川西岷江松潘段第四纪与新构造运动特征分析

在已有调查研究的基础上,通过野外地质调查和剖面测量,重点分析了岷江松潘段的漳腊盆地、斗鸡台盆地地貌特征、第四纪沉积物类型、物质成分、空间分布等特征,并系统测量和研究了松潘段岷江干流及其支流的河流阶地特征。研究表明,新构造运动控制了松潘段第四纪盆地的形态和地貌演化过程,漳腊盆地和斗鸡台盆地形成于中新世末至上新世初,西侧控盆断裂为东倾正断层,东侧为西倾逆断层,盆地为断块发生西降东升的翘板式断块运动过程中形成的,称之为"翘板式箕状盆地"。松潘段岷江河谷地貌呈现出宽谷和窄谷交替出现的特点,岷江干流及其支流中发育多处湖相地层,沉积特征表现为堰塞湖。岷江上游松潘段最多发育6级阶地,以侵蚀阶地和堆积阶地为主,主要形成于中更新世晚期—全新世时期。阶地级数具有分段性特点,不同区段阶地阶面宽窄不一,受区内新构造活动控制明显。岷江上游新构造运动表现为南北条带性和东西向差异掀斜抬升的特点,红桥关以上整体为构造隆升区,至少具有3次构造隆升,岷江上游斗鸡台盆地构造隆升强度整体上大于漳腊盆地。在尕米寺地区可能发生了6次构造抬升,红桥关一带构造抬升明显要强于漳腊盆地。     

浅覆盖区第四系三维立体透视方法研究--以太湖西北地区为例

采用剖析图法从三维透视角度研究了太湖西北地区浅覆盖区第四系。该剖析图较直观、清晰地展示了新近纪、第四纪各地层的岩性、厚度、沉积结构特征及其在三维空间的变化,并可反映当时的沉积环境及阶地上的岩性分布,同时显示了基底(前新近系)的起伏变化特征,为该区新构造运动的研究、区域地层的对比以及建立该区沉积结构模型等提供了新的视角和较全面的基础地质资料。在简要介绍了剖析图方法的同时,着重强调要通过柱状地层对比,进行第四纪地层的多重划分,确定第四纪地层划分原则。     

Lithostratigraphic development and neotectonic significance of the Quaternary sediments along the Kachchh Mainland Fault (KMF) zone,western India

The Kachchh Mainland Fault (KMF) is a major E–W trending seismically active fault of the Kachchh palaeorift basin whose neotectonic evolution is not known. The present study deals with the eastern part of the KMF zone where the fault is morphologically expressed as steep north facing scarps and is divisible into five morphotectonic segments. The Quaternary sediments occurring in a narrow zone between the E–W trending KMF scarps and the flat Banni plain to the north are documented. The sediments show considerable heterogeneity vertically as well as laterally along the KMF zone. (The Quaternary sediments for a northward sloping and are exposed along the north flowing streams which also show rapid decrease in the depth of incision in the same direction.) The deposits, in general, comprise coarse as well as finer gravelly deposits, sands and aeolian and fluvial miliolites. The Quaternary sediments of the KMF zone show three major aggradation phases. The oldest phase includes the colluvio-fluvial sediments occurring below the miliolites. These deposits are strikingly coarse grained and show poor sorting and large angular clasts of Mesozoic rocks. The sedimentary characteristics indicate deposition, dominantly by debris flows and sediment gravity flows, as small coalescing alluvial fans in front of the scarps. These deposits suggest pre-miliolite neotectonic activity along the KMF. The second aggradation phase comprises aeolian miliolites and fluvially reworked miliolites that have been previously dated from middle to late Pleistocene. The youngest phase is the post-miliolite phase that includes all deposits younger than miliolite. These are represented by comparatively finer sandy gravels, gravelly sands and sand. The sediment characteristics suggest deposition in shallow braided stream channels under reduced level of neotectonic activity along the KMF during post-miliolite time evidenced by vertical dips of miliolites and tilting of gravels near the scarps. The tectonically controlled incision and dissection of the Quaternary deposits is the result of neotectonic activity that continues at present day. The overall nature, sedimentary characteristics and geomorphic setting of the sediments suggest that the KMF remained neotectonically active throughout the Quaternary period.     

