Stratigraphic responses to a major tectonic event in a foreland basin: the Ecuadorian Oriente Basin from Eocene to Oligocene times

The Eocene to Oligocene sediments of the Ecuadorian Oriente Basin record two kinds of second-order stratigraphic response to the tectonic evolution. Lower Eocene shows evidences of local scale syntectonic deposits. This tectonic activity can be related to right lateral convergent movements inverting pre-cretaceous extensional structures. Upper Eocene and Oligocene sediments are integrated as the expression of an isostatic rebound characterizing a basin scale syntectonic deposition. This response is evidenced by a reciprocal architecture of the depositional sequences identified in the sedimentary formations. These data have allowed us to propose a new geodynamic model for the Paleogene evolution of the Oriente Basin.     

Facies and depositional settings of the Middle Eocene-Oligocene carbonates in Kutch

Middle Eocene Fulra Limestone and Oligocene Maniyara Fort Formation represent platform carbonate deposits of Kutch at the north-western margin of India. These carbonates contain larger benthic foraminifera, including Alveolina, Assilina, Discocyclina, Lepidocyclina, Miogypsina, Nummulites and Spiroclypeus. This study presents paleodepositional and paleobathymetric interpretations for both formations using benthic foraminifera in combination with lithological association, sedimentary structures and early diagenetic features. The six carbonate facies comprising the Fulra Limestone indicate a depositional spectrum ranging from bar-lagoon to mid-ramp depositional conditions. It records several shallowing upward cycles, leading to emergence and formation of paleokarst. The four carbonate facies of the Maniyara Fort Formation represents deposition within the inner ramp setting in bar-lagoon and patch-reef environment, while intervening fine siliciclastics correspond to episodes of relative sea level fall. Nummulitic accumulations form low-relief bars within the fair weather wave base in both the formations. The depositional setting of the Paleogene carbonate in Kutch broadly resembles Eocene platformal deposits in the circum-Tethys belt.     

柴达木盆地归属问题的讨论

柴达木盆地西部已找到17个第三系油源的油田，其主要烃源岩层位是陆相始新统下干柴沟组。也有论文提出下干柴沟组是海侵湖泊沉积，并被命名为下干柴沟海侵。最近又有论文提出该组地层不是深湖相，应属于泻湖相，是塔里木盆地西南始新世海湾泻湖相带被阿尔金断裂东错的残留泻湖部分，或塔里木盆地原型盆地的东部被错移部分，并提出重新认识柴达木盆地西部的油气勘探方向。本文针对上述观点展示了塔里木盆地西部海湾古新统-始新统的吐依洛克组、阿尔塔什组、齐姆根组、盖吉塔格组、卡拉塔尔组的沉积相和典型的海相生物化石群，它完全不同于柴达木盆地古新统-始新统的路乐河组和下干柴沟组沉积相和陆相湖泊生物化石群，两者是截然不同的。不能支持柴达木盆地西部与塔里木盆地西南海湾在老第三纪时属于同一盆地或同一沉积单元。“源控论”依然是指导柴达木盆地西部陆相沉积油气勘探的理论依据。把塔里木盆地西南已知油气田的烃源岩划归老第三系海相沉积，显然是误解，把塔里木盆地西南老第三系海相油气勘探部署推广到柴达木盆地西部陆相沉积区也是一种误导。科学的古地理观将有助于勘探工作的正确部署。     

Paleogene tectono-sedimentary evolution of the Alicante Trough (External Betic Zone,SE Spain) and its bearing on the timing of the deformation of the South-Iberian Margin

The Paleogene Alicante Trough of the South-Iberian Margin (External Betic Zone) consists of a narrow sedimentary basin that has active margins located to the north-northwest (active mainly during the Eocene) and to the south-southeast (active during the Oligocene). Both margins, consisting of shallow unstable platforms, were the source areas for the external-platform slope (in the opposite margins) and deepbasin (in the middle) depositional realms. The southern margin, lost under the Mediterranean Sea, is recognized only by the reconstructed Oligocene slope sediments.

The eight successions studied, on opposites external-platform-slope margins and the deep within the central part of the basin, lead us to divide the basin into two depositional realms: the subsident Western Depositional Area (WDA) and the not subsident Eastern Depositional Area (EDA). This study has also enabled us to divide the infilling of the basin into two depositional sequences: Eocene p.p. (EDS) and Oligocene p.p. (ODS) in age, respectively, bound by two sequence boundaries (unconformities) at the Early Eocene (P6 zone) and Early Oligocene (P19 zone). The EDS and ODS are comprised of turbiditic and olisthostromic deposits and frequently slumps, evidencing an active tectonic in the margin-basin system.

