共查询到20条相似文献，搜索用时 33 毫秒
1.
The legacy of repeated Pleistocene glaciations has endowed many Welsh river valleys with locally thick successions of glacial and alluvial sediments. Investigations of a well-preserved flight of terraced sediments with good exposures at Capel Bangor, on the Afon Rheidol, mid-Wales, has allowed its Quaternary valley fill stratigraphy to be examined in detail. Study has revealed five terraced fills consisting of seven distinct sedimentary units. These range from Late Devensian ice-contact and ice-marginal deposits, to Holocene high-sinuosity stream sediments with episodes of man-induced accelerated deposition of fine-grained alluvium, and to aggradation and subsequent incision associated with historic metal mining. Examination of general sedimentary properties (e.g., granulometry, sedimentary structures, terrace surface morphology) show both differences in the pattern and controls of deposition and also progressive changes over Late Devensian and Holocene times. The sediments of the Rheidol Valley record the response and subsequent recovery of a drainage basin to glaciation, and the increasing influence of man on sediment yields, channel processes, and sediment quality. 相似文献
2.
Lawson M. Smith 《Engineering Geology》1996,45(1-4):139-165
The Lower Mississippi Valley (LMV) has been one of the most intensively studied alluvial valleys in the world in terms of it's geological and geomorphic framework and history. A brief outline of the history of the major geological and geomorphological investigations of the LMV is provided. The results of these investigations are discussed in terms of the fluvial geomorphic framework of the valley and the apparent significant changes in the regime of the Mississippi River during the Late Wisconsinan and Holocene stages.
The LMV occupies the broad deep synclinal trough of the Mississippi Embayment which extends from Cairo, Illinois, to the Gulf of Mexico in a slightly sinuous north-south trend. The embayment is filled with a north to south thickening wedge of non-marine and marine sediment ranging in age from Jurassic to Holocene. The major landscapes of the LMV may be considered in four regions: (1) a narrow active meander belt in a broad valley of Late Pleistocene valley train in the northern third; (2) a wide mosaic of interwoven Holocene meander belts in the middle third; (3) a relatively narrow valley of the Atchafalaya Basin bounded on each side by narrow meander belts in the upper part of the lower third; and (4) the broad distributary wedge of the deltaic plain in the southernmost region of the valley. The valley trains vary in age and landform with the oldest occurring as slightly dissected low ridges and the youngest as broad flats separated by shallow interwoven former braided channels. Meander belts formed throughout the Holocene are comprised of low natural levee ridges flanking abandoned courses and bordered by crescent-shaped oxbow lakes and ridge and swale topography. In the middle third of the valley, meander belts are separated by expansive backswamps of very little relief. The deltaic plain is also exceptionally flat, interrupted by the low natural levee ridges of the abandoned deltaic distributaries.
The floodplain of the LMV is a complex mosaic of fluvial features and landscapes within the four landscape regions. Included in this mosaic are abandoned channels and courses, lateral accretion topography of ridges and swales, natural levees, crevasses and crevasse channels, distributary channels, backswamps and rimswamps, alluvial fans and aprons, valley trains (braided stream terraces), lakes and lacustrine deltas, terraces, and the alluvial valley bluff.
Changes in the hydraulic regime of the Lower Mississippi River (LMR) since the Late Pleistocene have played a major role in the development of the landscape of the valley. The most important regime change was the diminishment of the influence of Wisconsinan glaciation in the upper Midwest and the resultant evolution of the Mississippi River from a broad braided outwash channel to a more narrow but sinuous meandering channel at the end of the Pleistocene. During the Holocene, the Mississippi River undoubtedly responded to major climatic changes, rising sea level, tributary stream influence, and possibly tectonism, diapirism, and subsidence through the growth and evolution, and abandonment of it's meander belts and deltas. 相似文献
3.
