Autochthonous block fields in southern Norway: Implications for the geometry,thickness, and isostatic loading of the Late Weichselian Scandinavian ice sheet     

Atle Nesje  Svein Olaf Dahl 《第四纪科学杂志》1990,5(3):225-234

The consistent geographical and altitudinal distribution of autochthonous block fields (mantle of bedrock weathered in situ) and trimlines in southern Norway suggests a multi-domed and asymmetric Late Weichselian ice sheet. Low-gradient ice-sheet profiles in the southern Baltic region, in the North Sea, and along the outer fjord areas of southern Norway, are best explained by movement of ice on a bed of deforming sediment, although water lubricated sliding or a combination of the two, may not be excluded. The ice-thickness distribution of the Late Weichselian Scandinavian ice sheet is not in correspondence with the modern uplift pattern of Fennoscandia. Early Holocene crustal rebound was apparently determined by an exponential, glacio-isostatic rise. Later, however, crustal movements appear to have been dominated by large-scale tectonic uplift of the Fennoscandian Shield, centred on the Gulf of Bothnia, the region of maximum lithosphere thickness.  相似文献   

南祁连山前区中生代晚期古构造特征的研究     

肖安成  汪立群杨树锋  马立协沈中延  王亮  吴磊  陈元忠 《地质科学》2010,45(1):146-156

南祁连山前区可以分为露头和盆地区两个不同的大地构造单元,本区晚中生代构造活动强烈,控制了新生代的沉积过程和现今中生界残余层序的分布。本文提出了均匀平板状沉积体后期的构造变形可以利用古地质图以及高精度残余地层厚度的变化规律判断古构造带的分析方法,并且对于研究区中生代晚期的古构造特征进行了分析。露头区主要利用古地质图分析方法,研究区集中在赛什腾山-埃姆尼克山北缘的鱼卡和红山地区。盆地区主要利用中生界残余厚度图的分析方法,研究区集中在赛什腾山-埃姆尼克山南侧的赛什腾南部凹陷和马海凸起地区。通过这4个地区古构造特征的研究,提出南祁连山前区中生代晚期在区域性隆升的背景下,形成了一系列古构造带,古构造活动的特点是形成北西-北北西走向的背斜和向斜构造,这些褶皱的波长为15～20 km,为中尺度规模。同时指出,中国西部多数地区均缺失上白垩统,暗示着当时的中亚地区存在一个广阔的晚白垩世古高原。  相似文献   

滑动构造影响下煤层厚度与构造破碎带关系分析     

王德伟 《中国煤炭地质》2010,(3):4-7

徐庄滑动构造是河南省荥巩煤田主要构造之一,对区内二1煤层的赋存特征影响较大。经对大量计河井田勘查资料分析,发现滑动构造破碎带厚度与其下伏二1煤层厚度相关程度较高,表现为两者在中、浅部厚度变化大,并沿倾向呈薄、厚相间的条带状展布,大致在二1煤层-300m水平附近,滑动构造破碎带厚度变薄尖灭,煤层厚度亦相应变小且趋于稳定。通过对钻孔数据的回归分析,认为二1煤层厚度与其上滑动构造破碎带厚度呈正相关关系,这一结论对后期矿山开发中工作面的布置及做好安全防范措施有指导意义。  相似文献   

综合物探技术在煤系上覆薄硬岩矿区的应用初探——以山西潞安集团司马矿区为例   总被引：1，自引：0，他引：1  

郭粤莲  李宏  石君华  马瑞华 《中国煤炭地质》2010,(9):55-58

山西潞安集团司马矿区东高西低,西部延至长治盆地,矿区水系发育。主采3#煤层埋藏较浅,层位稳定。新生界不整合于下伏基岩之上,厚度变化较大,属典型的薄硬岩煤矿区。为准确提供矿区煤炭开采上限的地质依据,采用了综合勘探技术,其中利用三维地震勘探技术追踪新生界底面反射波及第四系"天窗"位置,利用直流电法与瞬变电磁法提供电性分层,并对其解释结果进行相互印证。勘探实例表明,三维地震勘探、电法勘探与钻探的综合运用不仅可解决薄硬岩煤矿区新生界厚度、含水层富水性及第四系缺失等问题,还可提供新生界含水层与基岩含水层之间的水力联系、制约因素等资料。  相似文献   

