琼东南盆地井震地层对比分析及区域地层格架的建立

琼东南盆地历经断陷、断坳、裂后热沉降和裂后加速沉降等一系列的构造变动,沉积环境由始新世的滨海环境发展为现今的深水环境,形成了一套包括滨岸沉积、滨浅海沉积、陆架和陆坡沉积、以及半深海沉积的地层组合,具有良好的油气资源的生储盖条件,已成为当前油气资源勘探开发的重点区域。本文首先对盆地区域内钻井和地震剖面进行了主要地层界面(T20、T30、T40、T50、T60和T70)的识别和提取(点),继而结合连井地震剖面(线)和盆地区域过井地震剖面(面)对主要地层界面做了追踪对比分析,再依据古生物年代,建立了适用于琼东南盆地的区域地层年代格架。在琼东南盆地浅水区主要沉积了新近系地层(T60-T20),断裂基本不发育,地层厚度变化不大,极少有明显的上超和削截,局部地区发育有利于油气储集的三角洲沉积体系,表明琼东南盆地新近纪时期受构造作用影响较小。在深水区,新近系地层(T60-T20)和浅水区特征相似,仅反射特征有所不同;古近系地层(T100-T60)内部层序结构主要为楔状或近平行状,具有明显的上超和削截,地层厚度较大,断裂明显并导致地层错断,表明琼东南盆地深水区在古近纪时期主要受构造作用控制,并伴随着强烈的拉张和快速沉降作用,沉积环境主要为浅海。在近东西向的中央峡谷内存在有三期砂体:第一期砂体(井深3 528~3 336m,厚约192m)形成于距今11.6~5.5Ma(T40-T30),分布范围跨越中央峡谷的陵水-松南-宝岛段,沉积物构成包括浊积水道沉积、浊积席状砂、块体流沉积、深海泥质沉积、天然堤及漫溢沉积等;第二期砂体(井深4 100~3 900m,厚约200m)形成于距今5.5~4.2Ma(T30-T29),分布范围跨越中央峡谷的乐东-陵水段,以重力流沉积为主;第三期砂体(深度3 630~3 400m,厚约230m)发育于距今4.2~3.6Ma(T29-T28),分布于峡谷的乐东-莺东段,以浊积水道沉积为主。三期砂体在琼东南盆地中央坳陷带自东向西、由老到新依次展布,构成了良好的油气储层体。     

Benthic assemblage composition on subtidal reefs along a latitudinal gradient in Western Australia

At regional scales, the distribution of species and the structure of assemblages vary with latitude within many marine and terrestrial systems. The oligotrophic coastal waters of Western Australia (WA) support highly speciose and endemic assemblages, yet spatial patterns in benthic structure are currently poorly known. We examined benthic assemblage composition along a latitudinal gradient of 28.5–33.5°S and a depth gradient of 14–62 m, on subtidal reefs in warm-temperate WA. We surveyed benthos using a remotely triggered digital stills camera. In total, we sampled macroalgae and sessile invertebrates at 201 sites spread across four locations. Percent cover of coarse taxonomic groups and dominant species was estimated from over 2000 photoquadrat samples. We recorded significant differences in benthic assemblage composition between locations, and along depth gradients within each location. However, the magnitude of change with depth was not consistent between locations, and shifts in assemblage composition along the depth gradients were not as pronounced as expected. The percent cover of all dominant benthic groupings differed between locations, and several key taxa, such as the kelp Scytothalia dorycarpa, brown foliose macroalgae, hard corals and sponges, changed predictably along the latitudinal gradient. Our study adopted a coarse taxonomic, but assemblage-wide, approach to describing macrobenthic assemblages, and clear differences between locations and depths were detected. The surveys have provided baseline data on broad scale ecosystem structure against which to detect future ecological change.     

