拉萨北部旁多群坠石沉积的发现及其意义

报道了新发现的旁多群中部的打鲁雄剖面及其含有典型坠石的沉积特征。该剖面旁多群中部以陆源碎屑少、悬浮泥质沉积为主的欠补偿的深水盆地相沉积为特征，同时夹有水下冰碛岩、重力流沉积等。纹层状一薄层状的粘土质岩层内分布着粒径是基质的100-1000倍的棱角状一次棱角状、长轴垂直近垂直于纹层面或层面的碎屑和砾石。砾石上下的泥质岩具有顶凸下挠的现象。碎屑和砾石及其对上下地层的影响表明其为坠石沉积。旁多群中指示冰川、冰筏沉积作用存在的坠石的发现，有力地证明了青藏高原石炭纪——二叠纪冈瓦纳相地层形成于受到冈瓦纳大陆冰川影响的海相环境。     

冈底斯东段色日绒地区冈瓦纳相冰海杂砾岩特征及其意义

色日绒地区冰海杂砾岩产于砂泥质为主的陆缘碎屑岩段中,累计出露厚度约325 m。岩石学及沉积学特征指示其沉积于滨海—上部浅海环境;顶部的化石生物组合指示此段岩层沉积于晚石炭世—早二叠世的冷水型海洋环境。岩层中的坠石结构、压裂面以及与其同层位产出的冷水型生物群为冰海杂砾岩的成因提供了有力的证据,指示其形成于冰川作用下,是由冰筏搬运的海相沉积。通过资料综合收集、对比,确定了冰海杂砾岩形成的古构造及古地理、古气候控制条件。根据古构造位置及古地理特征,大致总结出了以该地区为代表的冈瓦纳相冰海杂砾岩的沉积及成因模式。     

青藏高原羌塘南部冰海杂砾岩的成因与物源——以冈玛错地区为例

青藏高原及其邻区石炭纪—二叠纪地层中广泛分布的漂砾层、杂砾岩、含砾板岩等是一套特殊的冰海相沉积岩,称为冰海杂砾岩,前人已对它的成因环境做了初步的研究,但没有获得统一的结论。本次以青藏高原羌塘南部冈玛错地区冰海杂砾岩的砾石为研究对象,观察它们的野外特征和镜下特点,并对与冰海杂砾岩互层产出的石英砂岩做了粒度分析。结果表明,冰海杂砾岩是在冈瓦纳大陆冰川呈消融状的情况下,冰阀搬运沉积的产物。通过碎屑锆石和岩性对比,初步认为冰海杂砾岩的物源为冈瓦纳大陆,并简单论述了冰海杂砾岩各类砾石的可能来源。以上研究成果为探讨冈瓦纳大陆的沉积环境提供了依据。     

青藏高原羌塘南部冰海杂砾岩的成因与物源——以冈玛错地区为例

青藏高原及其邻区石炭纪—二叠纪地层中广泛分布的漂砾层、杂砾岩、含砾板岩等是一套特殊的冰海相沉积岩,称为冰海杂砾岩,前人已对它的成因环境做了初步的研究,但没有获得统一的结论。本次以青藏高原羌塘南部冈玛错地区冰海杂砾岩的砾石为研究对象,观察它们的野外特征和镜下特点,并对与冰海杂砾岩互层产出的石英砂岩做了粒度分析。结果表明,冰海杂砾岩是在冈瓦纳大陆冰川呈消融状的情况下,冰阀搬运沉积的产物。通过碎屑锆石和岩性对比,初步认为冰海杂砾岩的物源为冈瓦纳大陆,并简单论述了冰海杂砾岩各类砾石的可能来源。以上研究成果为探讨冈瓦纳大陆的沉积环境提供了依据。     

