北海组的地质时代及其沉积环境

雷州半岛和海南岛北部新生代以来是一沉陷区,第四系发育较完整,从老到新有早更新世湛江组、中更新世北海组、晚更新世八所组、全新世早期石岛组、全新世中期灯楼角组、全新世晚期鹿回头组及烟墩组.第四纪以来曾有四期火山岩:早更新世湛江火山岩、早更新世晚期石峁岭火山岩、晚更新世湖光岩火山岩和全新世雷虎岭火山岩.现仅就第四系中的北海组进行论述.本文是我队共同劳动成果,由薛万俊同志执笔,文中谬误之处,请批评指正.一、北海组的岩性北海组主要分布于雷州半岛北部、广西北海地区及海南岛沿岸.前人最早在北海市发现该地层,故称“北海组”.北海组呈棕红、棕黄色,有的地方可见到网纹,按岩性分为两层,上层为粘土质砂,下层为砂砾.各地岩性略有差异,详见以下剖面.     

西沙礁序列的磁性地层学研究

利用西沙群岛西琛一井３３０ｍ以上井段的１４９块岩心标本，用美国２－Ｇ型超导磁力仪进行了古地磁测定，获得了一个从更新世至中新世晚期包括布容，松山，高斯和吉尔伯特四个极性时及若干亚极性的磁性地层柱，为礁序列的划分对比，提供了新的依据。     

松嫩平原第四纪磁性地层的初步划分

松嫩平原西部近200m厚的第四系,基本记录了距今约300万年来地球磁场所经历的极性时与极性亚时的周期变化.东部高平原第四系仅厚70—80m,岩心自上而下记录了布容正向极性时和松山反向极性时的上部.讨论了第四纪底界与内分层、早更新世晚期地层缺失及关于林甸组与泰康组地层断代等问题.     

渭南阎村W7孔岩心样品的古地磁学研究

对渭南阎村W7孔岩心地层样品的磁性地层学研究,确定了黄土组、三门组地层的时代。这一地区的黄土/古土壤层形成始于松山反极性时晚期,约为1.1MaB.P.。按照地层样品的剩磁特征和岩性特征对黄土/古土壤层作更精细地划分,这一地区的黄土/古土壤层相当于马兰黄土、离石黄土层,缺失午城黄土。地层的剩磁极性资料表明,三门组地层形成于高斯极性时晚期—松山极性时中期,按照奥尔都维正极性亚时为第四纪下限的年代准则,确定三门组地层的时代为晚上新世。 W7孔岩心的地层样品的剩磁极性序列与已有的地磁极性年代表的磁极性序列大体相当,本项研究也揭示了二个短周期极性事件的存在,位于第5黄土层的安比拉事件(Emperor)发生的年代约为0.445—0.458Ma B.P.。位于第9黄土层的后期哈拉米洛事件(Post-Jaramillo)发生的年代约为0.77—0.81MaB.P.。 磁性地层学研究表明这一地区在松山反极性时中晚期出现过沉积间断,持续时约0.5Ma。 根据W7孔的地层学研究认为,选择以奥尔都维正极性亚时末期的年代(1.60MaB.P.)作为第四纪下限是有利于第四纪地层的划分和对比的。     

东亚和东南亚第四系时间界面的建议

在东亚和东南亚第四系对比中,有关的几条界限,本文建议如后。采用Globorotalia truncatulinoides的初现位作为本区海相第四系的下界,其位置大致在古地磁Olduvai亚时的下界,时间约为距今1.9Ma。在南中国海、东海及沿岸地区,发现了以G.truncatulinoides的初现位为代表的一系列有意义的生物事件,如Pulleniatina finalis的初现位,Globigerinoides obliquus和Globoquadrina altispira的灭绝位,以及Globorotalia menardii和Pulleniatina obliquloculata壳体旋向的变化。此界限在东亚和东南亚也是相当稳定的。在陆相地层中,以泥河湾组为代表,狭义的泥河湾动物群(相当于晚维拉方动物群)所在地层的底界,其古地磁位置为Olduvai亚时的底界。以此作为陆相第四系的下界,与上述海相第四系底界一致。 以古地磁布容/松山界线作为中更新世和早更新世的界限,其年代为0.73MaB.P.。中国中更新世的标准地层周口店组,其底界恰为布容/松山的转换面,北京猿人的年代为0.60—0.23MaB.P.。在洛川黄土剖面上,布容/松山界线为古土壤S_7的底界。雷琼地区中更新统下部的北海组的底界也是布容/松山界线,所产的玻璃陨石的裂变径迹年龄为0.687—0.733MaB.P.。在黄海,布容/松山界线是第Ⅶ海侵层的顶界。通过岩石地层标志,以及动物群、古人     