Aerial photography and satellite imagery reveal manifold geomorphological evidence of a dynamic evolution of past and present rivers in the Bolivian Amazon. Comparison of oxbow lake and meander scar dimensions along an inactive meander belt of the Río Mamoré (Llanos de Moxos, north-eastern Bolivia) and its modern counterpart suggests significant regional paleohydrological variability. We used these features as geomorphological and sedimentary archives to enhance our understanding of longer-term variations of the fluvial system. Late Pleistocene to Holocene hydrological changes of the Río Mamoré are inferred from: (i) the analysis of satellite imagery, (ii) discharge estimates from meander morphology, (iii) stratigraphic, and (iv) chronological information based on luminescence and radiocarbon dating. The combined data from three oxbows indicate that the now abandoned meander belt – the paleo-Mamoré – continued to be active at least until ∼5 ka, and likely even postdating 3 ka. An up to threefold increase in discharge is estimated for the modern Río Mamoré versus the paleo-Mamoré. The altered runoff regime may have triggered an avulsive shift towards the currently active Río Mamoré. The preceding increase in discharge in turn, was possibly related to a shift in climatic conditions, which changed markedly between the mid- and late Holocene in tropical South America. In addition, it may have been the indirect result of capturing the avulsive Río Grande system to the east of the Río Mamoré. Alternative explanations for the differences in dimensions of the paleo versus the modern Río Mamoré, i.e. contemporaneous activity of both rivers or alteration of site factors such as the channel/floodplain relationship, are considered to be unlikely. 相似文献
4.
The paleoenvironmental history of the Beilun River estuary on the coast of Beibu Gulf in the northwest South China Sea is reconstructed based on fossil diatoms, isotopic dating, sedimentary grain size data, mineralogy and geochemistry in three sediment core samples. Results show that the estuary has experienced significant environmental changes since deposition began about 20,000 yr ago. Freshwater runoff of the Beilun River initially was strong. However, the freshwater runoff reduced significantly after a transgressive event. Subsequently the estuary’s position began to migrate to the northeast. At the end of the Late Pleistocene the estuary shifted gradually towards the southwest. In the Early-Mid Holocene, the estuary’s geomorphology was shaped by seawater transgressing into the ancient river channel. The basin was filled continuously but slowly to form the present Beilun River estuary. Holocene transgression in this area could be divided roughly into three stages, including oscillation period 1, the maximum transgression period, and oscillation period 2. 相似文献
5.
Discharge estimation from planform characters of the Shedhi River, Gujarat alluvial plain: Present and past 总被引：1，自引：0，他引：1
Alpa Sridhar 《Journal of Earth System Science》2007,116(4):341-346
In the absence of long-term hydrologic and streamflow records an understanding of river morphology (present and past) can
help delineate changes in magnitudes of water and sediment discharges. The relict drainage system of Gujarat alluvial plain
provides an opportunity to reconstruct the palaeochannel morphology-related discharge estimations. In this paper, based on
the geomorphological evidence and channel geometry, an attempt has been made to reconstruct the palaeohydrological condition
in the Shedhi River during the Holocene. A comparison of the present day channel of the Shedhi River with that of its palaeo
counterpart reveals that the former was carrying much higher bankfull discharge (∼5500m3 s−1) as compared to the present (∼200m3 s−1). This is attributed to a larger drainage area and enhanced precipitation in the Shedhi River basin. 相似文献
6.
