东海陆缘(闽北段)晚第四纪沉积的硅藻学研究   总被引：10，自引：1，他引：10  

王开发  支崇远  郑玉龙  王洪根 《沉积学报》2002,20(1):136-143

对东海陆缘 (闽北段 )晚第四纪沉积 4口钻井岩心进行系统的硅藻分析研究,获得丰富的硅藻化石,共发现硅藻 117种和变种,分属于 33个属。根据剖面硅藻组合特征变化,结合最优分割法和对应序分法的计算机运算结果,可以详细划分为 12个硅藻带,自下而上为 :1.Cascinodiscusargus-Cos.wittiomus-Cyclotellastriata硅藻带,2.Cos.blandus-Cyclotellastriata硅藻带,3.Cos.excentricus-Trbliepteychuscocconiformis硅藻带,4.Gomphonema-Cos.blandus-Actnolychusralfsii硅藻带,5.Cos.-Cyclotellastriata-Actinocyclusralfsii硅藻带,6.Cos.-Actinolychusralfsii硅藻带,7.贫乏硅藻带,8.Cos.lineatus-Cos.rothii-Actinolyclusralfsii硅藻带,9.Gomphonema-Cyclotellastriata-Cocconeisplacentulavareuglypta硅藻带,10.Cos.rothii-Cyclotellastriata-Actinolychusralfsi,11.Cymbel laaffinis-Cyclotellastriata-Gomphonema硅藻带,12.Coscinodiscuswittinus-Cyclotellastriata-Epithemiahynd manii硅藻带,建立了该区晚第四纪硅藻组合序列,并探讨其相应的古环境演变。  相似文献   

西藏岗巴古新世地层及构造作用的影响   总被引：13，自引：1，他引：13       下载免费PDF全文

万晓樵  梁定益等 《地质学报》2002,76(2):155-162

西藏岗巴地区出露有完整的晚白垩世至古近纪地层，地层中化石丰富，根据化石研究准确地进行了地层时代的划分，本文认为该区白垩系－古代系界线位于宗山组和基堵拉组之间，以底栖有大孔虫Orbitoides-Omphalocyclus动物群的消亡和Rotalia-Smoutina-Lockhartia动物群的始现为标志。界线上下岩层为假整合接触，期间有一短暂的暴露面。古新世的砂砾岩直接覆于晚白晋世的陆棚碳酸盐岩沉积之上，沉积的重大转变代表一次构造运动，印度大陆北缘与冈底斯南缘直至白垩纪末均具有明显的浅海生物地理分区现象，期间被深海盆地地所阻隔。古新世开始浅海相动物群在该地显示同一生物地理区系特征，说明两大陆间深水盆地的阻隔已消失，南北生物地理区同归于一残留海盆，沉积类型转变和地层古生物特征为印度－亚洲板块的起始碰撞时间研究提供了基础资料，据此推测大陆早期碰撞发生在白晋系－古近系的界线时期（约65Ma)，古新世中一晚期碳酸盐台地遭受不断的挤压与变形，进一步说明大陆的碰撞在古新世之初就已发生。沉积地层的破碎变形和滑塌堆积是持续碰撞与挤压的结果。  相似文献   

中下扬子区二叠系露头层序地层研究   总被引：15，自引：1，他引：15  

张克信  刘金华等 《地球科学》2002,27(4):357-365

按新近国际年代地层划分方案（ICS，2000），下扬子区二叠纪地层自下向上分为3统，9阶和相对应的华南传统6阶划分。二叠系从阿瑟尔阶至长兴阶（44Ma)共划分出14个三级层序，每个三级层序平均时限约为3.14Ma，其中“紫松阶”）相当阿瑟尔＋2／3萨克马尔阶）1个（船山组中上部）、“隆林阶、（相当1／3萨克马尔阶＋阿丁斯克阶）2个（分别对应船山组上部和梁山组或镇江组）、“栖霞阶”（相当库班甘德阶＋1／3罗德阶）3个（栖霞组），“茅口阶”（相当于2／3罗德阶＋沃德阶＋卡皮丹阶）4个（孤峰组，茅口组，堰桥组，银屏组和武穴组），吴家坪阶2个（龙潭组或吴家坪组），长兴阶2个（长兴组或大隆组）；共归并为4个层序组（sequence set)。  相似文献   

