Stratigraphy and sedimentology of the Upper Cretaceous to Paleogene Kilwa Group, southern coastal Tanzania   总被引：2，自引：0，他引：2  

Christopher J. Nicholas  Paul N. Pearson  Paul R. Bown  Tom Dunkley Jones  Brian T. Huber  Amina Karega  Jackie A. Lees  Ian K. McMillan  Aoife O&#x;Halloran  Joyce M. Singano  Bridget S. Wade 《Journal of African Earth Sciences》2006,45(4-5):431-466

The geology of southern coastal Tanzania has remained poorly understood since the first comments on its stratigraphy were made over 100 years ago. However, new field surveys combined with shallow drilling along the coast between Kilwa and Lindi are beginning to resolve the depositional history and structural evolution of this region over the past 85 Ma. Here we present the first attempt to synthesize the results of these studies to provide a coherent sedimentological, litho- and sequence stratigraphic framework, including new geological maps, for the Upper Cretaceous and Paleogene of the coastal zone.Santonian to Oligocene sediments crop out along a broad coastal belt south of the Rufiji River from the Kilwa peninsula to Lindi Creek in southern Tanzania. During 55 Ma, over 1 km of a broadly homogeneous, mid to outer shelf clay-dominated succession was deposited across the passive margin, which we define here as the Kilwa Group. This lies disconformably across the shelf on Albian marls and is itself unconformably overlain by shallow water Miocene clays and more recent limestones, sands and gravels. Four formations can be identified within the Kilwa Group on the basis of characteristic secondary lithologies and facies, described here for the first time; the Nangurukuru, Kivinje, Masoko and Pande Formations. These formations include conformable stratigraphic intervals through both the Paleocene–Eocene and Eocene–Oligocene boundaries. Within the Kilwa Group, 12 sequence stratigraphic cycles can be identified at present, demonstrating relatively uniform and continual subsidence across the margin from Santonian to Early Oligocene time. A further major bounding surface is present between the Upper Cretaceous and Paleogene, but this may become partly conformable in the Lindi area. Although the principal lithology in all formations is clay or claystone, there are more permeable intervals containing pervasive coarser siliciclastic sediments and these have yielded traces of crude oil which is likely to have migrated from lower in the succession. The Kilwa Group thus also provides important new evidence for petroleum play development in the southern coastal zone.  相似文献   

城市群体建筑物震害模拟方法研究   总被引：2，自引：0，他引：2  

高杰  冯启民  张海东 《震灾防御技术》2007,2(2):193-200

本文针对目前进行城市群体建筑物震害预测时,在数据收集和计算工作中遇到的实际困难,提出了一种简化的震害计算方法——单元破坏度指数法。同时将该计算模型嵌入到ArcView 9.0的GIS平台中,并以Oracle数据库为支撑,结合青岛市的实际数据,对城市群体建筑物的震害进行了模拟。结果表明,单元破坏度指数法不仅大大简化了数据收集和处理的工作量,而且计算结果的精度同样能满足工程应用的要求,与GIS相结合可以客观快速地模拟出城市群体建筑物的震害程度及其空间分布。  相似文献   

青藏高原沱沱河盆地渐新世湖相叠层石:韵律纹层记录的古气候条件     

惠博  伊海生  时志强  夏国清  武向峰  陈三运 《地质通报》2010,29(1):62-69

沱沱河盆地通天河剖面渐新世雅西措群发现一套产于湖泛过程中的柱状叠层石。通过对叠层石纹层形态和显微组构的研究,发现这些叠层石具有典型的富藻纹层和富屑纹层交替的显微结构特征,发育三级生长节律,纹层对之间渐变接触,纹层带之间间断明显。采用激光微区取样的方法,针对4块样品的8个纹层对,系统采集了16对碳氧同位素数据,结果是富藻纹层同位素值整体上均高于富屑纹层,正相关性明显。这表明富藻纹层生长时期气候炎热湿润,富屑纹层生长时期相对寒冷干燥。认为湖相叠层石生长受周期性气候变化的控制,其韵律纹层记录了丰富的古气候信息。  相似文献   

Dwarf galaxies in the dynamically evolved NGC 1407 Group     

Neil Trentham  R. Brent Tully  Andisheh Mahdavi 《Monthly notices of the Royal Astronomical Society》2006,369(3):1375-1391

