Palynological Evidence of Late Pleistocene Soft-sediment Deformation Event in the Northeastern Margin of the Tibetan Plateau     

WEI Lijie  LI Zhenhong  DONG Xiaopeng  CUI Jiawei  HUANG Ting  KOU Linlin 《《地质学报》英文版》2023,97(3):841-854

The northeastern margin of the Tibetan Plateau is the youngest part of the Tibetan Plateau where tectonic activity is intense and climate change is complex. In this study, combined with field investigations, we explored accelerator mass spectrometry 14C and optically stimulated luminescence dating and palynological analysis of the sedimentary sequence in the Qingshuihe Basin to explain the origin of soft-sediment deformation layer. Dating and palynological results from the Sanchahe section in th...  相似文献   

碧口地块东-北缘中、新生代构造隆升及演化：来自磷灰石和锆石裂变径迹的证据     

金文正  白万奎  叶治续 《江苏地质》2023,47(3):231-241

青藏高原具有复杂的构造演化特征,该地区自中、新生代以来的构造隆升和构造演化机制一直是地质研究的热点。为精细刻画青藏高原板块、华北板块和华南板块之间的拼合关系及差异性隆升特征,对位于青藏高原东北端的碧口地块进行了磷灰石和锆石裂变径迹测试,以及热史模拟和岩石冷却速率计算。结果锆石和磷灰石裂变径迹年龄分别在（118±5～265±29）Ma和（29.0±2.7～54.0±7.0）Ma之间;碧口地块东北缘及北缘冷却速率接近,在3.125～3.448 ℃/Ma之间,东缘冷却速率相对较低,为2.041～2.273 ℃/Ma。结果表明,中、新生代以来,碧口地块及其周缘总体上经历了持续隆升过程,但不同地区隆升特征具有差异性：碧口地块北侧在早、中侏罗世（151±7）Ma经历了构造挤压和隆升过程;东部相对较晚,在晚侏罗世（143±11）Ma经历了构造隆升阶段;东北端在早白垩世才与华北板块拼接并进入持续构造隆升阶段。进入古近纪（54.0±7.0）Ma隆升阶段,即始新世早期后,碧口地块东缘在始新世中后期（44 Ma）开始发生构造隆升,北缘自渐新世中晚期（29～32 Ma）开始发生显著的构造隆升。上述区域在10 Ma（中新世晚期）共同进入快速隆升阶段。  相似文献   

Potential seismic landslide hazard and engineering effect in the Ya’an-Linzhi section of the Sichuan-Tibet transportation corridor,China     

《China Geology》2023,6(2):228-240

The Sichuan-Tibet transportation corridor is located at the eastern margin of the Qinghai-Tibet Plateau, where the complex topography and geological conditions, developed geo-hazards have severely restricted the planning and construction of major projects. For the long-term prevention and early control of regional seismic landslides, based on analyzing seismic landslide characteristics, the Newmark model was used to carry out the potential seismic landslide hazard assessment with a 50-year beyond probability 10%. The results show that the high seismic landslide hazard is mainly distributed along large active tectonic belts and deep-cut river canyons, and are significantly affected by the active tectonics. The low seismic landslide hazard is mainly distributed in the flat terrain such as the Quaternary basins, broad river valleys, and plateau planation planes. The major east-west linear projects mainly pass through five areas with high seismic landslide hazard: Luding-Kangding section, Yajiang-Xinlong (Yalong river) section, Batang-Baiyu (Jinsha river) section, Basu (Nujiang river) section, and Bomi-Linzhi (eastern Himalaya syntaxis) section. The seismic action of the Bomi-Linzhi section can also induce high-risk geo-hazard chains such as the high-level glacial lake breaks and glacial debris flows. The early prevention of seismic landslides should be strengthened in the areas with high seismic landslide hazard.©2023 China Geology Editorial Office.  相似文献   

Mapping degraded grassland on the Eastern Tibetan Plateau with multi-temporal Landsat 8 data — where do the severely degraded areas occur?     

