鄂尔多斯盆地华池地区中侏罗统延安组延9油层组河流沉积及演化

据新的地层划分方案及大量钻井、露头和岩心资料,详细研究了鄂尔多斯盆地华池地区延安组延9油层组（Y9）沉积体系特征及演化,认为延9油层组主要为河流沉积,是延10油层组的继承与发展,发育有辫状河、辫状型曲流河和网状河3种类型的河流。Y39油层是辫状河发育的油层,Y29油层在继承Y39油层河流的基础上发育辫状型曲流河,Y19油层则是在前两期逐渐填平补齐之后,在准平原条件下发育的网状河沉积。华池地区延9油层组发育辫状河-辫状型曲流河和网状河两种河流沉积模式。     

中国现代网状河流沉积特征和沉积模式

中国境内的许多河流发育有网状河段,从长江、黑龙江、珠江等这样的大型河流到嫩江、赣江等中小型河流都有。依据这些网状河的地理和构造背景的不同,可以把它们划分为:平原网状河流、山谷网状河流、入湖三角洲平原网状河流和入海三角洲平原网状河流四大类型。作者通过实地挖掘探槽、密集采样,对嫩江齐齐哈尔平原网状河段、赣江入湖三角洲平原网状河段、珠江入海三角洲平原网状河段沉积特征进行了详细描述和研究,并建立了网状河的沉积模式,探讨了网状河的成因。认为网状河流体系的发育不受气候和地理位置的限制,低坡降是形成网状河的必要条件,相对稳定的网状河道不同于曲流河和辫状河,湿地环境是网状河流体系中最发育的地貌单元,堤岸植被繁茂、粘结性高是河道稳定的重要因素,与曲流河和辫状河相比,网状河出现的几率较低。     

鄂尔多斯盆地镇-泾地区中侏罗统延安组沉积体系及聚煤特征

在前人研究的基础上,结合大量新的钻井、测井资料,以鄂尔多斯盆地镇原-泾川地区中侏罗统延安组为例,运用沉积学的方法详细阐述了研究区目的层位的沉积体系,以及重点沉积微相的发育特征。延安组自下而上由河流沉积体系逐渐过渡为三角洲沉积体系。沉积微相主要发育有河流体系的心滩、边滩、河漫滩和岸后沼泽,以及三角洲体系的分流河道、洪泛平原和平原沼泽等。另对研究区延安组的聚煤特征给予了分析,并从构造、环境、气候及古地形等方面讨论了该区的成煤控制因素。     

海南岛东部阳江红盆的沉积相研究

研究区沉积物自下而上可划分为白垩系鹿母湾组、抱万组、白石岭组，据红盆沉积物的性质、结构及原生沉积构造，将盆内沉积物划分为冲积扇相、瓣状河流相、洪冲积平原相及湖相4种不同的沉积相，河道、片汜、泥石流、泥流、筛积沉积等10种不同的成因类型。盆内沉积作用形成了冲积扇相、瓣状河流相和滨湖相3种不同的沉积体。     

东海西湖凹陷渐新统花港组海绿石的发现及其意义

在西湖凹陷渐新统花港组中首次发现非正常海相海绿石。可分为三种类型:即团粒状海绿石、胶结物海绿石和碎屑假象海绿石。前两者属沉积过程或成岩初期的产物。通过沉积学研究，结合微量元素及介质条件分析认为，花港组总体为滨岸湖泊三角洲－河流体系，但是曾程度不同地受到海水或咸水-半咸水影响。花港组的时代就可能归属为始新统。这一认识上的突破除了花港组年代地层的对比意义以外，还将引起对盆地演化阶段、沉积体系空间配置及油气有利相带预测等问题的重新认识。     

克拉玛依油田夏9井区八道湾组辫状河流相的特征

长期以来,对克拉玛依油田夏9井区下侏罗统八道湾组沉积相没有清晰的认识.为了更好地探明夏9井区八道湾组油气潜力,提供挖潜的有利区带,笔者应用现代沉积学理论,充分利用岩芯、钻井、测井等资料,深入细致地研究了八区八道湾组的沉积特征,认为夏9井区下侏罗统八道湾组主要为辫状河流相沉积.共识别出3种亚相、6种微相.本文详细地论述了该研究区八道湾组辫状河流相的识别依据及其沉积特征,并在此基础上总结出了该地区八道湾组辫状河流相的沉积模武.     

