塔里木盆地志留纪沉积层序构成及充填响应特征

塔里木盆地志留系是由角度不整合面所限定的一个区域性（二级）的沉积层序,其内可划分出5个三级沉积层序。总体上显示一个从水进到水退的沉积旋回,可识别出曲流河三角洲—辫状河三角洲、滨外陆棚及较深水盆地、无障壁碎屑滨岸—无障壁碎屑潮坪沉积体系组合,它们代表了二级沉积层序中相对低位、海侵和高位的3个沉积体系组合。研究区构造、沉积、古生物和古气候资料表明,层序1底界面和层序5顶界面是塔里木周缘板块构造挤压、盆地隆升作用的结果;层序2底界面是周缘板块强烈挤压、盆地挠曲下降作用结果,同期全球海平面快速上升;层序3、层序4和层序5的底界面是在构造作用稳定、全球海平面下降背景之上由相对海平面次一级旋回变化形成的,是古气候变化、沉积物供给及构造沉降共同作用的结果。     

影响沉积盆地相对海平面变化的多重因素和旋回层序响应

沉积盆地内相对海平面变化及沉积层序形成不仅受全球海平面变化旋回控制，而且沉积盆地所处的构造背景和相关因素，如：沉积物供给、盆底沉降和自然地理条件也对沉积层序及其内部组成——体系域具有极大的影响。对应于海平面变化发育的容纳空间旋回层序，沉积供给也可以形成特征的、可以鉴别的供给旋回层序。具有过渡性界线的三级或高频旋回层序受相对海平面变化和沉积供给双重因素控制。不同构造背景沉积盆地边缘发育不同的盆底沉降速率，相对海平面变化响应于盆缘沉降具有明显的构造－海平面分带，岸线在构造－海平面带中的地理位置决定了层序界面和层序堆叠样式，也同样影响着低位体系域的构成。深水盆地环境古地形特点及沉积物供给制约着深水沉积序列。构造运动显著地影响着沉积层序发育。碳酸盐缓坡和平顶镶边陆架的层序格架及体系域发育受其坡度、盆地深度及下降幅度的因素的作用。台地边缘和大陆边缘盆地浊积岩层序的发育和体系域组成受控于差异的沉积物源（平顶碳酸盐台地、镶边台地和陆源碎屑岩陆架）、古地理及构造活动性     

强迫型海退及强迫型海退楔体系域--对传统Exxon层序地层学模式的修正

传统Ｅｘｘｏｎ层序地层学模式把层序界面定义在下降拐点,低水位体系域则位于类型Ⅰ层序之底,且低水位体系域（ＬＳＴ）被定义为海平面相对下降期至初始上升阶段的产物;但是,在建立海平面变化曲线时,又假定层序界面位于海平面变化的最低点,从而造成层序地层学概念体系的下连贯性。强迫型海退被定义为与沉积物注入无关,而与相对海平面下降相关的滨线向海方向迁移的海退过程,由此而产生的一系列沉积体则构成强迫型海退楔体系域     

四川江油马角坝地区上石炭统层序地层研究

应用露头层序地层学基本原理和方法、结合碳酸盐岩微相、古生物学、成岩作用、沉积相和沉积事件等理论,对江油马角坝地区上石炭统碳酸盐岩地层进行了露头层序地层研究。研究表明,研究区晚石炭世为典型的陆表海沉积,地形平坦,地壳下降相对缓慢,海水较浅,沉积物界面与海平面接近,主体为碳酸盐岩开阔台地和浅滩沉积环境。水体主体深度为0~50m,为低幅高频低速的海平面变化。根据沉积层序界面的露头和镜下标志,共划分出7个三级层序,反映了研究区晚石炭世具有7次相对较大的海平面升降旋回。发育TST和HST,普遍缺失LST,局部CS难以识别。平均每个层序时限约为2.7Ma,并伴随着多次四级、五级乃至高频海平面变化,共同组成了研究区简单而复杂的碳酸盐岩地层格架。动力机制主要源于晚古生代冰川型全球海平面变化,其原因可能为晚古生代冰期(大洋水体积的周期型变化或大陆冰盖的增长和衰减)和风暴事件共同作用的结果,同时受到古地形、物源和沉积物供应量变化的制约。其中,CSQ1、CSQ3和CSQ4对应的海平面变化幅度较大,海平面变化速率主要为突发性的快递上升到缓慢下降或缓慢上升到相对下降的特点。CSQ2、CSQ5、CSQ6和CSQ7对应的海平面变化幅度不大,为缓慢上升和缓慢下降的特点。     

