扬子板块埃迪卡拉系(震旦系)陡山沱组层序地层划分与对比   总被引：3，自引：1，他引：2       下载免费PDF全文

杨爱华  朱茂炎  张俊明  赵方臣  吕苗 《古地理学报》2015,17(1):1-20

在对扬子板块埃迪卡拉系陡山沱组不同相区的25条代表性剖面野外研究基础上,通过沉积岩石学和岩相序列特征的系统分析,认为陡山沱组沉积时期曾发生3次二级海平面升降事件。依据3个海平面升降转换面,可识别出3个层序底界面:(1)陡山沱组底部与下伏南华系南沱组及其同期层位的冰碛杂砾岩之间的界面;(2)在浅水沉积区陡山沱组中部和上部分别出现喀斯特侵蚀面;(3)在深水沉积区相应层序界面为岩相结构转换面。依据火山灰锆石U-Pb同位素年龄,可将陡山沱组层序地层划分为2个半二级层序或超层序(SS1,SS2和SS3-TST),其中SS1时限为35Ma(635~600Ma),SS2时限为35Ma(600~565Ma),SS3-TST时限为14Ma(565~551Ma)。陡山沱组底部广泛发育的盖帽白云岩底和3个层序内的最大海泛面可以作为4个相对等时面,结合事件沉积标志层,可建立扬子板块陡山沱组从浅水沉积区至深水沉积区等时性二级层序地层划分对比格架。研究结果表明,三峡地区陡山沱组四段式划分方案不适用于整个扬子板块内陡山沱组的区域地层划分和对比。因而,建议扬子板块陡山沱组应该以二级层序地层为基础,结合化学地层和生物地层进行综合划分和对比。陡山沱组新的地层划分对比格架为研究陡山沱组古地理演变和编制该时期高精度的岩相古地理图奠定了基础。  相似文献   

平板冻结器超压事故的原因分析     

李敏  李湛 《广东海洋大学学报》2002,22(6):49-53

平板冻结器超压事故的发生主要由于使用设备时操作不当和设备质量不过关而引起。对设备超压原理分析和平板冻结器在不同温度条件下的充液比例进行理论计算 ,结果表明 ,停机时 ,在室温 35℃的条件下 ,蒸发器中的充液比例达到 0 .86 0 5时 ,会引起蒸发器发生超压而爆炸。当蒸发器中充液比例在 0 .86 0 5以下时发生的超压事故 ,肯定存在设备质量不过关的因素 ;而当充液比例在 0 .86 0 5或以上时发生的超压事故 ,则是由误操作引起。。  相似文献   

东南地洼区的地球物理特征及其深部构造力源机制探讨     

刘代志 《地球科学与环境学报》1988,(2)

本文较全面地探讨了东南地洼区反映深部构造特点的地球物理特征(波速结构,地温分布,电性,密度,重、磁场异常),综合分析了该区地洼构造形成、演化的力源机制,讨论了地洼构造与板块构造的力源机制关系问题。  相似文献   

The low seismic activity of the Korean Peninsula surrounded by high earthquake countries   总被引：1，自引：0，他引：1  

S.G. Kim  E. Lkhasuren  P.-H. Park 《Journal of Seismology》2004,8(1):91-103

Although the Korean Peninsula is locatednear several great earthquake regions suchas NE China and SW Japan, it has neversuffered from catastrophic earthquakes forthe last 2000 years according to historicaland instrumental records. We investigatedthe low seismicity of Korea based on thehypothesis of the Baikal-Korea Plate (BKP)or Amurian Plate movement which isinitiated by the Baikal Rift Zone spreadingin a southeastward motion with acounter-clockwise rotation due to thecollision of the Indian Plate against theEurasian Plate. Many disastrous earthquakesof NE China, SW Japan and Sakhalin releaselarge amounts of seismic energy along theboundary of the Baikal-Korea Plate. It isnecessary to compute the released seismicenergy along the presumed boundary of theBaikal-Korea Plate compared to the KoreanPeninsula in order to estimate themicro-plate boundary. The total energyreleases (1900–1999) from the majordisastrous earthquakes (M6.0) alongthe Baikal-Korea plate are about10³–10⁴ times as much as theKorean Peninsula (M3.0). The focalmechanisms for the intra-continentalearthquakes near and/or along theBaikal-Korea Plate boundary of NE China, SW Japan, Sakhalin and Mongolia mostlyrepresent the horizontal motions of theright-lateral strike slip type, indicatingthat the Baikal-Korea Plate is acounter-clockwise and transcurrent motion. The relative displacement vectors of GPS(global positioning system) also indicatedthat the Baikal-Korea Plate movescounter-clockwise around the KoreanPeninsula. These factors may indicate thatthe Korean Peninsula is not located at thePlate boundary, but just within a margin ofthe Baikal-Korea Plate which movessoutheastward with a counter-clockwiserotation from the Baikal Rift Zone in NEAsia. Therefore there is no enoughaccumulated strain to generate largeearthquakes in the Korean Peninsula and itmakes the Korean Peninsula free fromseismic hazard of large catastrophicearthquakes.  相似文献   