冈底斯带东段色日绒冈瓦纳相冰海杂砾岩特征

色日绒地区冰海杂砾岩产于砂泥质为主的陆缘碎屑岩段中,累积出露厚度325m,沉积于浅海环境。该段顶部化石生物组合指示其沉积于早二叠世阿丁斯克期的冷水型海洋环境。岩层地质构造特征,与同层位产出的冷水型生物群为冰海杂砾岩的成因提供了证据,指示其形成于冰川作用下,由冰筏搬运的海相沉积。通过收集资料对比,确定其在近似冰期南半球15°~35°的古纬度范围内,环境平均水温0~10℃。在陆内裂谷或被动陆缘裂谷形成的广阔岛块、谷槽相间的构造古地理格局下,冰筏携带基底砾石,在赤道洋流作用等因素影响下,在消融以后,下落至色日绒地区浅海环境中,与砂泥质、砂质基质一同沉积形成冰海杂砾岩层。     

西藏羌塘南部地区的冰海杂砾岩及其成因

青藏高原及邻区广泛分布的漂砾层、杂砾岩、含砾板岩是一种特殊的冰海相沉积岩，称为冰海杂砾岩（Ｉｃｅ－ｓｅａＭｉｘ－ｃｏｎｇｌｏｍｅｒａｔｅｓ）。它们和一起产出的冷水型动物群、耐冷植物群视为这一地区冈瓦纳相最典型的标志，代表着冈瓦纳大陆上塔尔切尔（Ｔａｌｃｈｉｒ）冰期所影响的时间和空间。除“标准型”冰海杂砾岩外，羌塘腹地发现了蛇绿质和钙质冰海杂砾岩。这两种冰海杂砾岩的发现，不但丰富了冰海杂砾岩的家族成员，同时也为冰海沉积、物质来源问题、冈瓦纳大陆北界及特提斯演化研究提供了新的信息。经研究，冰海杂砾岩中的砾石来自印度半岛──冈瓦纳大陆本体，以冰筏为载体融冰落石成因。     

中条山地区地质特征及铜矿床类型

中条山地区出露的地层主要有新太古界涑水麻粒岩-角闪岩相杂岩、绛县群角闪-绿片岩岩相变质岩、古元古界中条群绿片岩相变质岩、担山石群变质砾岩-石英岩、西阳河群安山岩、沉积岩和中新元古界沉积岩。区内岩浆作用强烈，以绛县期、西阳河期火山喷发、涑水期岩浆侵入为主，火山作用为铜矿床的形成提供了大量的成矿物质。深断裂构造和褶皱构造，特别是其交汇处为成矿物质的运移和沉淀提供了空间。按成因该区铜矿床可分为次火山-火山气液再造型、远火山-沉积变质型、沉积变质型、层控热液型和热液脉型铜矿床，代表性矿床有铜矿峪、筐子沟、胡家峪、横岭关、落家河等矿庆。     

大别山北麓石炭纪盆地沉积和构造研究

大别山加里东构造带北麓的石炭系为残留海盆地沉积 ,分布限制在潢川—固始—肥中断裂以南和信阳—商城—金寨—舒城断裂以北 ,保存在南翼向南倒转并有逆冲推覆构造的复式向斜中 ,中部被燕山期花岗岩侵入体破坏。排除构造重复 ,石炭系总厚 >2 0 0 9m (掩盖部分未计 ) ,按岩石地层单元分 5个组 ,各组之间均为断层接触。自下而上花园墙组为以复理石为代表的深水浊积扇和具有向上变细序列的陡坡扇沉积 ;杨山组为辫状河和滨岸辫状三角洲含煤沉积 ;道人冲组为辫状河、辫状三角洲、扇三角洲及滨浅海沉积 ;胡油坊组分布最广 ,为微咸水盆地陡坡扇、浊积扇沉积 ,有特征的复理石和滑塌沉积 ;杨小庄组为碎屑海岸含煤沉积。下统和上统的界限位于道人冲组中下部厚层砾岩的底部。古水流方向以自南指向北占优势 ,物源主要来自南侧的大别山区。石炭系下统砾岩为远源硅质正砾岩 ,含大量脉石英砾石 ,母岩为岩浆热液成因 ,现已无保存 ;上统砾岩为近源陡坡环境形成的复成分、多杂基的副砾岩 ,为浊积砾岩 ,其中脉石英砾石明显减少 ,含千枚岩和沉积岩砾石 ,母岩主要来自南侧的信阳群 /佛子岭群等。复理石、滑塌、浊积砾岩的存在表明石炭系具陡坡陆缘海活动大陆边缘的沉积特征 ,并发现有少量火山岩碎屑 ,可能形成于弧后盆地。稀?     

