河流层序地层学研究现状与存在的问题     

胡光明  倪超  王军  赵文栋 《地质科技情报》2011,30(6):55-59

河流层序地层学为河流沉积学研究注入了活力,但已有的河流层序地层模式还存在不少问题.在回顾已有河流层序地层模式的基础上,从河流层序的主控因素、层序内部的等时对比和体系域特征的描述3个方面分析了已有模式中存在的问题,并提出从河流阶地的成因入手分析河流层序的主控因素,基于河流形成过程划分体系域和进行等时对比,并从砂泥比、砂地...  相似文献   

Geometry and segmentation of an evaporite-detached normal fault array: 3D seismic analysis of the southern Bremstein Fault Complex,offshore mid-Norway     

《Journal of Structural Geology》2013

The Halten Terrace, offshore mid-Norway, is underlain by a Triassic evaporitic package that is rheologically weak, and led to decoupling of fault systems during Middle Jurassic to Early Cretaceous rifting. We use 2D and 3D reflection seismic data, constrained by wells, from the southern Bremstein Fault Complex of the Halten Terrace to map faults and key stratigraphic horizons, and analyse throw variations along faults, allowing us to constrain patterns of fault segmentation and linkage within the complex. The Bremstein Fault Complex has an overall tilted monoclinal geometry with localised fault systems at base salt level associated with overlying, highly distributed systems of normal faults. Vertical strain partitioning across the evaporite package means that sub-evaporite and supra-evaporite fault populations acted as semi-independent fault systems. Supra-evaporite faults are partly gravity-driven, and controlled by sub-evaporite faulting and consequent tilting of the evaporitic package. This behaviour leads to a wide variety of possible vertical linkage patterns of faults across the evaporite package. A greater variety of lateral segment linkage patterns occurs in evaporite-detached normal fault systems than in normal fault systems developed in the absence of evaporite units. Segment boundary styles can also be modified by migration of evaporite. Some segment boundaries are associated with a footwall anticline and hanging-wall syncline, in contrast to the footwall synclines and hanging-wall anticlines widely described in studies of normal fault systems.  相似文献   

晚第四纪以来香山-天景山断裂左旋走滑量研究   总被引：3，自引：1，他引：2  

尹功明  江亚风  俞岗  韩非  刘春茹 《地震地质》2013,35(3)

香山-天景山断裂是青藏高原东北缘弧形断裂带中一条重要的活动断裂,长期以来活动强烈,早期以挤压逆冲为主,可能在第四纪早期转变成以左旋走滑为主兼具逆冲性质的断裂.黄河在夜明山前缘穿过此断裂,在沙坡头大弯一带形成一个完美的“几”形拐弯.文中对沙坡头大弯一带黄河地貌、阶地特征、样品年龄进行了探查和分析测试,结果表明,距今170ka以来,香山-天景山断裂左旋位移量最大不超过880m,滑移速率＜5.18mm/a.  相似文献   

宁夏沙坡头黄河大弯的成因分析          下载免费PDF全文

江亚风  尹功明  俞岗  王躲 《地震工程学报》2013,35(3):631-640

黄河在宁夏沙坡头形成了"几"字形河曲地貌,并在河曲凸岸发育了3级河流阶地。本文针对沙坡头大弯河流阶地特征、阶地年龄,以及大拐弯的成因进行了分析,探讨本区地貌发育的机制。结果表明:(1)沙坡头大弯3级河流阶地形成的主要原因是构造抬升作用,气候变化对此处阶地形成的作用不明显。在区域新构造活动强烈的背景下,约中更新世末期中卫盆地开始抬升,黄河河道被固定,河流下切形成本区的最高阶地T3;约在70kaB.P.、8kaB.P.形成T2、T1阶地。(2)沙坡头黄河大拐弯是由香山—天景山断裂左旋走滑位错,以及水流受地球自转偏向力的河流内生动力共同作用的结果,并且河流的内生动力作用远大于前者的贡献。  相似文献   

The Geomorphology of Valley-Floor Troughs Illustrated From Depositional Sequences in the Durance Valley,Southeast France     

