黄土地层中奇异微颗粒的发现与初步研究   总被引：10，自引：1，他引：10  

徐和聆  安芷生 《海洋地质与第四纪地质》1993,13(3):57-66

通过蓝田段家坡黄土和红粘土剖面与第四纪3次巨大撞击事件年代相应的地层内奇异微颗粒的研究,将其划分为5种不同的形态类型,并主要据化学成分,将5类奇异微颗粒归纳为撞击、火山和生物等3种成因类型。文中还提出综合成因模式来解释不同奇异微颗粒赋存于同一撞击事件时段的地层及它们所显示的因果联系。  相似文献   

Significance of Shallow Bottom Friction in the Dynamics of the Tsushima Current   总被引：1，自引：0，他引：1  

Young Ho Seung 《Journal of Oceanography》2003,59(1):113-118

A simple analytical model is considered for the dynamics of volume transport of the Tsushima Current. This model is basically baroclinic but allows bottom friction over the shallow regions connecting the Pacific Ocean to the Japan Sea basin, and is thus different from previous models which are either purely barotropic with bottom friction predominating over the whole domain, or purely baroclinic with bottom friction completely ignored. Compared to the previous barotropic model, this model is not only more realistic but also gives much simpler results. It gives the observed downstream sea level slope, which is not seen in the previous baroclinic model. As a result, the estimated transport of the Tsushima Current is closer to the observational data than those of previous models. This model indicates that the localized bottom friction acting over the shallow regions not only controls the transport of the Tsushima Current but also moves the stagnation point of the western boundary current northward. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Comparison of volcanic rifts on La Palma and El Hierro, Canary Islands and the Island of Hawaii     

J. Acosta  E. Uchupi  D. Smith  A. Muñoz  P. Herranz  C. Palomo  P. Llanes  M. Ballesteros 《Marine Geophysical Researches》2003,24(1-2):59-90

The meso-scale (km) morphology of the well-studied volcanic rift zones on the Island of Hawaii is compared to the morphology of the lesser known rift zones of La Palma and El Hierro, Canary Islands. We find that there are both differences and similarities in their morphologic characteristics. In general, the rift zones on La Palma and El Hierro are shorter (a few tens of km in length) than those on Hawaii (ranging up to >100 km in length), perhaps reflecting both magma supply and composition. Many of the rift zones on Hawaii have well defined axial zones, both on-and offshore. In contrast, the rift zones on La Palma and El Hierro display various geometries ranging from linear ridges having smooth to irregular crests to structures with a broad fan-like morphology in plan view. The pronounced fanning may be a reflection of: 1) the stress field within the rift being insufficient to trap dikes within a narrow region, 2) dike injection and volcanism shifting laterally through time, 3) volcanoes building nearly one atop of another in the Canary Islands, superimposing the stress field of one structure on the other and thus yielding a more complex distribution of gravitational stresses, and 4) low rate of magma supply producing low magma pressures and thus randomly oriented dike injections. Irregularities and curvature along the axes of the rifts on La Palma and El Hierro may be a reflection of differences in the rate of magma production. Unlike the volcanoes on the Island of Hawaii there may be insufficient volumes of lavas erupted on La Palma and El Hierro to smooth out irregularities. The superposition of rifts from different volcanoes may also add to topographic irregularities in the Canary Islands, especially if eruption rates are low.  相似文献   

上海大气湿度的城、郊对比分析   总被引：5，自引：0，他引：5  

周淑贞 《海洋湖沼通报》1994,(2):13-25

本文通过对１９８４－１９９０年上海城区１１个气象站和近郊４个县气象站逐月平均水汽压及对１９８４年１、４、７、１０等４个月逐日０２、０８、１４、２０时等４个观测时刻气象观测资料的对比分析结合上海城市下垫面特征，阐明上海“城市”这个人为因子对大气湿度（水汽压ｅ）的影响，发现在年、月水汽压平均值上均是城区ｅｕ小于郊区ｅｒ，但在１、４、７、１０等月逐日４个观测时刻水汽压的城、郊水汽压差值△ｅｕ－ｒ上，却出  相似文献   

关于长山群岛土地利用总体规划的编制          下载免费PDF全文

张耀光  胡宜鸣 《海洋开发与管理》1994,11(3):21-26

对海岛土地利用的目的，依据、过程以及编制海岛土地利用总体规划的有关问题进行了分析和论述。  相似文献   

The ocean/continent transition along a profile through the Lofoten basin,Northern Norway     

Andreas Goldschmidt-Rokita  Knut J. F. Hansch  Hans B. Hirschleber  Takaya Iwasaki  Toshihiko Kanazawa  Hideki Shimamura  Markvard A. Sellevoll 《Marine Geophysical Researches》1994,16(3):201-224