利用地震属性预测煤层厚度及古河流冲刷带的方法     

吴奕峰  孟凡彬 《中国煤炭地质》2010,(10):52-56

根据山西宁武煤田某煤矿2#煤层采掘及钻孔揭露情况,发现该井田中部和南部存在古河流冲刷带。通过对比基于优选的4个地震属性的四元一次、四元二次多项式回归模型与BP神经网络预测模型,决定将BP人工神经网络模型预测煤层厚度数据应用于整个测区古河流冲刷带的预判工作。首先利用GeoFrame系统和Landmark公司Poststack模块,提取2#煤层反射波的各类沿层切片,分析并圈定出2#煤层古河流冲刷带的大致范围,在此基础上,利用垂直时间剖面中2#煤层反射波的各种波形特征,进一步判别2#煤层古河流冲刷带解释的可靠性,然后结合BP神经网络预测模型获得的2#煤层厚度变化趋势图,最终解释出2#煤层古河流冲刷带范围:勘探区内2#煤层厚度变化范围0～5.3m,根据其煤层厚度变化趋势,将全区划分出一大二小3个古河流冲刷带。  相似文献   

Seasonal changes in sea ice conditions along the Northeast Passage in 2007 and 2012     

Lei Ruibo  Li Na  Li Chunhua  Jónsdóttir Ingibj?rg 《极地研究(英文版)》2014,(4)

Remote sensing data from passive microwave and satellite-based altimeters, associated with the data measured underway, were used to characterize seasonal and spatial changes in sea ice conditions along...  相似文献   

Thickness distribution and extent of sea ice and snow in Prydz Bay and surrounding waters observed in 2012/2013 austral summer     

CHENG Peng  HAN Hongwei  LEI Ruibo  LI Zhijun  LU Peng 《极地研究(英文版)》2014,(1):1-9

Three ship-based observational campaigns were conducted to survey sea ice and snow in Prydz Bay and the surrounding waters(64.40°S–69.40°S, 76.11°E–81.29°E) from 28 November 2012 to 3 February 2013. In this paper, we present the sea ice extent and its variation, and the ice and snow thickness distributions and their variations with time in the observed zone. In the pack ice zone, the southern edge of the pack ice changed little, whereas the northern edge retreated significantly during the two earlier observation periods. Compared with the pack ice, the fast ice exhibited a significantly slower variation in extent with its northernmost edge retreating southwards by 6.7 km at a rate of 0.37 km?d-1. Generally, ice showed an increment in thickness with increasing latitude from the end of November to the middle of December. Ice and snow thickness followed an approximate normal distribution during the two earlier observations(79.7±28.9 cm, 79.1±19.1 cm for ice thickness, and 11.6±6.1 cm, 9.6±3.4 cm for snow thickness, respectively), and the distribution tended to be more concentrated in mid-December than in late November. The expected value of ice thickness decreased by 0.6 cm, whereas that of snow thickness decreased by 2 cm from 28 November to 18 December 2012. Ice thickness distribution showed no obvious regularity between 31 January and 3 February, 2013.  相似文献   