测井曲线旋回分析在碳酸盐岩层序地层研究中的应用*

在碳酸盐岩台地沉积层序的研究中,通过旋回计数和厚度测量,采用费希尔图解法解析高频米级旋回或副层序的叠置形式和空间结构,进而标定三级沉积层序的界面,是目前普遍采用的一个方法。但是,这一方法目前主要用于露头层序地层学研究,而在地下油气勘探区受到极大的限制。文中提出了一种新的计算方法,它可以根据测井资料求取任一地层段沉积旋回的个数和厚度。根据数值模拟,详细讨论了海平面变化周期和幅度与沉降速率、沉积速率的相关关系,提出高频沉积旋回的分布模式和叠加样式可以指示低频海平面变化的轨迹,这为划分三级沉积层序、标定层序界面提供了理论依据。最后,以川西北地区中三叠统雷口坡组为例,说明了应用自然伽马测井资料进行数据处理的流程和步骤,以及根据旋回厚度累积偏差曲线标定层序界面的位置、识别旋回谱系标志。     

碳酸盐岩米级旋回层序的成因类型及形成机制

在前人研究及自己野外观察的基础上,本文把碳酸盐岩米级旋回层序归为四大类:深水非对称米级旋回层序、L-M米级旋回层序、潮下碳酸盐米级旋回层序、潮坪碳酸盐米级旋回层序。米级旋回层序的形成机制是与米兰柯维奇旋回有关的高频率海平面振荡变化旋回所形成的间断-加积旋回沉积作用,它们的识别标志主要是岩石类型、界面特征、产出环境等。碳酸盐岩米级旋回层序的规则的垂直叠加形式是识别三级旋回层序的基础。     

塔里木盆地K2-E旋回层序与海平面变化

塔里木盆地西南缘K₂-E海相含碳酸盐岩地层中可识别出七种类型的高频旋回层序,主要有潮下缓坡型、台地型、台地边缘型碳酸盐旋回层序及以碎屑岩为主的潮间－潮上型旋回层序。平面上,不同类型高频旋回层序成为特定古地理背景下台地碳酸盐沉积体系、滨岸沉积体系和冲积沉积体系沉积层序的代表。纵向上,各类高频旋回层序的有序叠加,其类型的变化反映了沉积环境、沉积相的演变过程。研究结果表明,研究区各类高频旋回层序下部单元至上部单元微相的转变是受高频率海平面变化的影响,低频率海平面升降控制了高频旋回层序的叠加形式,造成沉积环境由下至上滨岸→碳酸盐台地→滨岸→河流的变化。正是由于不同周期海平面变化旋回的叠加形成了塔里木盆地西南缘K₂-E的复合海平面变化旋回层序。     

雾迷山旋回层的费希尔图解及其在定义前寒武纪三级海平面变化中的应用

天津蓟县剖面的中元古界雾迷山组是一套厚 3 3 0 0m的碳酸盐岩地层 ,其中广泛发育叠层石生物层及凝块石生物丘。这些生物层及生物丘与潮坪相白云岩和砂泥质白云岩一起构成具有近似对称相序组构的环潮坪型碳酸盐米级旋回层序 ,将其命名为“雾迷山旋回层”。这些旋回层常由泻湖相白云质泥页岩覆盖 ,在其顶常发育古土壤层 ,由此而表明雾迷山旋回层的界面多为瞬时暴露间断面。根据雾迷山旋回层在长周期三级层序中的有序叠加形式 ,可在雾迷山组中识别出 2 6个Ⅲ级层序 ,它们还可进一步归为 6个Ⅱ级层序。为了进一步研究三级海平面的变化幅度和Ⅲ级层序的大致形成时限 ,在露头发育良好的雾迷山组中上部共识别出 62 6个旋回层 ;考虑到雾迷山组的总体厚度 ( 3 3 0 0m)及其大致的总体形成时限 ( 10 3± 2 0Ma左右 ) ,可假定雾迷山组沉积期的总体地壳沉降速率为 2～ 4m/ 10万a。在上述假定的基础上 ,运用费希尔图解来估算三级海平面的变化幅度。     

