广西菜子岩剖面中上泥盆统界线附近沉积相与海平面变化*——兼论华南吉维期中期的海退及时间

广西菜子岩剖面处于台地边缘地带,含有底栖生物及浮游生物化石。综合岩相、生物相等资料,按牙形石带时限讨论了该地区吉维期—弗拉斯期早期主要的海平面变化历史。吉维期早期(相当于东岗岭组)经历了持续的海侵,大致下varcus带末期可能出现短暂的海退;“谷闭组”下部岩性复杂,海平面波动强烈,其中较大规模的包括了发生于上varcus带的海退(即吉维期中期海退)及下hermanni-cristatus带初期的海侵。吉维期晚期地层含有丰富的床板珊瑚以及其他礁体生物碎屑,产层孔虫、海百合等,意味着这个时期研究区可能处于礁前的上斜坡部位。“谷闭组”上部（牙形石falsiovalis带至transitans带下部）的岩性为中—薄层与厚层的灰岩互层,以正常的底栖生物为主,反映了由原来的礁前到滩前的变化,但水体深度在中—晚泥盆世界线前后可能总体相似。融县组(底部)以浅灰、灰白色的中—薄层至厚层—块状灰岩为特征,其沉积始于牙形石transitans带中部,证据表明此时海水可能变深。菜子岩剖面的白云岩位于上varcus带的下部,主要为细—中晶结构,见有灰岩残余以及正常海相生物碎屑。横向上与其他剖面对比表明,广西地区上varcus带可能出现了区域性的海退事件。     

华南泥盆系层序地层与岩石-年代地层界线间相关性探讨

以广西六景、象州大乐、桂林塘家湾及贵州独山与贵阳东北郊乌当剖面为例,在已有的地层、古生物、沉积相研究的基础上,开展了层序地层学研究.通过这项研究,认为那高岭组与莲花山组的界线是一年代地层、岩石地层及层序地层合一的界面;论证了大乐剖面应堂组的古琶段与贵州独山剖面的龙洞水组属于下泥盆统的可行性;总结了吉维特阶与艾菲尔阶间多处存在沉积间断面或沉积停滞面的客观事实,确认该界面为一符合实际又易于识别的自然界面,可作为D_2~2 /D_2~1的界面;讨论了存在于不同沉积相中的D_3/D_2界面,认为该界面置于D_2~2上部层序之上的海进体系域顶面,与以牙形类为准确立的界线很接近,但其更利于野外实际工作;对贵阳东北郊乌当剖面乌当组的归属提出疑问,并将其定为吉维特阶早期.     

扬子西缘龙门山区泥盆纪沉积旋回与相序样式

扬子西缘龙门山地区泥盆系可识别出一个二级、三个准二级、十八个三级沉积旋回和三十余种高频旋回,低级（高频）旋回往往以不同形式叠加构成高一级沉积旋回。高频旋回具有复杂的相序结构样式,大致可概括为非对称向上变浅、加深和对称型三种。整个泥盆纪沉积旋回的旋回演化作用早期为异旋回作用,中期为自旋回与异旋回作用交替,晚期则转变成自旋回作用为主。     

Palynological characterization of Givetian-Frasnian deposits in the reference Borehole section 1-Balneologicheskaya (Southern Timan)

A succession of seven palynological assemblages characterizing the Yuzhnyi Timan, Taman, Ust-Yarega, Domanik, and Vetlosyan formations of the southern Timan is established in the Givetian-Frasnian deposits recovered by Borehole 1-Balneologicheskaya and studied in detail. Five individual zones, which are distinguished within stratigraphic range of the optivus-krestovnicovii miospore zone, can be of basic importance for a high-resolution stratigraphic subdivision of the sedimentation stage under consideration. Phytostratigraphic boundary corresponding to the Frasnian Stage base in the East European platform is substantiated in palynological aspect.     

新疆东准噶尔扎河坝钾质玄武岩的地球化学特征及其构造意义

扎河坝钾质火山岩位于准噶尔盆地的东北缘,下泥盆统托让格库都克组内。这些火山岩以玄武岩为主,具有较高的K2O含量(1.66%～4.63%)和K2O/Na2O值(0.36～1.65),并富Sr(665×10-6～906×10-6)、Ba(680×10-6～1596×10-6)等大离子亲石元素和轻稀土(La/YbPM>8),显示出钾玄质岩石的特征。同时,这些岩石具有较高的TiO2(～1.7%),P2O5(～0.8%)和高场强元素含量,类似于高铌玄武岩。尽管具有较高的Nb含量(Nb=21×10-6～23×10-6),这些岩石仍呈现出明显的Nb～Ta亏损,显示了典型的岛弧特征。高的Nb/Yb(～5.9),Nb/Ta(19～21),Zr/Hf(46～51)值以及较高的钾含量表明这些岩石来自一个经交代作用富集的地幔源区。单纯的消减板块脱水难以造成高场强元素的富集,这些岩石较高的Ce/Th(47～50),Ce/Pb(13～19)和Ba/Th(341～777)值并缺乏明显的负铈异常等特征排除了消减沉积物熔体的加入。导致地幔富集的变质组份可能为来自消减板块的低程度熔体。扎河坝钾质玄武岩与稍早前报道的埃达克与富铌玄武岩一起,反映早泥盆世曾经出现过洋壳的消减事件。准噶尔盆地中存在的特征岛弧岩浆表明热消减机制曾经广泛地出现在准噶尔板块演化的不同历史时期,而岛弧地体在准噶尔盆地基底的组成中可能占有较大的比例。     

