德令哈盆地早侏罗世冲积扇—扇三角洲积体系及其马尔科夫链分析

德令哈盆地下侏罗统含煤磨拉石盆地组合是在以冲积扇-扇三角洲沉积体系为主的沉积环境下发育起来的.简要报道研究区冲积扇-扇三角洲体系沉积及其组合特征,在此基础上借助马尔科夫链建立冲积扇-扇三角洲体系沉积旋回的结构模式,并探讨该结构模式的地质意义.     

德令哈盆地早侏罗世冲积扇—扇三角洲沉积体系及其马尔科夫链分析

德令哈盆地下侏罗统含煤磨拉石盆地组合是在以冲积扇—扇三角洲沉积体系为主的沉积环境下发育起来的。简要报道研究区冲积扇—扇三角洲体系沉积及其组合特征 ,在此基础上借助马尔科夫链建立冲积扇—扇三角洲体系沉积旋回的结构模式 ,并探讨该结构模式的地质意义。     

砂砾岩沉积特征分析及有利储集相带确定--以玛北斜坡区百口泉组为例

为明确砂砾岩复杂储层的沉积特征及有利储集相带分布,通过岩心、测井、地震、实验分析等资料综合研究,认为玛北斜坡区百口泉组属近源快速堆积的扇三角洲沉积体系,主要发育扇三角洲平原辫状河道、扇三角洲平原/前缘砂质碎屑流、扇三角洲前缘近岸水下分流河道、远岸水下分流河道、河口坝五种主要沉积微相类型。发育牵引流、重力流两种搬运机制。主要发育夏子街扇、黄羊泉扇二大主扇体,夏子街扇细分为风南10、夏72、玛7三条支扇,西部的风南10支扇、东部的玛7支扇发育重力流(砂质碎屑流)沉积。夏72支扇位于玛北鼻状凸起上,鼻状凸起背景下发育的低缓沟槽控制着牵引流水系的展布。储层的成岩作用(压实、胶结)强度与沉积作用(泥杂基含量、粒度)关系密切,泥杂基含量、粒度为储层储集性能的主控因素。有利储集相带受沉积机制、沉积微相双重控制,重力流(砂质碎屑流)沉积整体物性最差;牵引流沉积视不同沉积相带,扇三角洲平原辫状河道、扇三角洲前缘远岸水下分流河道物性较差;扇三角洲前缘近岸水下分流河道、河口坝物性最优,优质储层主要分布在扇三角洲前缘近岸水下分流河道相带内。     

措勤地区竟柱山组沉积特征及构造意义

上白垩统竟柱山组在西藏措勤地区主要沿班公湖-怒江缝合带、且坎-古昌-阿索断裂带和塔若错北-达瓦错南-秋措麦凹陷带断续分布。主要为一套磨拉石的紫红色碎屑岩,其沉积环境以扇三角洲和三角洲为主。扇三角洲和三角洲的前积层理指示了其进积方向,表明早期物源来自北部,而晚期来自南部的陆源物质增加。竞柱山组磨拉石沉积的发育,是班公湖-怒江缝合带造山运动的证据。     

西藏仲巴县昂拉仁错-塔若错一带拉嘎组的地层特征及沉积环境

在西藏改则昂拉仁错地区测制了多条拉嘎组剖面,详细描述了改则县拉清乡蹦克弄拉剖面.讨论了拉嘎组的岩性组合特征及横向变化规律.首次在拉嘎组内建立了2个腕足类生物组合带,即Choristites xainzaensis-Eomarginifera组合带和Neospirifer kubeiensis-Fusisprifer plicatus-Stepanoviella(Bandoproductus)组合带,前者的时代为晚石炭世早期,后者为早二叠世,大致与萨克马尔-阿丁斯克(Sakmarian-Artinskian)期相当.拉嘎组为冰海陆棚沉积,根据冰碛物特征细分为坠石冰碛砾岩、块状冰碛砾岩和冰海水下扇砾岩3种类型,并认为拉嘎组从早到晚总体由冰海内陆棚→冰海外陆棚→冰海内陆棚构成一个完整的沉积旋回.     

