Age and genesis of the Shagou River terraces in eastern Qilian Mountains

The fluvial terrace sequence in eastern Qilian Mountains is a record of periodic uplift events of the Tibetan Plateau. Based on paleomagnetic dating, thermolumines-cence dating, radio carbon dating and loess-paleosol sequence on terraces, we preliminarily determine the ages of five major terraces of the Shagou River, northern side of the Qilian Mountains. The ages of five terraces were about 830, 418, 250,140 and 10 ka, respectively. Analysis on characteristics of terraces show that five major terraces were mainly tectonic genesis. Therefore, five major terraces recorded five strong rising events in the Qilian Mountains during the past 830 ka. The ages of those rising events are about the same as those terraces formation. Sub-terraces, constituting a main terrace, were perhaps mainly formed by climatic changes.     

祁连山东段冲积扇的发育时代及其成因

第四纪期间祁连山东段山麓地带广泛发育了多级冲积扇,它们是研究区域构造抬升与气候变化最为直接的载体.本文主要通过ESR,IRSL以及14C等绝对测年手段对该区冲积扇的形成年代进行研究,结果表明祁连山东段北麓最高级冲积扇形成于0.85 MaBP,而毛毛山南麓的最高级冲积扇形成于0.43 MaBP.随后各地又相继发育了0.25,0.16,0.06,0.01 MaBP等多级冲洪积台地.根据主要冲积扇的形成年代及其与区域构造气候事件的对比,认为它们是构造运动与气候变化共同作用的产物.     

Dating and genesis of the upper Weihe River terraces in Longxi basin, China

Seven terraces along the Weihe River in Longxi basin have been investigated. These terraces all consist of archetypal duality in structure, namely the floodplain deposits and the layer of gravels overlaid by varying thickness of the loess. By resorting to various dating approaches such as palaeomagnetic, optically stimulated luminescenece (OSL), 14C and loess-paleosol sequence, we provide preliminary timing of these seven terraces along upper Weihe River. Analysis on sedimentation characteristics and dating of these terraces showed that seven terraces may be jointly generated by tectonic uplifts and climatic changes. Tectonic uplifts may accommodate initial river incision, and climatic change may be responsible for processes of subsequent channel widening and aggradation. Aggradation normally occurs during glacial periods, in contrast to down-cuttings during transitions from glacial to interglacial period. Moreover, on the basis of the timings and heights of these terraces, we infer that the long-term rate of river incision was determined to be 0.2 m/kyr during the last 870 kyr, which differs from other river incision rates. This discrepancy may reflect spatio-temporal differentiation of tectonic activities in the Qinling orogenic belt during the Pleistocene.     

Dating and genesis of the upper Weihe River terraces in Longxi basin,China

Seven terraces along the Weihe River in Longxi basin have been investigated. These terraces all consist of archetypal duality in structure, namely the floodplain deposits and the layer of gravels overlaid by varying thickness of the loess. By resorting to various dating approaches such as palaeomagnetic, optically stimulated luminescenece (OSL), 14C and loess-paleosol sequence, we provide preliminary timing of these seven terraces along upper Weihe River. Analysis on sedimentation characteristics and dating of these terraces showed that seven terraces may be jointly generated by tectonic uplifts and climatic changes. Tectonic uplifts may accommodate initial river incision, and climatic change may be responsible for processes of subsequent channel widening and aggradation. Aggradation normally occurs during glacial periods, in contrast to down-cuttings during transitions from glacial to interglacial period. Moreover, on the basis of the timings and heights of these terraces, we infer that the long-term rate of river incision was determined to be 0.2 m/kyr during the last 870 kyr, which differs from other river incision rates. This discrepancy may reflect spatio-temporal differentiation of tectonic activities in the Qinling orogenic belt during the Pleistocene.     

云台山世界地质公园及周边地区河流阶地发育特征研究

云台山世界地质公园位于太行山的南部边缘,源于太行山腹地的一系列河流,切穿太行峰脊,形成众多山高谷深瀑水飞溅的峡谷群,成为南太行山旅游的核心地质遗迹景观。峡谷中河流阶地发育,通过对云台山及周边地区九条典型峡谷中河流阶地发育特征研究,探讨了河谷的发育历史;以及该地区不同时期的气候变化、新构造运动的性质和幅度,认为六级河流阶地在太行山河谷内普遍发育;但由于第四纪是强烈切割时期,所以这些河流阶地也大部分被剥蚀掉,仅在部分地区还不同程度残留有六级河流阶地的产物。     

