西藏申扎永珠乡晚石炭世和早二叠世的腕足动物化石     

刘发 《吉林大学学报(地球科学版)》1991,(3)

申扎地区石炭二叠系发育良好,化石丰富。本文描述的化石采自上下两个层位,下部化石少,以石燕贝类为主, 其组合特征反映了石炭纪腕足类的特点与改则县玛米雪山地区上石炭统所产相似;上部化石丰富,以石燕贝类的Spiriferella和Syrin-gothyris的出现为特征,共生还有长身贝类的Chonetinella,Echinauris,Tylo-pecta等。这个化石组合与西藏其他地区相同时代的化石组合不同。特别是Syringothy-ris在下二叠统的发现具有重要意义。  相似文献   

甘肃及其邻域地壳中间界面的某些性质     

董奇珍  李清河 《华南地震》1991,11(4):9-19

本文根据地壳中间界面上反射波的运动学和动力学参数，探测了地壳中间界面的埋深、复盖介质中波的传播速度、温度、压力、反射性、透过性、弹性等性质。  相似文献   

冀中中奥陶统高频率旋回层序的基本特征   总被引：2，自引：0，他引：2  

王立峰 《沉积与特提斯地质》1994,(6)

通过野外实测剖面及路线观察，河北中部中奥陶统马家沟群的高频率旋回可划分为三个级别，并与层序地层学术语可以对比，由低到高为；六级旋回──韵律层；五级旋回──准层序；四级旋回──准层序组。这些由米兰柯维奇驱动力所控制的旋回层序在不同的沉积环境中具有不同岩石组合特征，反映了高频率旋回的沉积模式。  相似文献   

新疆阿希地区大哈拉军山组火山岩金元素地球化学特征及其成矿关系   总被引：6，自引：4，他引：6  

漆树基  李长河 《新疆地质》1994,(2)

阿希地区下石炭统大哈拉军山组４个岩性段均由中酸性火山岩组成。各岩性段火山岩的金元素岩石－地球化学特征有着显著差异，与金矿成矿关系不尽相同。其中的酸性凝灰岩段金元素平均值１１０．６×１０－９，最高值１８０００×１０－９，浓集克拉克值２８，标准离差２２８，变异系数２．０６。该岩性段是阿希地区各种类型金矿的重要矿源层。  相似文献   

中层大气Rossby波与惯性重力波的非线性相互作用（Ⅱ）波包之间的相互激发     

熊建刚  易帆 《地球物理学报》1995,38(5):564-570

进一步讨论了大中尺度Ｒｏｓｓｂｙ波与惯性重力波的非线性相互作用问题．从共振相互作用曲线来看，Ｒｏｓｓｂｙ波和惯性重力波可以在相当广泛的角谱范围内发生共振非线性相互作用．在一定条件下，一个大振幅波包可以激发两个小振幅波包不稳定增长而出现参量不稳定现象，这三个波包可以是同种类型或不同类型的波包．当两个大振幅波包发生相互作用时，非线性过程会产生另一个波包并使它增长，并且增长速度大于仅有一个大振幅波包时的增长速度．大尺度Ｒｏｓｓｂｙ波包税发两个较小尺度惯性重力波的过程是一种重要的能量串级（ｃａｓｃａｄｅ）过程．  相似文献   

中层大气Rossby波与惯性重力波的非线性相互作用（Ⅱ）波包之间的相互激发          下载免费PDF全文

熊建刚  易帆  李钧 《地球物理学报》1995,(5)

进一步讨论了大中尺度Ｒｏｓｓｂｙ波与惯性重力波的非线性相互作用问题．从共振相互作用曲线来看，Ｒｏｓｓｂｙ波和惯性重力波可以在相当广泛的角谱范围内发生共振非线性相互作用．在一定条件下，一个大振幅波包可以激发两个小振幅波包不稳定增长而出现参量不稳定现象，这三个波包可以是同种类型或不同类型的波包．当两个大振幅波包发生相互作用时，非线性过程会产生另一个波包并使它增长，并且增长速度大于仅有一个大振幅波包时的增长速度．大尺度Ｒｏｓｓｂｙ波包税发两个较小尺度惯性重力波的过程是一种重要的能量串级（ｃａｓｃａｄｅ）过程．  相似文献   

近百年长江中游旱涝的变化   总被引：1，自引：0，他引：1  

叶愈源  赵文兰 《热带气象学报》1995,11(2):181-186

利用史料和器测雨量记录重建的近百年长江中游区域平均逐年旱涝等级指数序列研究了旱涝变化特征，发现：（１）２０世纪前涝后旱，（２）２２年、５－６年和２－３年的准周期振动，（３）６个交替出现的旱涝阶段。  相似文献   

Plate tectonics,palaeoenvironments and limestone geomorphology in West-Central Britain     

Ian Douglas 《地球表面变化过程与地形》1987,12(5):481-495

The variety of active, exhumed, and buried limestone landforms of northern England, North Wales, and the Isle of Man arises in part from the way in which Dinantian (Lower Carboniferous) sedimentation was affected by a tilt-block basement structure evolved during the closure of the Iapetus Ocean suture to the north, and partly to subsequent plate tectonic movements associated with the closure of the proto-Tethys ocean, the opening of the Atlantic Ocean and the Alpine orogeny. Landforms created during the Dinantian now form important exhumed and buried landscape features. The Permian half-graben structures of the eastern Irish Sea-Cheshire-Worcester Basins account for many of the contrasts between the upland karsts of the Pennines and the lowland karsts of coastal areas.  相似文献   

Note on Upper Cretaceous ostracods from south-western Morocco     

R. A. Reyment 《Cretaceous Research》1982,3(4):405-414

Cenomanian, Turonian and Coniacian ostracods from a borehole in the coastal zone of the Tarfayan Basin, south-western Morocco, display affinities with associations from Algeria, Tunisia and the Middle East as well as with the Iberian Peninsula. Relationships with central and southern West Africa are relatively slight, which could be a result of palaeoecological particularities.  相似文献   

Current-scattered (?) detrital remanence directions in the Zn-rich Pennsylvanian Stark black shale, USA     

K. Kawasaki  D. T. A. Symons  R. M. Coveney Jr  . 《Geophysical Journal International》2007,171(2):594-602

Palaeomagnetic results are reported from the metalliferous Stark black shale in the Upper Pennsylvanian (Missourian/Kasimovian) Kansas City Group. Palaeomagnetic analysis of 400 specimens from 28 sites gives a characteristic remanent magnetization in 17 sites of the shale that yields a Late Mississippian to Middle Pennsylvanian palaeopole at 32.2°N 128.5°E (dp = 4.7° and dm = 8.8°). The observed palaeomagnetic age is slightly older than the host rock, indicating that the mineralization of the Stark Shale has, excluding recent alteration, a primary sedimentary or syngenetic origin. The reason for the slightly older age is likely due to trace modern hematite that slightly steepens the remanence inclination. The large oval of 95 per cent confidence is interpreted to be caused by clay–magnetite aggregates that formed during sediment transport and the biasing effect of the gentle palaeocurrent at each site acting on the large aggregates. Therefore, the scattered distribution of the site mean remanence declinations found for the Stark Shale is evidence of a detrital remanent magnetization that is formed by primary sedimentary processes with an enriched metallic content and not remagnetization with mineralization by secondary hydrothermal processes.  相似文献