《自然地理学》2013,34(6):475-493

Three kinds of valley-floor troughs occur in the Durance catchment of southeast France. Details of widths and spatial variations of 10 different sedimentary forms are presented to show how these relate to the present types of troughs and their margins. Internal controls, such as geology, altitude, and available relief, provide a wide variety of conditions, which have been modified through time by external controls such as past and present climates and their hydrological regimes, as well as by anthropogenic activity over several millennia. The 10 sedimentary forms occupy more than 900 km² or 6.4% of the total catchment area, with the present enlarged floodplain having just over 50% of this area. The present channel occupies less than 10%, which is less than the Würm terrace (17.2%) but somewhat more than the marginal colluvia in the lower valley (8.6%). The other forms include older Pleistocene terraces, moraines from the last three glacial stages, and alluvial fans. It is the type of trough and its relative age that condition what, where, and how much of past and present sedimentary forms can survive.  相似文献   

华北地块中部活动构造特征及汾渭地堑成因探讨   总被引：1，自引：0，他引：1       下载免费PDF全文

吴奇  许立青  李三忠  刘鑫  王鹏程  曹现志  索艳慧 《地学前缘》2013,20(4):104-114

研究区位处华北克拉通中部,受太平洋构造域和特提斯构造域的影响,新生代开始裂解,先后形成了渤海湾盆地和汾渭地堑。第四纪以来,华北地块中部活动日趋活跃,不同走向的断裂和盆地也表现出不同的活动性。NW向和近EW向断裂主要表现为左旋走滑性质,而NE向断裂则主要表现为正断性质。NNE向断裂虽也表现出正断性质,但右旋走滑性质正逐渐占主导地位。汾渭地堑中,NE向盆地与NNE向的盆地也因此表现出一定的活动差异。盆地形成初期,两种走向的盆地沉降速率差别不大,但第四纪以来,NE向盆地的沉降速率已大大超过NNE盆地。对于第四纪以来这种构造运动的表现,同时结合GPS观测数据及青藏高原的大规模隆升与华北地块中部山地相对隆升和盆地沉降事件在时间上的高度一致性,推测华北地块中部中新世以来的构造活动主要受印度与欧亚板块碰撞的挤出作用影响,在NWW和NE向剪切应力的作用下,华北地块中部自南北两端受NWWSEE向拉张的合力作用下开始裂解。随着青藏高原隆升速度的加快,两种剪切应力也随之增强,其合力的影响范围逐渐向中心向东不断扩展,形成了一系列的NNE和NEE向盆地。同时,NE向剪切应力增幅明显强于NWW向剪切,导致其合力由NW向拉张逐渐转变为NNW向拉张,引起不同走向断层活动性的差异与不同走向盆地沉降速率的相应改变。  相似文献   

天山北麓黄土发育特征及形成年代   总被引：4，自引：1，他引：3  

LU Hong-Hua  吕红华  李有利  南峰  司苏沛 《地理科学》2008,28(3)

对天山北麓黄土年代的认识还存在一定分歧.文章在对天山北麓河流阶地进行划分的基础上,通过分析黄土分布与地貌单元(河流阶地与冲积扇)的依附关系,同时结合黄土-古土壤序列分析与ESR测年,初步确定天山北麓地貌面上覆盖的最老黄土年代为0.54Ma B.P.,这为分析黄土所赋含的环境信息提供时间标尺.  相似文献   

Modelling runoff and erosion for a semi-arid catchment using a multi-scale approach based on hydrological connectivity   总被引：1，自引：0，他引：1  

J.P. Lesschen  J.M. Schoorl  L.H. Cammeraat   《Geomorphology》2009,109(3-4):174-183