Origin of the northern Indus Fan and Murray Ridge, Northern Arabian Sea: interpretation from seismic and magnetic imaging     

Christoph Gaedicke  Hans-Ulrich Schlüter  Hans Albert Roeser  Alexander Prexl  Bernd Schreckenberger  Heinrich Meyer  Christian Reichert  Peter Clift  Shahid Amjad 《Tectonophysics》2002,355(1-4)

The nature and origin of the sediments and crust of the Murray Ridge System and northern Indus Fan are discussed. The uppermost unit consists of Middle Miocene to recent channel–levee complexes typical of submarine fans. This unit is underlain by a second unit composed of hemipelagic to pelagic sediments deposited during the drift phase after the break-up of India–Seychelles–Africa. A predrift sequence of assumed Mesozoic age occurring only as observed above basement ridges is composed of highly consolidated rocks. Different types of the acoustic basement were detected, which reflection seismic pattern, magnetic anomalies and gravity field modeling indicate to be of continental character. The continental crust is extremely thinned in the northern Indus Fan, lacking a typical block-faulted structure. The Indian continent–ocean transition is marked on single MCS profiles by sequences of seaward-dipping reflectors (SDR). In the northwestern Arabian Sea, the Indian plate margin is characterized by several phases of volcanism and deformation revealed from interpretation of multichannel seismic profiles and magnetic anomalies. From this study, thinned continental crust spreads between the northern Murray Ridge System and India underneath the northern Indus Fan.  相似文献   

Continental crust and lithospheric mantle interaction beneath North China: isotopic evidence from granulite xenoliths in Hannuoba, Sino-Korean craton   总被引：40，自引：0，他引：40  

Xinhua Zhou  Min Sun  Guohui Zhang  Shaohai Chen 《Lithos》2002,62(3-4):111-124

Mafic granulite and pyroxenite xenoliths from Cenozoic alkaline basalts at Hannuoba, Hebei Province, North China have been selected for a systematic geochemical and Sr–Nd–Pb isotopic study, which provides a unique opportunity to explore nature of the lower crust and the interaction between the continental crust and lithospheric mantle beneath an Archean craton. The major, compatible and incompatible elements and radiogenic isotopes of these xenoliths suggest great chemical heterogeneity of the lower crust beneath the Hannuoba region. Petrological and geochemical evidences indicate a clear cumulate origin, and most likely, they are related to basaltic underplating in different geological episodes. However, the Sr–Nd–Pb isotopic compositions of the xenoliths reveal a profound enriched source signature (EM I) with some influence of EM II, which implies that some portion of pre-existing, old metasomatized subcontinental lithospheric mantle could have played an important role in their genesis. It is suggested that the interaction between continental crust and subcontinental mantle as manifested by basaltic underplating would be closely related to regional tectonic episodes and geodynamic processes in the deep part of subcontinental lithospheric mantle.  相似文献   

Lithosphere structure of European sedimentary basins from regional three-dimensional gravity modelling     

T. P. Yegorova  V. I. Starostenko 《Tectonophysics》2002,346(1-2)

A three-dimensional (3D) density model, approximated by two regional layers—the sedimentary cover and the crystalline crust (offshore, a sea-water layer was added), has been constructed in 1° averaging for the whole European continent. The crustal model is based on simplified velocity model represented by structure maps for main seismic horizons—the “seismic” basement and the Moho boundary. Laterally varying average density is assumed inside the model layers. Residual gravity anomalies, obtained by subtraction of the crustal gravity effect from the observed field, characterize the density heterogeneities in the upper mantle. Mantle anomalies are shown to correlate with the upper mantle velocity inhomogeneities revealed from seismic tomography data and geothermal data. Considering the type of mantle anomaly, specific features of the evolution and type of isostatic compensation, the sedimentary basins in Europe may be related into some groups: deep sedimentary basins located in the East European Platform and its northern and eastern margins (Peri-Caspian, Dnieper–Donets, Barents Sea Basins, Fore–Ural Trough) with no significant mantle anomalies; basins located on the activated thin crust of Variscan Western Europe and Mediterranean area with negative mantle anomalies of −150 to −200×10⁻⁵ ms⁻² amplitude and the basins associated with suture zones at the western and southern margins of the East European Platform (Polish Trough, South Caspian Basin) characterized by positive mantle anomalies of 50–150×10⁻⁵ ms⁻² magnitude. An analysis of the main features of the lithosphere structure of the basins in Europe and type of the compensation has been carried out.  相似文献   