藏东吉塘地区冈瓦纳相冰海杂砾岩的特征及其意义

察雅县吉塘镇澜沧江以西的酉西和泄巴发现冰海杂砾岩,是藏东地区班公湖－怒江缝合带以东首次发现的冈瓦纳相沉积岩,基本特征与青藏高原南部的冈瓦纳相冰海杂砾岩相同,而吉塘镇澜沧江以东的石炭纪—二叠纪地层与古生物则是典型扬子型的。冰海杂砾岩的分布范围大致代表冈瓦纳大陆塔尔切尔冰期影响的空间,并具有时代对比价值。这些资料可能说明一个事实,藏东地区石炭纪—二叠纪冈瓦纳大陆的东部边界为北澜沧江断裂带。     

豫西鲁山地区新元古界罗圈组沉积环境分析

华北板块南缘新元古界罗圈组为一套特殊的杂砾岩层,其是否为冰川成因对于新元古代冰期的研究具有重要意义。在野外实测剖面的基础上,本研究对鲁山地区罗圈组岩性、岩相特征及冰蚀遗迹进行探索,恢复其沉积环境,结果显示:罗圈组底部存在冰溜面,主体为块状杂砾岩,砾石砾径差异较大,呈棱角及次棱角状,地层中含有砂岩透镜体及出现坠石构造;镜下观察砂岩分选磨圆差、颗粒支撑。上述特征说明豫西鲁山地区罗圈组为冰川成因,推断其为陆相冰碛岩及冰水环境形成的产物。本文建立了罗圈组冰川相、冰水相的沉积模式,对于确定该地区古环境、古地理及新元古代冰川发育范围具有一定的参考价值。     

Glacially-influenced deep-marine sedimentation of the Late Precambrian Gaskiers Formation, Newfoundland, Canada

The Late Proterozoic Conception Group, exposed on the Avalon Peninsula in Newfoundland, Canada, is a 4 km thick turbidite succession containing a conformable 300 m thick sequence of diamictites (the Gaskiers Formation) near the base. Massive and crudely-stratified diamictites form beds up to 25 m thick which have a tabular geometry with slightly erosive basal contacts and are interbedded with mudstones and fine-grained, thin-bedded turbidites. These diamictites are interpreted as submarine debris flow deposits. Disrupted diamictites form strongly deformed units that contain large, complexly folded rafts of mudstone and turbidite facies. These diamictite units are interpreted as submarine slumps. Diamictites contain glacially-striated and faceted clasts; clasts and matrix are predominantly of volcanic provenance. One outcrop shows interbedded volcanic agglomerate and diamictite, and volcanic bombs can also be identified. The interbedding of diamictites with turbidites and the stratigraphic context provided by the thick sequences of turbidites below (Mall Bay Formation) and above (Drook Formation) indicate a deep marine slope setting of diamictite deposition. Diamictite facies record remobilization and downslope transfer of large volumes of unstable volcanic and glacial debris initially deposited in a shallower water marginal marine zone. The regional tectonic framework suggests the Conception Group accumulated in a deep, southward-opening ensialic rift basin with active but waning volcanic centres to the north. The Gaskiers Formation may be representative of other Late Precambrian glacially-influenced diamictite sequences that were deposited around the North Atlantic region and in Europe. These deep marine diamictite sequences characterized by debris flows, turbidites, and slump deposits, can be contrasted with more extensive shallow marine shelf diamictite sequences found in association with dolomites and tidally influenced shallow water facies in other basinal settings.     

