淮、江淮地区水平温度平流及非绝热加热为正异常,而在华南地区为负异常,从而导致黄淮、江淮地区大气上升运动增强,降水增加;而华南地区下沉运动增强,降水减少.

     

Late Cenozoic volcanic activity in the Chugoku area, southwest Japan arc during back-arc basin opening and reinitiation of subduction

Abstract Temporal–spatial variations in Late Cenozoic volcanic activity in the Chugoku area, southwest Japan, have been examined based on 108 newly obtained K–Ar ages. Lava samples were collected from eight Quaternary volcanic provinces (Daisen, Hiruzen, Yokota, Daikonjima, Sambe, Ooe–Takayama, Abu and Oki) and a Tertiary volcanic cluster (Kibi Province) to cover almost all geological units in the province. Including published age data, a total of 442 Cenozoic radiometric ages are now available. Across‐arc volcanic activity in an area approximately 500 km long and 150 km wide can be examined over 26 million years. The period corresponds to syn‐ and post‐back‐arc basin opening stages of the island arc. Volcanic activity began in the central part of the rear‐arc ca 26 Ma. This was followed by arc‐wide expansion at 20 Ma by eruption at two rear‐arc centers located at the eastern and western ends. Expansion to the fore‐arc occurred between 20 and 12 Ma. This Tertiary volcanic arc was maintained until 4 Ma with predominant alkali basalt centers. The foremost‐arc zone activity ceased at 4 Ma, followed by quiescence over the whole arc between 4 and 3 Ma. Volcanic activity resumed at 3 Ma, covering the entire rear‐arc area, and continued until the present to form a Quaternary volcanic arc. Adakitic dacite first occurred at 1.7 Ma in the middle of the arc, and spread out in the center part of the Quaternary volcanic arc. Alkali basalt activities ceased in the area where adakite volcanism occurred. Fore‐arc expansion of the volcanic arc could be related to the upwelling and expansion of the asthenosphere, which caused opening of the Japan Sea. Narrowing of the volcanic zone could have been caused by progressive Philippine Sea Plate subduction. Deeper penetration could have caused melting of the slab and resulted in adakites. Volcanic history in the Late Cenozoic was probably controlled by the history of evolution of the upper mantle structure, coinciding with back‐arc basin opening and subsequent reinitiation of subduction.     

Comparison analysis of the summer monsoon precipitation between northern and southern slopes of Tanggula Mountains,Qinghai–Xizang (Tibetan) Plateau: a case study in summer 1998

Based on the precipitation data obtained through GEWEX Asian Monsoon Experiment–Tibet fieldwork from May to September 1998, this study investigated the features of the summer monsoon precipitation on the northern and southern slopes of the huge Tanggula Mountains in the Qinghai–Xizang (Tibetan) Plateau. The results show that the precipitation on the southern slope is about 50% higher than on the northern slope, whereas the frequency and diurnal pattern of the precipitation are very similar. The mean precipitation intensity on the southern slope is larger than on the northern slope. In most cases, the daily precipitation showed similar variation on both slopes, demonstrating that the precipitation processes might be similar. In the summer monsoon period, the local convective precipitation contributed to the total precipitation on both slopes and such a contribution on the southern slope is larger. Copyright © 2006 John Wiley & Sons, Ltd.     