Archean greenstone-tonalite duality: Thermochemical mantle convection models or plate tectonics in the early Earth global dynamics?   总被引：2，自引：0，他引：2  

Robert Kerrich  Ali Polat   《Tectonophysics》2006,415(1-4):141-165

Mantle convection and plate tectonics are one system, because oceanic plates are cold upper thermal boundary layers of the convection cells. As a corollary, Phanerozoic-style of plate tectonics or more likely a different version of it (i.e. a larger number of slowly moving plates, or similar number of faster plates) is expected to have operated in the hotter, vigorously convecting early Earth. Despite the recent advances in understanding the origin of Archean greenstone–granitoid terranes, the question regarding the operation of plate tectonics in the early Earth remains still controversial. Numerical model outputs for the Archean Earth range from predominantly shallow to flat subduction between 4.0 and 2.5 Ga and well-established steep subduction since 2.5 Ga [Abbott, D., Drury, R., Smith, W.H.F., 1994. Flat to steep transition in subduction style. Geology 22, 937–940], to no plate tectonics but rather foundering of 1000 km sectors of basaltic crust, then “resurfaced” by upper asthenospheric mantle basaltic melts that generate the observed duality of basalts and tonalities [van Thienen, P., van den Berg, A.P., Vlaar, N.J., 2004a. Production and recycling of oceanic crust in the early earth. Tectonophysics 386, 41–65; van Thienen, P., Van den Berg, A.P., Vlaar, N.J., 2004b. On the formation of continental silicic melts in thermochemical mantle convection models: implications for early Earth. Tectonophysics 394, 111–124]. These model outputs can be tested against the geological record. Greenstone belt volcanics are composites of komatiite–basalt plateau sequences erupted from deep mantle plumes and bimodal basalt–dacite sequences having the geochemical signatures of convergent margins; i.e. horizontally imbricated plateau and island arc crust. Greenstone belts from 3.8 to 2.5 Ga include volcanic types reported from Cenozoic convergent margins including: boninites; arc picrites; and the association of adakites–Mg andesites- and Nb-enriched basalts.Archean cratons were intruded by voluminous norites from the Neoarchean through Proterozoic; norites are accounted for by melting of subduction metasomatized Archean continental lithospheric mantle (CLM). Deep CLM defines Archean cratons; it extends to  350 km, includes the diamond facies, and xenoliths signify a composition of the buoyant, refractory, residue of plume melting, a natural consequence of imbricated plateau-arc crust. Voluminous tonalites of Archean greenstone–granitoid terranes show a secular trend of increasing Mg#, Cr, Ni consistent with slab melts hybridizing with thicker mantle wedge as subduction angle steepens. Strike-slip faults of 1000 km scale; diachronous accretion of distinct tectonostratigraphic terranes; and broad Cordilleran-type orogens featuring multiple sutures, and oceanward migration of arcs, in the Archean Superior and Yilgarn cratons, are in common with the Altaid and Phanerozoic Cordilleran orogens. There is increasing geological evidence of the supercontinent cycle operating back to  2.7 Ga: Kenorland or Ur  2.7–2.4 Ga; Columbia  1.6–1.4 Ga; Rodinia  1100–750 Ma; and Pangea  230 Ma. High-resolution seismic reflection profiling of Archean terranes reveals a prevalence of low angle structures, and evidence for paleo-subduction zones. Collectively, the geological–geochemical–seismic records endorse the operation of plate tectonics since the early Archean.  相似文献   