The correlation of the Paleogene sedimentary reconstructed in the Alicante Trough with other four synthetic successions throughout the External (three in the Subbetic Domain) and one in the Internal Betic Zone indicate a Paleogene generalised deformational framework. In addition, this evolution is contemporaneous to the Pyrenean, Iberian and the Nevado-Filabride Alpine deformation. The Paleogene tectonic recognised in the External Betic Zone is younger since the main orogenic deformation took place in the late Burdigalian to early Tortonian. The origin of these early tectonics is discussed in relation to the Nevado-Filabride Alpine deformation.     

Integration of outcrop and borehole image logs for high-resolution facies interpretation: example from a fluvial fan in the Ebro Basin, Spain

Electrical borehole image logs yield high-resolution information about variations in micro-resistivity along the borehole wall. To interpret these variations in terms of sedimentary structures and lithofacies types, calibration with real rock is needed. Normally, the only real rock available is core, and this only provides one-dimensional information. In this paper, the interpretation of fluvial facies types from borehole image logs was established by direct comparison with outcrops. Four fluvial facies associations were established in an outcrop study of a low net-to-gross fluvial succession: (i) meandering rivers, (ii) braided rivers, (iii) crevasse deltas, and (iv) crevasse splays. The lithofacies characteristics and palaeocurrent distributions of each fluvial facies association were established. Two 200 m deep wells were drilled behind the cliff face outcrops. One well was cored to a depth of 150 m and borehole image logs were recorded in both wells. The wells were correlated with the outcrop. The borehole image logs were analysed by their vertical colour succession and the dipmeter pattern. Image log facies were established, and these were interpreted in terms of the fluvial facies associations encountered in the corresponding outcrops. The study of borehole image logs yields a set of diagnostic criteria for a detailed fluvial facies interpretation and the establishment of depositional trends, and thus provides a powerful tool for the direct interpretation of fluvial facies in a reservoir setting.     

张性边缘海的成因演化特征及沉积充填模式——以珠江口盆地为例

珠江口盆地的形成和演化过程经历了晚白垩世至渐新世的裂陷-晚渐新世至中中新世的热沉降-晚中新世至今的断块升降3个演化阶段,沉积了陆相-半封闭海相-开阔海相3套不同的沉积体系组合。总结归纳出珠江口盆地新生代3个阶段的沉积充填模式,并发现：裂陷阶段以充填式堆积和河湖沉积为特征,形成盆地最重要的湖相烃源岩--文昌组泥岩;热沉降阶段以海陆交替、海相沉积体系为特征,为形成良好的储盖组合创造了条件,沉积了珠江口盆地内最主要的储油层系--珠海组、珠江组以及韩江组,主要为滨海相、三角洲相等碎屑岩沉积;晚期盆地整体下沉,区域性盖层形成。该沉积组合反映了张性边缘海盆地的演化特点,盆地演化与资源效应表现在裂陷期、热沉降期及断块升降期的生储盖配置,故勘探目的层段为热沉降阶段所形成的三角洲碎屑岩与陆棚碳酸盐岩。     

东海盆地新生代沉积环境

东海盆地是新生界为主的沉积盆地,根据地震和钻井资料分析,可划分为四套沉积层序:白垩统-古新统、始新统、渐新统-中新统和上新统-第四系.沉积环境经历了浅海、海陆交替相→海湾相→河湖交潜相→平原河流相→浅海(开阔海)相的发育历程.     

Anatomy of a Forearc Submarine Fan: Upper Eocene — Oligocene Andaman Flysch Group,Andaman Islands,India

Detailed facies analysis in the upper Eocene—Oligocene Andaman Flysch Group reveals fourteen different facies, grouped into three different associations. These facies associations represent two anatomical divisions of a submarine fan, viz. inner fan and depositional lobe in middle fan. Paleocurrent pattern, high percentage of quartz in the sandstones and outer arc derived clasts in the inner fan channel conglomerates suggest dual sediment supply in this fan. A longitudinal geometry of the basin has been inferred where juxtaposition of sediments of different proximality deterred development of any definite sequence pattern. A tectonically induced active sediment supply in a rising sea level stand is thought to be responsible for development of the fan.     

