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1.
Dredging the alluvial fans for repaving the international road located in the bottom of the Wadi Watir valley produced vertical cliff faces of different heights, and at different locations of the fans. The heights of the cliff faces resulted in considerable elevation differences between the surface of the dredged alluvial fans and the local base level provided by the Watir trunk valley. The principal geomorphic response to this anthropogenic intervention is triggering upstream channel incision waves at different intensities in the fluvial systems of the downstream reaches of the Watir drainage basin. The channel incision processes resulted in subsequent geomorphic adjustment scenarios that vary from widening the active channels on the surface of the dredged fans, triggering rockfalls from the adjacent hillslopes, and transporting coarse alluvial deposits from the main sediment sources of the fluvial systems, and eventually re-depositing them as sheetform gravel, channelform gravel, and new fan lobes. The major outcome of the various geomorphic adjustment processes was changing the role of the alluvial fans within the fluvial systems from buffer zones where fan aggradation was dominant into dynamic coupled zones. Being coupled zones, the dredged alluvial fans allowed high potential of mass transmission from the feeder catchment areas into the Watir trunk valley. Under such conditions, it could be stipulated that considerable changes in the morphology of landscapes are highly anticipated in response to flash flood events that intermittently occur in the Watir drainage basin. 相似文献
2.
祁连山东段宝积山—红会煤盆地沉积环境与聚煤规律 总被引：1，自引：0，他引：1
位于祁连山东段的宝积山—红会盆地是一个典型的侏罗纪沉积盆地,侏罗纪煤系由冲积扇沉积体系,经过河流、湖泊三角洲沉积体系向湖泊沉积体系过渡的沉积序列组成,并充填于印支运动后的裂陷盆地内。盆地活动断裂边界的内侧发育冲积扇裙,向着不活动边缘的另一侧,逐渐被河流沉积体系和湿地沼泽系统替代。扇前湿地是主要聚煤场所,形成的煤层层数少,主煤层厚度变化大,煤体呈简单指状。扇前湿地泥炭沼泽具有富滋养或低位性质,形成的煤层灰分产率高,硫含量有明显的分带性,其变化取决于泥炭沼泽与冲积扇体的相应空间位置。 相似文献
3.
The Lo River Basin (LRB) is one of several narrow sedimentary basins associated with the main faults of the Red River Fault Zone separating the South China and Indochina microplates. The basin is located on the NE boundary of the high-grade metamorphic Con Voi Massif and the sedimentary and metasedimentary Viet Bac fold zone in north-eastern Vietnam.The LRB is filled with over 6000 m of Oligocene/Miocene alluvial deposits. The source area was probably located on the NE margin of the basin and was composed mostly of low-grade metamorphic rocks with a minor component of sedimentary rocks. Three alluvial systems are recognised. The oldest system was a proximal braided river system, with the minor occurrence of alluvial fans. The younger systems record changes in clast composition and lithofacies, which suggests a transition from a distal braided river to a distal braidplain system. The LRB fill shows a range of features characteristic of strike-slip fault basins. The origin of the LRB is correlated with the left-lateral transtensional regime. The present shape of the basin is a result of post-sedimentation tectonic activity. 相似文献
4.
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
5.
The Pliocene–Early Pleistocene Mangas Basin in SW New Mexico, USA, was a N–NW-trending full graben that changed southward to an eastward-tilted half graben. Unlike the facies distribution predicted in existing models, the half-graben part of the Mangas Basin was characterized by broad alluvial fans derived from the footwall scarp, smaller hangingwall-derived alluvial fans, and a shallow, closed lake (Lake Buckhorn) that locally lapped onto the hangingwall hills. The distribution of facies within the full-graben part of the Mangas Basin was also unlike that predicted in current models, primarily because of a broad belt of alluvial-fan sediment derived from the eastern footwall scarp and a narrow belt of axial-fluvial sediment adjacent to the western footwall scarp. The distribution of facies in the Mangas Basin does not appear to have been controlled by the eastward tilt of the floor of the half graben or ‘see-saw’ motion of the floor of the full graben, as predicted by existing models, but rather by the large size of the alluvial fans on the eastern side of the basin. These fans were derived from large, high-relief catchments on the footwall scarp of the Mogollon Mountains, the uplift of which began during Early Miocene. This example illustrates how earlier uplift and drainage development in a mountain range may influence facies distribution in a younger extensional basin. 相似文献
6.
