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1.
湖泊三角洲的地层模式和骨架砂体的特征 总被引：16，自引：4，他引：16
大型湖泊三角洲主要形成于淡水或微咸水湖的滨岸地带。湖泊三角洲的突出特征是以分流河道砂体为骨架,河口坝沉积不发育.笔者按地层特征将湖泊三角洲分为两种基本类型:一种是缺乏完整进积序列的薄的浅水台地型三角洲,另一种是进积序列较完整的巨厚的深水盆地型三角洲。前者发育在基底稳定.水深很浅的滨岸带,后者是三角洲推进到有巨厚泥质充填物的深盆地区的产物。在大型湖盆中,随着盆地的充填作用,三角洲体系可以在空间上从“浅水”型向“深水”型过渡,在时间上从“深水”型向“浅水”型连续地演变。 相似文献
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G. W. FARQUHARSON 《Sedimentology》1982,29(5):717-725
Sedimentary rocks of late Mesozoic age exposed at Camp Hill, northern Antarctic Peninsula, are associated with calc-alkaline volcanic rocks. They represent deposition on a fault-controlled floodplain, with marginal alluvial fans, on a volcanic arc. Finely laminated mudstone and occasional graded laminae were deposited from suspension and by density underflow currents, respectively, in small shallow lakes. Thickening- and coarsening-upward sandstone bodies overlying the lake deposits are interpreted as lacustrine deltas of which two types are preserved: (1) Gilbert-type with steep foresets and (2) mouth-bar type which lack steep foresets. Sections through the latter type reveal the presence of sub-environments characteristic of fluvial-dominated marine deltas, i.e. prodelta, distributary mouth-bar and distributary channel. Abandoned mouth-bars resulting from avulsion are recognized. It is suggested that the processes which operated during formation of the mouth-bar deltas resulted from hyperpycnal flow. By contrast, the Gilbert-type delta is thought to be the consequence of a reduced inflow of suspended sediment causing homopycnal flow, and thorough mixing of the river and lake waters. 相似文献
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Lake Hazar lies within a small pull-apart basin along the East Anatolian Transform Fault in south-eastern Turkey. Deltas are formed where streams debouch into the low-energy lacustrine environment. The facies constituting the deltas include delta plain debris flow, braided stream, and marginal lacustrine deposits; delta front foreset and mouth bar deposits; prodelta and lacustrine deposits. The facies are spatially restricted with sharp transitions. Facies sequences and relationships indicate two distinct styles of deltaic sedimentation. Fan deltas with a tripartite structure characteristic of Gilbert-type deltas comprise the marginal drainage system and form along the basin margins. Mouth bar deltas develop where the axial drainage system of the basin debouches into the lake. The distribution of the two deltaic types is thought to be a function of gradient and controlled by position relative to faults within the basin. 相似文献
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Facies, depositional model and stratigraphic architecture of Pleistocene giant Gilbert-type fan deltas are presented, based on outcrop data from the Derveni–Akrata region along the southern coast of the Gulf of Corinth, Greece. The common tripartite consisting of topset, foreset and bottomset [Gilbert, G.K., 1885. The topographic features of lake shores: Washington, D.C., United States Geol. Survey, 5th Annual Report, 69–123.] has been identified, as well as the most distal environment consisting of turbidites, and is organised in a repetitive pattern of four main systems tracts showing a clear facies and volumetric