现代黄河三角洲北岸YRD-1101孔岩心磁性地层学

对渤海南岸黄河三角洲地区200.30m的YRD-1101钻孔进行了系统的岩石磁学和古地磁学研究。岩石磁学研究表明沉积物中主要载磁矿物是碎屑磁铁矿,部分样品含有少量铁硫化物和赤铁矿;古地磁学研究结果揭示了早、中更新世界线即布容(Brunhes)正极性时/松山(Matuyama)负极性时界限(B/M)位于该钻孔123.33m处,同时,发现在松山负极性时记录了不完整的奥尔杜威(Olduvai)正极性亚时(191.78~200.30m);根据沉积速率推测该孔底部200.30m的年代为1.885Ma。这一研究为该钻孔提供了可靠的年代标尺,为渤海湾南岸黄河三角洲第四系地层的划分和对比提供了新的依据。     

浙江宁波地区第四纪磁性地层的初步研究

本文根据宁波地区B12和LK1两孔472块古地磁样品的测定,结合微体古生物、孢粉和地层等资料,对宁波地区的第四纪磁性地层的划分与年代作一初步探讨.经分析表明,宁波地区迄今钻遇的第四系地层,在极性年表中属于73万年以来的布容正向时,未见早更新世的沉积;全新世底界以哥德堡亚时为标志,距今1.2—1.3万年;晚更新世底界应放在吉曼卡亚时为宜,距今19.8—21.5万年.     

东营市东辛2-4井磁性地层划分对比研究

本文通过东辛2—4井岩心样品的古地磁学研究,整段岩心呈现以正极性为主的混合极性特征。自上而下划分的布容、松山、高斯和吉尔伯特极性时和布容极性时内清晰显示出的哥德堡和布莱克亚时的界限分别位于井深28.0m、161.0m、274.5m和452.0m。据黄河口南北5个钻孔磁性地层的划分对比,长江口、苏北盆地和东营地区,吉尔伯特、高斯和布容极性时的沉积速度较快,松山极性时较慢或近于缺失;黄河口以北至河北地区,高斯极性时地层不发育,吉尔伯特、松山和布容极性时则较厚,表明它们所处的构造单元、地质基础和沉积环境有较大的不同。     

中国第四纪大陆海侵层磁性地层学的初步研究

磁性地层学是一门近年来新兴的学科.由于地磁极性变化具有全球性和同时性,这就提供了在地层形成过程中可将剩余磁性的极性变化,作为标准来进行地层对比.我国第四纪磁性地层学的工作是从七十年代初期开始的,在解决第四纪下限、第四纪地层的分层和时代、第四纪海侵层的对比和年代、古人类化石的年代等方面取得了一些成果.如得出早更新世泥河湾组地层年代为距今140—307万年左右,元谋组地层为距今150—315万年左右.北京顺 5孔中最早一次海侵的时代为距今 235万年左右.“元谋人”年代为170万年左右,“兰田人”年代为80万年左右.笔者曾     

东菲律宾海柱样沉积物的磁性特征

对东菲律宾海帕里西维拉海盆西侧F090102柱样进行了系统的古地磁和岩石磁学研究,测量了天然剩磁倾角、磁化率、饱和等温剩磁、非磁滞剩磁、-T曲线等磁学参数,进行了磁性地层的划分对比,识别出松山反极性时内的贾拉米洛和奥都维正极性亚时。对磁学参数及其有关比值的研究发现,岩心磁性矿物以低矫顽力磁铁矿为主,可能含有一定的钛磁铁矿。磁性矿物主要是陆源碎屑成因,岩心底段受到海底火山作用的影响。根据磁学参数随深度的变化将岩心分为3段,各段反映了沉积环境和古气候的变化。     

Origin of the hydrocarbon gases carbon dioxide and hydrogen sulfide in Dodan Field (SE-Turkey)