粤北锦江扶溪段河流阶地的光释光测年

南岭是我国重要的自然地理分界线和东亚季风环流屏障,第四纪期间粤北山地发育的多级河流阶地是研究南岭构造运动与气候变化的良好地质载体。粤北锦江扶溪段保留了5级阶地,运用光释光（OSL）技术对T2到T5级阶地的砾石层进行了测年,并从气候和构造角度分析了阶地成因。结果显示：T3形成于67 ka,对应于深海氧同位素的MIS4阶段;T2形成于51 ka,对应于MIS3b阶段;阶地沉积层堆积于冷期,气候变化影响着河流的侧蚀、堆积和下切作用交替进行,而新构造运动的构造抬升发动了足够的下切量使锦江扶溪段依次下切17 m、19 m、12 m和10 m形成T5、T4、T3和T2;南岸的河谷下切速率为0.3 mm/a,大于2倍的流域现代侵蚀速率,地貌发育符合年轻山地的抬升-下切-侵蚀模式。     

玛纳斯河流域地貌初步研究

玛纳斯河是天山北麓最大的一条河流,由于天山的隆升,在天山北麓形成了一系列的褶皱和断层,这一构造格局控制着玛纳斯河地貌的发育和演化.根据野外调查,玛纳斯河流域地貌由南向北横穿流域内的5个地貌带,即山地地貌带,山前褶皱低山丘陵带,串珠状冲积扇带,平原曲流带,玛纳斯河尾闾沙漠、湖泊带.同时玛纳斯河在不同地貌带塑造出了不同的河谷地貌.流域内新构造活动比较显著,表现为近东西向的活动褶皱与活动逆断裂,而且构造对地貌发育有明显控制作用,如山前褶皱丘陵形态为南翼缓,北翼陡,河流阶地发生拱曲和错断变形,冲积扇串珠状发育等.     

天山北麓玛纳斯河河流阶地变形与新构造运动

通过对玛纳斯河阶地的野外测量,研究了河流阶地的发育特征、拱曲变形和错断变形。阶地的变形特征表明山麓背斜带和玛纳斯背斜带一直在隆升,且隆起中心有向北迁移的趋势。阶地的错断状况表明断层F₂活动可以分为2个阶段,断层F₁的活动至少可以分为4个阶段。     

粤东地区的河流阶地

 依据广东东部超过32条河流、55处河流阶地、至少25个¹⁴C、热释光的冲积层测龄数据等情况,可知：粤东最多有6级河流阶地,最大阶地高度70 m且靠近现代主河床分布。从上游向下游第一级阶地明显变形：龙川县黎咀镇上游为常态阶地,黎咀镇下游至博罗县园洲镇为半埋藏阶地,园洲镇下游进入东江三角洲为埋藏阶地。而且该冲积物时代有渐新趋势,反映晚更新世河源地区的构造抬升较早或速率较快,中下游地区构造逐渐稳定或下沉。粤东至少有12处较典型的剥夷面砾石层。其特怔：① 分布海拔20～210 m,与当地剥蚀台地高度相似;② 位于当地级别最高、分布面积大的河流阶地上;③ 石岩镇玉律、平陵镇、东坑镇、水唇镇、龙母镇张坊等剥夷面砾石层由昔日河流形成,其谷中谷成为今日小河（只有狭窄河床河漫滩,或许有第一级河流阶地）,今昔河流发育相隔数十万年;④ 剥夷面有两个倾斜方向：流域内向河谷和向下游倾斜;总体上由南岭向南海倾斜。     

云南鹤庆西山地质构造对岩溶发育的控制作用分析

为探究地质构造对岩溶发育的控制作用,选择鹤庆西山为研究区,采用地质调查与钻探数据相结合的方法,分别对地层岩性、地质构造、地表与地下岩溶现象和分布规律进行综合分析.结果表明:受印支运动、喜山运动等多期构造运动影响,研究区整体形成以NNE-NE向为主的构造格局.根据规模的不同,将研究区构造划分成区域性断裂带、次级断裂、大型...     