Distribution and Habitat Preferences of the Introduced MummichogFundulus heteroclitus(Linneaus) in South-western Spain

The distribution and apparent habitat preference of the common mummichog (Fundulus heteroclitus) in south-western Spain were examined during summer–autumn 1996. This introduced species was more or less continuously distributed along the Atlantic coast of Spain, being more abundant in sites near the coastline (usually <10 km inland), mainly in four extensive marshes. The species preferred marsh-related mesohabitats, such as salt lagoons, saltmarsh fish ponds and marsh channels, both natural and man-modified.Fundulus heteroclituswas mostly found at salinities >25. It was the most frequently captured fish species, occurring at 81 of the 272 sites sampled; their frequency of occurrence was almost twice that of the second ranked species (Gambusia holbrooki). However, in over 80% of cases,F. heteroclituswas found alone or with only one sympatric fish species, which usually belonged to a group composed ofGobius niger,mugilids,Anguilla anguilla, Blenniussp.,Lebias ibera, Pomatoschistussp. andDicentrarchus labrax. Finally, the origin and dispersal of mummichog in the Iberian peninsula and the potential effects of this species on native fish populations is discussed.     

Possible effects of human impacts on epibenthic communities and coral rubble features in the marine Park of Bunaken (Indonesia)

Indo-Pacific coral reefs are considered among the most complex and biodiversified ecosystems in the world. Their existence is threatened by both natural and anthropogenic factors. Therefore, the assessment of anthropogenic disturbances is necessary to protect and manage these marine natural resources. In Bunaken Marine Park (North Sulawesi, Indonesia) epibenthic assemblages and coral rubble features at four impacted sites (each of them located close to villages and frequently exploited as recreational diving spots), and four well preserved sites (far from villages and scarcely frequented by divers), were investigated at 6, 12 and 18 m depth, in order to identify possible reef modifications. The assemblages were sampled by way of photographs. Coral rubble cover was estimated both by way of photographs and along belt transects, while grain size and the living fraction of the coral rubble were assessed by direct samples. The data showed significant differences between the study sites and between depths with regard to human activity. The hard coral cover and the assemblage heterogeneity are higher in control sites than in the impacted site where, especially in shallow water, the mechanical damage can strongly affect the assemblage structure.     

西南三江造山带火山岩—构造组合及其意义

岩石构造组合是指表示板块边界或特定的板块内部环境特征的岩石结合。中国西南“三江”造山带的火山岩可划分为五种火山岩－构造组合：洋脊型／准洋脊型组合，岛弧及陆缘弧组合，碰撞型组合，碰撞后组合及陆内拉张型组合。阐述了各种火山岩－构造组合的特点及构造含义。对在造山带火山岩岩石－构造组合分析中经常遇到的一些问题，如“构造岩片”研究方法、地球化学判别图解的使用条件、准洋脊型火山型组合的构造含义、蛇绿岩带－火山弧的成对性、岩浆作用的同步性和滞后性、以及火山岩的深部“探针”作用等问题进行了讨论。     

白垩系叶赫组及其外延的讨论

研究了叶赫组的层序、环境类型、生物群特征及外延后认为，叶赫组在大黑山东南侧、伊通－舒兰地堑及其周边均有不同程度的发育，基本上是泉头组之后至嫩江组之间的同期异相沉积。     

黄玉与红柱石,白云母,碱性长石之间的矿物平衡及其岩石学意义

黄玉的形成条件是阐明含黄玉岩石成因的关键。为定量解释黄玉的岩石学成因意义，本文利用黄玉和与其共存的矿物及流体组分的热力学性质，计算了花岗岩－Ｈ２Ｏ－ＨＦ体系中有关反应的ｌｏｇａＨＦ－ｌｏｇａＫＦ，ｌｏｇａＨＦ－ｌｏｇａＡＮ，ｌｏｇａＨＦ－Ｔ图及Ｔ－Ｐ图。利用上述计算结果，本文解释了含黄玉花岗质岩石及其极端分异产物的形成条件和斑岩Ｍｏ、Ｓｎ矿床蚀变分带的形成机制。     

The Nigerian manganese-rich iron-formations and their host rocks—from sedimentation to metamorphism