Temporal and spatial variations in water flow and sediment load in Narmada River Basin, India: natural and man-made factors 总被引：1，自引：0，他引：1
The Narmada River flows through the Deccan volcanics and transports water and sediments to the adjacent Arabian Sea. In a
first-ever attempt, spatial and temporal (annual, seasonal, monthly and daily) variations in water discharge and sediment
loads of Narmada River and its tributaries and the probable causes for these variations are discussed. The study has been
carried out with data from twenty-two years of daily water discharge at nineteen locations and sediment concentrations data
at fourteen locations in the entire Narmada River Basin. Water flow in the river is a major factor influencing sediment loads
in the river. The monsoon season, which accounts for 85 to 95% of total annual rainfall in the basin, is the main source of
water flow in the river. Almost 85 to 98% of annual sediment loads in the river are transported during the monsoon season
(June to November). The average annual sediment flux to the Arabian Sea at Garudeshwar (farthest downstream location) is 34.29×106 t year−1 with a water discharge of 23.57 km3 year−1. These numbers are the latest and revised estimates for Narmada River. Water flow in the river is influenced by rainfall,
catchment area and groundwater inputs, whereas rainfall intensity, geology/soil characteristics of the catchment area and
presence of reservoirs/dams play a major role in sediment discharge. The largest dam in the basin, namely Sardar Sarovar Dam,
traps almost 60–80% of sediments carried by the river before it reaches the Arabian Sea. 相似文献
7.
萨拉乌苏河流域位于我国北方沙漠/黄土过渡带和生态脆弱带,它对全球变化反映非常敏感,是研究全球变化的理想区域。本文根据地质测年、气候地层对比,以及地层中气候代用指标的分析,将萨拉乌苏河流域地层和气候变化划分为全新统的风成相与湖相沉积(0~11.5kaBP),早、中期气候较暖湿,晚期气候较干旱;上更新统城川组的风成相沉积(11.5~80kaBP),气候干旱寒冷;上更新统萨拉乌苏组的湖相沉积(80~140kaBP),气候温暖较湿润;中更新统上部的河流相与风成相互层(140~190kaBP),气候冷干与温凉半干旱波动;中更新统上部的冲洪积沉积(190~220kaBP),气候较暖湿等阶段。指出自中更新世晚期以来气候发生频繁波动,无论是暖湿还是冷干阶段,气候都波动频繁,气候变化不稳定性明显。 相似文献
8.
Late Quaternary Upper Mississippi River alluvial episodes and their significance to the Lower Mississippi River system 总被引：1，自引：0，他引：1
James C. Knox 《Engineering Geology》1996,45(1-4):263-285
The period in the Upper Mississippi Valley (UMV) from about 25 000 years B.P. until the time of strong human influence on the landscape beginning about 150–200 years ago can be characterized by three distinctly different alluvial episodes. The first episode is dominated by the direct and indirect effects of Late Wisconsin glacial ice in the basin headwaters. This period, which lasted until about 14 000 years B.P., was generally a time of progressive valley aggradation by a braided river system transporting large quantities of bedload sediment. An island braided system evolved during the second episode, which extended from about 14 000 to 9000 years B.P. The second episode is associated with major environmental changes of deglaciation when occurrences of major floods and sustained flows of low sediment concentration from drainage of proglacial lakes produced major downcutting. By the time of the beginning of the third episode about 9000 years B.P., most vegetation communities had established their approximate average Holocene locations. The change of climate and establishment of good vegetation cover caused upland landscapes of the UMV to become relatively stable during the Holocene in comparison to their relative instability during the Late Wisconsin. However, Holocene remobilization of Late Wisconsin age sediment stored in tributary valleys resulted in a return to long-term upper Mississippi River aggradation. The dominance of Holocene deposition over transportation reflects the abundance of sandy bedload sediment introduced from tributaries and the situation that energy conditions for floods and the hydraulic gradient of the upper Mississippi River are much less for the Holocene than they were for the Late Wisconsin and deglaciation periods.Outburst floods from glacial lakes appear to have been common in the UMV during the Late Wisconsin and especially during deglaciation. Magnitudes for the Late Wisconsin floods are generally poorly understood, but an estimate of 10 000–15 000 m3 s−1 was determined for one of the largest events in the northern UMV based on heights of paleo-foreset beds in a flood unit deposited in the Savanna Terrace. For comparison, the great flood of 1993 on the upper Mississippi River was about 12 000 m3 s−1 at Keokuk, Iowa, near the Des Moines River confluence where it represented the 500-year event in relation to modem flood series. Exceptionally large outburst floods derived from the rapid drainage of pro-glacial Lake Michigan and adjacent smaller proglacial lakes between about 16 000 and 15 500 years B.P. are a likely cause of the final diversion of the Mississippi River through the Bell City-Oran Gap at the upstream