Runoff and erosion processes are often non-linear and scale dependent, which complicate runoff and erosion modelling at the catchment scale. One of the reasons for scale dependency is the influence of sinks, i.e. areas of infiltration and sedimentation, which lower hydrological connectivity and decrease the area-specific runoff and sediment yield. The objective of our study was to model runoff and erosion for a semi-arid catchment using a multi-scale approach based on hydrological connectivity. We simulated runoff and sediment dynamics at the catchment scale with the LAPSUS model and included plot and hillslope scale features that influenced hydrological connectivity. The semi-arid Carcavo catchment in Southeast Spain was selected as the study area, where vegetation patches and agricultural terraces are the relevant sinks at the plot and hillslope scales, respectively. We elaborated the infiltration module to integrate these runoff sinks, by adapting the parameters runoff threshold and runoff coefficient, which were derived from a rainfall simulation database. The results showed that the spatial distribution of vegetation patches and agricultural terraces largely determined hydrological connectivity at the catchment scale. Runoff and sediment yield for the scenario without agricultural terraces were, respectively, a factor four and nine higher compared to the current situation. Distributed hydrological and erosion models should therefore take account of relevant sinks at finer scales in order to correctly simulate runoff and erosion-sedimentation patterns.  相似文献   

Performance evaluation of three DEM‐based fluvial terrace mapping methods          下载免费PDF全文

Austin J Hopkins  Noah P Snyder 《地球表面变化过程与地形》2016,41(8):1144-1152

The availability of high‐resolution digital elevation models (DEMs) derived from airborne light detection and ranging (LiDAR) surveys has spurred the development of several methods to identify and map fluvial terraces. The post‐glacial landscape of the Sheepscot River watershed, Maine, where land‐use change has produced fill terraces upstream of historic dam sites, was selected to implement a comparison between terrace mapping methodologies. At four study sites within the watershed, terraces were manually mapped on LiDAR‐DEM‐derived hillshade images to facilitate the comparison among fully and semi‐automated DEM‐based procedures, including: (1) spatial relationships between interpreted terraces and surrounding natural topography, (2) feature classification algorithms, and (3) the TerEx terrace mapping toolbox. Each method was evaluated based on its accuracy and ease of implementation. The four study sites have varying longitudinal slope (0.0008–0.006 m/m), channel width (< 5–30 m), surrounding landscape relief (20–80 m), type and density of surrounding land use, and mapped surficial geologic units. All methods generally overestimate terrace areas (average predicted area 210% of manually defined area) with the most accurate results achieved within confined river valleys surrounded by the steep hillslopes. Accuracy generally decreases for study sites surrounded by low‐relief landscapes (predicted areas ranged 4–953% of manual delineations). We conclude with the advantages and drawbacks of each method tested and make recommendations for the scenarios where the use of each method is most appropriate. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Extracting palaeoflood data from coarse‐grained Pleistocene river terrace archives: an example from SE Spain          下载免费PDF全文

Anne Mather  Martin Stokes 《地球表面变化过程与地形》2016,41(13):1991-2004

Field‐based palaeoflood event reconstruction has the potential to contribute to the development of our understanding of long‐term landscape evolution. However, the reconstruction of past flow event histories (magnitude and frequency) over long‐term (Quaternary) timescales is fraught with difficulties. Here we make a preliminary exploration of some of the practicalities of flood reconstruction from fluvial terrace archives using commonly available sedimentological and geomorphological observations from a field perspective. We utilize Manning and palaeostage indicators to reconstruct historic events that can be used as benchmarks for a lesser used competence based approach, which is applied to coarse‐grained strath terrace deposits. We evaluate the results against gauged records for extreme and catastrophic events that affected the same region in 1973 and 2012. The findings suggest that the competence approach is most effectively applied to terrace deposits if the channel geometry is taken into account when sampling both in cross‐section and in longitudinal section and calibrated against the sedimentology for palaeo‐flow depth. Problems can arise where constrictive channel geometries allow boulder jams to develop, acting as sediment traps for the coarsest material and leading to downstream ‘boulder starvation’. Useful sites to target for palaeoflood reconstruction, therefore, would be upstream of such constrictive reaches where the coarsest transportable bedload has been effectively trapped. Sites to avoid would be downflow, where the deposited material would poorly represent palaeoflood competence. Underestimation from maximum boulder preservation and limited section exposure issues would appear to outweigh possible overestimation concerns related to fluid density and unsteady flow characteristics such as instantaneous acceleration forces. Flood data derived from river terrace deposits suggests that basal terrace geometries and coarse boulder lags common to many terrace sequences are likely the result of extreme flow events which are subsequently filled by lesser magnitude flood events, in this environmental setting. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献