鄂尔多斯盆地及周缘地区中二叠统沉积特征*

鄂尔多斯盆地及周缘地区上古生界天然气资源丰富,中二叠统石盒子组是主力勘探层位,明确其沉积相及沉积特征对于该区油气勘探具有重要的意义。在野外剖面踏勘及钻井岩心观察的基础上,对研究区石盒子组地层及岩性特征、沉积相类型及沉积演化等进行系统分析。结果表明: 研究区中二叠统石盒子组主要发育粗粒陆源碎屑岩系。中二叠世研究区仍存在间歇性局部海侵,石盒子组主要以陆相沉积体系为主,包含冲积扇沉积相、河流沉积相、湖泊沉积相、三角洲沉积相等,同时发育障壁海岸沉积体系。研究区自北向南石盒子组依次发育冲积扇、河流、三角洲、滨浅湖等沉积,南缘、西南缘发育浅水三角洲沉积,南缘、东南缘障壁海湾中发育潟湖和障壁沙坝沉积。     

鄂尔多斯盆地及周缘地区中二叠统沉积特征

鄂尔多斯盆地及周缘地区上古生界天然气资源丰富,中二叠统石盒子组是主力勘探层位,明确其沉积相及沉积特征对于该区油气勘探具有重要的意义。在野外剖面踏勘及钻井岩心观察的基础上,对研究区石盒子组地层及岩性特征、沉积相类型及沉积演化等进行系统分析。结果表明:研究区中二叠统石盒子组主要发育粗粒陆源碎屑岩系。中二叠世研究区仍存在间歇性局部海侵,石盒子组主要以陆相沉积体系为主,包含冲积扇沉积相、河流沉积相、湖泊沉积相、三角洲沉积相等,同时发育障壁海岸沉积体系。研究区自北向南石盒子组依次发育冲积扇、河流、三角洲、滨浅湖等沉积,南缘、西南缘发育浅水三角洲沉积,南缘、东南缘障壁海湾中发育潟湖和障壁沙坝沉积。     

福建省晚泥盆世─中侏罗世沉积体系分析

本文应用沉积体系的研究方法,恢复了福建省晚泥盆世－中侏罗世地层的古沉积面貌。上泥盆统发育河流体系、三角洲体系和碎屑滨岸体系;石炭系发育冲积扇体系、河流体系、碎屑滨岸体系和陆架体系;二叠系发育河流体系、湖泊体系、三角洲体系、碎屑滨岸体系和陆架体系;下三叠统发育碎屑滨岸体系、陆架体系、陆坡体系和盆地体系;晚三叠世之后主要发育冲积扇体系、河流体系、湖泊体系和滨岸体系。     

永城煤田二叠纪网状河流沉积体系

永城煤田二叠系三、四煤组地层中,沉积相的空间配置、砂体特点等均显示出网状河流沉积体系的特征。这里的网状河流体系是在盆地整体沉降的背景中,在地形平坦、坡降低的三角洲平原上,受同沉积构造控制发育起来的。同沉积断裂和坳陷活动创造了长期相对低洼、可供河道发育的地形条件,加上繁茂的植被、沉降速度与补偿速度大体均衡、突发性海侵等因素的共同影响,网状水道得以较长时期地稳定发育     

Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia

Although facies models of braided, meandering and anastomosing rivers have provided the cornerstones of fluvial sedimentology for several decades, the depositional processes and external controls on sheetflow fluvial systems remain poorly understood. Sheetflow fluvial systems represent a volumetrically significant part of the non‐marine sedimentary record and documented here are the lithofacies, depositional processes and possible roles of rapid subsidence and arid climate in generating a sheetflow‐dominated fluvial system in the Cenozoic hinterland of the central Andes. A 6500 m thick succession comprising the Late Eocene–Oligocene Potoco Formation is exposed continuously for >100 km along the eastern limb of the Corque syncline in the high Altiplano plateau of Bolivia. Fluvial sandstone and mudstone units were deposited over an extensive region (>10 000 km²) with remarkably few incised channels or stacked‐channel complexes. The Potoco succession provides an exceptional example of rapid production of accommodation sustained over a prolonged period of time in a non‐marine setting (>0·45 mm year⁻¹ for 14 Myr). The lower ≈4000 m of the succession coarsens upward and consists of fine‐grained to medium‐grained sandstone, mudstone and gypsum deposits with palaeocurrent indicators demonstrating eastward transport. The upper 2500 m also coarsens upward, but contains mostly fine‐grained to medium‐grained sandstone that exhibits westward palaeoflow. Three facies associations were identified from the Potoco Formation and are interpreted to represent different depositional environments in a sheetflow‐dominated system. (i) Playa lake deposits confined to the lower 750 m are composed of interbedded gypsum, gypsiferous mudstone and sandstone. (ii) Floodplain deposits occur throughout the succession and include laterally extensive (>200 m) laminated to massive mudstone and horizontally stratified and ripple cross‐stratified sandstone. Pedogenic alteration and root casts are common. (iii) Poorly confined channel and unconfined sheet sandstone deposits include laterally continuous beds (50 to >200 m) that are defined primarily by horizontally stratified and ripple cross‐stratified sandstone encased in mudstone‐rich floodplain deposits. The ubiquitous thin‐sheet geometry and spatial distribution of individual facies within channel sandstone and floodplain deposits suggest that confined to unconfined, episodic (flash) flood events were the primary mode of deposition. The laterally extensive deposition and possible distributary nature of this sheetflow‐dominated system are attributed to fluvial fan conditions in an arid to semi‐arid, possibly seasonal, environment. High rates of sediment accumulation and tectonic subsidence during early Andean orogenesis may have favoured the development and long‐term maintenance of a sheetflow system rather than a braided, meandering or anastomosing fluvial style. It is suggested here that rapidly produced accommodation space and a relatively arid, seasonal climate are critical conditions promoting the generation of sheetflow‐dominated fluvial systems.     

Fluvial morphology and reservoir sand-body architecture in lacustrine rift basins with axial and lateral sediment supplies: Oligocene fluvial–lacustrine succession in the Xihu sag,East China Sea Shelf Basin

Abstract

The Xihu sag, which is the largest petroliferous sub-basin of the East China Sea Shelf Basin, formed in a continental back-arc setting. The Oligocene Huagang Formation consisting of a fluvial–lacustrine succession deposited during the compressional stage is the prime hydrocarbon-bearing interval in the Xihu sag. A third-order sequence-stratigraphic framework has been built, and component sand-body characteristics were investigated based on seismic attribute analysis and well-log correlation. Two overall upward-fining sequences, and an internal low-accommodation systems tract (LAST) (fluvial successions characterised by amalgamated fluvial channel sand bodies interlayered with rare overbank deposits) and high-accommodation systems tract (HAST) (intervals dominated by overbank or lacustrine deposits) have been identified. The thick, multi-storied channel-fill sandstone bodies deposited along the central depression belt, capped by extensive overbank or lacustrine mud deposits, characterise each sequence and form favourable reservoir–seal associations. Proximal-to-distal changes in lithofacies associations were also analysed. The sequence-stratigraphic and lithofacies analysis suggest the existence of an axial, large-scale river channel system in the Oligocene Xihu sag. On the basis of the restoration of basin geomorphology and seismic facies analysis, the depositional architectures of the axial paleodrainage system have been reconstructed. Overall, the Huagang sequences represent the sedimentary evolution of a large-scale fluvial system sourced from axial and lateral supply areas, to form river deltas into an interior-draining basin-centre lake. Two major fluvio-lacustrine transgression–regression cycles have been recorded. During the transgression cycle, the fluvial morphology was dominated by braided fluvial style; whereas during the regression cycle, the fluvial morphology was characterised by a combination of multiple fluvial channel styles in the LAST, from upstream to downstream low-sinuosity braided, high-sinuosity braided and anastomosing fluvial channel patterns were distributed and then replaced by large-scale lake flooding in the HAST. The braided channel centre, paleobathymetric lows of channel networks and delta-front bodies are sand-prone units. The fluvial sedimentation was governed by multiple parameters: tectonics, paleogeomorphology and climate fluctuations. This integrated study on fluvial sedimentation and evolution of the Oligocene drainage system enable us to propose a conceptual model depicting fluvial channel styles and component sand-body architecture in lacustrine rift basins with axial plus transverse sediment supplies. This model can serve as a reference to illustrate channel-sand-body and associated reservoir architecture in similar types of drainage systems in terrestrial basins.     

