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1.
本文通过对河道和河谷两个不同地貌单元特征的界定 ,澄清铀矿地质领域中对古河道型砂岩铀矿床与古河谷型砂岩铀矿床概念上的混淆。同时就河道与河谷对基准面变化的响应及充填序列特征作了探讨 ,为确定古河道在平面上的展布提供依据。 相似文献
2.
The geological characterization of the shallow subsurface in the unconsolidated sediments of the Atlantic Coastal Plain, and other unconsolidated sediment regimes, may involve jointing, faulting, and channeling not readily detectable by conventional drilling and mapping. A knowledge of these features is required in environmental, geotechnical, and geomorphological studies. Ground-penetrating radar (GPR) may be used to routinely map these structures. Three principal shallow subsurface features are readily detectable using GPR: paleochannels, joints or fractures, and faults. The detection of paleochannels is dependent on the scale of the GPR survey and the attitude of the channel within the survey area. Channel morphological features such as scour surfaces, point bars, and thalwegs are observable. Joints and fractures are more difficult to detect depending upon size, patterns, orientation, and fill material. Vertical joints may not be visible to radar unless they are wider than the sampling interval or are filled with radar-opaque materials such as limonite. Angled joints or fractures may be distinguished by an apparent continuous reflector on the radar profile. Faulting on radar profiles may be observed by the offset of reflectors, the image of the fault plane, or the coherent interpretation of a fault system. 相似文献
3.
基于岩性光谱特征的雄安新区地面古河道识别研究 总被引：1，自引：0，他引：1
雄安新区地面古河道与河漫滩岩性分别以砂土和黏性土为主,两种岩性所含矿物成分对电磁波的反射率不同。将地表岩性调查与光谱采集分析相结合,捕捉了这两种岩性在遥感影像中反射光谱的差异,在此基础上识别了古河道,并利用钻孔数据加以验证分析。结果表明:雄安新区表层砂土和黏性土在TM影像B5波段的DN值差值最大,该波段可作为识别河道砂体的必选波段;综合考虑波段信息量、波段之间信息重复程度,R(4)G(5)B(1)组合下河道砂体的形迹清晰可辨;钻孔数据与遥感解译结果吻合,岩心揭露的古河道发育深度在3.2~8.7 m之间;研究区古河道总体较发育,河道宽度多在0.5~2.0 km之间,多处分叉和汇聚后呈辫状河形态,河网密度约0.26 km/km~2;钻孔剖面显示河道地势高于河漫滩,属条状高地型古河道,河道有"游荡"痕迹;古河道的发育位置控制着区内居民地的分布。 相似文献
4.
根据二连盆地古河道沉积演化特点，笔者应用卫星遥感图像分析技术调查了内蒙古二连盆地马尼特坳陷、乌兰察布坳陷和川井坳陷的地貌形态、区域水文地质条件、古今河道－冲洪积扇（群）分布、地下潜水、层间水的补－径－排水动力条件及局部排泄源的空间分布，并以水成铀矿理论为指导，结合前人地质、物探、水文地质及铀矿化点、异常点等资料，综合分析研究内蒙古二连盆地古河道－冲积扇（群）与铀集散作用的环境关系，圈定了铀成矿远景区19片，指出了进一步寻找铀矿的方向。 相似文献
5.
Many Iron Age sites on the flood plain of the Mun River in northeast Thailand are encircled by channels commonly known as “moats.” Also, the sites are closely associated with complex paleochannels of the river. A comparison between the seemingly human‐constructed moats and paleochannels provided an opportunity to assess the relationship between prehistoric human settlement and paleohydrological conditions. In this study, the results of physical, sedimentological, and geochemical analyses are used to characterize sediments deposited within the channels around the Iron Age site of Ban Non Wat and within a paleochannel at nearby Ban Non Ngiu. This allowed us to test the results of previous research that has suggested significant changes in the floodplain hydrology and the geoarchaeologically important conclusion that Iron Age human activity was associated with one particular paleohydrological phase. Our analyses broadly confirm the results of previous stratigraphic studies, but add detail regarding sedimentation processes. The evidence indicates that there are significant sedimentological differences within the complex of archaeological channel features, differences that provide critical evidence for the formation and sedimentation processes of the channels. More importantly, comparison between the archaeological features and the natural channel fills highlights the relationships between the archaeological sites and landscape. Drawing also on previously published chronological, geomorphological, and stratigraphical data, it is possible to place the sites into a floodplain hydrological regime that may have been unique to the Iron Age. Specifically, the moats may have been constructed in response to enhanced water availability on the floodplain. The sites, therefore, may reflect a human response to increased availability of water beyond the main river channels. This water supply, however, appears to have been short‐lived (centuries at most), and with its loss, the human adaptation to this enhanced natural resource became unviable. © 2008 Wiley Periodicals, Inc. 相似文献
6.