STAGES OF THE NEOTECTONIC MOVEMENT IN THE MENYUAN BASIN, QINGHAI PROVINCE

STAGES OF THE NEOTECTONIC MOVEMENT IN THE MENYUAN BASIN, QINGHAI PROVINCE     

库车冲断带新构造遥感分析

库车坳陷区在新生代产生一系列向盆地逆冲的冲断构造,这些构造在遥感图象上表现明显。通过对区内４景ＴＭ数据数字镶嵌,编制了研究区岩性地层解译樗表并以此对全区进行了解译。根据遥感影象特征分析了该区的褶皱断裂构造分布,确定了库车县北部、喀拉玉尔滚区、库独公路段的各个新生代晚期背斜构客相关断层的空间分布,以及相应的次级剪切面构造。从第四纪沉积物、冲积物以及沟系的影象中撮相关构造信息,分析浅覆盖物下地质体界面     

柴达木盆地大浪滩盐矿床基本特征及形成机理

大浪滩盐矿床已定名的24种盐类矿物中,钾镁盐矿物占13种。光卤石为其中主要钾矿物,已富集成钾矿层。本文在对盐矿物分布规律及沉积物地球化球研究的基础上,阐明了盐湖演化发展规律及钾矿层与其他盐矿物的形成机理。     

青藏高原班公错的湖盆成因及构造演化

依据河湖相沉积物的沉积特征、沉积年龄和分布规律, 结合ETM+构造和第四系沉积地层的遥感解译, 对班公错湖盆的成因和构造演化特征进行系统的剖析.从地形地貌、沉积建造和构造上分析, 推断班公错湖盆为构造成因的拉分断陷湖盆.根据湖盆周边的断层活动特征和湖盆的沉积响应, 将班公错湖盆的演化分为4个阶段, 依次为湖盆打开的幼年期(晚于早中新世)、湖盆扩展的青年期(早于8.1±1Ma)、湖盆急剧扩展伴随湖盆中心南移的壮年期(晚于0.94Ma)和湖盆不对称萎缩的老年期(晚于0.23Ma).      

江汉盆地东部第四纪钻孔地层与沉积环境

为深刻理解江汉盆地第四纪新构造运动、气候变化与盆地沉积响应的关联,利用沔阳凹陷区第四纪典型钻孔样品进行系统岩石学、年代学与沉积学研究,首次建立了盆地东部沉积中心区可对比的地层序列.利用岩性、粒度、磁组构分析重建了研究区140万年以来依次经历的河流相、河湖交替相、湖相、河湖交替相、湖相、泛滥平原相演化过程.区域构造、沉积、气候资料综合对比表明,响应于新构造沉降,江汉盆地第四纪以来存在3大成湖期,即Qp₂/Qp₁之交、Qp₃与Qh中后期（古云梦泽）,其中MIS3以来古湖发育是新构造沉降与异常强盛夏季风的耦合,且湖相沉积的独特环境为盆地高砷地下水的形成提供了重要的物质条件.不仅为第四纪钻孔地层划分对比提供可靠基础资料,也为盆地地下资源调查与环境规划保护提供重要参考.      

察尔汗钻孔介形类记录及其对察尔汗古湖晚更新世高湖面的指示

察尔汗盐湖作为柴达木盆地第四纪的沉积中心,沉积了巨厚的第四系湖相沉积,其演化历史研究对于揭示柴达木盆地及青藏高原北部第四纪古气候、古环境演变历史具有重要意义。本文在AMS ¹⁴C测年的基础上,以察尔汗盐湖晚更新世钻孔(ZK53630-1)岩芯中介形类微体化石为研究对象,通过系统的采样和室内分析,共识别出7属10种。基于分类学研究,识别出2个介形类组合(自下而上):Ilyocypris biplicata-Limnocythere inopinata和Ilyocypris bradyi-Ilyocypris sebeiensis。介形类及其伴生化石均显示察尔汗古湖在距今34～28 ka期间的晚更新世晚期(MIS 3a)主体为淡水—微咸水湖泊,气候温暖湿润,与现今极端干旱的盐湖环境截然不同。     

Geomorphological investigations and luminescence dating in the southern part of the Khangay and the Valley of the Gobi Lakes (Central Mongolia)