partitioning.The first systems tract (ST1) is characterised by the lack of topset beds and the development of a by-pass surface instead, thick foresets and bottomset beds, and thick well-developed turbiditic systems. This systems tract (ST1) is organised in an overall progradational pattern. The second systems tract (ST2) is characterised by a thin topset and almost no foreset equivalent. This systems tract is not always well-preserved and is organised in an overall retrograding trend with a landward shift in the position of the offlap break. The offshore is characterised by massive sandy turbidites. The third systems tract (ST3) is characterised by small-scale deltas prograding above the staked topsets of the giant Gilbert-type fan delta. Those small Gilbert-type fan deltas are generally organised in a pure progradation evolving to an aggradational–progradational pattern. In the distal setting of those small Gilbert-type fan deltas, almost no deposits are preserved on the remaining topography of the previous Gilbert-type fan delta. The fourth systems tract (ST4) is characterised by continuous vertically aggrading topsets that laterally pass into aggrading and prograding foresets. Bottomsets and distal turbiditic systems are starved. This fourth systems tract (ST4) is organised in an overall aggrading trend.These giant Gilbert-type fan deltas correspond to the Middle Group of the Corinth Rift infill and their stratigraphic development was strongly influenced by evolving rift structure. They record the migration of the depocenter from the rift shoulder to the rift axis in four main sequences from ca. 1.5 to 0.7 Ma, related to the migration of fault activity. It is worth noting that the maximum paleobathymetry was recorded during the final stage of the progradation of the Middle Group, suggesting that the rift climax was diachronous at the scale of the entire basin. The rapid (< 1 Ma) structural and sedimentological evolution, the migration of fault activity as well as the youth of the Corinth Rift, are probably exceptional factors allowing the characterisation of such diachronism. 相似文献
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鄂尔多斯盆地南部延长组沉积体系和层序特征 总被引：29，自引：0，他引：29
鄂尔多斯盆地南部延长组沉积体系类型形成于不同的地质背景，物源方向和沉积环境也不同，因此沉积特征和分布规律差异较大。以主力含油层段长8油组为例，辫状河三角洲体系主要位于盆地西南缘较陡坡带，砂体为长石砂岩，以槽状层理构造发育、前三角洲中有重力流沉积为特征；重力流沉积主要分布在盆地南部渭北地区的长7油层段，以岩屑砂岩为主，形成于深湖环境中，发育的鲍玛组合层序有ABCE、ADE、AE和BCE型序列；东北方向水系形成了曲流河三角洲体系，主要位于盆地东北缓坡带上，三角洲分流河道伸展距离长，朵体规模大，以长石细砂岩为主，河口砂坝发育。 相似文献
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杜贵超 《沉积与特提斯地质》2014,(4):30-39
本文通过钻井、测井资料及露头地质剖面研究,对鄂尔多斯盆地三叠系延长组长62油层沉积相进行了系统分析。研究表明,研究区目的层发育三角洲前缘亚相沉积,其不具备吉尔伯特式三角洲模式的顶积层、前积层、底积层三层结构。沉积结构上,三角洲单体厚度薄、分布广,具有"毯状"沉积结构、水下分流河道砂体优势发育等特征。沉积微相发育是以分流河道砂体为骨架,河口坝一般不发育,分流河道遭受不同程度的席状化改造。一方面,当河道入湖后迅速扩展,形成面状流向湖盆中央推进,后期河道扩展后对前期沉积物进行冲刷及改造;另一方面,湖水波浪改造使河口处形成的河口坝沉积物难以保存。沉积微相组合具有以水下分流河道优势发育,水下分流河道砂体与水下分流间湾微相互层发育等特征。研究区三角洲沉积受构造演化、气候、水平面变化及供给体系等因素控制。长62油层沉积时期地形平缓,沉降速率缓慢,气候温湿,当河道携带细粒沉积物进入湖盆时,河道迅速扩展,水流分散形成面状流并向湖盆中央推进,形成"毯式"结构。总体呈水下分流河道砂体与泥岩互层发育。 相似文献
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鄂尔多斯盆地晚二叠世湖相沉积主要由灰棕色砂砾岩和红至灰色泥岩组成,厚500-600米。从该套沉积中已识别出五个主要相组合,即水下扇、湖岸冲积平原、湖成三角洲、边缘湖和滨外湖相组合。水下扇相发育于研究区西南缘,冲积平原相发育于研究区北部,湖成三角洲相发育于研究区北部和东部,边缘湖相发育于研究区中部,滨外湖相发育于研究区南部。 相似文献