南苏丹Melut盆地Palogue油田古近系Yabus组河型演化规律及主控因素分析*

针对南苏丹Melut盆地Palogue油田Yabus组独特的辫状河—曲流河沉积体系,利用定量统计和成因动态分析方法,通过引入“微相砂体密度”变量,深入总结了辫状河和曲流河不同的垂向岩相序列,从空间演化角度详细阐述了辫状河和曲流河的差异沉积过程及其河型转化规律,建立了同一物源体系下不同阶段河型转化的沉积模式,并明确了河型转化的主控因素。研究表明: Yabus组河流沉积体系先后经历了3个演化阶段。早期辫状河形成阶段,沉积物顺流加积形成垂向沙坝;中期辫—曲交汇沉积阶段,河流下切作用明显减弱,河流沉积作用转变为侧向加积,在辫状河道中形成斜列砂坝,且辫流坝开始向河道边部迁移形成曲流河点坝;晚期曲流河发育阶段,河道弯度大且砂体沉积规模小。     

Braided stream and flood plain architecture: the Rio Vero Formation,Spanish Pyrenees

Early- to middle-Miocene fluvial sandstones of the Rio Vero Formation were studied, in an area around the town of Barbastro, south central Pyrenees Spain. The outstanding quality of outcrops in this area allows a three-dimensional study of architectural elements.Six architectural elements are recognised, described in detail, and interpreted from three key localities. Seven main lithofacies were identified and sub-divided into gravelly, sandy and fine-grained lithofacies. The architectural elements and lithofacies have been combined with a hierarchy of depositional bounding surfaces to fully interpret the evolution of the depositional system at the meso- and macro-scale. Not only the different architectural elements and lithofacies of the complete braided fluvial system, but also the lateral variation of the architectural elements were emphasised in this study. Differential tectonic movements, seasonal climate change, and their effect on vertical and lateral evolution of the area were the main control on basin sedimentation, channel interconnection, palaeocurrent patterns, and consequently the fluvial architecture.The presence of lateral ramp anticlines caused the fluvial system to be laterally restricted, with the main channel-belts being located in the areas of highest subsidence and lowest topography. Intervening topographic highs acted as both flood plains and lateral barriers between the main channel systems. The proposed depositional model comprises broad, low-sinuosity, perennial, but seasonal moderate-energy streams. The sandstone architecture is dominated by channel-fill and sheet sands, and associated simple and more complex bars. Adjacent to the main channel-belts fine-grained sandstones, siltstones and immature paleosols occur.The along-strike relationship between major fluvial systems and their outlets into a foreland basin has important implications for the infill of the basin and the modelling of fluvial systems along mountain belt fronts.     

The Pleistocene climate-controlled fluvial sedimentary record in the Bełchatów mine (central Poland)

Sedimentological analyses of fluvial formations in the Bełchatów mine have yielded results that have more than regional significance. They concern the reaction of rivers to climatic changes in the Pleistocene. Changes in river geometry and their depositional records are examined from two fluvial formations. These formations represent different times, but show similar palaeoenvironmental changes. Cool temperate climate conditions resulted in meandering (or anastomosing) river sedimentation, which was controlled by equalized precipitation and by a well-developed vegetation cover. Cold periglacial climate conditions resulted in braided river sedimentation immediately before the Glacial Maximum, with high discharges and a high sediment load. The palaeoclimatic and palaeohydrologic analyses of the Weichselian fluvial deposits in Bełchatów provide additional information to that from similar studies in Germany and the Netherlands, thus jointly resulting in a consistent palaeogeographic model of western-middle Europe.     

新疆焉耆盆地开都河不同河型段砂砾质沉积特征与差异分析*

新疆焉耆盆地开都河自察汗乌苏水电站流入博斯腾湖的河口之间,发育单一物源供给下的山间河段、辫状河段、曲流河段、顺直河段以及三角洲平原顺直型分流河道段等多种类型河道沉积。通过探坑挖掘与观察、砂砾质沉积物结构的测量、碎屑组分与重矿物分析以及数据统计分析等方法,分析开都河不同类型河段的砾石质沉积特征与搬运距离关系、砾质与砂质组合特征、砂质碎屑组分与沉积构造特征及变化等,认为沉积地形与坡度、沉积物组成以及气候条件等因素控制了不同河段类型的变化与沉积特征的差异。同时,建立了不同河型段砾石径变化与沉积搬运距离的定量关系。在此基础上,统计了在干旱气候与充沛物源供给条件下,开都河不同河型沉积中的有利储集体分布范围及其比例关系数据,可为陆相湖盆河流沉积相图的编制提供重要的参考依据。     

