共查询到20条相似文献，搜索用时 62 毫秒
1.
贡嘎山海螺沟冰川沉积特征与冰下过程研究 总被引：4，自引：3，他引：1
贡嘎山海螺沟冰川是典型的海洋性冰川,粒度分析表明:冰下融出碛的细粒组分中粉砂占优势,压碎组分与磨碎组分界线在0.5 mm附近,说明其经历充分的研磨细化.与西藏枪勇冰川和天山乌鲁木齐河源冰川的矿物组成和化学成分对比,海螺沟冰川沉积物的经历的化学风化作用更强,即海洋性冰川冰下化学作用比大陆性冰川活跃.显微层理构造、正粒序层理和沉积透镜体反映海洋性冰川底部存在周期性沉积机制和明显的流水作用,显微滞碛是较常见的冰下融出碛类型.沉积物中显微褶皱和断层等反映海洋性冰川强烈滑动、剪切变形过程机制. 相似文献
2.
冰岩界面的冰川动力学是冰川系统的重要组成部分, 海螺沟冰川地处温暖湿润的海洋环境, 冰川运动速度较快, 冰川底部接近压融点, 是研究冰下过程的较理想地点. 在海螺沟冰川大型磨光面上浅显侵蚀坑内发现了碎屑物质. 对碎屑物质理化特征研究表明: 粒度特征、地球化学与石英砂SEM 分析表明沉积在冰岩界面上的物质来自于冰川底部的底碛层, 而不是冰上环境的产物. 偏光显微镜下观察到的冰下沉积物呈现出一系列塑性变形(微旋转、褶皱)和脆性变形(线性结构、支撑结构、断层)微观结构和构造. 两种变形结构的存在是碎屑物质在形成过程中其含水量波动情况的反映. 冰下碎屑物质是冰下融出、滞碛作用的共同产物. 在整个冰下碎屑物质形成与变形过程中, 由于冰下水系季节性变化带来的冰岩界面上冰川融水含量的波动起了决定性作用. 相似文献
3.
电子自旋共振(ESR)技术是一种确定物质成分和结构的顺磁性质的分析方法,也能够用于沉积物定年。该方法的测量技术和测年的物理机制等还处于发展阶段。冰川作用过程十分复杂,形成各种类型的冰川沉积物,其顺磁信号的归零机制有显著差异,ESR测年的实验方案也有所差异。因此,识别冰碛物类型,采集合适的样品对于ESR测年的准确性十分重要。冰下融出碛和滞碛经过了冰下磨蚀过程,结构致密,细颗粒基质含量高,石英砂中的一些杂质芯的ESR信号能够衰退。许多冰上融出碛,结构疏松,但细颗粒基质含量高,不但经过了搬运过程中的冰下磨蚀过程使ESR信号衰退,又经历了沉积时的冰上阳光直射过程使信号衰退,一些样品的ESR信号能够完全晒退。冰水湖泊和冰水河流沉积的细砂和粉砂来源于冰下研磨的产物,信号会衰退;在搬运沉积过程中又可能被阳光直射,信号进一步衰退。其它类型的冰碛物的ESR信号衰退机制不明,或粒径不适合用ESR方法测年。采集冰碛物ESR年代样品时,最好同时采集信号衰退机制相同的现代冰碛物样品,以便对照,并用于扣除可能的残留信号。 相似文献
4.
山地冰川沉积研究在中国有特殊重要性。因为欧、美对冰碛沉积研究多限于大陆冰盖,沉积环境比较单纯,冰水沉积比重很大,而中国山地冰川多限于山体内部,冰水沉积极不发育,且沉积环境很复杂,亚相变化也大。此外中国山地冰川多属大陆性,与欧、美海洋性冰川在物理性质和沉积特征上都有不同。如冰川磨蚀作用弱,冰碛中粉砂少,冰上融出碛发育而流碛和滞碛不发育,原生(同生)构造如粗糙斜层很发育等。这些都将丰富冰碛沉积学内容,并对科学地鉴别中国东部各种混杂堆积的成因有重要意义。如据现代冰川沉积指标庐山就没有任何冰川堆积。 相似文献
5.