青藏高原东缘古近纪粗碎屑岩沉积学及其构造意义

青藏高原东缘古近纪盆地的填图和沉积学研究表明,在青藏高原东缘区域性走滑-挤压构造背景下形成的古近纪盆地内广泛发育厚层—巨厚层状的紫红色粗碎屑岩系。其沉积特征指示为一种近源快速堆积的泥石流和辫状河道沉积体,形成于干旱炎热气候条件下的典型陆内冲积扇环境。盆地充填序列、粗碎屑岩层序、动植物化石和盆地内岩浆岩~(40)Ar-~(39)Ar年代学等综合研究结果表明,古近纪盆地内粗碎屑岩大约形成于38～29 Ma。该时期与青藏高原东缘北段(横断山地区)古近纪盆地的形成和南段(兰坪—思茅地区)大盆地的裂解时间基本一致,这很可能预示着青藏高原在晚始新世—早渐新世期间曾发生过整体的快速构造隆升。     

剑川-兰坪盆地古近纪沉积-构造变革及其区域构造意义

滇西新生代兰坪盆地和剑川盆地分别位于哀牢山–红河断裂带两侧,青藏高原东构造结内,其沉积过程和构造变形对青藏高原东南缘的构造演化有重要的启示意义。通过对这两个盆地古近纪沉积和构造过程的研究,我们发现兰坪盆地和剑川盆地及邻区的构造变形分为三期:始新世早期的强烈挤压变形、始新世中晚期的伸展变形、渐新世的走滑变形。始新世早期的挤压变形主要表现为兰坪地区的褶皱–冲断系统、哀牢山-红河断裂的逆冲活动和剑川盆地的宽缓褶皱。沉积方面,古新统勐野井组(E_1m)较为稳定的细粒滨湖相沉积转变为始新统宝相寺组(E_2b)较粗的具有前陆盆地性质的河流相沉积,特别是宝相寺组底部发育的一套快速堆积的磨拉石建造,可能是对始新世强烈挤压环境下的沉积响应。始新世中晚期伸展变形体现在盆地的构造环境由早期的挤压环境变为伸展环境和该时期大量富钾岩体和岩脉的侵入,沉积学上,下始新统宝相寺组的河流相转变为中始新统金丝厂组(E_2j)具有快速堆积磨拉石特征的曲流河沉积,极可能是对构造体制变革的沉积响应。渐新世的走滑变形则体现在渐新统的缺失和哀牢山–红河断裂的早期左行走滑。因此,我们认为剑川–兰坪地区在始新世中期和渐新世均发生了显著的运动学转换,这一认识也得到了始新世中期兰坪和剑川盆地物源明显变化的支持。结合青藏高原东南部始新世中晚期岩浆的活动,渐新世大型剪切带(崇山剪切带、高黎贡剪切带)的强烈走滑和保山块体的旋转,我们推测青藏高原东南缘古近纪的构造演化为古新世-始新世早期的挤压、始新世中晚期的伸展、渐新世的转换压缩。     

Sedimentary Characteristics and Reservoir Prediction of Paleogene in the East Part of Kuqa Foreland Basin

Being one of the largest gas fields ever discov-ered in the continental exploration of China , theKela-2 gas field in the Tari m basin has become afoundation for the reliable production of gas re-sources for the “West-to-East Gas Transmission”project . The Kuqa depressionis one of the most eco-nomically i mportant oil and gas prospecting districtsin the Tari mbasin, with a giant gas fieldfoundinitsnorthern central area . Many previous studies haveshown that the Paleogene Kuqa depression …     

Stratigraphy and sedimentology of the Upper Cretaceous to Paleogene Kilwa Group, southern coastal Tanzania

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.     

广西百色盆地沉积体系及煤、石油的聚集规律

从露头、钻孔岩芯、电测曲线及地震剖面入手对百色盆地进行了相分析及古流向分析,提出了盆地发育的四种沉积体系:冲积扇、河流、三角洲及湖泊。它们在空间上有一定展布规律,构成沉积体系域。它们在时间上前后相继,展现出盆地充填序列。油气及煤的聚集发生在盆地扩展期。富煤带及油气富集与扇—三角洲—湖体系域密切相关,分别位于该体系域的三角洲平原和三角洲前缘及扇砂体中。     

Timing of basin inversion on the Isle of Wight: New evidence from geophysical log correlation, seismic sections and lateral facies change in the Palaeogene Headon Hill Formation