Submarine fan facies of the Upper Cretaceous Great Valley sequence,northern and central California

The Upper Cretaceous part of the Great Valley Sequence provides a unique opportunity to study deep-marine sedimentation within an arc-trench gap. Facies analysis delineates submarine fan facies similar to those described from other ancient basins. Fan models and facies of Mutti and Ricci-Lucchi allow reconstruction of the following depositional environments: basin plain, outer fan, midfan, inner fan, and slope. Basin plain deposits are characterized by hemipelagic mudstone with randomly interbedded thin sandstone beds exhibiting distal turbidite characteristics. Outer fan deposits are characterized by regularly interbedded sandstone and mudstone, and commonly exhibit thickening-upward (negative) cycles that constitute depositional lobes. The sandstone occurs as proximal to distal turbidites without channeling. Midfan deposits are characterized by the predominance of coarse-grained, thick, channelized sandstone beds that commonly are amalgamated. Thinning-upward (positive) cycles and braided channelization also are common. Inner fan deposits are characterized by major channel-fill complexes (conglomerate, pebbly sandstone, and pebbly mudstone) enclosed in mudstone and siltstone. Positive cycles occur within these channel-fill complexes. Much of the fine-grained material consists of levee (overbank) deposits that are characterized by rhythmically interbedded thin mudstone and irregular sandstone beds with climbing and starved ripples. Slope deposits are characterized by mudstone with little interbedded sandstone; slumping and contortion of bedding is common. Progressions of fan facies associations can be described as retrogradational and progradational suites that correspond, respectively, to onlapping and offlapping relations in the basin. The paleoenvironments, fan facies associations, and tectonic setting of the Late Cretaceous fore-arc basin are similar to those of modern arc—trench systems.     

Glacial advance and retreat sequences in a Permo-Carboniferous section, central Transantarctic Mountains

Episodes of glacial advance and retreat can be recognized through analysis of vertical facies sequences in the Permo-Carboniferous Pagoda Formation of the Beardmore Glacier area, Antarctica. The formation includes a remarkably complete record of continental sedimentation near the terminus of a temperate glacier. Facies sequence is pre-eminent for inferring glacial advance and retreat. Other important criteria are abundance and geometry of sandstone interbedded with diamictite, diamictite character and nature of bed contacts. Using these characteristics advance and retreat sequences 5–60 m thick are recognized. A sharp contact, with a striated surface and erosional relief, overlain by structureless diamictite (lodgement till) is typical of grounded ice advance. Grounded ice retreat is characterized by structureless diamictite (lodgement till), overlain by crudely stratified diamictite (melt-out till) and then by diamictite interbedded with sandstone and conglomerate (flow till and glacio-fluvial or glacio-lacustrine deposits). Gradational contacts between shale overlain by diamictite and diamictite overlain by shale characterize advance and retreat, respectively, in subaqueous settings. Pauses in sediment accumulation, minor(?) fluctuations of the ice margin, and/or changes in subglacial dynamics are indicated by specific features within diamictite units such as probable frost-wedge casts, single layer boulder beds, sharp sedimentary contacts and changes in diamictite character. These minor(?) events are superimposed upon the main advance-retreat cycles. Study of both the overall facies sequence and of individual diagnostic structures, albeit in an incomplete stratigraphic record, permits a distinction between major and minor advance-retreat events. As many as six major advance-retreat cycles exist in some Pagoda sections, but the number of cycles present varies in different sections.     

Neoproterozoic environmental change recorded in the Port Askaig Formation,Scotland: Climatic vs tectonic controls