冰碛物ESR测年与天山乌鲁木齐河源末次冰期系列 总被引：8，自引：11，他引：8
采用ESR方法，对天山乌鲁木齐河源末次冰期的冰碛石英砂进行了测年，下望峰组冰碛层的年代与前人推测的年代不同，是50～70ka BP末次冰期早阶段形成的，分布下限可达海拔2300m左右的红五月桥附近，与AMS的测年结果相比，末次冰期晚阶段底碛的ESR年代与AMS的年代相当，而冰上融出碛ESR年代与AMS的年代相差较大，认为冰下的压碎和磨蚀作用可能导致冰碛中石英砂的ESR信号归零，从而使底碛的ESR测年成为可能。 相似文献
6.
针对冰川沉积系列细砂粉砂在埋藏前的曝光问题,笔者等人在帕米尔阿依直苏冰川做了观察.本文结合这些观察结果从沉积学角度讨论冰川沉积系列在产生、搬运、沉积过程中的曝光问题,并参考前人研究,将各类冰川沉积进行归纳.认为组成冰碛3个来源的细粒物质中,风成的全部曝光、岩壁风化碎屑部分曝光、冰川侵蚀岩屑不曝光;3个沉积系列中,冰水沉积完全曝光、冰川接触沉积中冰砾阜完全曝光、蛇形丘基本不曝光;冰碛物在沉积过程中,冰面融出碛基本上曝光、冰下滞碛和融出碛不曝光.本文根据分析,给出了冰川沉积系列曝光评估参考值. 相似文献
7.
希夏邦马峰东南富曲河谷的冰川沉积和冰川构造 总被引：2，自引：0，他引：2
在希夏邦马峰（海拔８０１２ｍ）东南富曲河谷，中更新世以来有三次冰期；即聂拉木、富曲和普罗冰期。它们均可再分为两个亚阶段。聂拉木南的高冰碛平台长３.５ｍ，宽１.５ｋｍ，厚２００ｍ。属于中更新世聂拉木冰期（聂聂雄拉冰期）的巨大山谷冰川沉积，中尼公路从高冰碛平台尾端通过，形成数公里长的冰碛剖面，呈现出美丽多姿的冰川成因类型沉积和冰川构造现象，包括冰下，冰上融出碛，冰内.冰下河道沉积，冰湖沉积，坠碛，流磺等。冰川运动时造成的冰川构造，如断层、滑动面-…等也很清楚，代表了海洋型（暖冰川）冰川沉积和冰川构造特征，是中国目前研究冰川构造最理想的场所。 相似文献
8.
西天山托木尔峰南麓大型山谷冰川冰舌区消融特征分析 总被引：4，自引：3，他引：1
基于对托木尔峰南麓托木尔型山谷冰川的野外考察和典型冰川的定位观测,对冰面被表碛广泛覆盖的所谓“托木尔型”冰川冰舌区表碛与冰面消融的关系进行了研究. 结果表明：表碛对冰面消融、冰川水文过程、冰川变化等均具有重要影响,当表碛厚度超过3 cm时,表碛对冰面消融就产生明显抑制作用,且随着厚度增加,冰面消融显明减弱. 科其喀尔冰川表面的观测表明,由末端向上,表碛厚度逐渐减薄. 受表碛影响,科其喀尔冰川区最大的消融量出现在海拔3 800~3 900 m之间、表碛物厚度小于10 cm的区域内;冰川消融强度由此向上随着海拔的升高而下降,向下随表碛厚度的增大而减弱. 冰面湖的发育是表碛覆盖冰川的又一主要特征,湖水对冰面的融蚀和快速排泄成为冰面产汇流的主要过程. 科其喀尔冰川研究表明,两三个冰面湖排泄形成的融蚀冰量就相当于冰川末端退缩造成的冰量损失. 因此,冰面湖等热喀斯特地形的形成、扩张融蚀、融穿排泄、形成湖区低地,这一周而复始的过程不仅是其主要消融方式之一,而且也强烈的影响着冰川水文及冰川变化. 托木尔峰南麓地区大型冰川变化主要以厚度减薄为主,而不是像大多数冰川显著的变化主要表现在末端和面积减少方面. 相似文献
9.