As achieves of regional environmental changes in the past, alluvial fans have received extensive attention from geoscience community. Tectonic activity and climate change are two of the main factors affecting the development of alluvial fans. The Qilian Mountains, which is located on the northeastern edge of the Tibetan Plateau, experienced severe uplift since the Cenozoic. With the huge relief from surrounding areas, a series of alluvial fans developed at the northern foot of the Qilian Mountains. That makes it become an ideal area to study the relationships between tectonic uplift, climate change, and alluvial fan development. In order to explore how climate and tectonic changes have effect on the formation and development of alluvial fans, based on stream power model and diffusion equations, a numerical model of the drainage basin-fan system was built. Xigou River and Dayekou River with their fans in Qilian Mountains were simulated by using the above-mentioned numerical model. The results show that both the change in precipitation and the uplift rate affect the fan slope. Either the increase in the uplift rate or the decrease in precipitation causes the increment of fan slope, and vice versa. Fan slope changes linearly with the uplift rate variation, while the effect of precipitation on fan slope is relatively small. The response of catchment to tectonic activity and precipitation disturbances, as the change of sedimentary flux, is also in different patterns. The research will provide a new perspective for understanding the influence of regional tectonic activities and climate change on the geomorphological process. 相似文献
7.
广西横县六景火车站南侧,角度不整合覆盖下泥盆统莫丁组和那叫组下段,被新近系大面积覆盖而呈两部分远距离割裂状态的一套“二元结构”特征显著的红色泥砂基底碳酸盐岩粗巨砾岩及其横向相变部分,长期以来未被将其作为一个冲积扇的有机统一体进行研究。经笔者两次实地踏勘,系统采样和分析,以现代山麓冲积扇鉴别特征为主,辅以古冲积扇特征,综合分析认为该套沉积系列相关分割露头分别为一古近系冲积扇所残存扇根、扇中和扇缘。该冲积扇为一典型的古近纪早期干旱气候条件下,母岩区为陡峻碳酸盐岩山体的古山麓冲积扇。 相似文献
8.
The Chitral district of northern Pakistan lies in the eastern Hindu Kush Range. The population in this high-relief mountainous terrain is restricted to tributary-junction fans in the Chitral valley. Proximity to steep valley slopes renders these fans prone to hydrogeomorphic hazards, including landslides, floods and debris flows.This paper focuses on debris-flow hazards on tributary-junction fans in Chitral. Using field observations, satellite-image analyses and a preliminary morphometry, the tributary-junction fans in the Chitral valley are classified into (1) discrete and (2) composite. The discrete fans are modern-day active landforms and include debris cones associated with ephemeral gullies, debris fans associated with ephemeral channels and alluvial fans formed by perennial streams. The composite fans are a collage of sediment deposits of widely different ages and formed by diverse alluvial-fan forming processes. These include fans formed predominantly during MIS-2/Holocene interglacial stages superimposed by modern-day alluvial and debris fans. Composite fans are turned into relict fans when entrenched by modern-day perennial streams. These deeply incised channels discharge their sediment load directly into the trunk river without significant spread on fan surface. In comparison, when associated with ephemeral streams, active debris fans develop directly at composite-fan surfaces. Major settlements in Chitral are located on composite fans, as they provide large tracts of leveled land with easy accesses to water from the tributary streams. These fan surfaces are relatively more stable, especially when they are entrenched by perennial streams (e.g., Chitral, Ayun, and Reshun). When associated with ephemeral streams (e.g., Snowghar) or a combination of ephemeral and perennial streams (e.g., Drosh), these fans are subject to frequent debris-flow hazards.Fans associated with ephemeral streams are prone to high-frequency (∼10 years return period) debris-flow hazards. By comparison, fans associated with perennial streams are impacted by debris-flow hazards during exceptionally large events with return periods of ∼30 years. This study has utility for quick debris-flow hazard assessment in high-relief mountainous regions, especially in arid- to semi-arid south-central Asia where hazard zonation maps are generally lacking. 相似文献
9.
Sedimentary Response of Different Fan Types to the Paleogene-Neogene Basin Transformation in the Kuqa Depression,Tarim Basin,Xinjiang Province 总被引：1，自引：0，他引：1
GAO Zhiyong GUO Hongli ZHU Rukai ZHANG Lijuan SUN Yushan Research Institute of Petroleum Exploration Development Petrochina Beijing China Research Institute of Petroleum Exploration Development Petrochina Tarim Oilfield Corporation Xinjiang China 《《地质学报》英文版》2009,83(2)
A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain,Kuqa Depression,Tarim Basin,Xinjiang province. Two types of fans occurred in the middle-late Paleogene Kumugeliemu and Suweiyi formations:one alluvial,and the other fan delta deposited in a lacustrine setting.Within the early Neogene Jidike Formation,coastal subaqueous fans developed,probably in a deeper water lacustrine setting.The three types of fans are stacked vertic... 相似文献
10.