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Sedimentology of a marine intermontane Pleistocene Gilbert-type fan-delta complex in the Crati Basin, Calabria, southern Italy 总被引：4，自引：0，他引：4
The Crati Basin is a Pliocene-Holocene extensional basin filled by the progradation of different types of marine fan-delta systems. Coarse-grained Gilbert-type fan-deltas developed during the Pleistocene. They represent the sedimentary response to a strong differential uplift involving the basin margins and the basin itself. The differential uplift was responsible for the fragmentation of the basin into several sub-basins, into which these fan-deltas prograded. The protection and lateral confinement by structural highs, steep coastlines and the absence of strong tidal action in the adjacent Ionian Sea, allowed the regular progradation of these fan-deltas in the restricted gulfs and narrow embayments of the Crati Basin. For the classical Gilbert-type (fan) deltas in lacustrine settings, homopycnal inflow favours a rapid mixing of water masses and deposition of sediment close to the river mouth. In the case of the example described here, the density contrast between the sea water and the inflowing river water caused the separation of the muddy fraction from the coarse sandy and conglomeratic part of the sediment. This allowed the development of steep mud-poor coarse-grained delta foresets. Slope instability features (slump scars, conglomeratic flow slides) are fairly scarce in the proximal parts of the San Lorenzo del Vallo system. Towards the north, where protection from the Ionian Sea was less, they increase in importance. 相似文献
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The Maesan fan-delta-fed slope system in the Miocene Pohang Basin occurs between two Gilbert-type fan deltas. Detailed analysis of sedimentary facies and bed geometry reveals that the sequence is represented by 13 sedimentary facies. These facies can be organized into three facies associations, representing distinct depositional environments: alluvial fan (facies association I), steep-faced slope (facies association II), and basin plain (facies association III). Subaerial debris flows and dense, inertia-dominated currents were transformed into subaqueous sediment gravity flows in steep-faced slope environments. Further downslope, these flows were channelized and formed lobate conglomerate and sandstone bodies at the terminal edge of the channels (or chutes). Interchannel and interlobe areas were dominated by homogeneous mudstone and muddy sandstone, deposited by suspension settling of fine-grained materials. Part of the steep-faced slope deposits experienced large-scale slides and slumps. The chutes/channels, lobes and splays on the steep-faced slope of the Maesan system are similar to those in modern subaqueous coarse-grained fan-delta systems. 相似文献
11.
利用盆地北部大量钻井资料、岩心及露头观察结果,结合古地质背景,以及粒度、岩矿等分析资料,对晚石炭—早二叠世广泛分布的含砾砂岩体沉积特征进行了深入的分析。结果表明:它们属于扇三角洲体系,并以河道化冲积的形式前积到陆表海盆地中,平面上分带性和纵向上退积结构较清楚,重力流沉积特征不明显,而水道化的牵引流成因沉积特征明显。以高能辫状水道、水下分流河道砂砾岩为主要骨架,河口坝不发育。而且,这些水道作用居重要地位的扇三角洲高能水道砂体因受物源、古地貌及潮汐等影响,往往被潮汐改造而形成障壁砂坝,也是有利储集体。它们之间因沉积特征不同,储集空间、储集性能和含油性也各具特色,但都以高能化水道形成的厚石英砂带为有利相带。 相似文献
12.
陕甘宁盆地晚三叠世的三角洲 总被引：1，自引：0，他引：1
引言陕甘宁盆地是一个矩形内陆构造盆地,晚三叠世盆地在左旋剪切力作用下形成后接受的第一套沉积物就是延长组,它是生储盖发育齐全配套的湖相沉积。横向上相带分布变化有序;纵向上湖进、成熟、湖退三大阶段发育明显。延长组的所有油层,均属低产低渗油层,勘探这套油层需要在沉积相研究的基础上,筛选出有利生、储油配置,即在低渗区中找相对高渗区,在低产区中找相对高产区。三角洲的研究是一个重要的方面。 相似文献
13.