基于ITRF2005框架的南美板块运动及形变分析     

敖敏思  胡友健  赵斌  叶险峰 《测绘科学》2012,(1):12-14,11

本文通过利用ITRF2005框架速度场以及IGS参考站近两年观测数据解算所得速度场对南美板块的运动及形变特征进行分析。结果表明,南美板块整体以约12.4mm/a的速率向北西方向运动,其欧拉矢量参数与NNR-NULVEL1A模型基本一致。形变特征表现为中南部区域西缘因纳兹卡板块俯冲向东凹陷,东侧受大西洋中脊海底扩张推力向西运动,东西向的挤压使其约以22mm/a的速度收缩并阻碍其北向运动。板块南端则受南极洲板块挤压向北西运动。  相似文献   

Evolution of east coast of India — A plate tectonic reconstruction     

N. K. Lal  A. Siawal  Anil K. Kaul 《Journal of the Geological Society of India》2009,73(2):249-260

The evolution of east coast of India sis discussed within the ambit of clearly identifiable four major tectonic stages which had a profound effect in shaping the tectonic grain of the east coast basins. The evolutionary process began with rift related crustal extension between India and Sri Lanka as a consequence of Africa-Antarctica rifting and development of Natal Basin. An arm of this rift led to initial extension in the Cauvery Basin and failed. Later, the India-West Australia rift propagated further in southwesterly direction initiating Mahanadi and Krishna-Godavari Basins. This extension was an oblique one with Nayudupeta high acting as pivot. The oblique extension followed by asymmetric seafloor spreading developed transpression along India-Sri Lanka and Antarctica junction, resulting in a NNW-SSE trending transcurrent fault along which Antarctica moved southward. Subsequently, entire east coast evolved through a more or less uniform post rift stage.  相似文献   

Principal faults in the Shatsky Rise and their influence upon the evolution of the geological structure in the East Black Sea Region     

A. L. Meysner 《Moscow University Geology Bulletin》2009,64(4):214-219

A fault was traced along the southwestern margin of the Shatsky Rise. It extends to land where it crosses the Mountainous Crimea. Interpretation and analysis of marine seismic and magnetic survey data, as well as geological data on land, allow stating that the fault originated during the rift evolution stage of the East Black Sea Basin. Currently, the fault is in the sea and is a channel for migrating hydrocarbon fluids. Another fault was traced from the West Caucasus into the sea, where it separates the Shatsky Rise into two structural units.  相似文献   

四川后高坪地区晚泥盆世植物和遗迹化石的新发现   总被引：2，自引：0，他引：2  

张立军  龚一鸣 《地层学杂志》2009,33(2)

在扬子板块西缘后高坪地区新发现植物化石Cyclostigma kiltorkense(平圆印木)和Lepidodendropsis hirmeri(希氏拟鳞木),以及遗迹化石Zoophycos(动藻迹)和Chondrties(丛藻迹),据此及相关地层和沉积相标志,确定该地层时代为晚泥盆世,沉积环境为由早期为滨岸较粗碎屑岩和浅海中上部细碎屑岩沉积,晚期为碳酸盐台地相。  相似文献   

西藏班公湖-怒江板块结合带岩金遥感找矿模式   总被引：1，自引：0，他引：1  

白朝军  陈瑞保  王跃峰  张玉明  左爱萍 《国土资源遥感》2003,14(2):15-18

西藏班公湖-怒江板块结合带地质构造复杂,成矿条件优越,具备形成金矿的地质背景条件,是西藏最具潜力和规模巨大的贵金属成矿带.但由于该区地质工作程度较低和对成矿规律认识不清,至今没有一个可供开发的岩金矿产地.通过班公湖-怒江板块结合带砂金、岩金矿(化)点,地球化学异常和重砂异常的分布并进行控矿因子分析,建立了该带两种岩金遥感找矿模式,通过验证发现该区具有大型远景规模的岩金矿产地,并认为蚀变岩型金矿和穆龙套型金矿是该带最重要的两种矿床类型,具有巨大的找矿潜力.  相似文献