Prediction of oil or gas pool sizes when discovery record is available

The Upper Devonian Bashaw reef play of the Western Canada Basin was used to demonstrate: (1) estimation of pool size distribution by means of a discovery model, (2) the usefulness of a feedback mechanism in petroleum resources evaluations, and (3) enhancement of reliability by reducing uncertainty associated with estimates. The feedback mechanism presented herein allows us to challenge geological interpretations. For example, given the second largest pool size, the largest pool size can be estimated, and vice versa. In evaluations of petroleum resources, the uncertainty inherited from superpopulations is inevitably associated with the estimates. This type of uncertainty can be reduced to a certain extent if additional information is included in the estimation procedures and, consequently, the reliability of the estimates is enhanced. The additional information used may, for example, be the geological interpretation of a particular play. To achieve maximum effectiveness, resource evaluation methods should possess these types of flexibility. This study also estimated, with a 90% probability, that the remaining potential in the Bashaw reef play ranges from 32 to 50 millions of cubic meters (200 to 300 MM bbl) of oil in place.     

塔里木盆地上泥盆—下石炭统层序地层格架与古地理

利用110余口钻井的录井和测井资料,结合地震资料,运用沉积学原理和层序地层学原理,建立了塔里木盆地上泥盆-下石炭统层序地层格架.自下而上,塔里木盆地上泥盆-下石炭统发育东河层序(SQd)、巴楚1层序(SQb1)、巴楚2层序(SQb2)、卡拉沙依1层序(SQk1)共4个三级层序,每个层序均可划分出海侵体系域(TST)和高...     

Coupling relationships between brachiopods and Girvanella during the Late Devonian F-F transition in Guilin, South China

The abundance curves derived from area proportions of brachiopods and Girvanella in the thin sections from the Yangdi section, South China, exhibits complex relationships during the Late Devonian Frasnian-Famennian transition. The living activity of brachiopods such as grazing and borrowing did great damage to the growth of Girvanella. However, there was more to just a mere a survival competing relationship between them, Girvanella actually improved marine environments by oxygenating the dysoxic ambient sea-water through photosynthesis in the lower Kellwasser Horizon. Profited from this improvement brachiopods' abundance increased subsequently and suppressed Girvanella again. Nonetheless, without Girvanella's photosynthesis, brachiopods were wiped out by the farther anoxic environments in the upper Kellwasser Horizon. The complex relationships between Girvanella and brachiopods may be a key to unlocking the relationships between geomicrobes and metazoans in the geological overturn periods.     

青海东昆仑莫河下拉银多金属矿区晚泥盆世花岗斑岩锆石U-Pb年代学及地球化学特征

莫河下拉银多金属矿床是青海省东昆仑成矿带上近些年新发现的矿床。笔者对矿区平硐口花岗斑岩进行了LA-ICP-MS锆石U--Pb测年和岩石地球化学特征研究,以期揭示岩体的成岩时代、岩浆源区和形成的构造背景。锆石测年结果显示岩体形成于古生代晚泥盆世(371.6±2.9Ma)。元素地球化学特征表现为高硅、高碱、富铁铝、相对富钾和贫钙镁的特征;微量元素表现为明显富集Rb、Th、La、Ce、Nd、Zr、Sm和Gd等元素,强烈亏损Ba、Sr、P、Ti等元素、相对亏损Nb和Ta的特征;稀土元素表现为轻稀土元素(LREE)明显富集和Eu的强烈负异常。综合研究认为,矿区平硐口花岗斑岩的成因类型为A2型花岗岩,形成物质来源主要为部分熔融的长英质地壳,形成的大地构造背景为晚泥盆世万宝沟大洋玄武岩高原和苦海古陆拼贴到柴达木地块南缘后的后碰撞伸展环境。     

The ‘old red sandstone’ of county mayo,Northwest Ireland

The distribution and stratigraphic relations of the Old Red Sandstone of the Clew Bay area. County Mayo are described. They comprise two groups both dominated by conglomerates, one Lower Devonian and one Middle Devonian, which have differing clast contents and which are separated by faults. The sediments are described in terms of five facies which are all interpreted as alluvial fan deposits. Provenance data from palaeocurrents and clast composition suggest transport predominantly to the west-northwest but one formation shows an opposite sense of transport. The rocks are folded about northeast-southwest axial traces and are affected by numerous faults. Structures are more complex than those of the Lower Carboniferous rocks which unconformably overlie the Devonian. A similar tectonosedimentary setting to the Old Red Sandstone of parts of the Scottish Caledonides is indicated.