This investigation deals with the Nigerian iron-formations and their host rocks and is based on about 560 mineral analyses (electron-microprobe) and 93 whole-rock analyses (64 iron-formations and 29 host rocks). The manganese-rich and Al-bearing iron-formations occurring in various schist belts of the northern and southern part of West-Nigeria consist of the magnetite-free silicate, the magnetite–silicate and the quartz-rich hematite facies.Iron-formations and host rocks originated from submarine-volcanogenic exhalations enriched in Fe, Mn and CO₂ and from Al₂O₃, SiO₂ and alkali (K₂O and Na₂O)-rich continental-derived pelitic to psammitic material. From these sources and their interaction and controlled by the volcanogenic activity, differently composed protoliths were deposited in the marine basin during the Birimian time. Subsequent metamorphism of greenschist to low amphibolite facies conditions during the Eburnian time led to the formation of the metaprotoliths of the magnetite–silicate (consisting of predominantly magnetite and quartz and subordinate of garnet and amphibole), the silicate facies (consisting of garnet, amphibole and rarely Mn-bearing ilmenite and quartz) and the metasediment phyllite. Garnets are predominantly almandine–spessartine solid solutions, whereas amphiboles are Mn and Ca-bearing grunerite–cummingtonite solid solutions. In the course of a second tectono-metamorphic event of Pan-African age, the magnetite–silicate facies iron-formation/phyllite association was transformed into the hematite facies and muscovite/biotite schists, whereas the silicate facies is characterized by extensive silicification features. The hematite facies and the silicified silicate facies are restricted to southern Nigeria where the second and heterogeneous tectono-metamorphic event is more pronounced (amphibolite facies conditions) than in northern Nigeria.The genesis, summarized as the metamorphic model, shows that the carbonate-rich (siderite, rhodochrosite and subordinate magnesite and calcite) protoliths were metamorphically transformed into the silicate and magnetite–silicate facies. The separation of Mn and Fe, leading to manganese-bearing iron-formations and iron-bearing manganese-formations was explained by varying pH-conditions, under which siderite (pH: 6.8–9.4) and rhodochrosite (pH: 9–11) precipitated.Similar to the Gunfit and Biwabik iron-formations of Minnesota, USA, the iron-formation of Bingi (Maru schist belt), now present in the form of the fayalite bearing silicate facies, was overprinted by contact metamorphism caused by a gabbro intrusion.     

Discovery of Paleogene palynological assemblages from the Wanbaogou Group-complex in western part of the Eastern Kunlun orogenic belt and its geological significance

The studied region is located in the Northern Qing- hai-Tibet Plateau, the southern fringe of the Qaidam Basin, about 80 km south away from Golmud City of Qinghai Province (Fig. 1). The Eastern Kunlun oro- genic belt tectonically belongs to a joint zone between the Paleo-Asian Tectonic Domain and the Tethyan- Himalayan Tectonic Domain. Owing to the repeated tectonic movements, its geological structures have become much complicated and the degrees of defor- mation, metamorphism and disl…     

塔西南坳陷侏罗系的扇三角洲沉积

塔西南坳陷侏罗系广泛发育扇三角洲沉积。在论述沉积特征的基础上,确认本区的扇三角洲是一个典型的退积型层序。该层序三层结构明显,下部为扇三角洲平原,中部为扇三角洲前缘,上部为前扇三角洲。反映了该区在早中侏罗世时处于活动盆地边缘,湖水由浅变深,沉降速率大于沉积速率的特点。通常扇三角洲的形成受湖盆边界类型和源区距湖盆距离及古气候３个主要背景条件的约束,因此,本区的扇三角洲一般发育在源区距湖盆距离短,靠近山前植被不发育的地带。塔西南坳陷侏罗系生储盖组合发育齐全,湖相暗色泥岩为主要烃源岩,扇三角洲前缘砂体是较好的储集层,上白垩统和第三系膏泥岩则起着主要的封盖作用。本区侏罗系有着良好的油气勘探前景。