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221.
222.
晚新生代温泉沉积盆地,是青藏高原腹地在南北向挤压、东西向伸展的构造背景下,沿南北向边界走滑断层,经边界正断层和内部张剪断层的进一步发展而形成的近南北向单断单剪楔形半地堑活动沉积盆地。它可能代表了晚新生代青藏高原第三期强烈挤压隆升事件,是侧向向东剪切挤出的结果。笔者以盆地充填序列和TL、ESR测年资料为主要依据,推测唐古拉山在30 0~2 5 0ka前后全面进入冰冻圈;而以温泉活动沉积盆地为代表的中更新世晚期(2 2 4 .0~1 5 0 .2ka)的冰碛 冰水堆积则对应于青藏高原第三期隆升的断陷盆地发育阶段;中更新世晚期—晚更新世中期(1 4 4 .0~5 6ka)为湖相沉积;晚更新世中期至今(35~0ka)对应于高原缓慢隆升与夷平发育阶段。长江溯源在35ka切割通天河盆地,形成通天河;而在1 6ka侵蚀切穿雁石坪 温泉兵站峡谷,形成布曲河。 相似文献
223.
GaoYongqun YangFengqing PengYuanqiao 《中国地质大学学报(英文版)》2005,16(1):1-10
INTRODUCTIONThe Shaiwa Section is located in the town ofSidazhai, Ziyun County, Guizhou Province, south western China ( Fig. 1 ). This area belongs to theNanpanjiang basin of the Yangtze platform. A greatdeal of work purely on the subdivision of the stratahas been carried out in this region (Guizhou Bureauof Geology and Mineral Resources, 1987). However,studies on recoveries of the paleoenvironments of thisarea are rarely reported. Due to rifting and su… 相似文献
224.
Analysis of rock structure stability in coal mines 总被引:1,自引:0,他引:1
In this paper, the theory of limit point instability is used to analyse the stability of rock structures in coal mines. A general method of analysing stability of rock structures is put forward and a uniform instability condition of rock structures is set up. Some instability phenomena, such as rock bursts in circular roadways, pillars and long walls, and the outburst of coal and gas from circular roadways, are discussed analytically. At a later stage, the critical point of rock structure instability is determined. The influence of relative parameters (such as the mechanical properties of rock, coal, and the geometric sizes) on the stability of the rock structures is carefully analysed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
225.
三江并流世界自然遗产地丰富独特的旅游地质景观是多种地质作用与不同成景岩组交互叠加作用的结果。其发育的地层基础主要为碳酸盐成景岩组、变质岩成景岩组、碎屑岩成景岩组以及岩浆岩成景岩组等,典型内力成景地质作用为板块缝合作用、断裂成景作用、变质成景作用,外力作用则主要有河流、冰川、丹霞、地热、喀斯特作用等。 相似文献
226.
GPS Solutions - The GPS satellite transmitter antenna phase center offsets (PCOs) can be estimated in a global adjustment by constraining the ground station coordinates to the current International... 相似文献
227.
228.
New magnetostratigraphic and pedostratigraphic investigations of loess deposits in north‐east China and their implications for regional environmental change during the Mid‐Pleistocene climatic transition
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229.
Fan Yuxin Li Zhenjun Yang Guangliang Yi Shuangwen Zhang Qingsong Liu Wenhao Mou Xuesong 《第四纪科学杂志》2020,35(8):994-1006
The timing of high lake-level stands during the Late Pleistocene in western China remains controversial. Here we report new results from Megalake Tengger based on a study of palaeo-shorelines and a drill core from Baijian Lake in the northwestern Tengger Desert. Multiple dating methods, based on luminescence signals (quartz optically stimulated luminescence, K-feldspar post infrared-infrared stimulated luminescence) and electron spin resonance signals of quartz, were used to date beach sands from palaeo-shoreline profiles at altitudes of ~1310 m (+20 m above lake level), ~1320 m (+30 m) and ~1350 m (+60 m), and from the top 20 m of sandy sediments from the drill core obtained from the modern beach of Baijian Lake. The dating results show that high lake-level stands associated with the previously reported Megalake Tengger (~1310–1320 m) occurred during the late Early to Middle Pleistocene, which is much earlier than previously reported. In addition, no geomorphological evidence of shorelines and sedimentary evidence from the drill core profile were found to support the previously reported Late Pleistocene lake levels. Our results indicate that the exact age of the previously reported ‘high lake level event’ in a large part of northwestern China during the Late Pleistocene needs to be re-evaluated. 相似文献
230.
Influence of a coarse interlayer on seawater intrusion and contaminant migration in coastal aquifers
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Vertical 2D slice laboratory experiments were carried out in homogenous and layered sand tanks to elucidate the effects of a highly permeable (coarse‐grained sand) interlayer on seawater intrusion and transport of contaminants to a coastal sea. Tidal fluctuations produced oscillations in the seawater–freshwater transition zone, fluctuations of the contaminant infiltration rate and a zigzag contaminant plume outline. The seawater wedge became discontinuous at the (vertical) edges of the interlayer because of increased lateral movement of the seawater–freshwater interface within the interlayer. The contaminant plume formed a tail within the interlayer depending on the tidal stage, and similar to the wedge, its movement was accentuated. A simple analytical model that neglected vertical flow reliably predicted steady‐state seawater intrusion into the coastal aquifer. Numerical modeling was used to gain insight into the groundwater hydrodynamics and contaminant migration. The numerical results confirmed the experimental findings, i.e. that a highly permeable interlayer can provide a rapid transit path for contaminants to reach the seaward boundary and that the interlayer amplifies the effects of tidal fluctuations, resulting in wider transition zones for the seawater wedge and contaminant plume. Numerical simulations further showed that, with increasing interlayer hydraulic conductivity, the maximum seawater intrusion distance inside the interlayer increases approximately linearly. For the fixed‐head contaminant injection condition used, the model showed that contaminant infiltration increases approximately logarithmically with increasing interlayer hydraulic conductivity (other factors held fixed). Copyright © 2013 John Wiley & Sons, Ltd. 相似文献