喀喇昆仑断裂北段晚第四纪活动特征及其构造意义     

赵一霖  刘健  姜科庆  祝明伟 《地球学报》2019,40(4):601-613

右旋走滑的喀喇昆仑断裂(KK F)作为青藏高原的西部边界, 在印度板块与欧亚板块碰撞引起的陆内变形过程中扮演了重要的角色。近年来KK F北段全新世以来的活动特征存在争议。通过遥感解译和野外观测, 在喀喇昆仑断裂(KK F)的北段——新疆卡拉苏地区, 对KK F及其两条分支断裂的几何学、运动学进行了研究, 获得了现今发育的冰水扇被右旋错断和冰水扇上分布羽列式T张破裂等指示KK F右旋走滑的证据。采集了KK F控制的浅冰水湖相沉积中贝壳的AMS 14C样品, 获得年龄分别为(5.20±0.03) ka、(5.61±0.03) ka 和(9.95±0.04) ka。表明KK F北段晚全新世以来仍在活动, 其右旋走滑速率约为3.7 mm/a, 累计垂向滑移速率约为1.7 mm/a。据前人在KK F中部的研究成果, 推测KK F北段在卡拉苏地区由南东往北西右旋走滑速率有增大的趋势。  相似文献   

Character and origin of De Geer moraines in the Seacoast region of New Hampshire,USA          下载免费PDF全文

Samantha N. Sinclair  Joseph M. Licciardi  Seth W. Campbell  Brian M. Madore 《第四纪科学杂志》2018,33(2):225-237

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基于VAP卫星的等离子体层顶电子密度波动统计分析          下载免费PDF全文

王玉尤婷  张效信  何飞  林瑞淋  吕景天 《地球物理学报》2020,63(6):2141-2148

基于范艾伦辐射带探测卫星的观测数据(2012年9月至2015年11月),收集了584个等离子体层顶密度波动事件,研究了这些事件分布随磁地方时、磁壳值以及地磁活动的变化关系,并使用快速傅里叶变换分析了全部事件平均功率谱.统计结果表明,等离子体层顶密度波动事件主要发生在磁地方时黄昏扇区,其分布与磁地方时和地磁活动具有明显的相关性.等离子体层顶密度波动在1～100mHz区间内具有接近-5/3的功率谱斜率,表明存在二维磁流体动力学湍流.本文统计结果将有助于进一步深入理解等离子体层顶密度波动在内磁层中能量传输的具体作用,并且将促进对等离子体层顶波动的激发、增强与传播过程的进一步研究.  相似文献   

High‐resolution bathymetric mapping reveals subaqueous glacial landforms in the Arctic alpine lake Tarfala,Sweden     

Nina Kirchner  Riko Noormets  Jakob Kuttenkeuler  Elias Strandell Erstorp  Erik Schytt Holmlund  Gunhild Rosqvist  Per Holmlund  Marika Wennbom  Torbjrn Karlin 《第四纪科学杂志》2019,34(6):452-462

In Arctic alpine regions, glacio‐lacustrine environments respond sensitively to variations in climate conditions, impacting, for example,glacier extent and rendering former ice‐contact lakes into ice distal lakes and vice versa. Lakefloors may hold morphological records of past glacier extent, but remoteness and long periods of ice cover on such lakes make acquisition of high‐resolution bathymetric datasets challenging. Lake Tarfala and Kebnepakte Glacier, located in the Kebnekaise mountains, northern Sweden, comprise a small, dynamic glacio‐lacustrine system holding a climate archive that is not well studied. Using an autonomous surface vessel, a high‐resolution bathymetric dataset for Lake Tarfala was acquired in 2016, from which previously undiscovered end moraines and a potential grounding line feature were identified. For Kebnepakte Glacier, structure‐from‐motion photogrammetry was used to reconstruct its shape from photographs taken in 1910 and 1945. Combining these methods connects the glacial landform record identified at the lakefloor with the centennial‐scale dynamic behaviour of Kebnepakte Glacier. During its maximum 20^th century extent, attained c. 1910, Kebnepakte Glacier reached far into Lake Tarfala, but had retreated onto land by 1945, at an average of 7.9 m year^–1. Copyright © 2019 John Wiley & Sons, Ltd.  相似文献   