青藏高原东北缘循化盆地渐新世—上新世沉积相分析与沉积演化

位于循化盆地南缘的积石镇羊圈贡拜—西沟上庄剖面发育连续完整的晚渐新世—上新世地层, 从老至新依次出露渐新统—中新统他拉组、中新统咸水河组(中庄段、上庄段、东乡段)和中新统—上新统临夏组(柳树段和何王家段).沉积相分析认为, 他拉组以冲积扇相为主, 咸水河组以富含膏盐层的咸化湖相—三角洲前缘相为主, 临夏组以湖相—三角洲前缘相夹水下扇相为主.通过对沉积序列中古流向的系统测量和分析, 揭示他拉组、咸水河组沉积期的古水流方向多在SE-NW之间, 结合物源分析, 表明当时西秦岭北缘逆冲带和拉脊山逆冲带均已隆起并遭受剥蚀成为循化盆地沉积物的物源供应区; 而在临夏组沉积期, 古水流以NWW为主, 推测循化盆地东部的积石山隆起成为物源的主要供应区.剖面粒度概率累积曲线和C-M图分析结果印证了对剖面沉积相的划分, 并指示盆地沉积时期的三角洲前缘和水下扇发育区存在牵引流.      

准噶尔盆地红山嘴地区三叠系克上组两类粗粒三角洲的沉积记录差异及其成因

准噶尔盆地红山嘴地区三叠系克上组存在扇三角洲与辫状河三角洲这两类粗粒三角洲,其界定在油气沉积学领域一直备受关注,而基于岩相类型及其垂向组合特征的沉积作用研究,辅以砂体宏观展布规律将有助于这两类三角洲的判别。红山嘴地区克上组扇三角洲以发育各种交错层理砾岩相(Gi、Gt、Gp)与块状砾岩相(Gmm、Gcm、Gcs)为特点,而辫状河三角洲则发育各种砂岩相(St、Sp、Sm和Sh等);扇三角洲6种岩相组合显示其碎屑流与密度流沉积相对发育,韵律特征不明显,而辫状河三角洲的7种岩相组合均显示其牵引流沉积作用更为显著,且正韵律居多;坡度陡、物源足造就了扇三角洲"砂体发育而分布局限、切割叠置频繁"的沉积响应特点,辫状河三角洲则因坡度中等且物源供给弱而具有"砂体薄而广布、多为孤立式接触"的响应特点。     

东营凹陷北带古近系沙四段砂砾岩体沉积特征及沉积模式

综合岩心观察、薄片鉴定、砂砾岩厚度及百分含量等资料,对东营凹陷北带沙四段砂砾岩的沉积特征、成因类型及沉积演化模式进行了系统研究。结果表明,东营凹陷北带沙四段砂砾岩储层中块状层理、粒序层理、平行层理、叠覆冲刷构造、交错层理发育,同时变形构造、泥岩撕裂屑、重荷模和火焰构造常见。碎屑颗粒表现为无分选-中等分选、棱角状-次棱角状到次圆状的近物源沉积特征。岩相类型以块状层理砾岩相、递变层理砾岩相、递变层理砂质砾岩相、交错层理砾质砂岩相、平行层理砾质砂岩相、块状层理砾质砂岩相、块状砂岩相、平行层理砂岩相、块状层理砂岩相、变形层理砂岩相、泥质撕裂变形砂岩相、薄层透镜状或压扁层理砂岩相为主。综合古地貌、砂砾岩沉积特征及沉积机制等,认为东营凹陷北带沙四段主要发育近岸水下扇、湖底扇和扇三角洲等成因类型的砂砾岩扇体。在沉积演化上,沙四下亚段沉积时期,胜坨地区和民丰地区发育近岸水下扇沉积,利津地区发育扇三角洲沉积,扇体规模较小,横向连续性较差;沙四上亚段沉积时期,胜坨地区和民丰地区广泛发育近岸水下扇-湖底扇沉积,利津西部地区发育扇三角洲沉积,扇体规模较大,横向连片发育。     

喜马拉雅造山带北缘大反转逆冲断层（GCT）东段的活动时限及构造演化

喜马拉雅造山带北缘的大反转逆冲断层(GCT)位于印度-亚洲的碰撞边界,平行雅鲁藏布江缝合带展布,向北逆冲使特提斯喜马拉雅地体向北叠覆在冈底斯地体之上。大反转逆冲断裂制约了中新世Kailas式系列磨拉石盆地(Kailas、秋乌、大竹曲、罗布莎以及朗县)的发育,自西向东磨拉石盆地中砾石变形逐渐增强。本文通过GCT东段"罗布莎-郎县砾岩"的研究,获得罗布莎-朗县变形砾岩中的碎屑锆石的沉积上限年龄为早渐新世(28.7~29.1Ma)。罗布莎-郎县砾岩具有基质糜棱岩化、发育地震化石假熔岩和向北剪切指向的特征,表明其经历了受GCT断裂控制的砾岩盆地在浅部形成、插入10~15km深部并受地震影响形成假熔岩,然后折返到地表的过程。     