塔中地区奥陶系米级旋回层序分析

塔中地区奥陶系米级旋回层序非常发育且典型多样,孕含着丰富的构造、海平面变化及沉积物堆积作用等方面的信息。在认真总结前人研究成果的基础上,结合区域地质资料及详细的岩芯观察和描述,将本区奥陶系米级旋回层序分为四大类:远洋-半远洋L-M型米级旋回层序、下斜坡-深水盆地非对称型米级旋回层序、潮下型米级旋回层序及环潮坪型米级旋回层序。在相序组构特征上,都表现为发育在瞬时淹没间断面之上以反粒序序列为特征的米级旋回层序和发育在瞬时暴露间断面之上以反粒序或正粒序序列为特征的米级旋回层序,并且在长周期三级层序中表现为有序的垂直叠加形式。这些米级旋回层序的沉积速率及形成周期与米兰柯维奇(Milankovitch)天文旋回轨道及周期变化具有明显的相关性。因此,塔中地区奥陶系米级旋回层序的发育主要受高频率海平面变化的控制,而这种高频率海平面升降则是由米兰柯维奇天文旋回轨道及周期变化所造成全球气候变化及大陆冰川的消长所控制。     

柴达木盆地北缘上石炭统碎屑岩—碳酸盐岩高频转换过程及驱动机制

碎屑岩和碳酸盐岩分别产自"外源、浑水"与"内源、清水"环境,二者的交替互层沉积可反映古水体性质、物源供给及气候等环境要素的频繁改变。晚石炭世,柴达木盆地北缘构造相对稳定,盆内发育巨厚的、多级次嵌套的"碎屑岩—碳酸盐岩混积层系",记录了"冰室地球"冰川活动下的古海平面大幅度升降和古气候、古环境频繁交替信息。文中以柴达木盆地北缘连续完整露头剖面和钻井取心剖面为研究对象,结合区域地质资料、前人研究成果,通过详细的岩心、露头及镜下薄片观察,在研究区重点层段识别出下切谷充填型碎屑岩沉积和碳酸盐岩台地沉积组成的频繁互层序列。碎屑岩—碳酸盐岩互层组合序列在垂向上的有序叠加,构成了复合海平面变化旋回层序,其从碳酸盐岩—改造型台地沉积开始,向上依次发育碎屑岩下切谷充填序列的底部冲积河道沉积、中部河口湾序列和顶部代表海泛面的泥岩沉积,最后转变为碳酸盐岩向海到向陆台地亚相,反映了一个显著的早期海退—中期逐渐海侵—后期再次海退的旋回过程。冰川期急剧变冷的气候和冰川型高频的大幅度海平面升降,驱动滨线及相带迁移,影响到碎屑岩供给速率和碳酸盐生产率,造成了碎屑岩—碳酸盐岩的高频转换。     

Progradational Holocene carbonate tidal flats of Crooked Island,south‐east Bahamas: An alternative to the humid channelled belt model

The stratigraphic record of many cratonic carbonate sequences includes thick successions of stacked peritidal deposits. Representing accumulation at or near sea‐level, these deposits have provided insights into past palaeoenvironments, sea‐level and climate change. To expand understanding of carbonate peritidal systems, this study describes the geomorphology, sedimentology and stratigraphy of the tidal flats on the Crooked‐Acklins Platform, south‐east Bahamas. The Crooked Island tidal flats extend continuously for ca 18 km on the platformward flank of Crooked Island, reaching up to 2 km across. Tidal flats include four environmental zones with specific faunal and floral associations and depositional characteristics: (i) supratidal (continuous supratidal crust and pavement); (ii) upper intertidal, with the mangrove Avicennia germinans and the cyanobacteria Scytonema; (iii) lower intertidal (with the mangrove Rhizophora mangal) and (iv) non‐vegetated, heavily burrowed subtidal (submarine). These zones have gradational boundaries but follow shore‐parallel belts. Coring reveals that the thickness of this mud‐dominated sediment package generally is <2 m, with depth to Pleistocene bedrock gradually shallowing landward. The facies succession under much of the tidal flat includes a basal compacted, organic‐rich skeletal‐lithoclast lag above the bedrock contact (suggesting initial flooding). This unit grades upward into rhizoturbated skeletal sandy mud (subtidal) overlain by coarsening‐upward peloid‐foraminifera‐gastropod muddy sand (reflecting shallowing to intertidal elevations). Cores from landward positions include stacked thin indurated layers with autoclastic breccia, root tubules and fenestrae (interpreted as supratidal conditions). Collectively, the data reveal an offlapping pattern on this prograding low‐energy shoreline, and these Holocene tidal flats may represent an actualistic analogue for ancient humid progradational tidal flats. Nonetheless, their vertical facies succession is akin to that present beneath channelled belt examples, suggesting that facies successions alone may not provide unambiguous criteria for prediction of the palaeogeomorphology, lateral facies changes and heterogeneity in stratigraphic analogues.     