A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain, Kuqa Depression, Tarim Basin, Xinjiang province. Two types of fans occurred in the middle–late Paleogene Kumugeliemu and Suweiyi formations: one alluvial, and the other fan delta deposited in a lacustrine setting. Within the early Neogene Jidike Formation, coastal subaqueous fans developed, probably in a deeper water lacustrine setting. The three types of fans are stacked vertically in outcrop with the sequence in ascending order: bottom alluvial, middle fan-delta, and top subaqueous. The subaqueous is a typical coarse-fan deposit occurring in the glutinite member of the Jidike Formation in some wells. Laterally, from the foreland to the lacustrine settings, the distribution pattern of sedimentary facies represents the same three fan types sequentially. The spatial distribution of these fans was controlled by the Paleogene–Neogene Basin transformation, and evolution with different types of fans developed in the Kuqa Depression in response. In the Paleogene, the Kuqa Depression was a rift basin where an alluvial fan was deposited in the foreland setting, which, by early Neogene, became a foreland basin when the lake level changed. With any rise in lake level, fan-deltas migrated from lacustrine to foreland settings, whereas when the lake level fell, fan migration was reversed. In the early Neogene, with increasing slope and rising lake level, fans progressed and covered the previous fan-delta and lacustrine mudstone. Eventually, subaqueous fans developed, forming the present spatial configuration of these three fan types. 相似文献
11.
通过岩心观察,将克拉玛依油田三叠系克下组砾岩分为杂基支撑角砾岩(砾石成分同基岩)、弱胶结砾岩(严格意义上未胶结成岩)、泥质杂基支撑砾岩、砂砾质支撑砾岩和分选极好的细砾岩几种类型。通过岩心岩石特征与现代洪积扇沉积物特征对比,确定了每一类砾岩的形成环境。克下组沉积早期,气候干旱,洪积扇为干旱型,可与现代扎伊尔山山麓洪积扇(堆)沉积物特征相类比。克下组沉积后期气候变得潮湿,洪积扇类型逐渐转变为以河流作用为主,可与阜康市白杨河洪积扇沉积物特征相类比。克下组洪积扇在垂向上为向扎伊尔山后退的沉积序列。 相似文献
12.
Late Quaternary activity and dextral strike-slip movement on the Karakax Fault Zone, northwest Tibet 总被引：1，自引：0，他引：1
Field observations and interpretations of satellite images reveal that the westernmost segment of the Altyn Tagh Fault (called Karakax Fault Zone) striking WNW located in the northwestern margin of the Tibetan Plateau has distinctive geomorphic and tectonic features indicative of right-lateral strike-slip fault in the Late Quaternary. South-flowing gullies and N–S-trending ridges are systematically deflected and offset by up to ~ 1250 m, and Late Pleistocene–Holocene alluvial fans and small gullies that incise south-sloping fans record dextral offset up to ~ 150 m along the fault zone. Fault scarps developed on alluvial fans vary in height from 1 to 24 m. Riedel composite fabrics of foliated cataclastic rocks including cataclasite and fault gouge developed in the shear zone indicate a principal right-lateral shear sense with a thrust component. Based on offset Late Quaternary alluvial fans, 14C ages and composite fabrics of cataclastic fault rocks, it is inferred that the average right-lateral strike-slip rate along the Karakax Fault Zone is ~ 9 mm/a in the Late Quaternary, with a vertical component of ~ 2 mm/a, and that a M 7.5 morphogenic earthquake occurred along this fault in 1902. We suggest that right-lateral slip in the Late Quaternary along the WNW-trending Karakax Fault Zone is caused by escape tectonics that accommodate north–south shortening of the western Tibetan Plateau due to ongoing northward penetration of the Indian plate into the Eurasian plate. 相似文献
13.
通过天山北缘白杨河及玛纳斯河现代辫状河沉积作用为主的洪积扇的研究,认为此类洪积扇以活动的辫流带和洪水
期才发生沉积的漫洪带为特征。扇面上不能全区同时发生沉积,而是选择扇面低势能区发生沉积。辫状河道呈条带状分
布,与常规砾质辫状河沉积特征类似,并向扇缘散开,沉积的砾石条带物性好。洪积扇的发育受构造、气候、水系的共同
控制,这些条件决定了洪积扇的沉积特征及发育规模。准噶尔盆地西北缘三叠系古代洪积扇以辫状河道沉积作用为主,是
发育在盆地边缘低坡度洪积扇,更倾向于辫状河沉积特征。 相似文献
14.
