A new conception on the formation of the first bend of Yangtze River: its relations with Eocene magmatic activities

Based on field observations, the author proposes a new understanding on the formation of the first bend of the Yangtze River. The relationship between the formation of the first bend of the Yangtze River and Eocene magmatic activity is expounded, suggesting that the first bend of the Yangtze River is the result from choking of the strong magmatic activity in Eocene. As a result, the upstream became a natural reservoir, whose riverside between Mt. Yulong and Mt. Haba was burst, guiding Jinshajiang River running eastward. At the same time, the drastic uplift of the Qinghai-Tibet Plateau led to the deep dissection of the river cut down the channel, resulting in the formation of the Tiger Leaping Gorge. The magnitude of uplift in the study area (located in the eastern of the Tibetan Plateau) is calculated. Taking Mt. Yulong as a base, the magnitude of lift is 3,300 m from Eocene to Pliocene, adding 700 m since Pleistocene, totaling up to 4,000 m or so.     

滇西北老君山地区岩浆活动与 长江第一弯形成的关系

在野外观察的基础上，对长江第一弯的形成提出了新认识，首次研究了始新世岩浆活动与长江第一弯形成的关系。提出长江第一弯为始新世滇西北老君山地区（金沙江古河道）强烈的岩浆活动阻塞了古金沙江，导致其上游形成堰塞湖，并在玉龙雪山和哈巴雪山之间决口，在高原隆升的同时河道快速下切，形成虎跳峡，是河水改道东流的结果；计算了处于青藏高原东端研究区的隆升的幅度，对玉龙雪山而言，始新世至更新世，隆升幅度为3300m，加上更新世以来的隆升高度700m，累计隆升高度为4000m左右。     

长江第一弯成因及形成时代探讨

长江第一弯成因及形成时代关系到金沙江—长江水系的形成演化、西南纵向岭谷地理环 境演化、青藏高原隆升对周边环境的影响等重大科学问题, 故近百年来一直为学术界所关注。本 文通过综合考察、地貌和沉积物等的综合分析认为: 长江第一弯是在金沙江水系未曾溯源连通至 三江口段之前的古金沙江与古冲江河、水洛河的汇流口。长江在三江口袭夺了水洛河, 导致水洛 河倒流, 古金沙江与三江口下的长江贯通, 才形成真正的金沙江—长江水系。根据玉龙山强烈隆 起时间、周边层状地貌发育年代、中国水系大局形成等进行推断, 长江第一弯形成时代为中更新 世以来, 说明昆黄运动为本区构造地貌—水系发育的重大转型事件。     

金沙江虎跳峡成因及形成时代探讨

虎跳峡是金沙江峡谷的典型代表,其成因及形成时代涉及金沙江-长江水系发育及其环境效应问题。文中分析研究了虎跳峡附近发育的夷平面、剥蚀面、阶地等区域性的层状地貌,并认为虎跳峡上下游河谷发育历史具有一致性;从地质构造上的分析表明,虎跳峡两侧的玉龙雪山、哈巴雪山为一相对完整的地块,不存在虎跳峡大断裂,因而虎跳峡峡谷是在区域地壳抬升、先成河深切作用下而形成的。根据相关盆地沉积物、玉龙雪山的冰川发育状况、前人在附近发现的哺乳动物化石等,初步认为虎跳峡峡谷形成于中更新世。     

Characteristics of total suspended particulates in the atmosphere of Yulong Snow Mountain,southwestern China

The measurement of black carbon(BC) and organic carbon(OC), dust in total suspended particulates(TSP) was carried out at Yulong Snow Mountain(Mt. Yulong) and Ganhaizi Basin, in the Mt. Yulong region, southwestern China. TSP samples were analyzed using a thermal/optical reflectance carbon analyzer. Results show that average BC and OC concentrations in TSP in the Mt. Yulong region were 1.61±1.15 μg/m3 and 2.96±1.59 μg/m3, respectively. Statistical results demonstrated that there were significant differences in mean BC and OC contents between Ganhaizi Basin and Mt. Yulong at the 0.05 level. Strong correlations between BC and OC indicate their common dominant emission sources and transport processes. Temporal variations of BC, OC, and optical attenuation(ATN) values were consistent with each other in carbonaceous aerosols. The ratios of OC/BC in monsoon season were significantly higher than in non-monsoon in aerosols from Ganhaizi, which is closely related to the formation of secondary organic carbon(SOC) and extensive motor vehicle emissions from tourism activities. The temporal variations of BC, OC and ATN in carbonaceous aerosols in Ganhaizi and Mt. Yulong were totally different, probably due to elevation difference and diverse tourism activity intensity between the two sites. Time-averaged aerosol optical depth(AOD) at the wavelength of 550 nm in Mt. Yulong was higher than that of the inland of the Tibetan Plateau(TP). Source apportionment indicated that intensive exhaust emissions from tourism vehicles were the main local sources of atmospheric pollutant in the Mt. Yulong region. Biomass-burning emissions released from South Asia could penetrate into the inland of the TP under the transport of summer monsoon. Further study is needed to assess light absorption and radiative forcing of carbonaceous aerosols, and modeling research in combination with long-term in-situ observations of light-absorbing particulates(LAPs) in the TP is also urgently needed in future work.     