We present a study that reconstructs the ancient courses of the Euphrates in part of the Mesopotamian floodplain west and southwest of the ancient site of Babylon. The focus is on tracing paleochannel courses, determining when these paleochannels were active, and understanding the patterns of avulsion. The research was carried out using a combination of geological, geomorphological, remote sensing, historical, and archaeological approaches. Fieldwork included “ground truthing” of the remote sensing work, manually drilling boreholes (up to 7 m in depth), sedimentary and geomorphological documentation and sample collection for radiocarbon dating. As a result, five main courses of the Euphrates in five different periods have been mapped in this area, including four previously unidentified and/or unlocated migrations that linked the different periods. The main courses are the Purattum Course (before 3100–1000 BC), the Arahtum Course (1000–125 BC), the Sura Course (125 BC to AD 1258), the Hilla Course (13th to 19th century AD), and the Hindiya Course (19th to 20th century AD). There has been an overall migration of the main channel from east to west across the study area over time. The location of avulsion nodes changed along the length of the river, mainly downstream over time, but with a cluster of avulsion events near Babylon and a notable man‐made interference in the 20th century at the Hindiya Barrage. 相似文献
7.
T. J. Majumdar 《Natural Hazards》2013,69(1):729-747
Geological, geomorphological and tectonic element studies of the Kachchh region have been carried out and correlation between them with the seismic data has been attempted. Study and analysis of Bhuj region using various remote sensing techniques including surface temperature changes, InSAR studies and GPS have also been attempted to identify earthquake precursors on different scales and the areas susceptible to damage or disaster on different degrees. The Kachchh region is located in Mesozoic rift environment that was earlier characterized by tensional stresses, but present-day compressive stress regime suggests that this region is undergoing a stage of inversion tectonics. The present work aims at the application of remote sensing techniques in developing a long-term precursor in the form of landscape changes, before the occurrence of a major earthquake as a result of crustal stress accumulation. It is, therefore, necessary to find out with the help of other precursors whether or not the area is accumulating stress. A minute observation of all the acquired multi-temporal imageries could demarcate minute geomorphological changes in this region, for example, shifting of drainage patterns since the development of paleochannels, slow upliftment/depressions, etc. Moreover, a distinct change in temperature (~5 to 6 °C) could be observed on April 6, 2006, and again on April 10, 2006, in the Kachchh region before the occurrence of tremor, particularly along the Kachchh Mainland Fault, indicating that such tremor generates sufficient stress before the earthquake particularly along the fault line. b values study over the region during last 50 years has also clearly indicated the drastic stress changes particularly before the occurrence of a big earthquake. GPS observations have also indicated a major thrust region lying along ENE–WSW with stress alignment along ENE–WSW. The region on the west of the Kachchh Mainland Fault and the South Wagad Fault can be called as seismic gap region as very few major earthquakes have taken place in this region. 相似文献
8.
Paillou et al. (2009) mapped a 900 km-long paleodrainage system in eastern Libya, the Kufrah River, that could have linked the southern Kufrah Basin to the Mediterranean coast through the Sirt Basin, possibly as long ago as the Middle Miocene. We study here the potential connection between the terminal part of the Kufrah River and the Mediterranean Sea through the Wadi Sahabi paleochannel, which may have constituted the northern extension of the lower Kufrah River paleodrainage system. New analysis of SRTM-derived topography combined with Synthetic Aperture Radar images from the Japanese PALSAR orbital sensor allowed the mapping of seven main paleochannels located west of the Kufrah River, each of which is likely to have formed a tributary that supplied water and sediment to the main paleodrainage system. The northernmost four paleochannels probably originated from the Al Haruj relief, a Pliocene alkaline basaltic intracontinental volcanic field, and potentially connected to the Wadi Sahabi paleochannel. The remaining three paleochannels are in the more southerly location of the Sarir Calanscio, North-East of the Tibesti mountains, and barely present a topographic signature in SRTM data. They end in the dunes of the Calanscio Sand Sea, forming alluvial fans. The most southern paleochannel, known as Wadi Behar Belama, was previously mapped by Pachur (1996) using LANDSAT-TM images, and was interpreted by Osborne et al. (2008) as representing part of an uninterrupted sediment pathway from the Tibesti mountains to the Mediterranean Sea. Processing of SRTM topographic data revealed local depressions which allow to connect the seven paleochannels and possibly the terminal alluvial fan of the Kufrah River to the Wadi Sahabi paleochannel, through a 400 km-long, south-north oriented, paleocorridor. These new findings support our previous hypothesis that proposed a connection between the lower Kufrah River in the region of the Sarir Dalmah and the Wadi Sahabi paleochannel, which connected to the Mediterranean Sea. Including the newly mapped paleochannels, the Kufrah River paleowatershed, at its maximum extent, would have covered more than 400,000 km2, representing close to a quarter of the surface area of Libya. 相似文献
9.