页岩孔隙结构是控制与影响海相页岩储层质量的主要参数之一，对于页岩气资源评估、勘探和开发极其重要.为阐明泸州地区深层五峰-龙马溪组页岩孔隙结构，基于氦气膨胀法测孔隙度、矿物组分分析、TOC测试，采用CO2和N2吸附、高压压汞联合表征页岩全孔径，并与氧化-还原条件、水分、TOC等因素藕合，探讨页岩孔径分布的主控因素.结果表明：页岩中以介孔为主，微孔次之，宏孔较少，平均分别占总孔隙的73%、23%、4%；孔径分布与孔隙体积从五峰组向上先增加后降低；TOC与低孔径孔体积相关性高；水分占据页岩孔隙，大幅降低页岩孔隙体积和表比面积.因此，页岩孔径分布受沉积条件、TOC、水分共同控制. 相似文献
10.
页岩孔隙结构及差异性是页岩含气性和产能评价的基础性问题.针对川东南彭水地区五峰组与龙马溪组页岩的孔隙结构已有若干研究成果,然而在页岩孔隙结构差异性和有机孔定量特征方面还缺乏研究.利用低温低压氮气吸附测定和氩离子抛光-场发射扫描电镜（FE-EM）技术,对页岩样品纳米孔隙进行了二维观察与统计以及分形特征计算,研究了3nm至几百nm页岩孔径范围的孔隙结构及其差异性.研究区五峰组-龙马溪组页岩有机孔十分发育;氮气吸附测定页岩孔隙形状包含开放型圆筒状、层状结构狭缝状和墨水瓶状等;扫描电镜观察有机孔形态主要有近圆形、椭圆形和多角形等.五峰组和龙马溪组页岩孔隙结构具有明显的差异性,主要体现在孔径大小、形态和数量上.氮气吸附测定表明,五峰组页岩孔隙比表面积和总孔容较龙马溪组大,微孔所占总孔的比例也较高;五峰组页岩孔径相对龙马溪组更细窄.扫描电镜二维图像观察与统计结果表明,五峰组有机孔径以小于3nm为主,形态以多角形为主;龙马溪组有机孔径以小于0nm为主,形态多呈近圆形和椭圆形.五峰组页岩的分形维值大于龙马溪组页岩,说明前者孔隙复杂程度较高. 相似文献
11.
Central Ethiopia comprises a high plateau at 2000–3000 m, formed from Tertiary lava flows and bisected by the Eastern African Rift. Ten volcanic mountains rise to altitudes of just over 4000 m, but on only three has Quaternary glaciation been substantiated by published field observations. On the Bale Mountains (4400 m), a previous report based on limited evidence proposed an ice‐cap extending to 600 km2. Based on aerial photographs and ground surveys, this paper reports evidence of a more complex situation. A wide spread of large erratic boulders on the plateau records a central ice cap of 30 km2, though ice probably extended for a further 40 km2. Further north two groups of deeply incised and clearly glaciated valleys contain moraines and roches moutonnées (60 km2). On interfluves between them and on the open north slopes are moraines from an earlier stage of the same glaciation or from a distinct older event. Altogether about 180 km2 may have been glaciated. Cores dated by 14C from inside and outside the glaciated area suggest that at least the northern valley glaciers may date from the Last Glacial Maximum. Estimated equilibrium line altitudes for these glaciers and the ice‐cap are 3750–4230 m. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
12.
Between 1985 and 1991, two new mountain protected areas (MTNPA) covering more than 35,000 km2 and based on participatory management models — the Makalu-Barun National Park and Conservation Area, Nepal, and Qomolangma Nature Preserve, Tibet Autonomous Region — were successfully established through the collaborative efforts of Woodlands Mountain Institute and conservationists in China and Nepal. Characteristics common to both projects include the importance of establishing (1) effective rationales, (2) local support constituencies, (3) a senior advisory group, (4) a task force, (5) linkages between conservation and development, and (6) fund raising mechanisms. The lessons derived from the experiences of Woodlands Mountain Institute are of significant value to others in preserving MTNPA. Increased collaboration and communication between all interested in conservation, however, will remain a critical component for expanding mountain protected area coverage to throughout the world. 相似文献
13.