西南季风对中国自然环境影响的区域变化研究

西南季风作为亚洲季风重要组成部分，对中国自然环境也有较大影响。西南季风建立以后，因青藏高原高度不足以阻止西南季风这一深厚的大气环流系统，加之西南季风厚度随着山地尤其是横断山脉的上升而不断增厚、增强。南支西风急流的气旋性质对西南季风深入有引导作用，西南季风较东南季风活动性强，影响区域范围大，影响到太行山以西中国大部分地区。中更新世时，青藏高原隆升至海拔平均约3000m的高度，同时期也出现了第四纪最大冰期与最大温暖期，高原热力和动力作用得到了进一步加强，西南季风厚度加大，西南季风对中国自然地理环境深化起到重要作用。晚更新世以来青藏高原隆升至现今的平均约4500-5000m的高度，特别是喜马拉雅山脉的隆起，足以阻挡大部分西南季风进入西藏高原和中国内陆地区，西南季风影响范围退缩到长江上游以南的西南地区局部和青藏高原东部地区。     

The five major changes in the evolution of the Loess Plateau

On the basis of the geomorphology, paleosol, paleoclimate and loess age, major changes of the Loess Plateau were studied. There are five major changes in the evolution of the Loess Plateau in China. Among them, the first, second, third and fourth major changes have taken place since the formation of the Loess Plateau, and the fifth major change will happen in 100 years. The first major change, which occurred at about 2.50 Ma BP, was a transition from red earth plateau to the Loess Plateau, and reflects the climate from the warm-sub-humid to the alteration between cold-and-dry and warm-and-humid. The driving force of this first major change was climate. The second major change, which took place at about 1.60 Ma BP, was a vital transition of the main rivers in this area from non-existence to existence, and represented an important change on the Loess Plateau's neotectonic uplift from the slow rising to periodically accelerated rising, and making the river's erosion go from feeble to strong. The driving force of the second major change is tectonic uplift. The third major change which occurred at about 150 ka, was a great transition of the Yellow River's inpouring from a lake outlet to a sea outlet. At that time, the Yellow River cut the Sanmen Gorge. The transition led to the transformation of loess material from internal transportation to external transportation. The driving force of the third major change was running water erosion. The fourth one that occurred at about 1.1 ka was a change of the Loess Plateau from natural erosion to erosion accelerated by human influences. The driving force of the fourth major change is mainly human activities. The fifth major change, which is the opposite change to the fourth one, in which the motive power is human activity, too.     

黄土高原0.8Ma以来地面抬升的时空特征研究

根据黄土高原地区黄河阶地的形态特征和成因分析,认为其形成主要是地面抬升所致并且在黄河达到均衡状态下形成,可以推断黄土高原的地面抬升。根据对黄土高原地区黄河0.8 Ma阶地的研究并结合相关文献资料,选取兰州段、黑山峡段、晋陕峡谷段和三门峡段作为典型研究区域,得出黄土高原0.8 Ma以来的地面抬升存在显著的时空特征,即空间特征表现为地面抬升量有西大东小的规律,时间特征表现为地面抬升速率有后期加速趋势、特别是晚更新世以来。并认为黄土高原0.8 Ma以来的地面抬升与青藏高原的构造抬升有成因上的联系。     

青藏高原东南部地貌边界与金沙江水系发育

4000米山顶面高程等值线,可定为高原东南部与外围地区间的地貌界线。低于山顶面的高原面的形成与上新世一早更新世古谷地、盆地的加积相关。元谋运动以来,地貌边界带的发展与高原整体的隆升同步,1500米大河河床高程等值线环绕高原分布,现代水系相继发育。金沙江与长江贯通后东流入海,这是中国大陆地势最终转变为西高东低的标志。     

