The radiolarian assemblages of the Bonarelli Horizon in the Umbria-Marche Apennines and Southern Alps, Italy     

Giovanni Salvini  Marta Marcucci Passerini 《Cretaceous Research》1998,19(6):777-804

The Bonarelli Horizon is an important regional marker level in the Umbria-Marche Apennines. It is characterized by consisting of black bituminous shales that yield a distinctive radiolarian fauna. Black shales referable to the Bonarelli Horizon are also present in the Southern Alps. The horizon is of uniform lithology and contains radiolarian assemblages of late Cenomanian-early Turonian age throughout both the Umbria-Marche Apennines and Southern Alps. Several new radiolarian taxa have been recognised and described from the Bonarelli Horizon of both areas. Two new species are defined in this paper, namelySethocapsa bossoensisandXitus picenus.  相似文献   

Response of deep-sea ostracod assemblages to Late Cretaceous palaeoceanographical changes: ODP Site 689 in the Southern Ocean     

Stefan Majoran  Joen G.V. Widmark 《Cretaceous Research》1998,19(6):843-872

Twenty-six deep-sea ostracod species are described from the late Campanian to late Maastrichtian of ODP Site 689 in the Southern Ocean. Three are described as new:Cytherelloidea megaspirocostata,Agulhasina sudoceanicaandPennyella foveolata. Correspondence analysis identified three faunal sample groups. The first is mainly characterised byA. sudoceanica,Kirthesp. andCytherellasp. This is replaced, first temporarily (betweenc. 71 and 69 Ma) by a group mainly characterised byArgilloeciaspp. andC. megaspirocostata, possibly a consequence of a short-lived global palaeoceanographic event marked by increased ventilation and cooling of intermediate waters at site 689. It then reappears before finally being replaced by a third group largely characterised byEucytherecf.circumcostata,P. foveolataandDutoitella mimicaDingle. This final change is coeval with a marked increase in the faunal density of ostracods, probably owing to an increase in food supply. However, the oxygen isotopic records of benthonic foraminifera suggests that the replacement of the first ostracod group by the third is a result of the long term Maastrichtian cooling of intermediate waters at high latitudes. This replacement is also coeval with a gradual change in benthonic foraminiferal assemblages at site 689. It is suggested, therefore, thatPennyellaandDutoitellahad a greater potential of adapting to successively colder palaeoceanographical conditions thanAgulhasina. The former genera have a cosmopolitan deep-sea distribution today.  相似文献   

分层式金刚石锯片刀头结构的研究   总被引：1，自引：0，他引：1       下载免费PDF全文

段隆臣  汪国香  杨凯华  汤凤林 《探矿工程》1998,(4):43-46

在阐述了锯齿的磨损机理和分析了圆弧状凸齿产生的原因之后,从理论上推算出了分层式刀头的纯合金层的厚度,并结合生产试验得出了切割花岗岩用锯片刀头层数的计算公式。  相似文献   

秦岭东段金红石矿床成矿构造环境分析   总被引：7，自引：2，他引：5  

李博昀 《化工矿产地质》1998,20(1):17-24

通过对秦岭东段主要金红石矿床赋矿层位地质及地球化学特征的研究及对矿源层形成时的构造环境的分析 ,划分出 4种不同的成矿构造环境。中元古代以来 ,本区地壳处于强烈的陆 洋壳演化分异阶段 ,在北秦岭宽坪小洋盆、桐柏 大别古陆形成了与幔源成因有关的矿源层 ;在杨子地块北缘的被动陆缘拉张海盆形成了与沉积有关的矿源层。晚古生代以来 ,本区处于陆壳演化阶段 ,成矿构造环境为陆缘裂陷海槽环境 ,矿源层的形成与壳源岩浆有关  相似文献   

对南方碳酸盐岩地震攻关的刍议   总被引：2，自引：2，他引：0  

陆邦干 《海相油气地质》1998,3(4):8-13

中下扬子地台和滇黔桂以古生代为主的广大碳酸盐岩地区,由于地下构造和地面地形复杂,长期以来地震资料难以过关。因而南方碳酸盐岩地震攻关是一项艰巨的战略性任务,是须长期奋斗的一项复杂的系统工程,其攻关技术应从采休阶段的优化设计,接收条件,爆炸条件,严格管理,处理阶段的静校正,速度研究,去噪,偏移,解释阶段的叠前深度偏移等几个方面考虑,介绍了速度模型求取及复杂构造成像技术的运用成果。  相似文献   