《Boreas: An International Journal of Quaternary Research》2018,47(4):973-1002
This study presents a synthesis of the geomorphology, facies variability and depositional architecture of ice‐marginal deltas affected by rapid lake‐level change. The integration of digital elevation models, outcrop, borehole, ground‐penetrating radar and high‐resolution shear‐wave seismic data allows for a comprehensive analysis of these delta systems and provides information about the distinct types of deltaic facies and geometries generated under different lake‐level trends. The exposed delta sediments record mainly the phase of maximum lake level and subsequent lake drainage. The stair‐stepped profiles of the delta systems reflect the progressive basinward lobe deposition during forced regression when the lakes successively drained. Depending on the rate and magnitude of lake‐level fall, fan‐shaped, lobate or more digitate tongue‐like delta morphologies developed. Deposits of the stair‐stepped transgressive delta bodies are buried, downlapped and onlapped by the younger forced regressive deposits. The delta styles comprise both Gilbert‐type deltas and shoal‐water deltas. The sedimentary facies of the steep Gilbert‐type delta foresets include a wide range of gravity‐flow deposits. Delta deposits of the forced‐regressive phase are commonly dominated by coarse‐grained debrisflow deposits, indicating strong upslope erosion and cannibalization of older delta deposits. Deposits of supercritical turbidity currents are particularly common in sand‐rich Gilbert‐type deltas that formed during slow rises in lake level and during highstands. Foreset beds consist typically of laterally and vertically stacked deposits of antidunes and cyclic steps. The trigger mechanisms for these supercritical turbidity currents were both hyperpycnal meltwater flows and slope‐failure events. Shoal‐water deltas formed at low water depths during both low rates of lake‐level rise and forced regression. Deposition occurred from tractional flows. Transgressive mouthbars form laterally extensive sand‐rich delta bodies with a digitate, multi‐tongue morphology. In contrast, forced regressive gravelly shoal‐water deltas show a high dispersion of flow directions and form laterally overlapping delta lobes. Deformation structures in the forced‐regressive ice‐marginal deltas are mainly extensional features, including normal faults, small graben or half‐graben structures and shear‐deformation bands, which are related to gravitational delta tectonics, postglacial faulting during glacial‐isostatic adjustment, and crestal collapse above salt domes. A neotectonic component cannot be ruled out in some cases. 相似文献
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库车坳陷中生界三种类型三角洲的比较研究 总被引：34，自引：3，他引：31