新疆柴窝堡盆地新构造运动对地下水的影响

新疆柴窝堡盆地属天山地槽褶皱带博格达复背斜的一个中新生代山间盆地 ,含有丰富的地下水资源。柴窝堡盆地总的轮廓和结构 ,严格受构造控制 ,而地形和微地貌则主要受河流水系的制约。根据新构造格局 ,把柴窝堡盆地分割成三个独立的水文地质区 ,提出新构造断块上升 ,盆地沉降 ,不但控制了柴窝堡盆地第四纪沉积物厚度和岩性 ,也控制了地下水的补给、径流、排泄条件。     

Terrace dating as an archive of the run-through of the Sanmen Gorges

Analysis of morphological properties in the Sanmen Gorges region of the Yellow River shows that four river terraces have been developed at the entrance to the gorges. Commonly, thick aeolian loess-paleosol sequence was deposited on the terraces, which makes it easy to date the terraces. The dating of paleomagnetic, loess-paleosol sequence matching and thermoluminescence show that terraces T₂, T₃ and T₄ were formed 0.129 Ma, 0.625 Ma and 0.865 Ma ago, respectively. The formation of these terraces in this region indicates that the Yellow River has experienced four intensive downcutting events during the last 0.9 Ma. The Yellow River cut through the Sanmen Gorges and inpoured into the East China Sea no later than 0.865 Ma.     

柴达木盆地小柴旦地区构造演化对烃源岩热演化的控制作用

柴达木盆地小柴旦地区是发育在元古界结晶基底上的中新生代叠合盆地,构造上具有南北分带的特征,形成6个典型的构造单元。中生代以来受燕山运动和喜山运动改造,形成两期区域不整合,不整合界面相互叠置,多期改造,且剥蚀作用涉及地层层系多、范围广。在主要不整合界面地层剥蚀量恢复基础上开展了骨干剖面构造演化研究,针对研究区具体情况采用针对性参数,系统开展了不同构造带中下侏罗统烃源岩埋藏史和热演化史分析。结果显示,不同构造带形成时期与四个演化阶段的沉降抬升幅度具有一定差异,构造演化的差异性也导致了中下侏罗统烃源岩在地质历史时期埋藏过程的差异性。区内烃源岩热演化可总结为山前推覆深埋型、持续埋深成熟型、抬升成熟型和抬升低熟型等四种类型。不同构造带烃源岩热演化的差异性也导致了研究区目前的油气发现主要集中于山前带及其周缘,但凹陷内也具备低熟油形成的条件。     

柴达木盆地中新世中期以来构造的运动学模型

柴达木盆地是位于青藏高原内部的山间盆地,盆地新生代的变形受到两侧山体隆升的主导.通过贯穿盆地地震剖面的精细构造解释和分析,依据生长地层的结构,我们认为自中新世中期以来昆仑山前冲断楔体以平均4.7 mm/a的速度向盆地逆冲,导致盆地南斜坡向昆仑山方向仰冲;这为东昆仑山北麓出露的倾向北向南逆冲的多条断层和盆地南部向南逆冲的断层控制的断层相关褶皱作用所证实.盆地北部祁连山前冲断楔体向盆地方向逆冲,导致盆地北部向北逆冲的断层在地表形成北翼陡、南翼缓的断层相关褶皱背斜,向北逆冲的断层在盆地东部局部位置出露地表.昆仑山前冲断楔体和祁连山前冲断楔体的楔顶已经相向冲断至盆地中部,并造成第四系的变形.     

Formation of the Yazi Spring Stream and its significance on tectonics-climate on the northern slope of Kunlun Mountains

The sequences of fluvial terraces in the Yazi Spring Stream are signs of the stepwise uplift of the Kunlun Mountains in the northern part of the Tibetan Plateau since the Late Pleistocene. Geomorphic and sedimentary features of the terraces reveal that they have resulted from the phased tectonic uplift and the consequent river incision in the northern plateau. Using the method of Single-aliquot Regenerative-dose （SAR） Protocol and Radiocarbon ^14C dating, the deposit ages of three-grade terraces were obtained, which are 57.5, 12.8 and 5.7 kaBP, respectively. The features and ages of terraces reveal that the incision rate of the stream accelerated at the beginning of the Holocene. The incision rate changed suddenly at 12.8 KaBP, from 0.43±0.07 mm/a to 1.59±0.55 mm/a. This implicates that uplift of the Kunlun Mountains is intensive at the first onset of the Holocene, corresponding to the obvious change of slip-rate on the AItyn Tagh Fault. But its uplift rate is much lower than that of the latter, which suggests that growth of the northern margin of the Tibetan Plateau is stronger than its interior.     

