New Late Jurassic palaeomagnetic data from the northern Sichuan basin: implications for the deformation of the Yangtze craton     

Masahiko Yokoyama  Yuyan Liu  Yo-ichiro Otofuji  & Zhenyu Yang 《Geophysical Journal International》1999,139(3):795-805

Upper Jurassic red sandstones and red siltstones were collected from 67 layers at 12 localities in the Penglaizhen formation. This formation is in the north of Bazhong county (31.8°N, 106.7°E) in the Sichuan basin, which is located in the northern part of the Yangtze craton. Thermal demagnetization isolated a high-temperature magnetic component with a maximum unblocking temperature of about 690 °C from 45 layers. The primary nature of the magnetization acquisition is ascertained through the presence of magnetostratigraphic sequences with normal and reversed polarities, as well as positive fold and reversal tests at the 95 per cent confidence level. The tilt-corrected mean direction of 36 layers is D = 20.0°, I = 28.8° with α ₉₅ = 5.8°. A Late Jurassic palaeomagentic pole at 64.7°N, 236.0°E with A ₉₅ = 7.0° is calculated from the palaeomagnetic directions of 11 localities. This pole position agrees with the two other Late Jurassic poles from the northern part of the Yangtze craton. A characteristic Late Jurassic pole is calculated from the three poles (68.6°N, 236.0°E with A ₉₅ = 8.0°) for the northern part of the Yangtze craton. This pole position is significantly different from that for the southern part of the Yangtze craton. This suggests that the southern part of the Yangtze craton was subjected to southward extrusion by 1700 ± 1000  km with respect to the northern part. Intracraton deformation occurred within the Yangtze craton.  相似文献   

Surface vertical displacements, potential perturbations andgravity changes of a viscoelastic earth model induced by internal point dislocations   总被引：1，自引：0，他引：1  

Hansheng Wang 《Geophysical Journal International》1999,137(2):429-440

Using the viscoelastic correspondence principle, we utilize the surface coseismic spheroidal deformation fields (i.e. vertical displacements, potential perturbations and gravity changes) of SNREI earth models caused by four typical types of point dislocation, derived by Sun & Okubo (1993 ), to deduce the fundamental formulas for spheroidal fields relevant to viscoelastic earth models. In computations, we employ a strike-slip dislocation on a vertical plane buried at the bottom of the lithosphere to estimate the maximal viscous relaxation responses to this kind of source that possibly exist on the surface of the earth. We take the seismic moment as 10²²  N  m, which is characteristic of an average large earthquake. The numerical results demonstrate that, if we take the viscosity as 10¹⁹  Pa  s in the asthenosphere, and 10²¹  Pa  s in the other mantle layers, the rates of surface vertical displacements and gravity changes within about 2.5° for the 10 postseismic years are respectively 1.5–8.1  cm  yr⁻¹ and 4.0–14.9  μgal  yr⁻¹ : the viscous relaxation for this mantle viscosity profile proceeds much faster than for a constant mantle viscosity of 10²¹  Pa  s.  相似文献   

扬子地台西北缘前陆逆冲带及煤田构造特征   总被引：2，自引：2，他引：0  

张德民  景玉龙 《煤田地质与勘探》1997,25(4):4-7

扬子地台西北缘前陆逆冲带(即龙门山逆冲带)的形成和演化控制着扬子地台内部及其西北缘煤炭资源的聚积和赋存。它可分为根带、中带、锋带三部分。根带无煤聚积,工业煤炭资源赋存在中带,锋带的煤系埋藏过深。前陆逆冲带内的煤田构造变形是适应前陆逆冲挤压应力作用的结果,以发育有冲断叠瓦扇、双冲构造、平行褶皱、斜歪褶皱、飞来峰、逆冲岩席、断夹块等构造样式为特征。前陆逆冲带的形成是特提斯构造域长期演化、沿三条缝合带发生三次碰撞的结果。   相似文献   