Paleogene thickness patterns across the Bouldnor Syncline and Porchfield Anticline in the northwestern Isle of Wight have been deduced using outcrop information, borehole correlation, gamma-ray logs and seismic reflection data. The thickness patterns provide evidence for an early phase of basin inversion at around the Bartonian-Priabonian boundary (Late Eocene) in the Isle of Wight. Paleogene strata older than the Becton Sand Formation show little evidence for significant lateral changes in thickness, even though the boreholes are located at various structural positions around the Bouldnor Syncline and Porchfield Anticline. In contrast, both seismic reflection and borehole data provide evidence for marked thinning of Paleogene strata onto the Porchfield Anticline at around the level of the Becton Sand Formation and basal Headon Hill Formation (Totland Bay Member) which probably results from an episode of basin inversion and growth folding. The inversion event was relatively minor and short-lived and continues to point toward the main phase of the basin inversion being late Oligocene or younger. However, it still has important implications for understanding structural control on sedimentation patterns in the Headon Hill Formation, with the migration of sandy channelised depositional systems into the axis of the Bouldnor Syncline, and the sequence stratigraphic significance of the important Bartonian-Priabonian regression event, which may related to tectonics rather than global sea-level change.     

Cenozoic sedimentary dynamics of the Ouarzazate foreland basin (Central High Atlas Mountains, Morocco)

Cenozoic continental sedimentary deposits of the Southern Atlas named "Imerhane Group" crop out (a) in the Ouarzazate foreland basin between the Precambrian basement of the Anti Atlas and the uplifted limestone dominated High Atlas, and (b) in the Aït Kandoula and Aït Seddrat nappes where Jurassic strata detached from the basement have been thrust southwards over the Ouarzazate Basin. New biostratigraphic and geochronological data constraining the final Eocene marine regression, the characterization of the new "Aït Ouglif Detrital Formation" presumed to be of Oligocene age, and the new stratigraphic division proposed for the Continental Imerhane Group clarify the major tectonogenetic alpidic movements of the Central High Atlas Range. Four continental formations are identified at regional scale. Their emplacement was governed principally by tectonic but also by eustatic controls. The Hadida and Aït Arbi formations (Upper Eocene) record the major Paleogene regression. They are composed of margino-littoral facies (coastal sabkhas and fluviatile systems) and reflect incipient erosion of the underlying strata and renewed fluvial drainage. The Aït Ouglif Formation (presumed Oligocene) had not been characterized before. It frequently overlies all earlier formations with an angular unconformity. It includes siliciclastic alluvial deposits and is composed predominantly of numerous thin fining-upward cycles. The Aït Kandoula Formation (Miocene-Pliocene) is discordant, extensive, and represents a thick coarsening-upward megasequence. It is composed of palustro-lacustrine deposits in a context of alluvial plain with localized sabkhas, giving way to alluvial fans and fluviatile environments. The Upper Conglomeratic Formation (Quaternary) is the trace of a vast conglomeratic pediment, forming an alluvial plain and terraces. The second and third formations correspond to two megasequences engendered by the uplift of the Central High Atlas in two major compressive phases during late Oligocene and Miocene-Pliocene times. These two geodynamic events were separated by a tectonically calm phase, materialized by palustro-lacustrine sedimentation (Görler et al. 1988). Tectono-sedimentary analysis of the two megasequences shows that the basin structure and depositional processes were controlled by the compressive tectonic context generated by the collision of North Africa and Iberia in Tertiary times (Jacobshagen et al. 1988). The Quaternary Formation was apparently controlled by a tectonic continuum and by climatic variations.     

南海西南部北康盆地新生代沉积演化史

北康盆地位于南沙地块的西南边缘，为南沙中部海域的新生代沉积盆地，具有良好的含油气潜力。近年广州海洋地质调查局在盆地六万多平方千米范围内完成了近2000km的地震测线，及相应的重力与磁力测量。本文在区域地质背景分析基础上，对盆地进行了地震地层对比和详细的地震相分析，划分了3个超层序、7个层序，对其中的5个层序进行了沉积相分析，并编制了沉积相平面图。晚始新世以前，北康盆地位于古南海西北缘，盆地西北部为陆相环境。东南部为滨－浅海环境。晚始新世－早渐新世早期，南沙地块从华南陆块裂离向南漂移，随古南海洋带的被动消减和新南海的扩张，盆地水体加深，除西北尚有陆相沉积外，主要为海相环境。早渐新世后，南沙地块与婆罗州地块拼贴，北康盆地逐渐处于浅海－半深海环境。与盆地沉积演化规律相对应，早第三纪发育的湖相和沼泽相泥岩及早中新世发育的浅海相泥岩为有利烃源岩， 同期的三角洲相砂岩、滨海相砂岩及晚中新世发育的浊积岩为主要储层，区域性盖层为晚各新世以来的 浅海－半深海相泥岩、砂质泥岩、局部性盖层有湖相泥岩、浅海相砂质泥岩、泥岩和灰质泥岩。     