The snowball Earth hypothesis suggests that the Neoproterozoic was characterized by several prolonged and severe global glaciations followed by very rapid climate change to ‘hot house’ conditions. The Neoproterozoic Port Askaig Formation of Scotland consists of a thick succession of diamictite, sandstone, conglomerate and mudstone. Sedimentological and stratigraphic analysis of Port Askaig deposits exposed on the Garvellach Islands was carried out to establish the nature of Neoproterozoic palaeoenvironmental change preserved in this thick succession. Particular emphasis was placed on identifying and distinguishing between climatic and tectonic controls on sedimentation.Port Askaig Formation diamictite units are attributed to deposition by sediment gravity flow processes or ‘rainout’ of fine-grained sediment and ice-rafted debris in a glacially influenced marine setting. Associated facies record various depositional processes ranging from sediment gravity flows (conglomerate, massive sandstone and laminated mudstone) to deposition under other unidirectional currents (cross-bedded and horizontally laminated sandstone). The Port Askaig Formation is also characterized by abundant soft sediment deformation features that occur at discrete intervals and are interpreted to record episodic seismic activity.Stratigraphic analysis of the Port Askaig Formation on the Garvellach Islands reveals three phases of deposition. Phase I was dominated by sediment gravity flow processes and sedimentation was primarily tectonically controlled. Phase II was a transitional phase characterized by continued tectonic-instability, an increased supply of sand to the basin and the preservation of current-generated facies. In the third and final phase of deposition, the interbedded units of sandstone and diamictite are interpreted to reflect development of large sandy bedforms and ice margin fluctuations in a tectonically stable marine setting.Sedimentological and stratigraphic analysis of the Port Askaig Formation demonstrates that tectonic activity had a significant influence on development of the lowermost parts of the succession. Climatic influences on sedimentation are difficult to identify during such phases of tectonic activity but are more easily discerned during episodes of tectonic quiescence (e.g.,, Phase III of the Port Askaig Formation). The thick succession of diamictite interbedded with current-deposited sandstone preserved within the Port Askaig Formation is not consistent with deep freeze conditions proposed by the snowball Earth hypothesis.     

Fluvial, tidal and storm sedimentation in the Chilhowee Group (Lower Cambrian), northeastern Tennessee, U.S.A.

The Lower Cambrian Chilhowee Group of northeastern Tennessee consists of the Unicoi, Hampton and Erwin Formations, and is divided into four facies. The conglomerate facies occurs only within the lower 200 m of measured section (the Unicoi Formation) and consists of fine-grained to pebbly quartz wacke with rare thin beds of laminated siltstone. Low-angle to horizontally laminated, fine-grained sandstone with laminae and lenses of granules and pebbles represents upper flow-regime, overbank deposition within a braided stream system that was close to a coastline. Medium-scale, planar-tabular cross-stratified conglomerate in which megaripple bedforms are preserved is interpreted as representing deposition in interbar pools of braided channels, as flood stage waned and larger bedforms ceased to migrate. Large-scale, planar-tabular cross-stratified conglomerate beds represent migration of large transverse bars within a broad braided stream channel during high flood stage. The sandstone facies occurs throughout the Chilhowee Group, and is therefore interbedded with all other facies. It consists of mainly medium- to very coarse-grained, subarkosic to arkosic arenite. Thinly interbedded, laminated siltstone and sandstone, which may exhibit wavy or lenticular bedding, represents deposition during slack water periods between ebb and flood tides. Large-scale planar-tabular and trough cross-stratification reflects deposition within the deepest areas of subtidal channels, whereas medium-scale cross-stratification represents deposition in shallower water on shoals separating channels. Fining- and thinning-upward sequences most likely resulted from the longshore migration of channels and shoals. The hummocky facies occurs only in the Erwin Formation and consists of horizontally laminated to hummocky stratified, fine-grained arkosic to subarkosic arenite interbedded with equal amounts of bioturbated mudstone. It represents deposition between storm and fairweather wave-base by combined-flow storm currents. The quartz arenite facies is characterized by an absence of fine-grained units and lithologically consists of a super-mature, medium- to coarse-grained quartz arenite. Large-scale planar-tabular cross-stratification and abundant low-angle cross-stratification with rare symmetrical ripples (lower quartz arenite facies) occurs interbedded with the braided fluvial conglomerate facies, and was deposited within either a ridge-and-runnel system or a system of nearshore bars. Large-scale, planar-tabular cross-stratification (upper quartz arenite facies), which forms the top of two 40 m-thick coarsening-upward sequences of the type: hummocky faciessandstone faciesquartz arenite facies, probably represents deposition on sand ridges that formed on a sand-starved shelf as transgression caused the detachment and reworking of shoreface channel-shoal couplets. Palaeocurrent data for the Chilhowee Group are unimodal but widely dispersed from 0° to 180°, and exhibit a minor mode to the west. The data are interpreted to reflect the influence of longshore, tidal and storm currents. The ichnofossil assemblage changes upsection from one characterized only by Paleophycus to a Skolithos ichnofacies and finally to a Cruziana ichnofacies. The facies sequence, biogenic and palaeocurrent data reflect the interaction through time of (I) non-marine and marine processes; and (2) transgression coupled with shoreline progradation. The Chilhowee Group represents an overall deepening from terrestrial deposition to a marine shoreface that experienced both longshore and tidal currents, and finally to a storm shelf environment that periodically shoaled upward.     