陕甘宁盆地中部马五1潮缘碳酸盐岩沉积旋回及其成因探讨

陕甘宁盆地中部马五₁段由多个向上变浅的潮缘碳酸盐岩沉积序列重复叠置组成,并可分为十三种沉积 -成岩微相和六个沉积相带。这种沉积序列的韵律性重复叠置的形成方式为潮缘进积楔的简单退覆和阶段式退覆,其形成机制为自旋回。     

Facies architecture and cyclicity in a mosaic carbonate platform: effects of fault-block tectonics (Lower Lias, Causses platform, south-east France)

In the Causses platform (south‐east France), Late Hettangian to Sinemurian deposits were interpreted previously as shallow‐water carbonate ramp deposits. A new look at these deposits has shown a fault‐controlled mosaic carbonate platform that is different from the carbonate ramp models. Within the platform mosaic, 15 lithofacies have been recognized, which are organized in four facies associations, including peritidal, restricted shallow sub‐tidal, sand dunes and sub‐tidal shelf facies associations. The rapid lateral and vertical facies changes, and the lack of consistent landward or seaward direction indicated by the pattern of facies changes, question the existence of a shoreline suggested by the traditional models for this region. Instead, the facies organization and cycle stacking pattern suggest deposition in a mosaic of intertidal islands between which sub‐tidal restricted or open conditions could coexist in very close proximity. Such a platform mosaic would have been defined by tectonic activities along normal faults which segmented the shallow‐water Causses platform. The facies and facies associations are arranged into metre‐scale, peritidal and sub‐tidal cycles that are also variable. Certain cycles show the same stacking pattern in all the sections and seem to be traceable over tens of kilometres. On the contrary, other cycles cannot be correlated; they are present only in specific sections and have a maximum lateral extension of 1 or 2 km. These metre‐scale cycles stack to form four medium‐scale cycles bounded by surfaces that display sub‐aerial exposure features. Medium‐scale cycles stack into two larger‐scale cycles (tens of metres thick) and are bounded by well‐defined karstic surfaces. Based on their lateral continuity and their stacking pattern, the metre‐scale cycles are controlled probably by high frequency eustatic variations overprinting the topographic irregularities formed by differential subsidence of fault‐bounded blocks. Episodic fault activities may reorganize the topography so that, even if eustatic changes may still be the major control of cycles, the expression and number of cycles could be different. Cycles of medium and large‐scale are interpreted as being allogenic, controlled by changes in eustasy and/or subsidence rates as evidenced by their lateral continuity and the correlations of the large‐scale cycles with third‐order depositional sequences.     

长江三角洲南汇潮滩沉积速率及其影响因素

近100余年来,南汇潮滩尤其是中、高潮滩,以淤涨为主,使岸线迅速向海推进。但潮滩沉积并 非连续,而是以冲、淤相间,长期净淤积的方式进行。潮滩沉积剖面主要由风暴成因的小型层序组成,粗、细 粒交替分别代表风暴与平静天气的产物。潮滩沉积环境的不稳定性使其难以满足两种常用来计算210Pb沉积速率 的方法---CIC （稳定的初始比度） 模型和CRS（稳定的沉降通量） 模型的前提条件。在实验时,如果只选择 代表平静天气沉积的细颗粒层进行210Pb活度分析,则可能得到一组相对符合CIC模型的数据,利用此方法计算 出南汇潮间带环境的平均沉积速率为6.11~6.23 cm/yr。对历史海图数字化建立的数字高程模型（DEM） 分析 表明,中、高潮滩近50余年的平均沉积速率为1.91~2.05cm/yr,不及210Pb沉积速率的一半。造成这种差异的 原因有：（１） DEM法在高程推算过程中使用简单的潮滩纵剖面模型,导致计算的沉积速率偏低;（２）210Pb法受 到沉积过程中强烈的物理混合作用和沉积后的生物扰动、化学迁移作用等影响,使计算的沉积速率偏高。推断 近50余年来,南汇中、高潮滩的沉积速率为4～5cm/yr。     