DYNAMIC AND THERMOHALINE PROPERTIES OF THE MINDANAO UNDERCURRENT,PART Ⅱ: THERMOHALINE STRUCTURE     

王凡  胡敦欣 《中国海洋湖沼学报》1998,(3)

INTRODUCTI()NThenorthwardflowingMUCbelowtheMCwasfotmdandnamedbyHuandCui(1989,l99l)usinghydrographicdataofOctoberofl987and1988gatheredddringtheChineseAcademyofSCiencesmtilti-institutionalpro~onAirSeaInteractionintheWesternTropicalPacificandIntemalCliInaeChange(CAS)-Recently,WangandHu(l997,hereinafer,wn)eednedtheMUCdrodricstmctUreusinghydrOgraPhicdataof1lcmisesconductedatnear8"NzonalsectionsbytheCASprograrnandthePRC-USJointProgramonAir-SeaInteractionintheWestemEqUatorialP…  相似文献   

Dynamic and thermohaline properties of the Mindanao Undercurrent, part II: Thermohaline structure   总被引：2，自引：0，他引：2  

Wang Fan  Hu Dun-xin 《中国海洋湖沼学报》1998,16(3):206-213

Hydrographic data from eleven 1986–1991 cruises at zonal sections near 8°N from the Philippine coast to 130°E were used to examine thermohaline structures and water mass properties of the western boundary currents there, especially those of the Mindanao Undercurrent (MUC). The finding that the MUC consisted of two water masses with salinity of 34.6 at 26.9 σ_t and 34.52 at 27.2 σ_t which were remnants of the lower part of the Southern Pacific Subtropical Water (SPSW) and of the Antarctic Intermediate Water (AAIW) of South Pacific origin, respectively, showed that the MUC was not a local transient but originated elsewhere. As the MUC flowed from 7.5°N to 8°N, part of it carrying the SPSW turns anticyclonically and eastward. The Northern Pacific Intermediate Water (NPIW) often joins the MUC, which suggests that the NPIW carried by the MC partly returns northward as a result of the shear between the MC and the MUC or other processes. The shear instability provides the energy for the irregular fluctuation of the MUC. Contribution No. 3256 from the Institute of Oceanology, Chinese Academy of Sciences. Project 49176255 and 49706066 supported by NSFC, and also by Foundation of Post-doctoral Research.  相似文献   

辽南金矿集中区卫星图像构造解译及构造控矿模型探讨   总被引：2，自引：0，他引：2  

吕贻峰  李江风  秦松贤 《国土资源遥感》1998,9(4):43-49

辽南地区是我国最重要的五大金矿床集中区之一,大、中、小型矿床、矿点众多,矿床类型复杂,控矿因素多样。与国内外大多数金矿一样,在诸多控矿因素中,构造变形因素最为重要,而且有其自身的变形特点和特殊的控矿类型。本文旨在着重讨论辽南这一特定的金矿集中产出地所具有的构造控矿特征和构造控矿模型,为研究大型金矿区或金矿群的形成条件提供借鉴。  相似文献   

南海南部海洋环流研究的新进展   总被引：16，自引：0，他引：16  

方文东  方国洪 《地球科学进展》1998,13(2):166-172

综合近期南海南部环流研究的主要成果，描述南海南部的主要流系及其变化。指出研究海区环流主要由季风所驱动。东北季风期，其西部主要由气旋式环流所控制，东部则受较弱的反气旋式环流控制，在二者结合部形成强的逆风海流。西南季风期，海区大部分受反气旋式环流控制，其北侧为一气旋式环流，二者结合部形成强的东向离岸流。还讨论了环流的演变特性和流涡的形成机制。  相似文献   

The impact of base-level analyses on stratospheric circulation statistics for the Southern Hemisphere     

David J. Karoly 《Pure and Applied Geophysics》1989,130(2-3):181-194

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