Anatomy and evolution of a Lower Cretaceous alluvial plain: sedimentology and palaeosols in the upper Blairmore Group, south-western Alberta, Canada

The Lower Cretaceous (Albian) upper Blairmore Group is part of a thick clastic wedge that formed adjacent to the rising Cordillera in south-western Alberta. Regional transgressive intervals are superimposed on the overall regressive succession. Alluvial conglomerates, sandstones and mudstones were deposited in east-north-eastward draining fluvial systems, orientated transverse to the basin axis. Five facies associations have been identified: igneous pebble conglomerate, thick sandstone, interbedded lenticular sandstone and mudstone, thick mudstone with thin sandstone interlayers, and fossiliferous sandstone and mudstone. The facies associations are interpreted as gravelly fluvial channels, sandy fluvial channels, sand-dominated floodplains, mud-dominated floodplains, and marine shoreline deposits, respectively. Five types of palaeosols are recognized in the upper Blairmore Group based on lithology, the presence of pedogenic features (clay coatings, root traces, ferruginous nodules, slickensides, carbonate nodules) and degree of horizonization. The regional distribution of the various types of palaeosols enables a refinement of the palaeoenvironmental reconstruction permitting an assessment of the controls on floodplain evolution. In source-proximal areas, palaeosol development was inhibited by high rates of sedimentation. In source-distal locations, poor drainage resulting from high watertables, low topography and lower rates of sedimentation also inhibited palaeosol development. The best-developed palaeosols (containing Bt horizons) occur in intermediate alluvial plain positions (tectonic hinge zone) where the floodplains were most stable due to a balance between sedimentation, erosion and subsidence rates. Extrapolating from the upper Blairmore Group suggests that the tectonic hinge zone of continental foreland basins can be established by palaeosol analysis. At the hinge zone, soil development is controlled primarily by climate and tectonics and their effect on sediment supply, whereas closer to the palaeoshoreline, relative sea level fluctuations, resulting in poor drainage, may have a more significant influence.     

Terrestrial-marine transition in the Cambrian rocks of Kangaroo Island, South Australia

The upper part of the Lower Cambrian succession in northeast Kangaroo Island comprises three interbedded facies associations. The fine-grained association is composed of siltstone, mudstone and minor sandstone. It contains flat lamination and abundant ripple cross-lamination which shows bipolar palaeocurrents, and occurs in combinations of flaser bedding, lenticular bedding and wavy lamination. Although body fossils are relatively rare, trilobite traces and desiccation cracks are common, and the association is interpreted as a predominantly subtidal to intertidal deposit. The conglomerate facies association contains horizontally bedded cobble to boulder conglomerate, with subordinate trough cross-stratified coarse sandstone to granule/pebble conglomerate. Fabrics and structures in the coarse conglomerates are consistent with alluvial transport (stream and debris flow), but not beach deposition. The conglomerate association is attributed to tectonic uplift and erosion of a Precambrian-Lower Cambrian succession developed adjacent to the present north coast of Kangaroo Island. Southward progradation of an alluvial fan complex occurred across east-west oriented tidal flats on which limited wave activity reworked sand and fine gravel, but not coarser material. The sandstone facies association mainly comprises trough cross-stratified and plane-laminated sandstone, the latter with current lineation predominantly sub-parallel to the east-west shoreline. Trough cross-stratification is ascribed to onshore waves and longshore currents, and current lineation to predominantly shore-parallel tidal currents, augmented by longshore drift and storm surge. Tectonic movements gave rise to cycles of transgression and regression as tidal and alluvial processes dominated alternately.     