1990—2018年中巴经济走廊冰湖时空变化特征     

姚超  王欣  赵轩茹  魏俊锋  张勇 《冰川冻土》2020,42(1):33-42

中巴经济走廊是贯通南北丝路的关键枢纽。在全球变暖的背景下， 区域内冰川变化情况复杂， 部分冰川出现前进或跃动现象， 冰湖溃决的风险在不断上升， 进而威胁中巴经济走廊的建设与民生安全。基于1990—2018年Landsat TM/ETM+/OLI遥感影像， 利用目视解译方法提取了中巴经济走廊3期冰湖编目数据， 并分析了28年来该区域内冰湖的总体变化趋势、 空间异质性以及成因。结果表明： 中巴经济走廊目前共发育有2 380个冰湖， 总面积为（131.76±19.08） km²， 集中分布于喀喇昆仑山脉和喜马拉雅山脉； 1990—2018年期间， 冰湖总体面积扩张速度为0.48%·a^-1， 但各个山脉不同规模冰湖面积变化差异较大。中巴经济走廊在气温和降水的共同作用下， 区内冰湖面积呈扩张趋势， 同时气温和降水变化率的空间差异使得冰湖面积变化存在空间差异； 冰川的快速退缩增加了区内冰湖溃决的风险。  相似文献   

Paired 10Be sampling of polished bedrock and erratic boulders to improve dating of glacial landforms: an example from the Western Alps     

Charlotte Prud'homme  Riccardo Vassallo  Christian Crouzet  Julien Carcaillet  Jean-Louis Mugnier  Joaquin Cortés-Aranda 《地球表面变化过程与地形》2020,45(5):1168-1180

Cosmogenic nuclide dating of glacial landforms may lead to ambiguous results for ice retreat histories. The persistence of significant cosmogenic concentrations inherited from previous exposure may increase the apparent exposure ages for polished bedrocks affected by limited erosion under ice and for erratic boulders transported by glaciers and previously exposed in high-altitude rock walls. In contrast, transient burying by moraines, sediments and snow decreases the apparent exposure age. We propose a new sampling strategy, applied to four sites distributed in the Arc and Arve valleys in the Western Alps, to better constrain the factors that can bias exposure ages associated with glacial processes. We used the terrestrial cosmogenic nuclide ¹⁰Be (TCN) to estimate the exposure time from paired sampling of depth profiles in polished bedrock and on overlying erratic boulders. For a given sampling site, the exposure ages for both the polished bedrock and boulder are expected to be the same. However, in six cases out of seven, boulders had significantly higher ¹⁰Be surface concentrations than those of the associated polished surfaces. In present and past glacial processes, the ¹⁰Be distribution with depth for boulders and bedrocks implies the presence of an inheritance concentration of ¹⁰Be. Our study suggests that ¹⁰Be concentrations in erratic boulders and in polished bedrocks provide maximum and minimum exposure ages of the glacial retreat, respectively. © 2019 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Classification of glacial lakes using integrated approach of DFPS technique and gradient analysis using Sentinel 2A data     

Prateek Verma  Sanjay Kumar Ghosh 《国际地球制图》2019,34(10):1075-1088

It is important to identify and locate glacial lakes for assessing any potential hazard. This study presents a combination of semi-automatic method Double-Window Flexible Pace Search (DFPS) and edge detection technique to identify glacial lakes using Sentinel 2A satellite data. Initially, Normalized Difference Water Index (NDWI) has been used to identify water and non-water areas, while DFPS and Edge detection technique has been used to identify an optimum threshold value to distinguish between water and shadow areas. The optimal threshold from DFPS process is 0.21, while threshold value of gradient magnitude using edge detection process is 0.318. The number of glacial lakes identified using the above algorithm is in close agreement with previously published results on glacial lakes in Gangotri glacier using different techniques. Thus, a combination of DFPS and edge detection process has successfully segregated glacial lakes from other features present in Gangotri glacier.  相似文献   