Study and review on crust-mantle velocity structure in Bohai Bay and its vicinity   总被引：3，自引：0，他引：3  

张成科  张先康  赵金仁  任青芳  张建狮  海燕 《地震学报(英文版)》2002,15(4):447-455

Introduction Bohai Bay, along with its adjacent areas, is one of the seismically active areas in North China. Understanding its crust/upper-mantle structural characteristics and lateral heterogeneity of the medium in this area is of great significance to the study of seismogenic environment, thus improvimg the level of earthquake prediction. For years, scientists have studied the area by gravity and magnetic methods (FENG, et al, 1989), geothermal field (WU, et al, 1988; TIAN, ZHANG, 19…  相似文献   

有限弹性变形地壳中的地震波     

范家参 《地震研究》2002,25(1):48-52

地壳由半无限大的基岩上一层厚度为H^-的表土层组成，入射地震波为垂直的SH波，产生水平地面运动。当浅源大地震发生时，在极震区以外行波传播产生地面运动将使地壳介质有非线性的有限弹性变形。用小参数摄动法使非线性控制方程为线性化的小参数各阶控制方程，得出头两阶线性控制方程的解析解。  相似文献   

Modes of raising northeastern Tibet probed by explosion seismology   总被引：4，自引：0，他引：4  

Audrey GalvéAlfred Hirn  Jiang MeiJosep Gallart  Béatrice de VoogdJean-Claude Lépine  Jordi DiazWang Youxue  Qian Hui 《Earth and Planetary Science Letters》2002,203(1):35-43

New wide-angle reflection and refraction seismic data provide constraints on the structure of the upper lithosphere, and test models of its evolution to raise the northeastern part of the Tibetan Plateau. Amplitudes observed for reflections from the crust-mantle boundary are sufficiently large to suggest that there is no significant partial melt in the deep crust. The data show an increase of the crustal thickness between terranes from north of the Kun Lun Fault into the Qang Tang of central Tibet, and a contrast among their intracrustal images and compositions. In the north, P and S velocities are consistent with a dominantly felsic composition and show that only the upper crust thickened. South of the Kun Lun Fault a thicker crust made of two layers could result from the superposition of the originally thin crust of the Bayan Har terrane on the lower part of the crust of the domain to the north, which upper crust it shoved and thickened. Different modes of crustal thickening, either by thickening of individual layers or superpositions and imbrication among them appear to work jointly to raise the topography.  相似文献   

中朝地台东北缘地区的地震层析成像   总被引：24，自引：5，他引：24       下载免费PDF全文

卢造勋  蒋秀琴  潘科  白云  姜德录  肖立萍  刘建华  刘福田  陈辉  何建坤 《地球物理学报》2002,45(3):338-351

根据中朝地台东北缘地区 (东经 1 1 7°0 0′— 1 2 6°0 0′ ,北纬 36°0 0′— 44°0 0′) 1 980— 1 997年的 380 0 0余条P波走时数据 ,利用正交投影法重建了该区地壳和上地幔的三维速度结构 .通过分析及同人工地震测深剖面的详细对比 ,证明了成像结果的可靠性 .结果表明 :中朝地台东北缘地区地壳上地幔介质存在显著的横向不均匀性 ,直至 1 2 0km深度处依然明显 ;地壳上部的速度图像清楚地反映了不同岩石单元的分布与该区不同性质的基岩分布基本吻合 ;从上、中地壳的速度图像中发现了研究区存在海城、朝阳、义县、丹东南、唐山等几个低速异常区(即速度逆反层区 ) ,其中海城、唐山、朝阳等地区的壳内低速层已由深地震测深资料所证实 ;研究区陆地发生的几次强震均发生于壳内低速层上方的高速脆性介质内 ,而渤海发生的强震 ,此现象不明显 ,但都发生于横向介质速度显著突变的位置 ;在地壳不同深度上发现了普兰店至山海关横跨渤海的北西向低速异常带 ;地震层析二维速度图像与深地震测深资料的对比表明 ,研究区利用地震层析成像技术 ,在一定条件下可以获得与人工地震测深相似的效果  相似文献