高顶山矿区位于广安华蓥市城区东南约5km处。长期的采矿活动,导致区内矿山地质环境问题突出,严重影响华蓥山地区人民的生命财产安全。矿山地质环境问题亟待解决。本文通过分析区内主要存在的矿山地质环境问题,提出通过矿山地质灾害、矿山土地恢复、矿山地形地貌景观恢复治理,河道综合整治、道路修复、生态保育、产业提升等措施;消除安全隐患,保障区内人民生命财产安全;改善生态环境,实现华蓥山地区生态环境全面恢复,生态环境质量提升,提高环境承载力,实现区内"山青、水秀、林美、田良"的目标。并对区内的产业转型升级进行了探讨,提出将高顶山矿区建设成具有科普和教育价值的旅游景观目的地;利用矿区独具特色工业人文景观和别致的自然景观,将高顶山矿区建设成集"科普、休闲、康养、户外、探秘"五大功能于一体的矿山公园,推动矿业经济转型升级,促进产业结构转型和经济社会可持续发展。 相似文献
14.
This study examines the groundwater characteristics in the Silver Bell Mountains, Arizona, USA, using a numerical model. Groundwater modeling is developed to describe the flow pattern in the study area and subsequently explores the possible interaction with regional porphyry copper deposits. A conceptual model is developed for the study area and regional hydrogeological conditions are simulated using the finite-difference groundwater flow model, MODFLOW-2005. The model results show that groundwater flow in the Silver Bell Mountains is strongly influenced by topography and its velocity varies with depth. In addition, the numerical model supports the idea of a continuous sustained interaction between groundwater flow and porphyry copper deposits in the Silver Bell Mountains. This interaction may result in continuing leaching of trace elements from the ore deposit, an important implication for continuing supergene alteration and enrichment of the porphyry copper deposit. 相似文献
15.
The Caribou Mountain pluton is a small trondhjemitic body thatintruded semipelitic schist of the Stuart Fork terrane in lateMiddle Jurassic to Early Cretaceous time. Its emplacement followedthe intrusion of an adjoining body of hornblende quartz dioritecalled the Middle Fork pluton and the mode of its emplacementwas as an asymmetric ballooning diapir (Davis, 1963), as shownby concentric foliation, radial late-stage dikes, foliated enclaves,and folded blocks of schlieren-banded tonalite. Coarse-grainedhornblende-bearing trondhjemite is the dominant rock type inthe Caribou Mountain pluton, and it is called the ‘maintrondhjemite’. It was followed by medium-grained ‘latetrondhjemite’ and by late-stage trondhjemitic and granodioriticdikes. All the trondhjemitic rock types are characterized bylow alkali contents, high light rare earth elements, low initial87Sr/86Sr, and low 18O. However, the late trondhjemite has higherNa2O and a higher initial 87Sr/86Sr value than the main trondhjemite,and the two units cannot be related by fractional crystallization.The late granodioritic dikes are richer in Ba, Rb, Y, and Scthan the late trondhjemite and probably reflect assimilationof Stuart Fork metasedimentary rocks by late-stage trondhjemiticmagma. Mafic enclaves in the main trondhjemite contain xenocrysts ofquartz and plagioclase derived from the host by magma mixing.The enclaves have K2O, Ba, and Rb contents similar to, or higherthan those of the host rocks. Their rare earth element (REE)patterns display strong middle REE enrichment caused by accumulationof hornblende, probably as the result of filter pressing. The main trondhjemite cannot be derived from Middle Fork magmabecause the initial 87Sr/86Sr of the Middle Fork pluton is lowerthan that of the trondhjemite. The absence of parental maficmagmas of appropriate composition suggests that the CaribouMountain trondhjemitic magmas formed by partial melting of anamphibolitic source rock compositionally similar to low-K tholeiite. 相似文献
16.