Waterlogging is a complex phenomenon, the severity of which depends on a number of natural as well as anthropogenic factors. The present study pertains to the evaluation of control exerted by various factors, viz geomorphology, relief, groundwater fluctuation, rainfall, catchment area and canal–road network density, on waterlogging in the north Bihar region of Gangetic Plains. Satellite images IRS P6 LISS III acquired in the years 2005 and 2006 were used to map temporal variability in surface waterlogging which revealed a reduction of 52 % in the waterlogging area during the pre-monsoon. The seasonal groundwater fluctuation was examined using 2005–2006 pre- and post-monsoon water level data. It clearly indicated that a large portion of the area was also under highly critical groundwater level occurring at a depth of less than 1 m belowground surface during the post-monsoon periods. The percentage of waterlogged area per square kilometer in each geomorphological unit clearly depicts that the Kosi megafan (Lower), because of a high density of paleochannels, comprises the highest post-monsoon waterlogged area. The Tropical Rainfall Measuring Mission (TRMM) data were analyzed for the period 1998–2009 to examine the spatial variability of rainfall over the entire catchment during the monsoon period. The high incidence of post-monsoon surface waterlogging delineated through satellite data and high average rainfall (>1,100 mm) in the same area indicates a positive relationship between rainfall and surface waterlogging. Waterlogging is more prominent in the lower relief zones, but anomalous relative rise in waterlogging within 40–50 m of relief zone was attributed to anthropogenic factors primarily related to the development of canal network. 相似文献
10.
David Alexander 《Natural Hazards》1991,4(1):57-80
This paper examines the scope and limitations of geomorphological investigation of the sites of architectural and engineering works. Various degrees of vulnerability, forms of impact, and types of applied geomorphological response are summarized. Aspects of land development and construction practice that may increase the vulnerability of buildings and structures to geomorphological hazards are discussed. Strengths and weaknesses of the geomorphological input to hazard mitigation are reviewed. Examples are described that show both negative and positive influences exerted by geomorphological site analysis on urban and regional planning for unstable terrains in Italy. It is concluded that societal choice, within the overall matrix of a society's culture (sensu largo), will influence the way in which vulnerability is managed at sites, and hence the scope for utilizing geomorphological analysis of the physical risks. 相似文献
11.
Early Cretaceous, retro-foreland basin fluvial deposits throughout Wyoming record interactions between orogenesis, subsidence, sediment accumulation, basin physiography, and syndepositional structural deformation associated with the early stages of the Sevier Orogeny. Quantitative paleochannel reconstructions presented here are important for understanding these interactions, evaluating controls on alluvial architecture, and can be applied to basin-modeling studies. Most paleochannel sandstones and conglomerates represent point bars associated with meandering rivers, although some rivers may have been braided. Paleoflow of earliest Cretaceous Cloverly A-interval paleochannels (forebulge depozone, central WY) was generally to the north, northeast, and east, which suggests that most are deposits of basin-axial rivers. Discharges of overlying B-interval paleochannels are less than most of those of the A interval, possibly reflecting a temporal decrease in water supply related to the eastward expansion through time of an orographic rain shadow caused by progressive rising of the Sevier Orogen to the west. The Bechler (western WY), Cloverly B (central WY), and Lakota L2 (eastern WY) intervals are correlative and record deposition throughout the basin in the foredeep, forebulge, and backbulge depozones, respectively. Paleocurrents suggest that Bechler paleochannels are deposits of basin-transverse rivers that flowed to the east, whereas B and L2 paleochannels are deposits of basin-axial rivers that flowed dominantly to the north and northeast. The scales and discharges of most L2 paleochannels are much greater than those of the Bechler and B-interval. This eastward increase in discharge may reflect an eastward increase in precipitation related to the spatially decreasing effects of an orographic rain shadow caused by the Sevier Orogen to the west. Additionally, or alternatively, the higher discharges of most L2 rivers may indicate that they represent a more distal part of a tributary fluvial system than B-interval rivers (consistent with some lower slopes of L2 paleochannels).The alluvial architecture of thick foredeep deposits contrasts markedly with that of stratigraphically equivalent, much thinner deposits farther east that were associated with the forebulge and backbulge depozones. Foredeep deposits are dominated by overbank and lacustrine mudstones, and channel deposits tend to be isolated with limited lateral extents typically on the order of 10's of meters. Forebulge and backbulge channel deposits tend to be laterally and vertically connected forming sandstones and conglomerates with lateral extents on the order of 10's of km to >100 km. Long-term compacted sediment accumulation rates for the foredeep (generally 10−2 mm year−1) are an order of magnitude greater than those for the forebulge and backbulge depozones (10−3 mm year−1). Quantitative simulations of channel-deposit proportions indicate that basin-wide differences in alluvial architecture are attributable to differences in sediment accumulation rates, which, in turn, reflect variable subsidence rates of the different depozones. Additionally, in some areas of the fore- and backbulge depozones, alluvial architecture was controlled by local syndepositional structures. However, the alluvial architecture in areas influenced by syndepositional structures is broadly similar to that in areas where such structures were absent, both reflecting the same general tectonic setting that experienced limited regional subsidence. Hence, the two cases are not easily distinguished solely on the basis of alluvial architecture. 相似文献
12.