end of the Lower Mississippi Valley (LMV). The largest outburst flood from northern extremities of the UMV appears to have occurred between about 11700 and 10 800 years B.P. when the southern outlet of Lake Agassiz was incised. Based on the probable maximum capacity of the Agassiz flood channel 600 km downstream near the junction of the Wisconsin and Mississippi Rivers, the Agassiz flood discharge apparently did not exceed 30 000 m3 s−1. However, if the Agassiz flood channel here is expanded to include an incised component, then the flood discharge maximum could have been as large as 100,000 to 125 000 m3 s−1. The larger flood is presently viewed as unlikely, however, because field evidence suggests that the incised component of the cross-section probably developed after the main Agassiz flood event. Nevertheless, the large Agassiz flood between about 11 700 and 10 800 years B.P. produced major erosional downcutting and removal of Late Wisconsin sediment in the UMV. This flood also appears to be mainly responsible for the final diversion of the Mississippi River through Thebes Gap in extreme southwestern Illinois and the formation of the Charleston alluvial fan at the head of the LMV.After about 9000 years B.P. prairie-forest ecotones with associated steep seasonal climatic boundaries were established across the northern and southern regions of the UMV. The general presence of these steep climatically sensitive boundaries throughout the Holocene, in concert with the natural tendency for grasslands to be especially sensitive to climatic change, may partially explain why widespread synchroneity of Holocene alluvial episodes is recognized across the upper Mississippi River and Missouri River drainage systems. Comparison of estimated beginning ages of Holocene flood episodes and alluvial chronologies for upper Mississippi River and Missouri River systems with beginning ages for LMV meander belts and delta lobes shows a relatively strong correlation. At present, dating controls are not sufficiently adequate and confidence intervals associated with the identified ages representing system changes are too large to establish firm causal connections. Although the limitations of the existing data are numerous, the implicit causal connections suggested from existing information suggest that further exploration would be beneficial to improving the understanding of how upper valley hydrological and geomorphic events are influencing hydrological and geomorphic activity in the LMV. Since nearly 80% of the Mississippi River drainage system lies upstream of the confluence of the Mississippi and Ohio Rivers, there is a strong basis for supporting the idea that UMV fluvial activity should be having a strong influence on LMV fluvial activity. If this assertion is correct, then the traditional assignment of strong to dominant control by eustatic sea level variations for explaining channel avulsions, delta lobes, and meander belts in the LMV needs re-examination. A stronger role for upper valley fluvial activity as a factor influencing lower valley fluvial activity does not disregard the role of eustatic sea level, tectonic processes or other factors. Rather, upper valley fluvial episodes or specific events such as extreme floods may commonly serve as a “triggering mechanism” that causes a threshold of instability to be exceeded in a system that was poised for change due to sea level rise, tectonic uplift, or other environmental factors. In other situations, the upper valley fluvial activity may exert a more dominant control over many LMV fluvial processes and landforms as frequently was the case during times of glacial climatic conditions. 相似文献
9.
This study attempts to assess the spatial variation of fluvial hydraulics with special emphasis on hydrological components at upper, middle and lower part of the Kharsoti river basin. The study encompasses the scenario of a micro bedrock river of India in the post monsoon period. This paper includes the study of hydrological components such as discharge, velocity, shear stress, stream power, specific stream power, width-depth relation and roughness and its interrelationships with different parts of the river basin with related mathematical equations and identification of major river bed erosive zones coupled with geo-hydrological components with geological explanation. Kharsoti is a typical example of rejuvenated antecedent tributary river of Subarnarekha River basin in Chota Nagpur Plateau. It is necessary to give a new threshold to the quantitative methods regarding the fluvial hydraulic studies under a systematic scientific geographical and hydrological background. The results also involve some specific techniques, equations and GIS mapping. The result of this study will help to open the scenario of hydraulics of a micro river basin in a contemporary method. 相似文献
10.