The Late Jurassic Tithonian, a greenhouse phase in the Middle Jurassic–Early Cretaceous 'cool' mode: evidence from the cyclic Adriatic Platform, Croatia

Well‐exposed Mesozoic sections of the Bahama‐like Adriatic Platform along the Dalmatian coast (southern Croatia) reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding Late Jurassic (Tithonian) shallow platform‐interior (over 750 m thick, ca 5–6 Myr duration). Facies within parasequences include dasyclad‐oncoid mudstone‐wackestone‐floatstone and skeletal‐peloid wackestone‐packstone (shallow lagoon), intraclast‐peloid packstone and grainstone (shoal), radial‐ooid grainstone (hypersaline shallow subtidal/intertidal shoals and ponds), lime mudstone (restricted lagoon), fenestral carbonates and microbial laminites (tidal flat). Parasequences in the overall transgressive Lower Tithonian sections are 1–4·5 m thick, and dominated by subtidal facies, some of which are capped by very shallow‐water grainstone‐packstone or restricted lime mudstone; laminated tidal caps become common only towards the interior of the platform. Parasequences in the regressive Upper Tithonian are dominated by peritidal facies with distinctive basal oolite units and well‐developed laminate caps. Maximum water depths of facies within parasequences (estimated from stratigraphic distance of the facies to the base of the tidal flat units capping parasequences) were generally <4 m, and facies show strongly overlapping depth ranges suggesting facies mosaics. Parasequences were formed by precessional (20 kyr) orbital forcing and form parasequence sets of 100 and 400 kyr eccentricity bundles. Parasequences are arranged in third‐order sequences that lack significant bounding disconformities, and are evident on accommodation (Fischer) plots of cumulative departure from average cycle thickness plotted against cycle number or stratigraphic position. Modelling suggests that precessional sea‐level changes were small (several metres) as were eccentricity sea‐level changes (or precessional sea‐level changes modulated by eccentricity), supporting a global, hot greenhouse climate for the Late Jurassic (Tithonian) within the overall ‘cool’ mode of the Middle Jurassic to Early Cretaceous.     

鄂北南化地区寒武纪缓坡沉积及层序

出露于鄂北南化地区的寒武纪地层，总厚约１４００ｍ，主体为一套碳酸盐岩。对沉积岩相及相组合的分析表明，本区寒武系主要是形成于碳酸盐缓坡之上，并可以划分出四种主要的沉积相带:浅水陆棚、深水缓坡、浅水缓坡建隆和近岸浅水缓坡。本文还初步研究了区内寒武系露头的层序地层学特征，划分出两个亚层序，并探讨了亚层序内部岩相的不同叠置类型及其在时间上的演化与相应的海平面升降变化。通过与已有的旋回性海平面变化模式相对比，得出了本区寒武纪层序内部的次级旋回可能指示第三级海平面变化旋回的认识。     

A depositional model for storm- and tide-influenced prograding siliciclastic shorelines from the Middle Devonian of the central Appalachian foreland basin, USA