晋冀蒙地区的垂直形变特征     

陈阜超  陈聚忠  郑智江 《大地测量与地球动力学》2015,35(3):453-456

基于1998、2006和2013年3期水准复测资料,平差计算得到1998~2006年和2006~2013年的垂直形变速率及其垂直形变速率梯度。根据计算结果研究晋冀蒙地区的地壳垂直形变运动趋势以及主要断裂带的活动性,分析区域垂直形变速率和垂直形变速率梯度的演变。结果揭示出吕梁山地块后一时段上升速率增加、太行山地块由前一时段上升变为后一时段下降、盆地地带变化复杂的垂直形变态势。  相似文献   

新疆觉罗塔格韧性变形带组构及动力学意义     

徐兴旺  马天林  孙立倩  李贵书 《地质力学学报》1998,4(1):25-32

新疆觉罗塔格韧性变形带,惯称秋格明塔什-黄山韧性剪切带,发育于吐哈地块和中天山地块之间的EW向石炭系火山-沉积建造中,由一组走向EW、产状陡立的透入性片理组成。韧性变形带内韧性构造形迹发育,并可分为4个等级:大型构造、小型构造、微观构造和超微观构造。不同级别构造形迹的组构分析表明,觉罗塔格韧性变形带的内部组构是对称的,这意味着其成因于对称的构造变形。与主界面平行的大量压性构造形迹的产出,说明该对称组构成因于与垂直变形带(面)的共轴挤压作用,即觉罗塔格韧性变形带是一个韧性挤压带。   相似文献   

岩石变形图像分析的计算机统计方法初探     

石磊  黄维平  孟宪刚 《地质力学学报》1998,4(3):91-96

本文利用岩石变形形成的显微构造现象(如压力影、亚颗粒、位错、动态重结晶颗粒等),通过图象分析计算机数理统计方法,来推测地质体变形特征、变形环境、应力状态等。   相似文献   

被动陆缘盆地陆隆斜坡对盐构造形成的影响 ——来自物理模拟实验的启示     

王殿举  李一赫  于法浩  王志琛  刘志强 《地质学报》2022,96(3):854-862

被动陆缘盆地盐构造形成的影响因素及时空演化分析受到了国内外学者的高度重视.丰富的油气资源促进了被动陆缘盆地地震资料品质的不断提升,高精度地震数据的解译结果表明,被动陆缘盆地盐层下的地形往往具有大型的起伏特征,而前人在基底构造形态对盐构造形成影响方面的研究并未取得共识,仍需要深入研究和探讨.为此,本文基于前人的研究认识,...  相似文献   

Dynamic Analysis of Deformational Structures of the Xianniishan Fault Zone in the Three Gorges of the Yangtze River     

WU Shuren Institute of Geomechanics  CAGS  Beijing  WU Ganguo China University of Geosciences  Beijing Liu Xinzhu 《《地质学报》英文版》1999,73(2)

Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannushan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of σI is N-S in direction with differential stresses of 150-250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.  相似文献   

Dynamic Analysis of Deformational Structures of the Xiannüshan Fault Zone in the Three Gorges of the Yangtze River     

WU Shuren  WU Ganguo 《《地质学报》英文版》1999,73(2)

Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannüshan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of (1 is N-S in direction with differential stresses of 150(250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.  相似文献   

影响煤层构造变形特性与机理的关键因素   总被引：1，自引：0，他引：1  

周建勋 《煤田地质与勘探》1999,27(3):10-12

3个煤级的煤样高温高压实验结果表明,煤是一种温度敏感性较弱的岩石。影响煤层构造变形机理的关键因素是煤级,随煤级增高煤层塑性减弱、脆性增大。韧性变形主要发生在煤级较低的煤层,煤级较高煤层主要发生脆性变形。不能完全用煤层本身强度特性解释煤层容易发生强烈流变或成为拆离、滑脱层的现象,需考虑其它可能因素。   相似文献