Valley sequences of Late Quaternary alluvial units reflect alluvial preservation as well as alluvial production factors. Effects of lateral channel migration, incision, aggradation and channel stability on preservation potential are explored and then considered in the light of 14 available data sets: cartographically dated and model data based on lateral channel migration; well‐mapped and dated Late Quaternary valley unit surveys; and composite age–frequency plots for dated alluvial units and flood sediments. Despite much expectable variation between sites, and the complex effects of river‐activity combinations, a common characteristic of the data sets examined is the significance of preservation factors. Lateral migration tends to eliminate older units as it creates new alluvial deposits, whereas incision may lead to the preferential preservation of older units beyond the incision slot. Aggradational environments are likely to preserve more complete records, although simultaneous lateral migration may eliminate, possibly repeatedly, the upper parts of alluvial units. The common pattern of inset and incised streams within Pleistocene and early Holocene fills or bedrock gives finite extent to later units within narrowing valleys so that development of new valley‐floor units is necessarily at the expense of reprocessing earlier ones. Floods associated with both slack water deposits and berms are also responsible for the removal of accessible earlier materials, thus limiting the preserved record of earlier events. In light of these censoring effects of river activities, the sequence of preserved Late Quaternary units within UK sequences is reconsidered. It is concluded that preservation potential factors have led to spatial and temporal bias in the alluvial record, and that both here and elsewhere preservation potential needs to be considered systematically alongside variable sedimentation resulting from allogenic environmental factors when interpreting the alluvial archive. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
11.
云南三江一河典型地区河谷第四系发育特征 总被引：6，自引：1，他引：6
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。 相似文献
12.
《Quaternary Science Reviews》2007,26(22-24):2758-2782
The paper discusses the Quaternary evolution of the Danube and Tisza rivers and their main tributaries in the context of evolution of the entire Pannonian Basin, which is Europe's largest intramontane basin, within the Alp–Carpathian orogen. The palaeo-drainage reconstruction of the Pannonian Basin for the pre-Quaternary period is outlined in connection with the gradual regression of Lake Pannon since the Late Miocene. Deltas of rivers that entered the basin from the northwest and northeast were gradually transformed into extended alluvial plains; thus, the earliest possible ancestor of the Danube coming southeastwards from the Alps could be as old as Late Miocene. By the Pliocene the whole Lake Pannon was infilled. The former extensional basin formation was replaced by a compresional stress field, which resulted in an uplift of the marginal flanks and late-stage subsidence anomalies. The increasing relief led to the formation of the Quaternary drainage pattern. The actively subsiding young basins were filled by fluvial sediments, transported by the Danube and Tisza river systems from the uplifting mountains. Between the subsiding regions of the Little and Great Plains, the Danube has formed an antecedent valley with terrace staircases between the uplifting sections of the Transdanubian Range and the North Midmountains. The formation of the terraces is attributed to periodic climate changes during the Pleistocene combined with differences in the uplift rate. The paper gives a complex overview of the classical chronology of the six terraces based on various data sources: mostly dating of loess/paleosol sequences, travertines, aeolian sand, and tephra strata overlying the fluvial sediments, complemented by scattered vertebrate faunal data and archaeological evidence directly from the terrace sediments.The Quaternary drainage pattern evolution of the Great Plain, with a strong tectonic control, is discussed in detail. Rivers originating from the uplifting marginal areas were drawn towards the subsiding depressions which served as local base level. Changes in subsidence rates in space and time throughout the Quaternary resulted in the evolution of a complex drainage pattern. A special emphasis is placed on the Late Pleistocene–Holocene development of the Middle–Tisza region and the Körös basin, where the Berettyó–Körös Rivers form an eastern tributary system of the Tisza River. A comparative evaluation of these two areas is especially relevant, as they provide insights into large-scale Late Pleistocene avulsion of the Tisza River. OSL dating, complemented with inferred transport directions determined from heavy mineral analysis of fluvial sediments in the Körös basin, has revealed an ancient large meandering river system that can be identified with the palaeo-Tisza, which was flowing along a tectonically controlled depression during the Late Pleniglacial. Successions in the Middle Tisza region have allowed differentiation between the older channels of the palaeo-Bodrog River and the Sajó–Hernád alluvial fan and the younger meander belts of the new course of the Tisza. In the Tisza system, changes in river style (braided to various scales of meandering) show correspondence to millennial-scale climate changes of the last 25 ka, while in the Körös basin the effects of tectonics are overprinted onto the regional climatic signals. 相似文献
13.