基于卫星高度计的北极海冰厚度变化研究   总被引：5，自引：3，他引：2  

毕海波  黄海军  苏乔  严立文  刘艳霞  徐秀丽 《海洋学报(英文版)》2014,33(11):134-140

A modified algorithm taking into account the first year(FY) and multiyear(MY) ice densities is used to derive a sea ice thickness from freeboard measurements acquired by satellite altimetry ICESat(2003–2008). Estimates agree with various independent in situ measurements within 0.21 m. Both the fall and winter campaigns see a dramatic extent retreat of thicker MY ice that survives at least one summer melting season. There were strong seasonal and interannual variabilities with regard to the mean thickness. Seasonal increases of 0.53 m for FY the ice and 0.29 m for the MY ice between the autumn and the winter ICESat campaigns, roughly 4–5 month separation, were found. Interannually, the significant MY ice thickness declines over the consecutive four ICESat winter campaigns(2005–2008) leads to a pronounced thickness drop of 0.8 m in MY sea ice zones. No clear trend was identified from the averaged thickness of thinner, FY ice that emerges in autumn and winter and melts in summer. Uncertainty estimates for our calculated thickness, caused by the standard deviations of multiple input parameters including freeboard, ice density, snow density, snow depth, show large errors more than 0.5 m in thicker MY ice zones and relatively small standard deviations under 0.5 m elsewhere. Moreover, a sensitivity analysis is implemented to determine the separate impact on the thickness estimate in the dependence of an individual input variable as mentioned above. The results show systematic bias of the estimated ice thickness appears to be mainly caused by the variations of freeboard as well as the ice density whereas the snow density and depth brings about relatively insignificant errors.  相似文献   

江西会昌周田镇地面塌陷灾害CSAMT法勘查实例分析     

张焱孙 《江苏地质》2014,38(4):682-686

介绍了江西会昌县周田镇地面塌陷灾害物探CSAMT法勘查技术、资料分析、勘查成果及验证情况。对了解塌陷区盖层有效厚度、塌落现状、塌陷区后续具体治理方案及决策有十分重要的意义,对在类似地电条件下地质灾害物探勘查方法的选择、资料解释等具一定的借鉴意义。  相似文献   

西秦岭印支期高Sr/Y花岗岩类的成因及动力学背景——以同仁地区舍哈力吉岩体为例   总被引：5，自引：4，他引：1  

黄雄飞  莫宣学  喻学惠  李小伟  杨梦楚  罗明非  和文言  于峻川 《岩石学报》2014,30(11):3255-3270

西秦岭印支期花岗岩类分布十分广泛,形成时代集中于248~234Ma和224~211Ma两个阶段.其中,夏河岩体(248~238Ma)和温泉岩体(223~216Ma)的部分样品被厘定为埃达克岩(Sr>400×10^-6,Yb<2×10^-6),指示陆壳厚度大于50km.本文对西秦岭同仁地区舍哈力吉岩体进行了锆石U-Pb定年、岩石学、地球化学和Sr-Nd同位素研究.舍哈力吉岩体主要由石英二长岩组成,同时含有许多暗色镁铁质微粒包体(MME).寄主岩中发育少量的钾长石巨晶,并且部分巨晶具有环斑结构.舍哈力吉石英二长岩化学成分比较均一,而且也显示出类似埃达克岩的一些地球化学特点,如富SiO₂(66.07%~67.52%)和Al₂O₃(14.85%~15.95%),高Sr(560×10^-6~692×10^-6),低Y(11.4×10^-6~12.9×10^-6)和Yb(0.99×10^-6~1.09×10^-6),并具有较高的(La/Yb)_N比值(27.8~34.3)和微弱的负Eu异常(δEu=0.77~0.95).锆石U-Pb测年结果为234.1±0.5Ma,表明其形成于印支早期.岩石为偏铝质、高钾钙碱性系列且K₂O/Na₂O>1,高Mg^#(59~60)、Cr(69.1×10^-6~81.2×10^-6)和Ni(31.6×10^-6~36.1×10^-6),以富集大离子亲石元素(Rb、Ba、Th、U)而相对亏损高场强元素(Nb、Ti、P)为特征,(⁸⁷Sr/⁸⁶Sr)_i=0.7075~0.7077,ε_Nd(t)=-6.3~-6.1,亏损地幔模式年龄为1.25~1.33Ga.舍哈力吉石英二长岩起源于石榴角闪岩相古老下地壳的部分熔融,之后经历了壳幔岩浆混合作用和以斜长石为主的分离结晶作用.寄主岩的环斑结构和相对一致的地球化学特征,很可能是高温幔源熔体对壳源富钾高黏度岩浆改造所导致的晶粥快速再活化的结果.西秦岭在印支早期可能并未经历显著的地壳加厚过程.西秦岭印支早期花岗岩类形成于活动大陆边缘局部伸展环境,可能与古特提斯洋壳俯冲极性的改变有关.  相似文献