黄土高原发展过程中的五大转折

1 Introduction W hatim portanttransform ations have taken place during the form ation ofthe Loess Plateau in China? Research on this problem has especially im portantscientific significance forus to learn ofthe evolution oftheLoessPlateau and predictthe f…     

1954年长江巨洪中物理因子的叠加作用

分析了形成1954年长江巨洪的物理因子,指出现有研究主要侧重单个物理因子对1954年长江巨洪的影响。事实上,1954年长江巨洪是这些因子叠加作用的结果,并且因子越多,叠加作用越强,巨洪的量级也就越大。     

晚更新世以来贵州清水江阶地发育及地貌意义

对贵州清水江上游马寨、翁东、三江、施洞沿江4个剖面的阶地特征、年代学结果进行了综合分析。发现以凯里断层为界,上游地区的马寨和翁东2个剖面的T2阶地形成时代约为51~57 ka B.P.,T1阶地的形成时代约为25 ka B.P.,下游地区的三江和施洞2个剖面的T2阶地形成时代约为122~102 ka B.P.,T1阶地的形成时代约为78 ka B.P.。选取各剖面的T2阶地的基座高度来计算了河流下切速率,发现上游地区2个剖面（马寨、翁东）的河流下切速率较接近,约为0.41~0.34 m/ka,明显高于下游地区的2个剖面（三江、施洞）的0.16~0.20 m/ka,表现为上游下切速率高,越往下游方向下切速率逐渐降低。这表明自晚更新世以来,清水江上游区域受到构造作用的影响而发生差异抬升,具体表现为西部构造抬升幅度大,阶地下切速率快;东部构造抬升幅度小,阶地下切速率慢。     

黄山北麓青弋江发育原因及其与长江贯通的关系

基于前期研究工作成果和外部环境变化因素分析,探讨了青弋江发育原因及其与长江贯通的关系。研究表明：① 昆黄运动可能在长江中下游地区产生了区域构造响应,导致研究区断层被激活而发生了较大幅度的断块抬升运动,进而为青弋江发育提供了下切驱动力,驱动了青弋江发育;② 东亚夏季风在约1.3 Ma和约0.9 Ma发生的2次显著阶段性减弱事件,引起区域降水量显著增加,进而为青弋江发育提供了下切媒介和持续水流,控制了青弋江发育年代;③ 青弋江发育与长江贯通可能都是昆黄运动区域构造响应与东亚夏季风强度阶段性减弱共同作用的结果,并且长江贯通后所形成的新局部侵蚀基准面也可能促进了青弋江发育,因此青弋江发育年代在一定程度上能反映长江贯通年代。     

鄂尔多斯高原周缘黄河阶地的形成与青藏高原隆升

构造运动和和气候变化是河流阶地形成的两个重要因素。学术界对于构造运动与气候变化中哪个因素是河流阶地形成的控制因素尚未形成一致观点。本文选择位于鄂尔多斯高原周缘的河流阶地,综述了前人在兰州段、中卫段和晋陕峡谷段3个河段的黄河阶地上的研究成果,结合2万年以来的古洪水记录与古地震活动等证据,对比了河流阶地形成、气候变化以及青藏高原的幕式隆升的时间。对比结果显示,鄂尔多斯高原周缘多级河流阶地的形成时间与青藏高原阶段性隆升的时间比较一致,而与气候冰期—间冰期变化之间没有明显规律,这一结果支持构造运动是鄂尔多斯高原周缘的河流阶地形成的控制因素。     

Characteristics of abrupt changes of snow cover and seasonal freeze-thaw layer in the Tibetan Plateau and their impacts on summer precipitation in China

In this paper, a variation series of snow cover and seasonal freeze-thaw layer from 1965 to 2004 on the Tibetan Plateau has been established by using the observation data from meteorological stations. The sliding T-test, M-K test and B-G algorithm are used to verify abrupt changes of snow cover and seasonal freeze-thaw layer in the Tibetan plateau. The results show that the snow cover has not undergone an abrupt change, but the seasonal freeze-thaw layer obviously witnessed a rapid degradation in 1987, with the frozen soil depth being reduced by about 15 cm. It is also found that when there is less snow in the plateau region, precipitation in South China and Southwest China increases. But when the frozen soil is deep, precipitation in most of China apparently decreases. Both snow cover and seasonal freeze-thaw layer on the plateau can be used to predict the summer precipitation in China. However, if the impacts of snow cover and seasonal freeze-thaw layer are used at the same time, the predictability of summer precipitation can be significantly improved. The significant correlation zone of snow is located in middle reaches of the Yangtze River covering the Hexi Corridor and northeastern Inner Mongolia, and the seasonal freeze-thaw layer exists in Mt. Nanling, northern Shannxi and northwestern part of North China. The significant correlation zone of simultaneous impacts of snow cover and seasonal freeze-thaw layer is larger than that of either snow cover or seasonal freeze-thaw layer. There are three significant correlation zones extending from north to south: the north zone spreads from Mt. Daxinganling to the Hexi Corridor, crossing northern Mt. Taihang and northern Shannxi; the central zone covers middle and lower reaches of the Yangtze River; and the south zone extends from Mt. Wuyi to Yunnan and Guizhou Plateau through Mt. Nanling.     