贺兰山中南段米钵山组沉积特征及其物源分析

贺兰山中南段米钵山组地层岩性主要为钙质角砾岩、砾岩、互层状的砂岩或含砾砂岩以及页岩、含砾页岩、颗粒灰岩等,是一套区域浅变质、厚度巨大、具不同程度变形和深水陆源浊积岩组合的斜坡沉积,发育有复理石韵律层理及典型的浊积岩鲍马序列。研究表明中奥陶统米钵山组沉积期是贺兰“冷”裂谷活跃的时期,该时期的沉积特征对探讨贺兰山早古生代的构造格局及岩相古地理方面尤为重要。对米钵山组的地球化学分析结果表明,稀土元素La、Ce、∑REE、δEu等特征值与大陆岛孤和活动大陆边缘构造环境相似。综合该组沉积的矿物特征、构造环境及区域背景,其物源应来源于其南部的祁连造山带及邻区阿拉善地块,具有二元物源供给的近源沉积特征。     

塔里木盆地西南部下白垩统克孜勒苏群沉积特征与成矿成藏作用*

通过对塔里木盆地西南部(塔西南)江格结尔地区下白垩统克孜勒苏群地层剖面测量,该地区的克孜勒苏群分为5个岩性段,岩性主要为泥质粉砂岩、岩屑砂岩、含砾砂岩、砾岩等,沉积相主要为辫状河三角洲相;其上覆的上白垩统库克拜组为介壳灰岩、膏质泥岩,沉积相为浅海相、滨海潟湖相; 下伏的上侏罗统库孜贡苏组岩性主要为杂砾岩、含砂杂砾岩和石英砂岩等,沉积相为冲积扇相;三者呈整合接触。从该区下白垩统克孜勒苏群的沉积特征来看,早白垩世为陆源碎屑沉积环境,在晚白垩世转入海相沉积环境。对比该区北侧陆内造山带中的拉分断陷盆地(萨热克巴依盆地)中下白垩统克孜勒苏群的地层层序,该区仅沉积了下白垩统克孜勒苏群下部3个岩性段而缺失上部岩性段,表明在早白垩世后期塔里木盆地北侧西南天山发生过一次抬升作用。下白垩统克孜勒苏群是铜铅锌铀矿等金属矿产的赋矿层位,同时也是塔里木盆地石油和天然气的重要储集层位,在铜铅锌等矿石中常可见大量的沥青等有机质,这些有机质主要源于下伏侏罗系的煤系烃源岩,并通过成矿流体参与了金属矿产的成矿作用,因而这种多矿种“同盆共存”的现象,在沉积盆地的研究中作为整体的成矿系统来研究将更有意义。     

东营凹陷永55区块沙四上亚段深水浊积扇沉积与油气

深水浊积扇是东营凹陷北部陡坡带永55区块沙四上亚段最发育的沉积相,也是最有利的砂砾岩储层。在岩心观察基础上,通过薄片鉴定、粒度分析等测试手段,综合地质、物探和测井资料,对永55区块砂砾岩体储层的沉积特征进行了研究。结果表明,本区深水浊积扇沉积具有如下特征：(1)岩石成分成熟度和结构成熟度均较低;(2)碎屑物质以递变悬浮搬运为主;(3)沉积构造具有典型的重力流成因特征;(4)岩心中见典型鲍马沉积序列。建立了深水浊积扇退积型沉积模式,并进一步细分为内扇、中扇和外扇3个亚相及4个微相。位于中扇的辫状沟道砂体物性好,可以构成优质储层,较深湖暗色泥岩为主要的烃源岩和盖层,本区生、储、盖发育齐全,有着良好的勘探开发前景。