Geomorphological investigations in the catchment area of the Baydragiyn river along the southern slope of the Khangay and in the Valley of the Gobi Lakes in western Mongolia provide evidence for Late Quaternary glaciations and lake‐level changes. Thermoluminescence (TL) and infrared optically stimulated luminescence (IRSL) dating of aeolian and colluvial sediments from the central Khangay place the sediments that overlie fluvial and glaciofluvial terraces in the Holocene. An age of 21 ka is determined for a sand deposit overlying the terrace that is related to the last glacial ice‐margin. Lacustrine sediments from higher beach lines in the Valley of the Gobi Lakes provide evidence for a slightly more humid period around 1.5 ka, and a larger extent of the lakes in the Early Holocene at about 8.5 ka, as also reported from other parts of Central Asia. Remnants of lacustrine sediments buried by alluvial gravel, and indicating a huge palaeolake in the basin of the Orog Nuur, however, date to the early stage of the last glaciation around 70 ka. Copyright © 2001 John Wiley & Sons, Ltd.     

岷江源地区新构造运动特征

为了深入了解岷江断裂带晚新生代以来的构造活动,以岷江源地区河谷地貌、新生代盆地、夷平面为主要研究内容,研究区内新构造运动的特征。结果表明该区河谷地貌以宽谷和窄谷的交替出现为特点,源区发育三级夷平面,新构造运动强烈,地貌差异显著。该区新近纪以来主要经历了早期(5.3 Ma)伸展断陷和中期(1.8 Ma)逆冲推覆兼左行走滑及晚期(0.13 Ma)掀斜抬升演化过程。岷江源区河谷地貌的演化严格受新构造运动的影响,构造运动控制了河谷以及第四纪断陷盆地的形态,影响了河岸两侧阶地的分布、形态与结构。本区新构造运动具有南北分带型和东西向掀斜运动的不对称性等特征。本研究为进一步研究青藏高原东缘的活动构造提供了重要的地貌证据。     

峨眉山玄武岩作为长江上游特征源岩对三峡贯通的指示

峨眉山玄武岩作为长江上游攀西地区广泛分布的岩类,具有形成环境独特、出露面积大、岩石易鉴定的特点,可作为长江三峡贯通物源示踪研究的指示标志.通过对长江中上游阶地和江汉平原周老孔第四纪岩心沉积物中的玄武岩砾石和岩屑(1~2 mm)进行研究发现,峨眉山玄武岩砾石在长江上游很常见,在三峡以下很少;玄武岩岩屑在长江上游沉积物中非常普遍,而且在周老孔岩心沉积物中的很多层位都有出现.对玄武岩岩屑基质中的斜长石做了微量元素微区原位分析(LA-ICP-MS),分析表明,在周老孔中含峨眉山玄武岩岩屑的岩心层位最大深度为156 m,该层位古地磁年龄约为1.7 Ma,此时长江已经形成且三峡已经贯通.      

云南三江一河典型地区河谷第四系发育特征

三江一河（金沙江、怒江、澜沧江、红河是流经云南境内的４条主体水系，将上述４条河流河谷第四系的野外观察加以总结得出；金沙江河谷局部发育早一中更新世的湖相层和河湖相层，常形成晚期阶地的基座，晚更新世至全新世冲积层构成四级阶地；怒江河谷第四系发育较差，在六库的上游河谷中冲积层极不发育，只有局部地方有少量的河漫滩砂砾层（全新世），在六库至过街河段中，尤其是过街盆地，发育有中更新世至全新世的冲积层和洪积层，前者构成五级阶地，后者形成巨大的洪积扇分布在河流右岸的谷底或苍坡上；澜沧江除景洪、勐罕（橄榄坝）盆地外，其它河段主要为峡谷，第四系很少，在景洪盆地中发育有第二、第一级阶地和河漫滩冲积层；红河的第四系有中更新世至全新世的冲积层，并构成五级阶地。基于上述第四系特点，简要地讨论了这４条河流的形成时代。     