Gas occurrences consisting of carbon dioxide (CO₂), hydrogen sulfide (H₂S), and hydrocarbon (HC) gases and oil within the Dodan Field in southeastern Turkey are located in Cretaceous carbonate reservoir rocks in the Garzan and Mardin Formations. The aim of this study was to determine gas composition and to define the origin of gases in Dodan Field. For this purpose, gas samples were analyzed for their molecular and isotopic composition. The isotopic composition of CO₂, with values of −1.5‰ and −2.8‰, suggested abiogenic origin from limestone. δ³⁴S values of H₂S ranged from +11.9 to +13.4‰. H₂S is most likely formed from thermochemical sulfate reduction (TSR) and bacterial sulfate reduction (BSR) within the Bakuk Formation. The Bakuk Formation is composed of a dolomite dominated carbonate succession also containing anhydrite. TSR may occur within an evaporitic environment at temperatures of approximately 120–145 °C. Basin modeling revealed that these temperatures were reached within the Bakuk Formation at 10 Ma. Furthermore, sulfate reducing bacteria were found in oil–water phase samples from Dodan Field. As a result, the H₂S in Dodan Field can be considered to have formed by BSR and TSR.As indicated by their isotopic composition, HC gases are of thermogenic origin and were generated within the Upper Permian Kas and Gomaniibrik Formations. As indicated by the heavier isotopic composition of methane and ethane, HC gases were later altered by TSR. Based on our results, the Dodan gas field may have formed as a result of the interaction of the following processes during the last 7–8 Ma: 1) thermogenic gas generation in Permian source rocks, 2) the formation of thrust faults, 3) the lateral-up dip migration of HC-gases due to thrust faults from the Kas Formation into the Bakuk Formation, 4) the formation of H₂S and CO₂ by TSR within the Bakuk Formation, 5) the vertical migration of gases into reservoirs through the thrust fault, and 6) lateral-up dip migration within reservoir rocks toward the Dodan structure.     

华南沿海B／M界线附近的群发地质事件

在距今0.7Ma的B/M古地磁极性界线附近,华南沿海发生了一系列地质事件,其中包括火山喷发、断裂、褶皱、不整合、侵蚀、玻璃陨石撒落及气候突变事件。这种突发性的事件群是受地球星体运动统一控制的,并具有某种周期性,可与中国北方和其他大陆对比。文中提出了新灾变论的观点。     

中国沿海管角螺4个自然群体形态差异的比较

运用多变量形态度量学方法,采用7个形态性状对中国北海、温州、湛江、连云港4个管角螺自然群体的形态变异进行分析研究.聚类分析和主成分分析结果表明,北海群体与湛江群体形态最为接近,而温州群体与连云港群体形态差异较大.主成分分析构建了4个主成分,其贡献率:主成分1为42.74%,主成分2为18.23%,主成分3为15.83%,主成分4为11.83%,累计贡献率为88.63%.建立了4个管角螺群体的判别函数,其判别准确率P_1为81.3%～95.6%,判别准确率P_2为75.0%～93.3%,综合判别率为87.3%.3种多元分析结果均认为,4个群体在形态上有一定程度的差异,与地理分布、环境、气候、生物饵料等因子有关,但差异尚未达到亚种水平.     

缅甸安达曼海域中部天然气成因与气源

位于主动大陆边缘的缅甸安达曼海域中部天然气资源丰富,成因多样。天然气成因类型直接影响勘探领域与方向的确定。通过气体组分、CH4和CO2碳同位素资料,对缅甸安达曼海域中部天然气成因类型及气源岩进行了判识。结果表明:上新统部分天然气具有较轻CH4碳同位素,为生物成因气,部分碳同位素较重的天然气属于热成因气;中新统及渐新统天然气CH4碳同位素均较重,属于热成因气;CO2碳同位素显示其存在无机、有机2种成因;此外,还存在少量生物气与热成因气或无机气的混源气。认为该区无机成因CO2与CH4共存体系通过基底断裂来源于地壳深部或上地幔;上新统生物气来自上新统未熟源岩;产于上新统、中新统热成因气,来源于上新统下部、中新统或渐新统上部等深层高-过成熟烃源岩。     

Facies and seismic analysis of the Late Carboniferous–Early Permian Finnmark carbonate platform (southern Norwegian Barents Sea): An assessment of the carbonate factories and depositional geometries