  相似文献   

The central density cusp of the Sagittarius dwarf spheroidal galaxy     

L. Monaco  M. Bellazzini  F. R. Ferraro  E. Pancino 《Monthly notices of the Royal Astronomical Society》2005,356(4):1396-1402

We present an analysis of the density profile in the central region of the Sagittarius dwarf spheroidal galaxy. A strong density enhancement of Sgr stars is observed. The position of the peak of the detected cusp is indistinguishable from the centre of M54. The photometric properties of the cusp are fully compatible with those observed in the nuclei of dwarf elliptical galaxies, indicating that the Sgr dSph would appear as a nucleated galaxy independently of the presence of M54 at its centre.  相似文献   

西天山木札尔特岩群地球化学与变形变质特征及构造演化     

姚世齐  于海峰  虞卫东  杨中柱  程培起 《新疆地质》2011,29(4):403-411

岩石地球化学特征显示,西天山木札尔特岩群成岩于塔里木原始古陆台内部毗邻陆缘活动带部位.后期木札尔特岩群总体经历3期变质作用和4期变形作用改造:早期低角闪岩相区域动力热流变质作用(M1)与前震旦纪塔里木运动(D1)相对应,构成近EW向断续展布的普通角闪石变质相带;主期角闪岩相区域动力热流变质作用(M2)与奥陶纪末至泥盆纪初的俯冲造山(D2)相对应,宏观上构成近NEE向展布的铁铝榴石-矽线石变质相带;晚期中高绿片岩相区域动力退变质作用(M3)与泥盆纪末至石炭纪末期的同碰撞造山(D3)相对应,宏观上构成叠加于先期变质相带之上的具网结状组构的动力变质带.  相似文献   

宁夏中奥陶统香山群徐家圈组内波、内潮汐沉积类型   总被引：1，自引：1，他引：0  

李向东  何幼斌  张铭记  刘训  姚建新 《地球科学进展》2011,26(9):1006-1014

内波、内潮汐沉积是深水沉积研究中一个非常年轻的研究领域,自发现到现在仅仅20年时间,对其沉积类型的研究目前尚未涉及。以宁夏香山群徐家圈组中的内波、内潮汐沉积为对象,详细描述了深水环境中形成的双向交错层理、单向交错层理、复合流层理及具有波状纹层、束状纹层和交错纹层透镜体的交错层理,并探讨了其成因机制,识别出了短周期内波沉...  相似文献   

保山腊西山铜铅锌多金属矿地质特征     

杨洪  胡成军  李泉  杨勇 《云南地质》2011,30(2):144-147

腊西山矿赋存在古生界崇山群变质岩系中,受区域性崇山西侧压扭性大断裂控制,矿(化)体分布于次级北西向断裂破碎带的矽卡岩碎裂岩内,矿化类型为矽卡岩型.  相似文献   

云南勐海盘龙山铁矿矿床成因     

范建辉  赵含军  李阿者 《云南地质》2011,30(3):323-325,304

盘龙山铁矿成矿物质在热动力条件下迁移,在区域变质及构造作用下,达到绿片岩相的热动力作用下富集成矿化体,之后经漫长风化淋漓富集,原地堆积形成工业矿体,属沉积—变质改造型铁矿之风化淋漓富集残坡积矿床。  相似文献   

福建东山县澳角村澳角群花岗质石榴黑云片麻岩锆石SHRIMP U-Pb定年及其地质意义   总被引：2，自引：0，他引：2       下载免费PDF全文

冯艳芳  邓晋福  肖庆辉  邢光福陆松年  崔显岳公凡影甄世民贾德龙齐钒宇 《中国地质》2011,38(1):103-108

本文对福建东山县澳角村澳角群花岗质石榴黑云片麻岩中17颗锆石进行了SHRIMP U-Pb同位素年龄测定。结果显示锆石Th/U比值变化于0.31~1.01,平均值为0.48,为典型的岩浆锆石;其中16个分析点在谐和图上分布较为集中,206Pb/238U年龄加权平均值为(152.8±1.6)Ma(n=17,MSWD=1.12);结合锆石自形、发育岩浆环带等特点,该年龄被解释为澳角群亲营山组花岗质石榴黑云片麻岩的形成年龄。其所指示的地质意义:(1)福建东山县澳角村澳角群亲营山组花岗质石榴黑云片麻岩形成于晚侏罗纪,而非前泥盆纪;(2)福建东山县澳角村澳角群亲营山组应解体为表壳岩与变质侵入体。  相似文献