青藏高原东缘龙门山北东段山前涪江冲积扇在武都盆地内的覆盖面积约为25 km2,区域构造上为江油断层、香水-让水断层等组成的江油断裂带右旋走滑构造域。通过宇宙核素成因埋藏年龄测试技术精确地测定发源于龙门山北东段主要河流-涪江自第四纪以来发育的三期冲积扇形成年代,即早更新世冲积扇（1.84 Ma）、中更新世冲积扇（0.54 Ma）和全新世冲积扇。由于龙门山北东段-江油断裂的右旋走滑兼逆冲运动,导致涪江早更新世冲积扇扇头右旋错动约3.2 km,之后形成新的冲积扇（中更新世积扇）。随着江油断裂继续的继续活动,中更新世冲积扇扇头又被右旋错动了约0.8 km,之后形成全新世的冲积扇。涪江形成以来总共右旋错动距离约为4 km。同时,早、中更新世冲积扇褶皱隆升了约50 m,早更新世冲积扇总共褶皱隆升了约100 m。这在一定程度上反映了龙门山构造带北东段第四纪以来沉积对构造演化的响应过程。 相似文献
14.
In this study, the distribution of channel‐bed sediment facies in the lowermost Mississippi River is analysed using multibeam data, complemented by sidescan sonar and compressed high‐intensity radar pulse seismic data, as well as grab and core samples of bed material. The channel bed is composed of a discontinuous layer of alluvial sediment and a relict substratum that is exposed on the channel bed and sidewalls. The consolidated substratum is made up of latest Pleistocene and Early Holocene fluvio‐deltaic deposits and is preferentially exposed in the deepest thalweg segments and on channel sidewalls in river bends. The exposed substratum commonly displays a suite of erosional features, including flutes that are quantitatively similar in form to those produced under known laboratory conditions. A total of five bed facies are mapped, three of which include modern alluvial deposits and two facies that are associated with the relict substratum. A radius of curvature analysis applied to the Mississippi River centreline demonstrates that the reach‐scale distribution of channel‐bed facies is related to river planform. From a broader perspective, the distribution of channel‐bed facies is related to channel sinuosity — higher sinuosity promotes greater substratum exposure at the expense of alluvial sediment. For example, the ratio of alluvial cover to substratum is ca 1·5:1 for a 45 km segment of the river that has a sinuosity of 1·76 and this ratio increases to ca 3:1 for a 120 km segment of the river that has a sinuosity of 1·21. The exposed substratum is interpreted as bedrock and, given the relative coverage of alluvial sediment in the channel, the lowermost Mississippi River can be classified as a mixed bedrock‐alluvial channel. The analyses demonstrate that a mixed bedrock‐alluvial channel boundary can be associated with low‐gradient and sand‐bed rivers near their marine outlet. 相似文献
15.