The late Palaeozoic buried Finnmark platform, in the Norwegian Barents Sea, is a depositional system which developed under major modifications of palaeoclimatic and palaeoceanographic conditions, given by the northward drifting of the Arctic depositional domain beyond the tropical belt, the activity of the Gondwanan icecaps, and the gradual closure of the Eastern European seaway. In this study, detailed core/microfacies analysis from the explorations wells 7128/4-1 and 7128/6-1, combined with new 2D seismic sections and available dataset from previous studies in the eastern Finnmark area, have allowed a re-evaluation of the depositional scenarios associated with the Ørn and Isbjørn/Polarrev Formations. The late Asselian–early Sakmarian depositional record of the Ørn Formation, followed by the middle Sakmarian transition to the Isbjørn/Polarrev Formations, shows depth-related variations in sedimentation modes and a change of the platform morphology.In particular, a shift from Chloroforam to Bryonoderm sedimentation mode took place through a stratified water column during the deposition of the Ørn Formation, over what we suggest was a distally steepened ramp. In the late Sakmarian, the deposition of the Isbjørn/Polarrev Formations, characterised by a full Bryonoderm sedimentation mode, took place through a cooler non stratified water column, leading to the gradual instauration of a homoclinal ramp profile.Among the other results, our integrated study suggests the development of subtidal heterozoan mounds associated with the Ørn Formation, predating the formation of the larger, stacked and well-known heterozoan distal complexes of the Polarrev Formation. Given the good potential of the Ørn Formation within the Finnmark depositional domain, our results may help to improve the assessment of future evaluations of reservoir properties in the area, which are closely associated with the depositional style and their post-depositional modifications.     

Characterization of the Karababa-C reservoir in the South Karaku oilfield, southeast Turkey

The South Karaku oil field is located in southeast Turkey, and produces, from the Late Cretaceous Mardin Group, carbonate reservoirs consisting of the Karababa, Derdere, Sabunsuyu and Areban Formations. The Karababa Formation is divided into three members, of which the productive Karababa-C member, discussed here, is composed of shallow marine bioclastic mudstone to wackestone. It is affected by early to late diagenetic processes that caused modification of the original pore system by cementation, dissolution and fracturing. Two petrophysical-petrologic facies can be discriminated by principal component analysis, and linear, multiple and stepwise multiple regression analysis of petrophysical data. These correspond to vuggy-moldic porosity and microporosity dominated reservoirs.     

我国东南沿海5个波纹巴非蛤(Paphia undulata)地理群体的形态差异分析

采用聚类分析、主成分分析和判别分析3种分析方法,对我国东南沿海5个野生波纹巴非蛤群体10个形态性状进行比较研究。聚类分析和主成分分析结果表明,广东东莞与福建厦门群体、广东湛江与海南海口群体的形态最为接近,广西北海群体的趋异程度最大。主成分分析构建了3个主成分,贡献率:主成分1为23.237%,主成分2为16.109%,主成分3为13.009%,累计贡献率为52.355%。判别分析结果表明,5群体间形态差异显著(P0.01)。建立了5群体的判别函数,判别准确率P1为47.1%—80.0%,P2为45.7%—80.0%,5群体的综合判别率为63.8%。Mantel检验结果表明欧氏距离与地理直线距离无明显相关性(r=0.0822,P=0.3820)。广西北海群体明显地与其它4个地方分开,可能已形成一个新的亚种。本研究可为我国巴非蛤种质资源保护及遗传育种提供依据。     

Upper Jurassic stratigraphy and sedimentary facies in the Central Outer Moray Firth Basin,North Sea

The Upper Jurassic of the Outer Moray Firth Basin can be divided into two main stratigraphic units — the Piper and Kimmeridge Clay Formations. In each of these formations five major sedimentary facies can be recognized. The Piper Formation, of late Oxfordian to early Kimmeridgian age, comprises very fine to coarse-grained sandstones and minor mudstone of clastic shelf to shoreline origin. Large scale upward-coarsening sequences are well developed in some areas, particularly in the reservoir sands of the Tartan oilfield, and are interpreted as regressive, possibly deltaic deposits. The unconformably overlying Kimmeridge Clay Formation ranges in age from late Oxfordian through Volgian to Ryazanian. The formation is predominantly argillaceous, but also contains locally thick accumulations of sandstone deposited by gravity flow processes. The Claymore Sandstone Member is proposed as a new name for these sandstones in the region of the Claymore oilfield, where they form the major reservoir. Sands of the Piper Formation were derived mainly from the south-west, although some input from the north may also have occurred. Deposition may have extended further eastwards than the present erosional limit of the sands. Thick sand sequences in the Kimmeridge Clay Formation are probably restricted to the margins of the Witch Ground Graben, where contemporaneous faulting occurred.     

海产腹足类性畸变现象的形态特征

本文选取我国东南沿海的重要港口海口、北海、湛江、汕头和厦门港等作为海产腹足类性畸变现象的现场调查区，结果发现有11种海产腹足类存在性畸变。文中对分布广泛、易采集、性畸变现象普遍的疣荔枝螺的性畸变特征的解剖观察结果进行了详细的描述，同时对其他几种海产腹足类性畸变特性作了对比。根据研究结果将疣荔枝螺性畸变雌体的阴茎和输精管的畸变程度划分为5个阶段。