1959-2017年天山乌鲁木齐河源1号冰川流域径流及其组分变化   总被引：1，自引：1，他引：0  

贾玉峰  李忠勤  金爽  徐春海  张明军  邓海军  梁鹏斌  刘爽爽 《冰川冻土》2019,41(6):1302-1312

冰川是气候变化的指示器，气候变化对冰川及其径流的影响研究是目前国内外关注的热点和前沿领域之一，目前的研究以模拟为主，实测资料十分有限且不确定性很大。以新疆天山乌鲁木齐河源1号冰川（简称“1号冰川”）流域为例，基于中国科学院天山冰川观测试验站1959-2017年观测数据，研究了中国西部典型小型冰川流域径流及其组分长期变化以及对气候变化的响应，为冰川径流长期变化过程的认识提供重要参考。结果表明，1号冰川流域径流主要由冰川径流和非冰川区降水径流组成，分别占70%和30%。其中冰川径流又可分为冰川区降水径流和冰川融水径流，分别占44%和26%。59年间，冰川径流整体呈上升趋势，在1992年之后出现了一个阶梯式的上升，与气温升高和降水的增加有关，1997-2007年达到高峰，2008年以后出现波动下降趋势，其原因除了与该时段的降水有所减少有关之外，冰川面积减小的影响也不可忽视。另外，还利用实测径流和冰川物质平衡值，通过水量平衡模型，检验了模型使用的冰川区和非冰川区径流系数。  相似文献   

晚第四纪MIS6以来柴达木盆地成盐作用对冰期气候的响应   总被引：2，自引：0，他引：2  

陈安东  郑绵平  宋高  王学锋  李洪普  韩光  袁文虎 《地质论评》2020,66(3):611-624

气候是控制柴达木盆地盐类沉积的主要因素之一,但是其作用机制尚待明确。作者以柴达木盆地察汗斯拉图盐湖的3个含盐剖面为研究对象,采用多接收电感耦合等离子质谱(MC-ICP-MS)铀系测年测定其沉积时代,并通过X射线粉晶衍射(XRD)分析测定其盐类矿物种类。铀系测年显示D18剖面石盐和芒硝层的沉积时代为13.1±2.0 ka BP～15.9±2.5 ka BP,其中芒硝沉积年代属于末次冰期MIS2晚期;MXK2剖面芒硝层的沉积时代分别为131.7±39.5 ka BP和158.3±10.8 ka BP,D12剖面芒硝层的沉积时代分别为166.6±20.2 ka BP和198.0±20.6 ka BP,可以对应于倒数第二次冰期MIS6。XRD分析确定了3个剖面的盐类矿物主要为芒硝、石盐和石膏。综合多个盐湖晚第四纪成盐数据,本文认为倒数第二次冰期MIS6和末次冰期MIS2是柴达木盆地晚第四纪重要的成盐期,冰期的冷干气候有利于石盐和芒硝等盐类沉积。柴达木盆地"冰期成盐"的根本原因,是由于冰期环境下盆地周边山体冰川规模的扩张以及干冷的冰期气候,共同造成了盐湖补给水量的减少。此外,晚第四纪MIS6和MIS2的冰期降温也是导致盆地中冷相盐类沉积的直接原因。  相似文献   

Acceleration of vegetation dynamics in hydrologically connected wetlands caused by dam operation     

Lilin Zheng  Jinying Xu  Dandan Wang  Guoyu Xu  Zhiqiang Tan  Ligang Xu  Xiaolong Wang 《水文研究》2021,35(2):e14026

The dynamic responses of wetlands to upstream water conservancy projects are becoming increasingly crucial for watershed management. Poyang Lake is a dynamic wetland system of critical ecological importance and connected with the Yangtze river. However, in the context of disturbed water regime in Poyang Lake resulting from human activities and climate change, the responses of vegetation dynamics to the Three Gorges Dam (TGD) have not been investigated. We addressed this knowledge gap by using daily water level data and Landsat images from 1987 to 2018. Landsat images were acquired between October and December to ensure similar phenological conditions. Object-oriented Artificial Neural Network Regression for wetland classification was developed based on abundant training and validation samples. Interactions between vegetation coverage and water regimes pre and post the operation of the TGD were compared using classification and regression trees and the random forest model. Since the implementation of the TGD in 2003, Poyang Lake has become drier, especially during the dry season. A more rapid plant growth rate was observed post TGD (44.74 km² year⁻¹) compared to that of the entire study period (12.9 km² year⁻¹). Average water level for the antecedent 20 days most significantly affected vegetation before 2003, whereas average water level for the antecedent 5 or 10 days was more important after 2003. The impoundment of the TGD after the flood season accelerated the drawdown processes of Poyang Lake, and the rapidly exposed wetlands accelerated vegetation expansion during the dry seasons, resulting in shrinkage and degradation of the lake area. This study deepens our knowledge of the influences of newly developed dams on lakes and rivers.  相似文献