《International Journal of Applied Earth Observation and Geoinformation》2015

The Tibetan Plateau in Western China is the world’s largest alpine landscape, sheltering a rich diversity of native flora and fauna. In the past few decades, the Tibetan Plateau was found to suffer from grassland degradation processes. Grassland degradation is assumed to not only endanger biodiversity but also to increase the risk for natural hazards in other parts of the country which are ecologically and hydrologically connected to the area. However, the mechanisms behind the degradation processes remain poorly understood due to scarce baseline data and insufficient scientific research.We argue that remote sensing data can help to better understand degradation processes and patterns by: (1) identifying the distribution of severely degraded areas and (2) comparing the patterns of key spatial attributes of the identified areas (altitude above sea level, aspect, slope, administrative districts) with existing theories on degradation drivers. Therefore, we applied four Landsat 8 images covering large portions of the three counties Jigzhi, Baima and Darlag in the Eastern Tibetan Plateau. The dates of the Landsat scenes were selected to cover differing phenological stages of the ecosystem. Reference data were collected with a remotely piloted aircraft and a standard consumer RGB camera. To exploit the phenological information in the Landsat data as well as deal with the problem of cloud cover in multiple images, we developed a straightforward PCA-based procedure to merge the Landsat scenes. The merged Landsat data served as input to a supervised support vector machine classification which was validated with an iterative bootstrap procedure and an additional independent validation set. The considered classes were “high-cover grassland”, “grassland (including several stages of grassland vitality)”, “(severely) degraded grassland”, “green shrubland”, “grey shrubland”, “urban areas” and “water bodies”. Kappa accuracies ranged between 0.84 and 0.93 in the iterative procedure, while the independent validation led to a kappa accuracy of 0.76. Mean producer’s and user’s accuracies for all classes were higher than 80%, and confusion mainly occurred between the two shrubland classes and between the three grassland classes.Analysis of the slope, aspect and altitude values of the vegetation classes revealed that the degraded areas mostly occurred at the higher altitudes of the study area (4300–4600 m), with no strong connection to any specific slope or aspect. High-cover grassland was mostly located on sunny slopes at lower altitudes (less than 4300 m), while shrubland preferred shady, relatively steep slopes across all altitudes. These observations proved to be stable across the examined counties, while the proportions of land-cover classes differed between the examined regions. Most counties showed 5–7% severely degraded land cover. Darlag, the county located at the edge of the permafrost zone, and featuring the highest average altitude and lowest annual temperature and precipitation, was found to suffer from larger areas of severe degradation (14%).Therefore, our findings support a strong connection between degradation patterns and climatic as well as altitudinal gradients, with an increased degradation risk for high altitude areas and areas in colder and drier climatic zones. This is relevant information for pastoral management to avoid further degradation of high altitude pastures.  相似文献   

大光斑波形数据在土地覆盖分类的适用性分析     

马利群  李理  刘俊杰  孙九林  秦奋 《测绘科学》2021,46(3):80-86,95

针对GLAS地学激光测高系统是冰、云和陆地高程卫星(ICESat)的唯一监测工具,能够记录地表光斑内的地物信息,是否能应用于黄土高原土地覆盖分类的问题进行了研究。利用粒子群和最小二乘法相结合的方法对GLAS波形数据进行高斯分解,获取高斯波个数、波形总能量、波形信号起始和信号结束位置4个波形参数;基于波形自动分类方法对黄土高原水体、森林、城市用地、其他地类(裸地、低矮植被等)进行分类。通过基于覆盖相同研究区域的30 m地表覆盖数据(Globe Land30),验证分类的准确性。结果表明,GLAS大光斑波形数据对黄土高原的4种地类能够很好地进行区分,总分类精度高达87.68%,Kappa系数为65.79%。研究表明,GLAS波形数据可以作为获取土地覆盖信息的有效数据源,为研究黄土高原土地覆盖变化提供更丰富的数据支持。  相似文献   

GRACE时变重力数据后处理方法评价     

姜永涛  王丽美  郭广猛  张子月  杨杰 《测绘科学》2021,46(3):21-26

针对GRACE Level2卫星时变重力数据后处理方法如何评价的问题,该文以中国数字地震观测网络获得的青藏高原地区地面重力变化图像为参考,基于平均结构相似性等图像相似度指标,研究了与该区域地面重力观测同期、不同后处理方法得到的GRACE卫星重力变化图像的可靠性。结果显示,GRACE卫星重力和地面重力观测结果具有一定的可比性,滑动窗口去相关滤波和高斯400 km滤波的组合方法可以获得最优的处理效果。本文的方法和结论对GRACE及GRACE Follow-On卫星重力数据应用中后处理方法和参数的选取有一定的借鉴意义。  相似文献   

青藏高原地区大气加权平均温度模型的构建     

石灵璠  王萍  黄良珂 《测绘通报》2021,(4):52-59

加权平均温度（T_m）是将天顶湿延迟转换为大气可降水量的关键参数,针对青藏高原地区海拔高、地形起伏大、水汽高度分布复杂的特点,本文利用2010—2014年GGOS Atmosphere T_m格网数据和地表高程数据建立T_m垂直递减率函数,进而建立一种顾及T_m垂直递减率变化的适合青藏高原地区的新模型（QTm模型）。此外,利用2015年青藏高原地区14个探空站和GGOS Atmosphere T_m格网数据评估模型精度和适用性。试验结果表明,与GGOS Atmosphere T_m相比,QTm模型的年均Bias和RMSE分别为0.29和2.49 K,相对于GPT2w-1和GPT2w-5模型,RMSE分别提升了38.97%、67.06%;与探空数据相比,QTm模型的年均Bias和RMSE分别为0.16和2.90 K,相对于GPT2w-1和GPT2w-5模型分别提升了31.12%、39.46%。新模型的构建为青藏高原地区提供了可靠的T_m值,进而提供实时、高精度GNSS水汽信息。  相似文献   