库车前陆盆地第三系沉积相配置及演化研究

以塔里木盆地库车前陆坳陷第三系的重点油气储层段—下第三系库姆格列木群和苏维依组,以及上第三系吉迪克组为主要研究对象,识别出区内主要发育了扇三角洲、三角洲、湖泊和潮坪—泻湖相等沉积相类型。结合对前陆构造运动和沉积古地理的综合分析,指出了库车坳陷第三系的沉积演化特点:北部山前带以发育扇三角洲相为典型特征,南部出现正常三角洲相,中部以湖泊相占优势,且沉积和沉降中心从库姆格列木群沉积时期至吉迪克组沉积时期有由西向东迁移的特点。      

Sedimentology of a lacustrine fan-delta system, Miocene Horse Camp Formation, Nevada, USA

A 1600-m-thick succession of the Miocene Horse Camp Formation (Member 2) exposed in east-central Nevada records predominantly terrigenous clastic deposition in subaerial and subaqueous fan-delta environments and nearshore and offshore lacustrine environments. These four depositional environments are distinguished by particular associations of individual facies (14 defined facies). Subaerial and subaqueous fan-delta facies associations include: ungraded, matrix-and clast-supported conglomerate; normally graded, matrix- and clast-supported conglomerate; ungraded and normally graded sandstone; and massive to poorly laminated mudstone. Subaqueous fan-delta deposits typically have dewatering structures, distorted bedding and interbedded mudstone. The subaerial fan-delta environment was characterized by debris flows, hyperconcentrated flows and minor sheetfloods; the subaqueous fan-delta environment by debris flows, high- and low-density turbidity currents, and suspension fallout. The nearshore lacustrine facies association provides examples of deposits and processes rarely documented in lacustrine environments. High-energy oscillatory wave currents, probably related to a large fetch, reworked grains as large as 2 cm into horizontally stratified sand and gravel. Offshore-directed currents produced uncommonly large (typically 1–2 m thick) trough cross-stratified sandstone. In addition, stromatolitic carbonate interbedded with stratified coarse sandstone and conglomerate suggests a dynamic environment characterized by episodic terrigenous clastic deposition under high-energy conditions alternating with periods of carbonate precipitation under reduced energy conditions. Massive and normally graded sandstone and massive to poorly laminated mudstone characterize the offshore lacustrine facies association and record deposition by turbidity currents and suspension fallout. A depositional model constructed for the Horse Camp Formation (Member 2) precludes the existence of all four depositional environments at any particular time. Rather, phases characterized by deposition in subaerial fan, nearshore lacustrine and offshore lacustrine environments alternated with phases of subaerial fan-delta, subaqueous fan-delta and offshore lacustrine deposition. This model suggests that high-energy nearshore currents due to deep water along the lake margin reworked sediment of the fan edge, thus preventing development of a subaqueous fan-delta environment and promoting development of a well-defined nearshore lacustrine environment. Low-energy nearshore currents induced by shallow water along the     

Deep-water fan-channel conglomerates of Late Cretaceous age, southern Chile

The exceptionally well exposed Lago Sofia conglomerate and sandstone lenses in the Upper Cretaceous Cerro Toro Formation of southern Chile are interpreted as the channel and channel margin facies of a deep-sea fan. The north-to-south oriented channels formed on an elongate fan in a narrow retroarc basin between a rising cordillera to the west and the South American craton to the east. The great length of some of the channels (> 120 km) seems to reflect the long duration (> 30 m.y.) and stable nature of the basin. Enclosing the lenses is the fine-grained Cerro Toro Formation which represents overbank turbidite flows and hemipelagic sedimentation on levee and levee flank areas. Foraminiferal assemblages suggest deposition in 1000-2000 m of water. Most of the conglomerate has features developed by tractive currents (parallel- and cross-stratified conglomerate). Most is moderately well sorted, imbricated, and has parallel to inclined stratification; large-scale dunes up to 4 m high are exposed. Typical sediment, gravity flow structures and bedding styles (e.g. pebbly mudstones, graded conglomerate, giant flutes) are not as common in the channel deposits as are tractive features. Tractive features in the gravels apparently were developed by rolling, sliding, and saltation as the bed-load component of highly turbulent, moderate- to low-density turbidity currents flowing in a confined channel. Graded-to-massive conglomerates appear to have been deposited rapidly from fully turbulent flows; diamictites were deposited from debris flows in which fluid viscosity, yield strength, and buoyancy of the fluid were dominant. The three major conglomerate classes recognized do not occur in a systematic manner; vertical and lateral heterogeneity is the rule.     