在构造-沉积-成矿背景、铀源地质体配置研究的基础上,选择滇西腾冲地块龙川江盆地南部团田地区老矿床外围部署验证工程,获得了重要找矿发现。本文以第一手钻探资料为素材,通过分析上新世龙川江盆地演化过程,建立含矿层系芒棒组的沉积体系和圈定有利赋矿微相组合,重建赋矿古冲积扇体的岩相古地理格局,为该地区和同类盆地砂岩型铀矿勘查提供科学依据。芒棒组沉积期,龙川江盆地演化经历了断陷成盆期、火山沉积期及盆地回返期3个阶段,其中断陷成盆期沉积了砂岩型铀矿主力发育层段—芒棒组下段,此时未形成具规模的湖盆,具备汇水盆地的古地理模式。盆地东、南部分布多个潜在赋矿的古冲积扇体,本文的研究重点团田地矿区位于旱坝寨扇体。团田矿区芒棒组下段识别出3种沉积相和6种亚相,根据其沉积演化序列显示,在冲积扇扇中/扇端沼泽的纵向序列转换面附近,形成“沼泽相炭质泥岩层-煤层/扇中砾质辫状河道”的有利控矿微相组合。分析团田矿区主矿层、矿层顶板层沉积期底古地理格局可发现,在扇中-扇端沉积转换期的湖泛(相对水位上升)控制下,受晚期扇端(沼泽)覆盖的早期扇中沉积相区是最有利的赋矿相区和部位。基于上述认识,提出砂岩型铀矿勘查应加强沉积微相和岩相古地理研究,建立赋矿有利相带的空间分布模式;结合铀源和成矿作用类型的分析,可更准确地定位潜在的铀矿体。 相似文献
15.
柴达木盆地处于古亚洲构造域和特提斯－喜马拉雅构造域的结合部，构造应力大而复杂，导致盆内地势起伏大，加上西南暖湿气流受喜马拉雅山系阻隔难以进入境内，盆内气候干旱，最终导致盆地内冲积扇极为发育。通过对大柴旦地区大头羊煤矿、鱼卡河、波门河和八里沟四个冲积扇的实地考察，共观测到3个亚相8个微相：扇根亚相沉积物最粗，分为古沟道、主水道和主水道间微相；扇中亚相沉积物偏细，成熟度增高，分为辫状水道、辫状水道间和纵坝微相；扇缘亚相沉积物最细，流体能量最低，分为水道径流和片流微相。不同沉积微相其沉积特征差异较大，认为古沟道、主水道和辫状水道微相具有较好的储集性能。勘探表明，冲积扇沉积与储层有着密切的关系，其内形成的油藏具有“自我保护”的能力；另外，冲积扇的形成很可能导致上覆地层形成扇背斜油藏，也可能导致下伏基岩形成基岩风化壳油藏。 相似文献
16.
冲积扇是发育于盆地边缘的一种重要的沉积相类型。近20年来,在冲积扇分布的控制作用、内部构型及储集层特征研究等方面取得了很大的进展:(1)深化了断层活动、物源岩性条件及不同级次基准面旋回对冲积扇沉积构型的控制作用机理;(2)建立了碎屑流主控、碎屑流与河流主控、河流主控的冲积扇以及末端扇的沉积构型模式;(3)分析了冲积扇沉积机制及沉积构型对储集层质量的控制作用。今后有必要充分应用水槽模拟实验、沉积数值模拟和探地雷达等先进技术,对冲积扇沉积过程、内部构型及储集层非均质性进行更为深入的研究。 相似文献
17.
