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1.
湖南石门杨家坪下寒武统杷榔组第三段主要为一套深灰色、灰绿色页状至薄层含粉砂水云母泥(页)岩与泥质粉砂岩夹透镜状、条带状粉砂岩，其沉积环境为斜坡环境。中上部透镜状、条带状粉砂岩中交错层理极为发育，纹层倾向既有沿斜坡向上和向下双向倾斜的，也有沿斜坡向下或沿斜坡向上单向倾斜的，它们不应是等深流沉积或浊流沉积，而应为内波、内潮汐产生的沿斜坡上下交替流动所形成的。笔者对寒武系内波、内潮汐沉积做了首次研究。 相似文献
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贺兰奥拉槽早古生代深水重力流体系的沉积特征和充填样式 总被引：6，自引：1，他引：6
位于鄂尔多斯西缘的贺兰构造带为一中元古代一古生代的奥拉槽。在区内的中寒武和中奥陶统中识别了一套巨厚的深水重力流沉积,其中包括下斜坡滑塌泥石流复合体、浊积扇以及碳酸盐岩斜坡扇裙等沉积类型。主要的相单元包括充填沟道或进入扇面形成的泥石流钙质角砾岩和砾岩、充填辫状水道的多层叠置的砂岩和砂砾岩、上叠扇的砂、泥岩互层以及浊积砂屑或含砾砂屑灰岩等。在中奥陶世该奥拉槽发展成一深水一半深水海槽,沿盆地西侧发育有浊积扇,而东侧仅有碳酸盐岩滑塌扇裙。它们可能是沿深水盆地两侧深大断裂产生的陡坡或水下断崖分布的,代表了早古生代贺兰奥拉槽在强烈沉陷期特定的深水盆地充填。 相似文献
3.
T. P. Young 《Geological Journal》1991,26(4):317-327
Pendent didymograptid graptolites are described from mudstones immediately overlying the Hen-dy-capel ironstone (St. Tudwal's Peninsula, Lly̌n, North Wales). The graptolites indicate a Llanvirn age for these beds, implying a Llanvirn or Arenig age for the ironstone, in contrast with the previous interpretation of a gracilis Biozone age. The redating of the ironstone horizon suggests that the Pen-y-gaer mudstones may be at the base of the local Nant Ffrancon Formation, rather than being equivalent to the lower Caradoc Tyddyn Dicwm beds above the Tremadog ironstone as widely supposed. The ironstones at Trefor, Betws Garmon, and Llandegai, which have been correlated with the Hen-dy-capel ironstone on the basis of acritarch assemblages, may also have a similar age. A reinterpretation of the age of these localities as Llanvirn would remove the stratigraphic problems introduced by their previously suggested early gracilis Biozone age. The Hen-dy-capel ironstone forms one of a large number of ironstones recorded from close to the Arenig-Llanvirn boundary in N. Wales, and elsewhere at high southern palaeolatitudes. 相似文献
4.