The Cenozoic margins of the Norwegian-Greenland Sea offer ideal conditions for passive margin studies. A series of structural elements, first observed on these margins, led to the concept of volcanic passive margins. Questions still remain about the development of such features and the location of the boundary between oceanic and continental crust. Despite the thin sediment cover of the margins, seismic reflection data are not able to image the deeper structures due to the occurrence of igneous rocks at shallow depth.This paper presents a 320-km long profile perpendicular to the strike of the main structural units of the Lofoten Margin in Northern Norway. A geological model is proposed, based on observations made with ocean bottom seismographs, which recorded seismic refraction data and wide angle reflections, along with a seismic reflection profile covering the same area. Ray-tracing was used to calculate a geophysical model from the shelf area into the Lofoten basin. The structures typical of a volcanic passive margin were found, showing that the Lofoten Margin was influenced by increased volcanic activity during its evolution. The ocean/continent transition is located in a 30-km wide zone landwards of the Vøring Plateau escarpment.The whole margin is underlain by a possibly underplated, high velocity layer. Evidence for a pre-rift sediment basin landwards of the escarpment, overlain by basalt flows, was seen. These structural features, related to extensive volcanism on the Lofoten Margin, are not as distinct as further south along the Norwegian Margin. Viewed in the light of the hot-spot theory of White and McKenzie (1989) the Lofoten Margin can be interpreted as a transitional type between volcanic and non-volcanic passive margin.  相似文献   

江苏岸外辐射沙洲区沙岛形成过程的初步研究   总被引：6，自引：1，他引：6  

张忍顺  王艳红  吴德安  沈永明 《海洋通报》2003,22(4):41-47

江苏岸外辐射沙洲曾经历了由暗沙到明沙的发育过程，进入20世纪90年代后，近岸的沙洲由于持续淤高并高出大潮平均高潮位而成为沙岛。通过卫片判读和实地观测对沙岛自然属性和形成机制进行了初步研究，认为条子泥西部多年来的持续淤积和潮沟的稳定是沙岛形成的关键，而潮汐和风暴潮是沙岛形成的动力因素。沙岛的形成说明辐射沙洲的发育进入一个新阶段即成岛阶段，并标志着沙洲并陆过程的开始。  相似文献   

一门新兴的边缘科学——火山岩储层地质学   总被引：10，自引：0，他引：10  

陈建文 《海洋地质前沿》2002,18(4):19-22

石油工业持续稳定的发展要求不断有效地寻找勘探新领域、新地区和新类型。随着国内外火山岩油气藏的发现，火山岩储层作为一种特殊的油气储层类型越来越受人们的重视。20世纪90年代末期，石油地质学中出现了一门生命力很强的边缘学科——火山岩储层地质学，其任务是深入研究火山岩油气储层的宏观展布、内部结构、储层参数分布、孔隙结构等特征以及在火山岩油气田开发过程中储层参数的动态变化特征，为油气田勘探和开发服务。其研究内容包括储层地质特征、储层物理性质及储层非均质性、储层孔隙类型与空隙结构、孔隙演化模式及其控制因素、储层地质模型、储层敏感性、储层预测与储层综合评价7个方面。  相似文献   

MINERALOGY OF COASTAL DEPOSITS OF NORTH-WESTERN SEA OF JAPAN   总被引：1，自引：0，他引：1  

N.G.Razjigaeva  L.A.Ganzey 《海洋地质与第四纪地质》1991,(4)

Distribution of heavy, light and clay minerals in Late Pleistocene—Holocene deposits from different coastal environments (beaches, lagoons, dunes, relict lakes, ria bays and inlets, open inlets) was analysed. It was established that mineralogical composition of coastal deposits was a result of provenance and its hypergenous changes, transformation of material within transit zone, and accumulative conditions of inshore zone. Contents of stable minerals increase in deposits of the inlets confined to mouths of the small streams and in horizons of the sections, formed during regressive phases. Unstable minerals amount is higher in deposits of inlets, confined to mouths of the large river. The clay mineral fraction of shelf sediments consists mostly of illite. Authigenous pyrites dominate in deposits of ria bays, lagoons and relict lakes, formed during transgressive phases. Volcanic glass, found in deposits, is product of Holocene eruptions of Baegdusan (Baitushen) Volcano.  相似文献   

Silica‐rich layering at Blanche Point,South Australia     

J. B. Jones  M. J. Fitzgerald 《Australian Journal of Earth Sciences》2013,60(4):529-551

The chemistry and mineralogy of much of the Late Eocene Blanche Point Formation of South Australia show that biogenic and volcanogenic products were the only significant contributor to the sedimentary record. Intermittent volcanic activity followed by dissolution of the resultant silicic ash and small scale migration of silicon with reprecipitation as the oxide, provides the simplest and most likely explanation for the repetitive nature of the silicification. Seemingly, this was controlled by local silica concentrations which in turn were apparently controlled by the biota. Changes in circulation patterns and/or water depth may have initiated the environmental variations recorded in the formation.  相似文献