An abandoned estuary within Marajó Island: Implications for late Quaternary paleogeography of northern Brazil 总被引：1，自引：0，他引：1
Several previous studies have recognized paleochannels as the most typical geomorphologic features imprinted in the modern
landscape of Marajó Island, northern Brazil. A characterization of these paleochannels by detailed mapping has not yet been
accomplished, despite their great potential for helping reconstructing the succession of events responsible for the origin
and evolution of the drainage system at the mouth of the Amazon River during the Quaternary. The present study aims to provide
a detailed mapping and characterization of these paleochannels using remote sensing (i.e., SRTM, Landsat 5-TM, and Landsat
7-ETM+), integrated with sedimentological and radiocarbon data obtained from outcrops and cores. The mapped paleochannels
allowed for the first time correlation of the channel-like morphologies with fining-upward sedimentary successions, typical
of channel deposits. The study focuses on the Lake Arari area located in the northeast of Marajó Island, where a complex fluvial
network dominated by a funnel-shaped structure attributed to a Late Pleistocene paleoestuarine system was recognized. The
inner estuary was connected to three fluvial channels that ran from the east-southeast throughout an area currently occupied
by Marajó Bay, implying that this bay did not exist when the estuarine system was active. Separation of the eastern side of
Marajó Island due to tectonic causes related to capture of Tocantins River by northeastward-orientated faults would have interrupted
the fluvial inflow, ultimately causing the abandonment of the estuarine system. Today, the central part of the funnel-shaped
structure related to the Late Pleistocene paleoestuary is occupied by Lake Arari, where sediments started to accumulate no
earlier than the mid-Holocene. It is proposed that this lake might have developed from the Late Pleistocene estuary as the
fluvial inflow was cut off during the detachment of Marajó Island. Marajó Island serves as an example of a very dynamic site
of changing landscapes throughout the Quaternary as a result of tectonic activity. 相似文献
13.
以54个浅层新钻孔和多个野外露头为研究对象,综合沉积物粒度、薄片、微体古生物、孢粉、14C测年及静力触探等资料,分析了鲁北平原晚第四纪的地层结构和沉积类型,总结了晚更新世晚期以来的沉积演化。研究表明,末次冰期盛冰期到冰后期,受地势、气候条件控制的黄河河道迁移和海水进退是影响地层结构和沉积特征的主要因素,南北地层结构差异明显,发育古河道、湖沼、黄土、三角洲、潮坪和滨浅海等沉积类型,其中古河道分布面积最广,自下而上可划分为三期。晚更新世晚期至早全新世早期,受干冷气候影响,发育第Ⅰ期古河道,小清河以南沉积黄土层;早全新世晚期至中全新世,气候转暖导致海平面升高,沿海地区形成海侵层和三角洲,内陆地区继承性发育第Ⅱ期古河道和湖沼沉积;中全新世末期或晚全新世以来,受黄河泛滥影响,沉积第Ⅲ期古河道和现代黄河三角洲。地层结构和沉积物分布的研究对于分析地下水位的变化规律,以及选择合适的地震激发层等均有重要的指导意义。 相似文献
14.