The Coarse-Grained Lacustrine Slope Apron Deposits in the Moliqing Area, Yitong Basin, Northeast China

Overlapping gravity accumulation bodies were formed on the northwestern steep slope of the Shuangyang Formation in the Moliqing fault depression of northeast China. This study analyzed in detail the spatial distribution of the lithofacies and lithofacies associations of these accumulation bodies based on more than 600 m of core sections, and summarized 12 major types of lithofacies and three types of lithofacies associations: (1) the proximal zone consists of gravelly debris flows dominated by alluvial channel conglomerates; (2) the middle zone is dominated by various gravity flow deposits and traction flow deposits; and (3) the distal zone is dominated by mudstones with intercalations of sandy debris and turbidites. Combining with the grain size cumulative probability curves analysis, we determined the transformation of debris flows to sandy debris flows and to turbidity currents in the slope zone of the basin margin, and further proposed a lacustrine slope apron model that is characterized by (1) an inconstant multiple source (line source), (2) an alternation of gravity flow deposits and traction flow deposits dominated by periodical changes in a source flood flow system, and (3) the transformation of sandy debris flow deposits into distal turbidity current deposits. This sedimentary model may be applicable to other fault depressions for predicting reservoir distribution.     

鄂尔多斯盆地南部三叠系延长组湖相重力流沉积细粒岩及其油气地质意义

随着页岩油气勘探开发和相关领域研究的不断深入,细粒沉积物的搬运和沉积已成为当前沉积学研究的热点问题之一,但中国中生代湖泊环境中的泥质重力流沉积尚未引起应有的关注。通过岩心观察、薄片鉴定等手段及综合研究,分析了鄂尔多斯盆地晚三叠世湖相泥质重力流沉积特征,探讨了其形成机制与成因分类。鄂尔多斯盆地三叠系延长组湖相泥页岩结构类型多样,发育泥质块体流沉积、泥质碎屑流沉积、泥质浊流沉积和泥质异重流沉积等多种重力流沉积类型。按照泥质含量将重力流划分为砂质重力流、泥质重力流和混合重力流3种亚类,并根据成因将重力流划分为滑塌体、碎屑流、浊流及异重流等4种亚类;结合成因和泥质含量,将重力流沉积共划分为12种类型。滑塌岩、碎屑岩分布于三角洲前缘斜坡脚附近;浊积岩、异重岩广泛分布于三角洲斜坡至沉积中心。认为泥质沉积物可以在强水动力条件下搬运-沉积;重力流沉积细粒物质在湖相沉积中占据很大的比例;泥质重力流对泥页岩中的碎屑物质、黏土矿物及有机质的搬运和沉积起到重要作用,因而对于页岩油气的生烃、储集性能和压裂工艺研究具有重要意义。     

黄河口凹陷A区古近系沙河街组三段沉积相

通过岩心观察描述和沉积相分析,结合地震、测井、录井、分析化验资料综合分析结果表明：黄河口凹陷A区沙河街组三段发育扇三角洲相、湖底扇相和湖泊相。沙三段下亚段沉积相特征在沙三段沉积时期具有代表性。沙三段下亚段主要储层沉积相类型为扇三角洲相和湖底扇相。扇三角洲相划分为扇三角洲平原、扇三角洲前缘和前扇三角洲3个亚相。扇三角洲平原亚相由泥石流和水道沉积组成。扇三角洲前缘亚相由近端坝和远端坝沉积组成。湖底扇相可分为内扇、中扇和外扇3个亚相。内扇主要由滑塌堆积和碎屑流沉积组成,中扇主要由碎屑流和浊流沉积组成,外扇主要由浊流沉积组成。沙三段下亚段沉积时期,沉积相的平面展布具有一定的规律性,表现为：靠近南部盆缘断裂发育扇三角洲相,向湖方向发育湖底扇相,向北逐渐过渡为湖泊相。沙三段下亚段沉积时期,盆地明显为南陡北缓的箕状断陷湖盆,陡坡带活动盆缘断裂控制了扇三角洲相的分布。     