青藏高原东缘虎牙断裂带南北段运动方式差异性机理：来自数值模拟的约束

虎牙断裂带作为青藏高原物质东向扩展的前缘断裂之一,其运动方式和强震活动类型表现出显著的南北差异.研究虎牙断裂带运动方式的差异性机理,对于认识地震发生机制与高原东向扩展模式有着重要意义.本文构建包含虎牙断裂带的三维黏弹性有限元模型,研究介质流变性差异与断层几何形态对区域地壳变形及断层三维滑动速率的影响.数值实验结果表明,在青藏高原物质东向挤出的动力学背景下,在虎牙断裂带南段,中下地壳介质流变性横向差异控制着断层以逆冲性质为主的运动,且随着中下地壳断层两侧流变性差异的增大,断层西侧物质的水平运动更易发生向垂向运动的转换.在断层两侧流变强度差1~2个数量级时,断层倾向滑动速率与走向滑动速率的比值达3.3~4.0,表现出显著的逆冲运动,与松潘—平武强震所反映的断层运动特征基本一致.相反,在断裂带北段,考虑断层两侧中下地壳较小的流变性差异时,断层即表现出明显的逆冲运动,这与九寨沟M_S7.0等强震反映的断层以走滑性质为主的运动明显不符,表明虎牙断裂带北段可能不存在中下地壳介质流变性的横向差异,断层以走滑为主的运动方式主要受断裂带几何展布控制.研究结果为认识青藏高原东缘同一构造区内断层运动方式差异与发震机制以及高原东向扩展模式提供了理论依据.

     

Spatial distribution and temporal trends of mean precipitation and extremes in the arid region,northwest of China,during 1960–2010

On the basis of daily precipitation records at 76 meteorological stations in the arid region, northwest of China, the spatial and temporal distribution of mean precipitation and extremes were analysed during 1960–2010. The Mann–Kendall trend test and linear least square method were utilized to detect monotonic trends and magnitudes in annual and seasonal mean precipitation and extremes. The results obtained indicate that both the mean precipitation and the extremes have increased except in consecutive dry days, which showed the opposite trend. The changes in amplitude of both mean precipitation and extremes show seasonal variability. On an annual basis, the number of rain days (R0.1) has significantly increased. Meanwhile, the precipitation intensity as reflected by simple daily intensity index (SDII), number of heavy precipitation days (R10), very wet days (R95p), max 1‐day precipitation amount (RX1day) and max 5‐day precipitation amount (RX5day) has also significantly increased. This suggests that the precipitation increase in the arid region is due to the increase in both precipitation frequency and intensity. Trends in extremes are very highly correlated with mean trends of precipitation. The spatial correlation between trends in extremes and trends in the mean is stronger for winter (DJF) than for annual and other seasons. The regional annual and seasonal precipitation and extremes are observed the step jump in mean in the late 1980s. Overall, the results of this study are good indicators of local climate change, which will definitely enhance human mitigation to natural hazards caused by precipitation extremes. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of precipitation and landuse on runoff during the past 50 years in a typical watershed in the Loess Plateau, China

In the past century, great progress has been made worldwide in our understanding of forest-water relationship. The successful forestation programs implemented in China-which have improved the ecological environmental conditions-have gained the attention of many researchers and highlighted the relationship between forestation and water yields. The arid and semi-arid Loess Plateau has received attention from water engineers and eco-hydrological researchers in China because of a shortage in water resources. We selected one of the oldest stations conducting soil and water conservation experiments, the Xifeng soil and water conservation station, and chose the Nanxiaohe catchment and its paired catchments （Yangjiagou catchment and Dongzhuanggou catchment） as our research areas. Trends in precipitation, air temperature, streamflow over the past 50 years, and the effect of changing land use on streamflow were analyzed. The Mann-Kendall test showed that precipitation had a negative trend （downward trend）, whereas air temperature showed a positive trend （upward trend） from the past to present in the Nanxiaohe catchment. However, the trends seen in precipitation, air temperature did not contain any ＂jumping points.＂ The paired catchment approach is used to detect the effects of land cover change on hydrology in the Yangjiagou and the contrast catchment, i.e., Dongzhuanggou catchment in our study. The results showed a large change in land use in the Yangjiagou catchment from 1954 to 2008. An increase in forested land （from 0% to 40.08% from 1954 to 2008） and a reduction of bare land （from 51.26% to 5.50% from 1954 to 2008） accounted for a large part of the change in land use. However, the land use changed little in the contrast catchment. The comparison of streamfiow in the paired catchments showed that forestation reduced streamflow by 49.63% （or 6.5 mm） each year.