The spatial distribution and several morphometric characteristics of the Quaternary alluvial fans of the San Juan River, in the province of San Juan, at the Central and Western part of Argentina, have been studied to classify them as paraglacial megafans, as well to ratify its depositional environmental conditions. The high sedimentary load exported by San Juan river from the Central Andes to the foreland depressions is estimated about 3,682,200 hm3. The large alluvial fans of Ullum-Zonda and Tulum valleys were deposited into deep tectonic depressions, during the Upper Pleistocene deglaciation stages. The outcome of collecting remotely sensed data, map and DEM data, geophysical data and much fieldwork gave access to morphometric, morphographic and morphogenetic data of these alluvial fans. The main drainage network was mapped on processed images using QGis (vers.2.0.1). Several fan morphometric parameters were measured, such as the size, the shape, the thickness, the surface areas and the sedimentary volume of exported load. The analyzed fans were accumulated in deep tectonic depressions, where the alluvium fill reaches 700 to 1200 m thick. Such fans do not reach the large size that other world megafans have, and this is due to tectonic obstacles, although the sedimentary fill average volume surpasses 514,000 hm3. The author proposes to consider Ullum-Zonda and Tulum alluvial fans as paraglacial megafans. According to the stratigraphic relationships of the tropical South American Rivers, the author considers that the San Juan paraglacial megafans would have occurred in the period before 24 ka BP, possibly corresponding to Middle Pleniglacial (ca 65–24ka BP). They record colder and more humid conditions compared with the present arid and dry conditions. 相似文献
18.
Alluvial fans in southern Monglia occur along a group of narrow discontinuous mountain ranges which formed as transpressional uplifts along a series of strike-slip faults. They provide information on the nature of neotectonic activity in the eastern Gobi Altai range and on palaeoclimate change. Alluvial fan formation was dominated by various geomorphological processes largely controlled by climatic changes related to an increase in aridity throughout late Quaternary times. Their sedimentology shows that initially they experienced humid conditions, when the sedimentary environments were dominated by perennial streams, followed by a period of increasing aridity, during which coarse fanglomerates were deposited in alluvial fans by ephemerial streams and active-layer structures were produced by permafrost within the alluvial fan sediments. With climatic amelioration during early Holocene times, the permafrost degraded and fan incision and entrenchment dominated. Sedimentation was then confined to the upper reaches of the fans, adjacent to steep mountain slopes, and within the entrenched channels. The alluvial fans have been neotectonically deformed, faulted and their surface warped by small thrust faults that propagate from the mountain fronts into their forelands. Localised uplift rates are in the order of 0.1 to 1 m Ka−1. © 1997 John Wiley & Sons, Ltd. 相似文献
19.
新疆乌恰萨热克铜矿北矿带库孜贡苏组沉积相、古流向、物源区及其找矿意义——来自砾石统计分析的证据 总被引：1，自引：1，他引：0
萨热克盆地库孜贡苏组是萨热克铜矿的赋矿层位,开展沉积相、物源区及古流向研究对隐伏铜矿的勘探具有重要意义。选取萨热克铜矿北矿带库孜贡苏组地表矿化最好的砾岩展开砾石统计分析,结果表明,偏斜度显示砾岩为冲积扇相沉积,砾石叠瓦状和砂岩斜层理产状统计显示古流向为北北东向;砾石成分主要为石英、石英砂岩、砂岩,石英岩等;粒度分布呈宽峰态或尖峰态;物源区为元古宇长城系阿克苏群变质岩剥蚀区;物源补给分为主河流补给和支河流补给2种方式。冲积扇相、古流向、物源区分析确定了矿体的范围、最优的勘探线布置方位和潜在的找矿靶区,具有很好的勘探意义。 相似文献
20.
Alluvial fan is a depositional fluvial landform that is characterised by sediment flow and hydrological processes and is also controlled by tectonic activity. These extraordinary features have always attracted researchers since the past as they preserve the past records, but now, this study is focused on the formation meso-level fans with its spatio-temporal dynamic nature. These tributaries have formed secondary alluvial fans at their debouching points. The dynamics of the fans are controlled by the hydrological responses and tectonic base and also by the sedimentation processes. The origin of these tributaries and their respective fans are related to the last stage of Himalayan uplift. This is the region of Himalayan foreland basin which contains the main frontal thrust and makes the region tectonically very active. The region is drained by many large rivers and their numerous tributaries. The active tectonism, the configuration of the basin and also the deposition of the sediments carried by these rivers have formed alluvial fans where the channel debouches into the widened valley. In the present study, the meso-level alluvial fans formed by River Gish and the Rivers Neora and Murti have been studied. Both these fans are present in the piedmont region of the Himalayas, but they deliver different characteristics, and the nature of their deposition is also different. This is mainly because of the influence of the minor faults in the region which control the channel pattern and also have a great influence in the sediment delivery to the downstream section of the channels. Thus, in order to understand the influence of tectonics in the dynamics of these fans, some morphotectonic parameters have been taken into consideration. These include mountain front sinuosity index, valley floor width-to-depth ratio, and tectonic tilt. The calculated hypsometric integral also depicts that the two fans are at different stages of development. 相似文献