古滦河冲积扇研究的关注点更多在全新世,对其更新世的演化与变迁一直没有进行过系统研究。根据古滦河冲积扇上PZK10、PZK20钻孔的磁性地层学、年代地层学、沉积学、测井沉积学、岩芯色度分析等,对古滦河冲积平原的第四纪三维地质结构、冲积扇体的规模以及迁移规律进行综合研究,结果表明：PZK10孔揭露了上新世时沉积的巨厚洪积成因“泥包砾”地层,早更新世时发育两个冲积扇-湖相旋回,中更新世时发育辫状河沉积,晚更新世发育湖相、冲积扇相、辫状河相沉积。PZK20孔上新世沉积了一套巨厚“泥包砾”层,早更新世为扇前平原-辫状河相沉积,中更新世为辫状河-冲积扇相沉积,晚更新世为辫状河沉积。古滦河发育两期冲积扇,第一期为早更新世早期,在沙流河镇一带出山口形成的规模较大的冲积扇;第二期为早更新世中期,古滦河在现今丘庄水库一带发生分流,在丰润区一带出山口形成的冲积扇。中更新世,第一期冲积扇开始萎缩,第二期冲积扇继续发育,形成巨厚砾石层;晚更新世,古滦河在迁西县城以北发生袭夺,东流迁移出研究区,在西峡口进入迁安盆地,形成以西峡口为顶点的冲积扇。 相似文献
16.
晋中盆地是位于汾渭地堑系中部的新生代陆内断陷沉积盆地,研究晋中盆地第四纪的沉积序列对于进一步认识该盆地区域构造和区域气候环境变化具有重要意义。为查明晋中盆地第四纪沉积序列结构、研究揭示晋中盆地第四纪沉积环境及演化,通过构造岩相学方法,对晋中盆地地表和钻孔内第四纪沉积物和沉积环境进行了研究。结果表明:晋中盆地清徐地区地表第四纪沉积序列结构为盆地内部沱阳组河床相和河漫滩相-盆地边缘汾河组河流相—盆山过渡带峙峪组河流相、汾河组冲积扇相及马兰组风积相-基岩山地（盆地外围）二叠系浅海相。钻孔岩芯内第四纪沉积序列结构为下更新统浅湖相和滨湖相—中更新统浅湖相和河流相—上更新统河流相和冲积扇相—全新统冲积扇相。研究认为晋中新生代陆内断陷盆地内沉积序列和演化结构为早更新世陆相湖盆沉积环境—中更新世萎缩湖泊环境—晚更新世强烈萎缩的湖泊和河流环境—全新世再度沉降的陆相湖盆;陆相湖盆从中心向山地沉积环境分带为湖泊沉积环境—河流和湖泊沉积环境—冲积扇沉积环境（盆地边缘出山口区）。盆山过渡带地区上更新世沉积物错位现象与同沉积活动断裂有关,断裂活动性揭示了晋中盆地阶梯式断陷成盆的动力学机制。这些研究成果为区域气候环境变化和晋中盆地区域构造研究提供了新证据,也为太原市城市群建设中工程场址的选择提了供参考。 相似文献
17.
LI Jiangang YUAN Sihu LIU Yongjiang LIU Xiaoyan BAI Xiangdong JIANG Jiyi LI Ying ZHAO Zhenhong 《《地质学报》英文版》2019,93(5):1219-1227
The Quaternary sediments in the Yili Basin can serve as archives for studying the Cenozoic basin–mountain relationship. In this study, based on typical natural sections and boreholes, the surficial sediments of the Huocheng area were studied, and their sedimentary ages were obtained using the optically stimulated luminescence(OSL) and electron spin resonance(ESR) dating methods. These dates, combined with changes in the sedimentary facies, provided details of the neotectonic movement in the Yili Basin and adjacent areas. By dating sediments from five sections and three boreholes, we determined that the surficial sediments of the Huocheng area were mainly formed in the Late Pleistocene, with scattered instances of Holocene sediments. The surficial sediments mainly consisted of alluvial fan facies, fluvial facies, lacustrine facies, and desert facies. Based on the activity on the Hongshanzui fault and the northern margin fault of the Wusun Mountains, the Huocheng area was uplifted synchronously with the Tianshan Mountains during the last stage of the Late Pleistocene, causing the desert facies sediments to be superimposed on the former paleo–lake sediments. 相似文献
18.