河南省济源盆地下侏罗统鞍腰组重力流沉积特征及其构造意义*

在详细野外剖面工作的基础上,通过岩性特征、沉积构造及沉积序列等的系统观察研究,发现济源盆地下侏罗统鞍腰组重力流沉积由滑塌沉积、砂质碎屑流沉积和浊流沉积构成。滑塌沉积以砂岩和泥岩的混杂、岩层的滑动变形以及泥岩呈碎块被卷入砂岩层中为特征;砂质碎屑流沉积常呈厚层块状,颗粒分选和磨圆较差,杂基较多,可见漂浮于层内的石灰岩砾石;常见的浊流沉积分为2种类型: 具有明显正粒序结构的浊流沉积和砂泥岩薄互层的浊流沉积,可用鲍马序列来描述。鞍腰组重力流沉积可划分为3个沉积序列: 序列A记录了滑塌沉积→砂质碎屑流沉积→浊流沉积→深湖沉积的转换过程;序列B表现为砂质碎屑流与浊流沉积的叠覆;序列C由浊流及湖泊沉积构成,并经历了由序列A→序列B→序列C的沉积演化过程。重力流的形成受秦岭造山带于早侏罗世沿三门峡—鲁山—舞阳断裂发生逆冲推覆作用的控制,其沉积演化指示了秦岭造山带造山作用由强到弱的过程。     

新疆奇台地区下石炭统扇三角洲沉积特征

新疆奇台地区下石炭统地层中发现一套冲积扇进积到湖泊中而形成的扇三角洲沉积体。三角洲层序完整，清楚地显示出湖退又湖进的沉积序列；其中，扇三角洲平原部分主要以泥石流成因的块状砂砾岩为主，夹扇面河道沉积的含砾砂岩、中粗粒砂岩透镜体及中薄层状漫流沉积；扇三角洲前缘以碎屑流沉积的块状砂砾岩为主，夹水下分流河道沉积的砂岩透镜体。前三角洲以深灰色泥岩、粉砂质泥岩为主．沉积体中含丰富的植物化石。     

扇三角洲沉积模式探讨:以准噶尔盆地玛北地区下三叠统百口泉组为例*

扇三角洲是一类非常重要的油气聚集场所,准确可靠的扇三角洲沉积模式,对储集层预测具有重要意义。准噶尔盆地玛北地区三叠系百口泉组发育一套扇三角洲沉积体系,虽然前人做了大量的研究,但在沉积模式方面仍存在一些争议。通过现代沉积考察、前人水槽模拟实验、研究区测井、岩心等资料综合分析发现: (1)玛北地区百口泉组扇三角洲平原发育3类微相,即辫状河道微相、砾质漫滩微相、水上朵前泥微相,同时可见泥石流沉积;玛北地区百口泉组扇三角洲前缘发育2种微相,即砾质浅滩微相、砂质浅滩微相,同时可见碎屑流沉积;(2)扇三角洲平原河道与河道间均为砂砾岩,河道砂砾岩的分选性明显好于河道间砂砾岩;(3)扇三角洲前缘不发育水下分流河道,扇三角洲前缘的砂砾岩主体是由扇三角洲平原片流入湖形成的,呈席状。     

Delta-fed turbidites in a lacustrine rift basin: the Eocene Dongying depression,Bohai Bay Basin,East China

Sediment avalanche from delta ramp is one of the significant development mechanisms for a turbidite system in a lacustrine basin. To advance our understanding of deep-water sedimentary processes in a lacustrine delta ramp, delta-fed turbidites in the Eocene Dongying depression of the Bohai Bay Basin were studied using core data, 3-D seismic data and well log data. Sandy debris flows, muddy debris flows, mud flows, turbidity currents, slides, sandy slumps and muddy slumps were interpreted based on the identification of lithofacies. Data indicates that deep-water sedimentary processes in the study area were dominated by debris flows and slumps, which accounted for ～68% and 25% (in thickness) of total gravity flow deposits, respectively; turbidity-current deposits only accounted for ～5%. Mapping of turbidites showed that most were deposited after short-distance transportation (<20 km), restricted by the scale of deep-water areas and local topography. Channels, depositional lobes, debris flow tongues, muddy turbiditic sheets, slides and slumps were identified in a delta-fed ramp system. Slides and slumps were dominant at the base of slopes or at the hanging walls of growth faults with strong tectonic activity. Channels and depositional lobes developed in gentle, low-lying areas, where sediments were transported longer distances. Sand-rich sediment supply, short-distance transportation and local topography were crucial factors that controlled sedimentation of this ramp system. Channels generally lacked levees and only produced scattered sandstones because of possible hydroplaning of debris flow and unstable waterways. In addition to lobes, debris flow tongues could also be developed in front of channels. These findings have significant implications for hydrocarbon exploration of deep-water sandstone fed by deltas in a lacustrine basin.     

The Maesan fan delta, Miocene Pohang Basin, SE Korea: architecture and depositional processes of a high-gradient fan-delta-fed slope system

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.