西昆仑山前河流阶地的形成及其构造意义

西昆仑山前河流普遍发育6级阶地,利用光释光（OSL）与热释光（TL）方法对采自西昆仑山前几条主要河流的低阶地堆积物样品进行年代测定。研究结果显示,主要河流低阶地的形成具有同时性,构造活动是河流阶地形成的主要控制因素。河流阶地的年龄测定结果表明,西昆仑山前河流阶地最早形成于约1.2Ma,T4、T3、T2阶地分别形成于约39ka、18ka和5ka。多级阶地的形成反映了河流自早更新世中期开始下切于活动抬升的西昆仑山。河流阶地的发育及区域对比揭示了西昆仑第四纪晚期以来的隆升过程,区域构造活动明显地影响河流的形态与行为。河流阶地的分布、地貌特征及区域对比表明,河流阶地的形成与演化受新构造活动、山脉隆升、气候变化等多种因素的影响。     

Einige Beispiele quartärer Tektonik in den Niederlanden

Quaternary deformations in the Netherlands are of several kinds. In the first place the country was part of the subsiding North-sea basin, as appears from the contour-map of the base of the Quaternary (fig. 1).In the SW. strong movements along faults took place, causing a horst and graben structure, being a continuation of that of the Lower Rhine. Quaternary terraces were affected by these (fig. 2). Recent levellings show that a general tilting and differential movements are still going on. Whether also true folding occurred during the Quaternary can not yet be said.     

纳木错湖相沉积与藏北高原古大湖

藏北高原古湖岸线分布广泛，湖相沉积与湖成地貌发育，目前，在纳木错沿岸可清晰地划分出4-6级湖岸阶地，最高湖相沉积高出现代湖面150m，沿岸堤可多达50条，雄曲-那曲谷地是连接纳木错盆地与其以西的仁错-久如错盆地的分水谷地，也是构成纳木错2湖岸阶地顶部的第四纪湖相沉积，构成宽谷的谷底，从最高湖岸线的分布与湖相沉积物、湖成地貌等标志综合判定，古大湖泊的面积要比现代湖泊面积大数十倍，末次古大湖的时代发生于末次冰期间冰段。     

藏南邛多江地堑的晚新生代沉积地层及对南北向裂谷形成时代的初步限定

邛多江地堑构成了藏南近南北向裂谷带最东侧的错那-沃卡裂谷中段,是由地堑西缘高角度正断层主控的半地堑式断陷盆地。详细的地质、地貌调查表明,该地堑内主要充填有晚新生代以来的多套河湖相、冰碛及冰水沉积地层。河湖相地层底部以黏土和粉砂为主,上部以砾石层为主,向上砾石砾径逐渐变大,顶部为早更新世冲积砾石层;冰碛主要发育于地堑中部山前地带,构成宽缓的冰碛台地或者终碛垄、侧碛堤。地层的测年结果表明,该区主要发育两套晚新生代河湖相地层,早期沉积时代早于5Ma,晚期为晚第四纪;而冰碛及冰水沉积的时代主要为中更新世。综合该区地质地貌、沉积和构造等分析结果表明,早期的河湖相沉积与盆地发生初始裂陷后的主边界正断层发生强烈垂直活动有关,而晚期的河湖相沉积主要形成于盆地后期萎缩过程中,成因可能与中更新世以来的冰川堰塞湖有关。由于邛多江地堑受控于西侧主边界正断层,早期沉积应晚于其初始裂陷时代。因此,进一步综合现有年龄数据资料认为,藏南近南北裂谷的初始裂陷时代应早于5~10Ma,但晚于约15Ma。     

Late Pliocene–Quaternary tectonics in the frontal part of the SE Carpathians: Insights from tectonic geomorphology