库车坳陷中生代呈北陡南缓的箕状,其内连续沉积了一套厚度巨大的冲积-湖泊碎屑沉积体。湖缘扇三角洲、辫状河三角洲及曲流河三角洲非常发育,它们的特征清楚、区别明显:（1） 扇三角洲为突发的、瞬时的灾变事件产生的重力流沉积与间灾变期正常牵引流沉积交替进行,并以重力流沉积占主导地位:其平原亚相类似于冲积扇沉积,河道砂体呈透镜状,厚度小、变化大。（2） 辫状河三角洲为正常的河流牵引流沉积,通常受到湍急洪水控制,为季节性沉积作用产物;平原亚相类似于辫状河沉积;河道沉积发育,砂体总体呈层状,内部由若干个下粗上细的河道砂岩透镜体相互叠置而成,交错层发育,尤以侧积交错层异常发育为特征,岩性以颗粒支撑的砂砾岩为主。（3） 曲流河三角洲为正常的河流牵引流沉积,沉积物输入量为相对连续的终年河流的产物,平原亚相类似于曲流河沉积:河道砂体呈层状,交错层发育,类型丰富。当然,这三种类型三角洲之间亦存在着密不可分的内在联系,不仅同一时期内可以并存,而且随着地质历史的演化可相互转化。 相似文献
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大型敞流坳陷湖盆浅水三角洲与湖盆中心砂体的形成与分布 总被引：34，自引：0，他引：34
大型敞流坳陷湖盆浅水三角洲及湖盆中心砂体已成为中国陆相盆地岩性油气藏最重要的勘探目标。通过对现代典型湖盆浅水三角洲的深入分析,结合我国中、新生代大型坳陷湖盆浅水三角洲及湖盆中心砂体的地质研究,取得以下主要进展与认识：①在分析浅水三角洲形成地质背景的基础上,按照供源体系、湖水深度及三角洲前缘倾斜坡度将湖盆三角洲分为9种成因结构类型;②建立了毯式浅水曲流河三角洲的沉积模式,指出末端分流河道及末端决口扇是浅水曲流河三角洲的典型微相类型;③分析了浅水三角洲砂体大面积分布的形成条件,指出敞流湖盆是湖盆中心浅水三角洲砂体发育的重要条件,敞流通道对湖盆中心砂体分布有重要控制作用;④湖盆中心发育河流、三角洲、湖流及密度底流砂体等牵引流成因砂体,也发育洪水浊积扇及滑塌浊积扇等重力流成因砂体;⑤大型浅水三角洲体系三级层序界面对岩性（成岩）圈闭的发育有重要控制作用,三角洲平原带层序界面上覆叠置砂体富集岩性油气藏,勘探潜力大。本文研究成果希对坳陷湖盆沉积学研究及岩性油气藏勘探能有推动作用。 相似文献
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在岩心观察的基础上,结合测井、地震和区域背景资料分析,认为王府凹陷泉三、四段沉积时期普遍发育浅水三角洲沉积。由于受地形、古气候和水动力条件等多重因素的影响,研究区发育的浅水三角洲在沉积构造、沉积序列、微相类型、三角洲内部结构以及地球物理响应特征等方面呈现出与经典三角洲不同的沉积特征:具有建设性三角洲沉积特征,平面上呈网状,前缘相带延伸较远。具有相对发育的水下分流河道,河口砂坝欠发育;垂向上发育多次间断正韵律。紫红色泥岩大面积展布,生物扰动强烈。砂岩中发育强水动力浅水沉积构造,Gilbert型三角洲的3层结构不明显。浅水三角洲识别出两个亚相和7个微相。研究区具有良好的生储盖配置关系,利于岩性油气藏的形成,其中水下分流河道和分流河道砂体储层物性好,为最有利储层。 相似文献
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陆相湖盆与海洋环境不同,具有水体浅、能量弱、湖进湖退频繁等特点。综合应用高精度层序地层学和地震沉积学等关键技术,通过中国东部及中西部典型陆相湖盆的勘探实践、野外露头解剖和现代沉积考察,总结了陆相湖盆三角洲—滩坝复合砂体的分布模式,并提出了复合砂体地质编图法。研究结果表明:(1)陆相湖盆的“湖—陆过渡沉积体系”不仅发育分流河道,还发育河口坝和沿岸砂坝,这些不同时期的分流河道、河口坝和沿岸砂坝交织叠加在一起,在古代地层和现代沉积中得以保存;(2)地形平坦处,水体浅、波浪作用不强、河流作用为主,形成河道砂体;湖岸较陡处,波浪作用强,分流河道砂体被波浪改造,形成沿湖岸分布的滩坝砂体;(3)在高频湖平面变化背景下,岸线的迁移导致沉积坡折的迁移,形成了多期垂直于岸线分布的树枝状三角洲分流河道砂体,和多期平行于岸线呈带状分布的沿岸滩坝砂体相互交织的陆相湖盆三角洲—滩坝复合砂体的特殊结构;(4)复合砂体地质编图法基于传统单因素法,以复合砂体分布模式为指导,主要针对发育在水体较浅、地形平坦开阔背景下的陆相湖盆三角洲—滩坝砂体。 相似文献
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Trapezoidal-type fan deltas, lacking bottomset deposits, were studied in two different tectonic settings: extensional (rifted), and compressional (piggy-back) basins. In both cases studied fan deltas were characterized by: (i) an absence of bottomsets; (ii) development in protected or narrow basins and sub-basins confined by intrabasinal basement highs or by topographic highs, respectively; (iii) coarse-grained sediment fluxes, dominated by mass-flows forming fan deltas that prograded from steep nearshore slopes basinwards; and (iv) a high-energy environment, with powerful underflows that probably bypassed the basins and transported fine-grained sediments outside the basins. The location of channels cut by such underflows is influenced by local tectonic style. When the supplied sediments in the rifted basins overstepped the intrabasinal basement highs, trapezoidal fan deltas were replaced upwards by Gilbert-type deltas, with bottomsets. 相似文献