东濮凹陷古近系伸展褶皱及形成机理

东濮凹陷是一个新生代裂陷盆地,古近纪为裂陷期,形成各种各样的褶皱构造及具有潜力的圈闭构造。本文在地震资料解释基础上,对东濮凹陷褶皱类型进行划分,讨论褶皱形成机制和油气地质意义。东濮凹陷古近纪褶皱,按照褶皱轴向与断层走向关系分为纵向、横向和斜向褶皱;按照褶皱与断层的成因联系,可划分为断弯褶皱、断展褶皱和变换褶皱等。褶皱作用分三个时期,即始新世、渐新世和始新世–渐新世。褶皱的形成机理为顺层剪切滑动和切层剪切滑动。褶皱的形成与断层紧密相关,是断面形态、断层多期活动和断层位移变化的结果。东濮凹陷油气圈闭与褶皱存在直接或间接的关系。     

A Natural Gamma Spectrometry approach to derive clay mineral composition and depositional environment of a reservoir facies in Ramnad sub-basin,Cauvery basin,southern India

The Ramnad sub-basin is one of the most explored for hydrocarbons in Cauvery basin. A number of exploratory wells have been drilled to delineate hydrocarbon bearing horizons. Nannilam Formation of Santonian–Campanian age hosts considerable thickness of reservoir facies. The reservoir facies is mainly clastics such as sandstone and siltstone with lot of clay content. In addition to normal logs, the NGS (Natural Gamma Ray Spectrometry) logs are widely employed to estimate sediment composition and broad depositional environment of reservoir facies. The present study employs and analyses NGS logs of four well sections from Kanjirangudi area of Ramnad sub-basin to determine the clay mineral composition and depositional environment of Nannilam Formation. Thorium (Th), potassium (K) and uranium (U) concentrations and their interrelationships reveal that montmorillonite, illite and kaolinite are the dominant clay minerals. The clay mineral composition suggests that the sediments of the Nannilam Formation were derived from a provenance of acid igneous rocks during warm, humid and tropical conditions. Also, the ratios of Th/K indicate a deep open marine condition under which the sediments of the Nannilam Formation were deposited. These results would aid a better understanding and characterization of reservoir facies in the sub-basin.     

北黄海盆地构造演化特征分析

依据最新油气资源调查资料,在简述北黄海盆地区域构造特征的基础上,重点分析了盆地的沉降史与构造演化特征。研究表明:(1)北黄海盆地的基本沉降曲线型式为7段折线状,其中晚侏罗世、早白垩世、始新世、渐新世、新近纪为曲线下降段,代表盆地5幕较明显的沉降;晚白垩世—古新世以及中新世早期为曲线上升段,反映盆地的抬升剥蚀。(2)盆地沉降作用自中生代至新生代总体由东向西迁移,东部坳陷以中生代沉降作用最为显著,中部坳陷主沉降期为始新世,而西部坳陷的快速沉降主要发生在始新世,并一直持续到渐新世。(3)盆地构造演化大致可划分为中生代断陷盆地、古近纪叠加断陷盆地以及新近纪坳陷盆地等3大发展阶段,其中,中生代断陷盆地发育阶段是北黄海盆地油气勘探研究的重点。     

珠江口盆地白云凹陷中央底辟带的发现及识别

白云凹陷属珠江口盆地的一个次级构造单元.通过对二维地震剖面上模糊带的分析, 凹陷中心发育北西西向展布、面积约1000km2的底辟带, 底辟幅度最大可达8km.高精度磁力资料显示底辟带为一个低磁异常区.底辟构造包括龟背上拱、弱刺穿、气烟囱、底辟断层(或裂缝)、海底麻坑等类型, 主要发源于断陷期深湖相的文昌组(始新统) —恩平组(上始新统-下渐新统), 其次为坳陷期浅海-深海相沉积的珠江组(下中新统) —韩江组(中中新统) 的两套巨厚富泥沉积层.白云凹陷具有快速沉降、细粒充填为主、以及新生代的右旋张扭性应力场, 共同造就了凹陷中央底辟带的发育.底辟构造的存在反映了白云凹陷中心曾经蕴育着高温、超压系统, 与之密切伴生的大量亮点指示着沿底辟构造的天然气垂向输导, 构成了古近系油气运移到新近系—第四系的成藏动力系统.