Two distinct crustal provinces have been identified in the southern mid-continent based on U–Pb crystallization ages. Both
contain large volumes of undeformed granite and rhyolite, with minor amounts of metamorphic rock and mafic intrusions. The
Eastern Granite-Rhyolite province is characterized by felsic rocks with crystallization ages of 1,470 ± 30 Ma and exposures
are restricted to the St. Francois Mountains in southeastern Missouri. Similarly, the Southern Granite-Rhyolite (SGR) province
is characterized by felsic units with ages of 1,370 ± 30 Ma with primary exposures in the eastern Arbuckle Mountains of southern
Oklahoma. Within the SGR province three magmatic pulses can be identified starting at 1,400, 1,370, and 1,340 Ma. Although
the crystallization ages are different, the Sm–Nd isotopic signatures are similar for the units exposed in these areas as
well as the buried basement in between. Depleted mantle model ages for rocks within the Arbuckle Mountains range from 1,530
to 1,430 Ma with ɛNd(t) values of +3.2 to +4.1 while units of the St. Francois Mountains range from 1,550 to 1,430 Ma and +4.5 to +4.7. Comparison
of Sm–Nd isotopic data also indicate similarities between the 147Sm/144Nd and 143Nd/144Nd ratios for the rock units in these areas suggesting a common source. 相似文献
17.
Slope deposits in the Snowy Mountains of south-eastern Australia have a wide distribution above 1000 m elevation on slopes between approximately 5° and 25° which are well stabilized by the existing forest vegetation. The present environment is not severe enough to initiate slope instability. 相似文献
18.
Geomorphological mapping revealed five terminal moraines in the central Verkhoyansk Mountains. The youngest terminal moraine (I) was formed at least 50 ka ago according to new IRSL (infrared optically stimulated luminescence) dates. Older terminal moraines in the western foreland of the mountains are much more extensive in size. Although the smallest of these older moraines, moraine II, has not been dated, moraine III is 80 to 90 ka, moraine IV is 100 to 120 ka, and the outermost moraine V was deposited around 135 ka. This glaciation history is comparable to that of the Barents and Kara ice sheet and partly to that of the Polar Ural Mountains regarding the timing of the glaciations. However, no glaciation occurred during the global last glacial maximum (MIS 2). Based on cirque orientation and different glacier extent on the eastern and western flanks of the Verkhoyansk Mountains, local glaciations are mainly controlled by moisture transport from the west across the Eurasian continent. Thus glaciations in the Verkhoyansk Mountains not only express local climate changes but also are strongly influenced by the extent of the Eurasian ice sheets. 相似文献
19.
ZYGMUNT BABIÑSKI 《Boreas: An International Journal of Quaternary Research》1982,11(4):291-298
On the basis of permafrost characteristics and summer degradation in the Bayan-Nuurin-Khotnor Basin in Mongolia the processes of pingo degradation are presented and discussed. Differentiation between these processes is interpreted to be associated mainly with the thermal influence of waters, e.g. with thermokarst phenomena and thermal erosion of artesian and river waters. The direct heating influence of solar radiation as well as littoral abrasion in pingo lakes seem to have subordinate significance. 相似文献
20.
The Cantabrian Mountains, containing about 70% of the total coals of the country and 95% of the anthracitic and bituminous resources, is the most important coal-mining district of Spain. Coal-bearing successions are Late Carboniferous in age and their deposition took place in a syn-orogenic context during the Hercynian activity, mainly in three different time-successive locations: foreland basins, intrathrust basins and intramontane fault-controlled basins. Foreland deposition occurred in strongly asymmetrical basins located ahead of thrust sheets units. Intrathrust basins resulted from folding and tightening of these units during or after their emplacement. Intramontane and fault-controlled basins were developed along lineaments with strike-slip movements and as a result of fold and fault reactivation. Peat mires in foreland and intrathrust coal basins mainly occupied broad areas on abandoned delta and fan delta lobes. Coals in intramontane and fault-controlled basins were related with alluvial fan and lacustrine environments. Coal ranks vary from high volatile bituminous coals to anthracite, depending on the structural location of the coalfields. Hydrothermal activity seems to be the most important factor in coal evolution. 相似文献