徐州城区是岩溶塌陷地质灾害危害严重的区域,已发生的塌陷均展布在废黄河断裂带内,有明显的规律性,为断裂带地下水富集区过量抽水所造成。研究表明,废黄河断裂带内岩溶发育,发育有向上开口的溶洞和裂隙,断裂带沟通了不同时代的含水层,形成了地下水强径流带或富集带;地堑式断裂带构成的负地形形成了晚更新世和全新世古河道,古河道区域形成"单一透水型盖层"和"透-阻型盖层",使黄河泛滥沉积的砂性土直接覆盖在岩溶含水层上,为过量抽水发生岩溶塌陷提供了重要水动力条件。因此,废黄河断裂带及其伴生断裂控制了岩溶塌陷的形成条件,特别是岩溶发育强度、岩溶水文地质结构和地下水富集规律。 相似文献
15.
S.J. Riley 《Sedimentary Geology》1975,14(4):253-258
The relation F = 255 M?1.08 does not hold for clay-bedded streams in the Namoi—Gwydir distributary system of eastern Australia. Of the streams studied, only those with mobile beds conform to the relation. The application of the relation in paleohydrologic studies must include investigations of the nature of the paleochannels. 相似文献
16.
In north Queensland, Australia, the ‘Great Divide’ forms the border between catchments draining into the Gulf of Carpentaria, including the Mitchell River, and those draining into the Coral Sea, including the Barron River. Until recently, it was commonly proposed that what is now the upper Barron River previously drained into the Mitchell River. However, little evidence was presented, and the assertion has been disputed. Our examination of borehole data, combined with accurate surveying of bedrock in the present Barron River channel, provides definitive evidence that paleochannels of the Mitchell River previously drained what is now the upper Barron River subcatchment. Lava that flowed down these channels at ca 1.79 Ma is evident in some of the boreholes and is exposed in the Barron River channel. The lava flows blocked the river channel, diverting the headwaters of the paleo-Mitchell River east into the Barron River, resulting in the western migration of the Great Divide. The consequent reduction in stream energy available to the truncated headwaters of Mitchell River has led to channel infill and aggradation of more than 40 m since the diversion of the Barron River. Subsurface paleochannels may be directing groundwater across the present drainage divide from the upper Barron River catchment into the Mitchell River catchment. 相似文献
17.
Structural and morphological analysis of the Miocene sediments that build up the Mekenzievi rock sequence at the Fiolent Cape
made it possible to define the major characteristics of its inner structure. The largely homogeneous carbonate sediments are
composed of clinoform complexes and bodies that fill in erosion paleochannels. The Mekenzievi rock sequence was formed under
tectonic activity in the basin with intensive hydrodynamics. Most of the Mekenzievi rock sequence is dated as Early Chokrakian. 相似文献
18.
上海地区全新世沉积物在区域上分异剧烈,由此,研究区内形成主要的古河道有四条。按其沉积相的层序组合可划分出三个基本类型,每个类型和古河道溺上各层序组合,反映了一种沉积环境和沉积过程。同时,它们的工程地质特征亦各自不同。本文对三个基本类型的古河道溺谷相沉积的桩基持力层的选择,应用找到了充分的依据。 相似文献
19.
Riverine water and sediment discharge to the Arctic Ocean is among the most important parameters influencing Arctic climate. It is clear that the evaluation of Arctic paleoclimate requires information on the paleodischarge of major rivers entering the sedimentation basin. Presently, the water discharge of the Ob River accounts for about 12% of the total input of river water into the Arctic Ocean. During the investigation of the Kara Sea in the framework of the Russian-German SIRRO Project, the history of Yenisei discharge received much attention in a number of publications. This paper presents the results of lithological and geochemical investigations with application to the Holocene discharge of the Ob River. Qualitative (SiO2, Al2O3, K2O, and some modules) and quantitative (sedimentation rates and absolute masses of sedimentary material) parameters were used to characterize the history of the Ob sediment discharge. It was shown that the investigated paleochannels of the Ob were initiated at the Pleistocene-Holocene boundary, and during the first half of the Holocene, the river discharge decreased irregularly with decreasing age of sediments. The observed maxima are in fairly good agreement with the data for the Yenisei. We proposed a hypothesis on the influence of glacioisostatic movements in the marginal region of the former Kara ice sheet of late Valdai age on the cessation of marine-fluvial glaciation in the paleochannels of Ob and Yenisei in the periphery of the Ob-Yenisei shoal. 相似文献
20.
L. Dvořák 《GeoJournal》1995,35(4):425-430
There are a lot of methods used in geomorphological research (Goudie 1992). However, sometimes it is very hard to find their application in practice. This paper deals with an application of geomorphological methods such as morphostructural analysis, detailed geomorphological mapping and computer analysis in the Geographical Information System ARC/INFO, in the field and discusses their application at the building trade, ecology, etc. The author applied them to geomorphological research in the northeastern part of the Hercynian Bohemian Highlands. 相似文献