Lithofacies and palaeosol analysis of the Middle and Upper Siwalik Groups (Plio–Pleistocene), Haripur-Kolar section, Himachal Pradesh, India

The Middle–Upper Siwalik Groups (Plio–Pleistocene) are exposed at Haripur-Kolar, Himachal Pradesh, India. The succession is 2800-m thick and has been subdivided into Unit M1 of the Middle Siwalik and four units U1–U4 of the Upper Siwalik Group, on the basis of facies associations, and type and degree of development of palaeosols. The available magnetostratigraphic ages for bases of Units U1, U3 and U4 are 5.5, 2.6 and 1.77 Ma, respectively. The top of the section has been dated as 19 ka.

Lithofacies association and palaeocurrent analysis indicates that the Middle and Upper Siwalik Groups were formed mainly by a basin transverse fluvial system. Two types of river systems, which differ in their size, can be documented in Unit-M1, Unit U1 and Unit-U2: one trunk river system similar to the modern Kosi and the other smaller river system, which formed tributaries to the former. The large rivers were mainly braided in nature. The Unit U3 and lower part of Unit U4 were deposited in the piedmont depositional system mainly by small braided streams and the upper part of the Unit U4 was deposited during a period of arid climate by sediment gravity-flows.

Integration of fluvial lithofacies and pedofacies helps to identify two fluvial depositional systems from the modern Indo-Gangetic Plains. The Lowland System involved deposition on alluvial megafans and interfan areas, which resulted in sand-rich and mud-rich sequences with weekly developed soils. The Upland System allowed large tracts to act as high ground for thousands of years, thereby giving rise to sandstone poor intervals with moderately to strongly developed soils. Occurrence of moderately to strongly developed soils was controlled by uplifting and tilting of large tectonic blocks, without any relation to distance from the main channels. Rate of subsidence apparently controlled the occurrence of Lowland and Upland systems. Deposition of the Unit M1, Unit U1 and Unit U2 took place under Upland and Lowland systems, very similar to those identified from the modern Indo-Gangetic Plains. The warm and humid climate between 5.3 and 2.6 Ma led to the formation of red Alfisols with calcrete nodules at places. Slightly cooler and drier climate starting at about 2.6 Ma and approximately coinciding with the onset of global-scale glaciation, produced poorly developed yellow soil with common development of nodular calcretic horizon and calcitc material disseminated in the groundmass. At ca. 0.9 Ma, a probable significant change to still drier and cooler climate produced typical sediment gravity-flows in the piedmont system, that continued until at least up to 19 ka.     

The Upper Pleistocene deposits at Cassington,near Oxford,England

For much of the Middle and all of the Upper Pleistocene the Upper Thames valley has remained outside the limit of ice advance. The main agents of landform evolution have been the River Thames and its tributaries, which have cut down episodically and in so doing have abandoned a series of river terraces. This study reports the findings of an investigation into exposures in the deposits underlying the Floodplain Terrace at Cassington, near Oxford, England. The sequence exposed reveals a stratigraphy of basal, predominantly fine-grained, lithofacies overlain by coarser gravel lithofacies. The fluvial architecture of these deposits indicates a major change in fluvial style from a low-energy (meandering) to a high energy (braided) channel system. The flora and fauna from the lower fine-grained lithofacies display a marked change from temperate at the base, to colder conditions towards the top, indicating a close association between deteriorating climate and changing fluvial depositional style. Amino acid and luminescence geochronology from the basal fine-grained lithofacies suggest correlation with Oxygen Isotope Stage 5 and hence it is argued that the major environmental change recorded at the site relates to the Oxygen Isotope Stage 5–4 transition. Deposition of much of the overlying gravel sequence probably occurred during Oxygen Isotope Stage 4, suggesting that the latter half of the Devensian may be less significant, in terms of fluvial landscape evolution in the Upper Thames valley, than was believed previously. © 1998 John Wiley & Sons, Ltd.