2000年以来青藏高原湖泊面积变化与气候要素的响应关系   总被引：1，自引：0，他引：1  

闾利  张廷斌  易桂花  苗加庆  李景吉  别小娟  黄祥麟 《湖泊科学》2019,31(2):573-589

青藏高原星罗密布的湖泊对气候变化十分敏感，在自然界水循环和水平衡中发挥着重要作用.以MODIS MOD09A1和SRTM DEM为数据源，提取了2000-2016年青藏高原丰水期面积大于50 km²的湖泊边界，从内外流分区、湖泊主要补给来源和湖水矿化度三个方面对2000年以来湖泊面积变化进行分析，并结合青藏高原近36年气象数据，根据气象要素变化趋势分区，初步探讨青藏高原湖泊面积变化与气候要素的关系.结果表明：青藏高原面积大于50 km²的138个湖泊整体扩张趋势显著，总面积增加2340.67 km²，增长率为235.52 km²/a.其中，扩张型湖泊占67.39%，萎缩型湖泊占12.32%，稳定型湖泊占20.29%.内流湖扩张趋势显著，外流湖扩张趋势较明显；以冰雪融水为主要补给来源的湖泊整体扩张趋势明显，以地表径流和河流补给为主要补给源的湖泊也呈扩张趋势；盐湖和咸水湖以扩张为主，淡水湖的扩张、萎缩和稳定三种类型较均衡.在青藏高原气候暖湿化方向发展背景下，湖泊面积变化与气候要素具有显著的区域相关性.气温和降水变化趋势分区结果表明，气温增加、降水增加强趋势的高原Ⅰ区湖泊扩张程度（78.18%）依次大于气温降低、降水量呈增加趋势的Ⅴ区（66.67%），气温、降水量呈增加趋势的Ⅱ区（60.78%），气温呈降低、降水量呈增加强趋势的Ⅳ区（58.83%）和气温呈增加、降水量呈减少趋势的Ⅲ区（50.00%）.湖泊面积变化对气候变化响应研究表明，升温引起的冰雪融水补给对Ⅰ区、Ⅱ区和Ⅲ区湖泊面积扩张的影响显著，加之降水量的增加，湖泊扩张速率明显；Ⅳ区和Ⅴ区湖泊面积扩张主要受降水量增加影响显著.整体而言，气温主要影响以冰雪融水为主要补给来源的湖泊，降水量主要影响以降水和地表径流为主要补给来源的湖泊.  相似文献   

1976-2016年青藏高原地区通达性空间格局演变   总被引：1，自引：0，他引：1  

高兴川  曹小曙  李涛  吕敏娟 《地理学报》2019,74(6):1190-1204

青藏高原地区是地球上最独特的地理—生态—人口—交通单元,区域内交通网络的发展特征及规律是人地关系协同发展的一个重要切入点,对青藏高原地区交通网络开展研究具有重要意义。据此,分析1976-2016年青藏高原地区交通网络演化特征,并以省会、地级市、县级市和县城为节点,采用网络分析的时间距离计算模型探讨其通达性演变过程。研究表明：① 青藏高原地区交通网络复杂性、区域连通性增强,初步形成格状交通网络;② 青藏高原地区中心城市、县城之间的平均最短通达时间已极大缩短至11.89 h、18.84 h,呈自东向西逐渐增大的空间格局,时空收敛效应显著,通达性变化程度与其初始值有关;③ 中心城市为该地区的发展极,其与周围城市通达状况有极大提高,可达时间平均值下降到16.49 h;④ 中心城市和县城交通圈演变过程一致,青藏高原地区各地到最近城市、县城的通达时间不断缩小,沿重要交通干线已形成中心城市4 h、县城2 h短时交通圈连片分布格局,湟水河谷地、一江两河地区逐渐形成交通廊道,乡镇对外交通联系得到改善。  相似文献   

Trends and risk evolution of drought disasters in Tibet Region,China     

Chen  Qiong  Liu  Fenggui  Chen  Ruijie  Zhao  Zhilong  Zhang  Yili  Cui  Peng  Zheng  Du 《地理学报(英文版)》2019,29(11):1859-1875

Journal of Geographical Sciences - The risk posed by natural disasters can be largely reflected by hazard and vulnerability. The analysis of long-term hazard series can reveal the mechanisms by...  相似文献