中国典型山地温冰川水化学空间分布特征与近期冰川动态

从我国玉龙雪玉典型温水王白水１号冰川不同区段表面融水,新近积雪和冰川初给河水采样分析结果表明,雪线以下降水中的稳定同位素的离子含量比雪线以下为高,低海拔河水比高海拨融水的氧同浓度为低,可能在来源上存在着差异,这种分布特征说明本温冰川区局部大气环流情况高度而不同,有可能存在季气候区所特有的“降水量效应”或“季节性效应”。冰川不同水体内离子浓度变化说明,冰川融水与地壳表面接触时间越久,其中的可融性离了     

川西高原杂谷脑河阶地的形成

根据野外实地地貌调查,确定了川西高原杂谷脑河理县段发育了8级阶地,并对阶地沉积物进行了ESR年代测试,初步确定杂谷脑河第II,III,IV,VI级阶地约形成于距今54,125,248,481ka。阶地成因分析表明这些主要阶地序列主要是构造隆升的结果,因此,杂谷脑河各级主要阶地分别代表了川西高原中更新世以来的几次隆升事件。根据阶地高程和阶地形成年代确定的杂谷脑河下蚀速率为0.39m/ka,与大地测量获得的龙门山隆升速率 (0.3~0.4m/ka) 相一致。     

贵州高原北部河流阶地发育与喀斯特地貌演化

贵州高原北部发育平缓丘丛和深切峰丛2种喀斯特地貌组合,保存于喀斯特山间盆地的河流阶地对区域地貌演化具有指示意义.本文根据阶地发育特征和光释光(OSL)测年,分析阶地形成的时代和动力,结合区域地质背景,探讨构造抬升和河流侵蚀对黔北喀斯特地貌演化的驱动作用.结果显示,绥阳盆地T1阶地时代18.8?8.2 ka,T2时代14...     

黄山北麓青弋江发育研究

青弋江位于黄山北麓,为长江下游最长的支流。野外考察发现青弋江泾县盆地段存在溪口剖面和城北剖面等2个天然剖面,共发育了1级洪积扇台地（P）和3级河流阶地（T3、T2和T1）,并相应堆积了4级砾石层。通过对砾石层进行砾组分析,并借助电子自旋共振（ESR）测年和古地磁测年等方法,初步探讨了青弋江发育的年代、过程和成因。研究结论为：① 砾组分析表明青弋江T3阶地是青弋江的最老阶地,并且其砾石层是青弋江的最老砾石层;② 测年结果表明青弋江发育的年代区间为1300~900 ka,其中~1300 ka为青弋江发育的最早年代,而~900 ka则为青弋江发育的最晚年代;③ 青弋江发育于~1377 ka前的洪积扇辫状河,并先后经历了洪积扇及辫状河发育、辫状河下切、青弋江形成等阶段,即所谓的源于洪积扇辫状河的青弋江发育过程;④ 青弋江发育可能是降水增加和构造抬升共同作用的结果。该研究有助于为中国东部地区中小河流发育研究提供参考。     

长江源区冰川对全球气候变化的响应

长江源区是青藏高原内部山地冰川集中分布的地区之一 ,其冰川储量都占长江流域冰川总量的一半以上。近几十年以来由于受全球气候变化的影响 ,长江源区气候呈暖干化的倾向 ,大多数冰川呈退缩状态 ,这对长江源区的生态环境产生深刻的影响 ,进而危及整个长江流域的生态安全。用英国Hadley气候预测与研究中心的GCM模型HADCM2预测长江源区未来的气候情景 ,结果显示在不同的实验条件下 ,气候都将由现在的暖干化趋势向暖湿化方向转变。通过建立长江源区对气候变化的响应模型 ,用来预测在未来气候情景下冰川变化的趋势 ,预计在本世纪的不同时期冰川零平衡线 (雪线 )将上升 16～ 5 0m。