A stratigraphic motif observed in many foreland basins is the development of basinward tapering siliciclastic wedges characterized by various scales of depositional cycles. The Middle Devonian (Givetian) Mahantango Formation in the central Appalachian foreland basin is such an example. It consists of both small-and large-scale thickening- and coarsening-upward cycles; the small-scale cycles are typically less than 10 m thick whereas larger-scale cycles are generally a few tens of metres thick and commonly contain several of the smaller-scale cycles. Outcrop-based facies analyses indicate that the depositional cyclicity resulted from episodic progradation of a regionally straight, tide-dominated shoreline onto a storm-dominated, shallow marine shelf. The depositional model for this ancient shallow marine system consists of a vertical facies succession in which storm-dominated offshore marine mudstone and fine sandstone pass gradationally upward into storm-dominated nearshore marine shelf and shoreface sandstone overlain by, in proximal sections, tide-dominated shoreline sandstone, pebbly sandstone and mudstone. Transgressively reworked lag deposits cap most of the thickening- and coarsening- upward packets. In this model, coarse-grained rocks, rather than implying basinward shifts of facies, are a consanguineous part of the stacked shoaling cycles. Lateral facies relationships show that the dominance of storm- vs. tide-generated sedimentary features is simply a function of palaeogeographical position within the basin; proximal sections contain tidally influenced sedimentary features whereas more distal sections only display evidence for storm-influenced deposition. These results suggest caution when inferring palaeoceanographic conditions from sedimentological datasets that do not contain preserved examples of palaeoshorelines.     

Transgression of an estuarine channel and tidal flat complex: the Lower Triassic of Barles, Alpes de Haute Provence, France

The Lower Triassic succession of Barles, Alpes de Haute Provence, France, comprises an unconformable quartz arenite sand body of 90m thickness. The succession may be informally divided into (i) lower channellized cross-bedded member overlain by (ii) an upper fining upward member. The lower member comprises vertically stacked, subtidal channel units separated into five major sand bodies by thin developments of fine grained channel margin and shoal deposits. Subtidal channel fill deposits are dominated by varying scales of cross bedding. These scales vary systematically from the base to the top of the member, with large scale planar sets dominating the lowest channel sand body (sand body 1), medium scale planar and trough cross bedding characterizing sand bodies 2-4, the largest scale planar sets in the highest sand body (sand body 5). This upward change in cross bedding scale is concomitant with a decrease in both the relief of major channel sand body erosion surfaces, and the proportion of preserved interchannel shoal deposits. The succeeding fining upward member comprises small scale tidal channel units overlain by channel shoal and tidal flat deposits. Tidal flat sequences are characterized by parallel laminated, wave and current rippled sandstones separated by bioturbated, fine grained siltstones and mudstones. The vertical variation in facies of the Lower Triassic succession suggests two main periods of deposition. The lower member is considered to preserve successively more seaward components of a transgressive estuarine complex. The overlying upper member records the seaward progradation of tidal channel, shoal and tidal flat environments. The unconformity bounded nature of the lower member, combined with its systematic variation in facies, suggests it may represent an incised valley-estuarine fill developed in response to an early Triassic relative sea level fall and subsequent rise. Succeeding tidal channel and tidal flat deposits forming the upper fining upward member reflect a change in sediment supply and/or rate of relative sea level rise comparable with a progradational shoreline. It is unclear whether this final depositional episode represents a period of highstand progradation or a later lowstand shoreline system developed following a further period of relative sea level fall and rise.     

华北石炭纪含煤建造的陆表海堡岛体系特点及其事件沉积

华北石炭纪含煤建造沉积属于陆表海性质,其岩相古地理特点为陆表海多堡岛浑水与清水混合沉积体系。主要成煤古地理条件是位于潮坪上不同类型的泥炭坪环境,因而煤层分布面积广,层位稳定。聚煤期盆地性的重大事件是风暴沉积和火山事件沉积。风暴岩的主要类型是:回流型远源碳酸盐风暴岩和近源碳酸盐风暴岩,搅动型碳酸盐风暴岩;近源型砂岩风暴岩,漫流型砂岩风暴岩和砾屑泥岩风暴岩。风暴沉积影响着煤层的形成与赋存。     

西藏措勤盆地下白垩统多巴组沉积环境分析

西藏措勤前陆盆地下白垩统多巴组是一套分布面积广大,比较特征的碳酸盐、陆源碎屑混合沉积的地层,本文通过对几条较完整的主干剖面的详细沉积相分析,揭示了多巴组的主要沉积环境包括潮坪、低能潮下带、近岸碳酸盐台地缓坡、台缘介壳滩及碳酸盐台地等几种主要类型,建立了多巴组的沉积相模式,并指出多巴组的沉积演化主要受控于盆地构造运动和全球海平面变化,这将有助于该地区的构造沉积演化研究。