C. Kasse S.J.P. Bohncke G. Gábris 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):180-194
The Weichselian Late Pleniglacial, Lateglacial and Holocene fluvial history of the middle Tisza valley in Hungary has been compared with other river systems in West and Central Europe, enabling us to define local and regional forcing factors in fluvial system change. Four Weichselian to Holocene floodplain generations, differing in palaeochannel characteristics and elevation, were defined by geomorphological analysis. Coring transects enabled the construction of the channel geometry and fluvial architecture. Pollen analysis of the fine-grained deposits has determined the vegetation development over time and, for the first time, a bio(chrono)stratigraphic framework for the changes in the fluvial system. Radiocarbon dating has provided an absolute chronology; however, the results are problematic due to the partly reworked character of the organic material in the loamy sediments. During the Late Pleniglacial, aggradation by a braided precursor system of the Tisza and local deflation and dune formation took place in a steppe or open coniferous forest landscape. A channel pattern change from braided to large-scale meandering and gradual incision occurred during the Late Pleniglacial or start of the Lateglacial, due to climate warming and climate-related boreal forest development, leading to lower stream power and lower sediment supply, although bank-full discharges were still high. Alternatively, this fluvial change might reflect the tectonically induced avulsion of the River Tisza into the area. The climatic deterioration of the Younger Dryas Stadial, frequently registered by fluvial system changes along the North Atlantic margin, is not reflected in the middle Tisza valley and meandering persisted. The Lateglacial to Holocene climatic warming resulted in the growth of deciduous forest and channel incision and a prominent terrace scarp developed. The Holocene floodplain was formed by laterally migrating smaller meandering channels reflecting lower bank-full discharges. Intra-Holocene river changes have not been observed. 相似文献
19.
《Quaternary Science Reviews》2007,26(22-24):2801-2822
Late Cenozoic fluvial successions are widespread in India. They include the deposits of the Siwalik basin which represent the accumulations of the ancient river systems of the Himalayan foreland basin. Palaeomagnetic studies reveal that fluvial architecture and styles of deposition were controlled by Himalayan tectonics as well as by major climatic fluctuations during the long (∼13 Ma) span of formation. The Indo-Gangetic plains form the world's most extensive Quaternary alluvial plains, and display spatially variable controls on sedimentation: Himalayan tectonics in the frontal parts, climate in the middle reaches, and eustasy in the lower reaches close to the Ganga–Brahmaputra delta. Climatic effects were mediated by strong fluctuations in the SW Indian Monsoon, and Himalayan rivers occupy deep valleys in the western Ganga plains where stream power is high, cut in part during early Holocene monsoon intensification; the broad interfluves record the simultaneous aggradation of plains-fed rivers since ∼100 ka. The eastward increase in precipitation across the Ganga Plains results in rivers with low stream power and a very high sediment flux, resulting in an aggradational mode and little incision. The river deposits of semi-arid to arid western India form important archives of Quaternary climate change through their intercalation with the eolian deposits of the Thar Desert. Although the synthesis documents strong variability—both spatial and temporal—in fluvial stratigraphy, climatic events such as the decline in precipitation during the Last Glacial Maximum and monsoon intensification in the early Holocene have influenced fluvial dynamics throughout the region. 相似文献
20.
ALLUVIAL STYLES AND ARCHITECTURE AS GUIDES TO CENOZOIC TECTONIC AND ENVIRONMENTAL EVENTS AT THE NORTHERN MARGINS OF THE QINGHAI—XIZANG PLATEAU 相似文献