黄河中游的地貌与地文期问题

上起积石峡下至三门峡的黄河中游地区在晚新生代期间发育了一级夷平面、一级剥蚀面和七级河流阶地。夷平面形成于２．４Ｍａ以前的晚第三纪，剥蚀面形成于２．４～１．８Ｍａ Ｂ．Ｐ的第四纪初期；黄河的七级阶地分别是开始于１３００、１１００、７８０、５９０、１４０、５０、１０ｋａ Ｂ．Ｐ的河流下切形成的，其原因在于构造的脉动式上升。基于上述研究成果，我们将每一地貌面形成的时期定义为一个地文期，它与其后因构造运动     

巧家盆地河流沉积与重矿物特征对金沙江贯通的指示

通过对云南巧家盆地第四纪河流沉积和重矿物特征的研究,探讨金沙江下游巧家段水系的发展和演化过程。研究结果表明:1.6 Ma B.P.之前巧家盆地开启后,古金沙江巧家段南流水系也随之形成,并在盆地内发育了至少3期河流沉积,当时为宽阔的辫状河沉积环境,物源区位于巧家以北至四川西昌-昭觉一带的黑水河和西溪河流域,河流将玄武岩、灰岩、砂岩等砂砾携带至盆地中堆积,重矿物组合为锆石-绿帘石-金红石-电气石-角闪石-磷灰石;在0.5 Ma B.P.之前,由于云南高原的隆升使得古金沙江巧家段水系南流受阻,并在古水系支流的溯源侵蚀下被袭夺,造成巧家河段的倒转北流,金沙江贯通,巧家段水系物源区发生巨大变化,河流开始将金沙江中上游流域的板岩、千枚岩、片岩以及石英岩等砂砾带至盆地,重矿物类型中也开始出现石榴子石,在构造活跃期河流不断向西迁移并进行下切,形成了金沙江4级阶地。巧家盆地河流沉积与重矿物特征及相关年代的研究显示,巧家段水系的袭夺倒流,金沙江的贯通应发生于0.5 Ma B.P.之前。     

Geomorphologic evolution and environmental changes in the Shaluli Mountain region during the Quaternary

Geologic and geomorphologic evidence from the Shaluli Mountain indicates that the planation surface that formed in the Late Tertiary disintegrated during the Late PUocene-Early Quaternary. At the same time, rift basins appeared on some parts of the planation surface, and began to accumulate fluvial-lacustrine sediment. These are interpreted as being the response of this region to Phase-A of the Qingzang Teetnnic Movement. After this, the Shaluli Mountain eontinued to rise in several pulses. Faulting and incision by some large tributaries of the Jinsha and Yalong Rivers resulted in several rift river valleys and the earliest terraces. Generally. the planation surface in this region had been uplifted to ahout 3500--3700 m a.s.I, no later than 550-600 ka BP. after the Kunlun-Huanghe Tectonic Movement, and coupled with global glacial climate, and resulted in the earliest glaciation recognized so far in the Hengduan Mountains. At the same time, Ioess was deposited in the Ganzi area of the northern Shaluli Mountain. During the last glacial period, the Shaluii Mountain approached its present altitude and developed several large ice caps, such as the Daocheng Ice Cap and Xinlong Ice Cap, as well as several huge valley glaciers. These paleoglaciers produced some of the most Spectacnlar glacial topography on the Tibetan Plateau.     

论新构造运动与地壳稳定性

所谓新构造运动是相对于老构造运动而言的．因为新构造运动是新生代后半期的构造运动，距现在最近、也最新，所以它与地壳的稳定性密切相关．又因为新构造运动具有活动时期与稳定时期的相互交替特性，所以地壳稳定性也具有不稳定时期与相对稳定时期的相互交替。在地貌表面上就留下了高度不同的多级夷平面与河流多级阶地．其中，活动构造地带时常发生．运动造成地震灾害，也是地壳最不稳定的地带．但不稳定地区中也有相对稳定的地块，被称为“安全岛”，为重大建设提供了基地．     

塔木素预选区第四纪构造活动性的光释光测年分析

内蒙古塔木素地区地处中蒙边境,位于阿拉善右旗,是高放废物粘土岩处置库的预选场址。预选区内大部分地区被第四系地层覆盖,发育多条断裂构造,断裂构造第四纪以来的活动性对于预选区有利地段的最终确定具有重要的科学和现实意义。本文以塔木素地区北部靠近控盆断裂的塔木素断裂为研究对象,利用光释光定年技术研究该断裂晚第四纪的活动性。通过野外地质调查和高分辨率卫星遥感影像发现塔木素断裂东段错段一条干枯的河流,我们对河流阶地采集光释光样品,测得光释光年龄为56.8±5.2ka,结合河流阶地的高程曲线可以看出塔木素断裂晚第四纪以来活动性弱。