The Romanian East Carpathians display large-scale heterogeneities along the mountain belt, unusual foredeep geometries, significant post-collisional and neotectonic activity, and major variations in topography, mostly developed in the aftermath of late Miocene (Sarmatian; 11 Ma) subduction/underthrusting and continental collision between the East European/Scythian/Moesian foreland and the inner Carpathians Tisza-Dacia unit. In particular, the SE corner of the arcuate orogenic belt represents the place of still active large-scale differential vertical movements between the uplifting mountain chain and the subsiding Focşani foredeep basin. In this key area, we have analysed the configuration of the present day landforms and the drainage patterns in order to quantify the amplitude, timing and kinematics of these post-collisional late Pliocene–Quaternary vertical movements. A river network is incising in the upstream a high topography consisting of the external Carpathians nappes and the Pliocene–Lower Pleistocene sediments of the foreland. Further eastwards in the downstream, this network is cross-cutting a low topography consisting of the Middle Pleistocene–Holocene sediments of the foreland. Geological observations and well-preserved geomorphic features demonstrate a complex succession of geological structures. The late Pliocene–Holocene tectonic evolution is generally characterised by coeval uplift in the mountain chain and subsidence in the foreland. At a more detailed scale, these vertical movements took place in pulses of accelerated motion, with laterally variable amplitude both in space and in time. After a first late Pliocene uplifting period, subsidence took place during the Earliest Pleistocene resulting in a basal Quaternary unconformity. This was followed by two, quantifiable periods of increased uplift, which affected the studied area at the transition between the Carpathians orogen and the Focşani foreland basin in the late Early Pleistocene and the late Middle to late Pleistocene. Both large-scale deformation events affected the western Focşani basin flank, tilting the entire structure with 9° during the late Early Pleistocene and uplifted it as a block during the early Late Pleistocene. The late Early Pleistocene tilting resulted in 750 m uplift near the frontal monocline and by extrapolation in a presumed 3000 m uplift near the central parts of the Carpathians. The late Middle to late Pleistocene cumulative uplift reaches 250 m and correlates with a contemporaneous progradation of the uplifted areas towards the Focşani Basin. The uplifting events are separated by a second Quaternary unconformity. On the whole, the late Pliocene–Quaternary evolution of the Carpathians orogen/Focşani basin structure indicate large-scale differential uplift during the latest stages of a continuous post-collisional orogenic evolution.     

Geochemistry of late quaternary sediments from Tecocomulco lake, central Mexico: Implication to chemical weathering and provenance

This paper presents the first detailed multi-element geochemical data from the late Quaternary sediments of the Tecocomulco lake basin (central Mexico) and rocks exposed in the basin catchments to understand the extents of chemical weathering and provenance of the siliciclastic fractions. Ternary diagrams of A-CN-K, A-C-N and A-CNK-FM and elemental ratios suggest that most of the lacustrine sediments were derived from mafic volcanic deposits comprising the Chichicuatla and the Apan-Peñon andesites and the Apan-Tezontepec basaltic-andesites. The felsic tephra layers have chemical compositions comparable to the Acoculco volcanic sequences. The calculated indices of chemical weathering such as chemical index of alteration (CIA), plagioclase index of alteration (PIA) and chemical index of weathering (CIW) indicate low to extreme chemical weathering for the lacustrine sediments and low chemical weathering for tephra layers. The varying degree of chemical weathering in lacustrine sediments is related to the fluctuating average annual precipitation during the late Quaternary. However, the low weathering of tephra layers are due to their higher rate of deposition. The dacite-rhyolitic tephra layers of ca. 31,000 ¹⁴C yr BP are relatively more weathered compared to the unweathered rhyolitic tephra of ca. 50,000 ¹⁴C yr BP. This could be due to the rapid deposition of ca. 200 cm of tephra layers during the ca. 50,000 ¹⁴C yr BP volcanic eruption that might have prevented the interaction between tephra layers and weathering agents.     

Paläogeographische Entwicklungen an mobilen Schollengrenzen im Westhindukusch (Bande Amir,Zentralafghanistan)

In the region of Bande Amir, located on the southern rim of the Tadschik basin, the Mesozoic section starts with detrital and conglomeratic limestones. These marine deposits of Upper Cretaceous age (Cenomanian-Turonian) disconformably cover a truncated complex of Upper Paleozoic rocks (Permian). After an interval of neritic sedimentation (Santonian, Campanian) the Upper Cretaceous sea (Maastrichtian) regressed from the Central Afghanian High. In the Hindukusch mountains the regression is related to crustal movements and regional uplifts, which hinged on the Herat lineament. Intermontane basins, developed on this mobile zone during mid-Tertiary time, gathered continental debris (Neogene conglomerates; Zohak-Formation) and led to the deposition of lacustrine sediments (Ghulghola-Formation). Orogenetic movements along the colliding edges of crustal blocks were rejuvenated in Plio-Pleistocene time, shifting the focus of deposition to the northwest. The basin was finally captured by the Amu Darja drainage system, leading to the development of canyon-like incisions. During warm periods of the Quaternary, fluviatile erosion in Bande Amir was interrupted at least four times by the retention of water behind large dams of travertine.