The possible role of benthic microbial mats during the formation of carbonaceous shales in shallow Mid-Proterozoic basins 总被引：2，自引：0，他引：2
JÜRGEN SCHIEBER 《Sedimentology》1986,33(4):521-536
A considerable portion of the upper member of the Mid-Proterozoic Newland Formation, Meagher County, Montana, consists of carbonaceous silty shales (striped shale facies). This type of shale facies is common in Proterozoic basins and is host to several major base metal deposits. The striped shales were deposited in a subtidal setting, basinward of carbonates characterized by cryptalgal laminites, mudcracks and flat pebble conglomerates. The carbonaceous silty shales are considered remnants of benthic microbial mats. Irregular internal laminae, patterns of particle trapping, mechanical deformation during penecontemporaneous soft-sediment deformation and filamentous microbiota provide evidence for this interpretation. The dolomitic clayey shale contains graded silt-clay couplets, and these are interpreted as storm layers. Modern subtidal microbial mats can only survive under special conditions, but in the Proterozoic, it is suggested that benthic microbial mats colonized the shallow seafloor during periods of low sediment input, leading to the formation of carbonaceous shales. 相似文献
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传统的沉积模式认为大部分细粒沉积岩（泥岩或页岩）的沉积发生在相对深水、低能的环境中。作为地表上分布最为广泛的沉积岩类型,泥页岩包含了对重构地质历史时期古地理、古气候的重要信息。泥页岩除了可以作为有效的烃源岩,勘探开发技术的进展更发掘出泥岩作为非常规油气储层的巨大潜力。近十年来,国内外对细粒沉积物的水槽实验、泥岩沉积微相的精细分析、以及泥岩岩相组成特征的研究取得了长足的进展。这些研究对泥岩的沉积过程和沉积模式在不同角度上提供了新的认知。大部分泥岩（甚至包括众多有机质含量高的泥岩）都可能沉积在相对浅水以及水动力条件相对较高的环境中。不同的沉积过程（底部水流）形成不同的泥岩沉积微相,并对有机质在泥岩中的埋藏富集具有重要的控制作用。以晚白垩纪北美西部内陆海道为例,总结在陆棚浅海环境中（最大水深< 200 m）,位于从近岸到远岸（> 500 km）不同沉积环境（包括前三角洲/下邻滨、内陆棚、中陆棚、和外陆棚环境）中的泥岩的主要沉积过程、沉积微相特征、以及富集有机质的潜力。由于沉积过程和沉积环境是决定泥岩成分、沉积相、和岩石物理特征非均质性的首要因素,不同浅海环境中的泥岩相特征和沉积模式可有助于利用泥岩地层进行古地理、古气候的重构,并能够对预测不同陆棚浅海环境中沉积的泥岩作为有效烃源岩或有效储层的潜力提供指导。 相似文献
7.
Varve-like parallel laminated and homogeneous muds on natural levees of submarine channels result from the spill-over of the dilute upper parts of channelized turbidity currents. On the levees of the Northwest Atlantic Mid-Ocean Channel, Labrador Sea, laminated turbidite muds show a systematic upward thickness variation of the granular silt laminae and the clay laminae. In many depositional units the former decrease logarithmically upwards in thickness while the latter increase logarithmically. The origin of parallel lamination in current-deposited, fine-grained sediments is interpreted in terms of the ‘burst-and-sweep model’ for the viscous sublayer of turbulent flows. Individual silt laminae of laminated turbidite muds form due to shear sorting during burst-and-sweep events which have a winnowing effect on the clay fraction. In contrast to sand-transporting flows the viscous sublayer of silt- and clay-carrying dilute turbidity currents cannot be permanently in a turbulent state. The presence of clay laminae suggests that the boundary layer relaminarizes periodically. It is speculated that this is caused by pressure waves with negative pressure gradients favouring the suppression of bursts and sweeps. The observed vertical thickness variations suggest that the periods of laminar boundary-layer flow increase in duration as turbulence of the main current decays. The upward thickness decrease of the silt laminae is explained in terms of decreasing supply rates to the boundary layer from the main flow. A multiple bursting-cycle mechanism is favored over a single bursting cycle mechanism for the formation of individual silt laminae by shear sorting. 相似文献
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The Lower Jurassic East Berlin Formation exposed in the centre of the Hartford Basin can be divided into six facies: (1) laminated black mudstone is composed of very finely-laminated, organic-bearing clay-stone with common millimetre-scale lenses of dolomitic siltstone; (2) planar laminated mudstone is commonly mudcracked and composed of thickly-laminated, red, green or grey mudstone with common centimetre-scale lenses of sandstones; (3) disrupted mudstone has a complex, desiccation-cracked fabric; (4) planar- and large-scale trough cross-stratified sandstones are composed of moderately well-sorted medium- to coarse-grained arkoses; (5) small-scale, cross-stratified silty sandstones with common climbing-ripple structure; and (6) interbedded sandstones and mudstones which commonly carry desiccation cracks. Mudstone facies are organized into repetitive, metre-scale facies sequences which change gradationally upwards from laminated black mudstones to planar-laminated mudstones to disrupted mudstones. Facies sequences have sharp tops and bottoms and record increasing desiccation upwards. There are 15 such cycles in the upper 100 m of the formation in central Connecticut. They record long periods of dry playa mudflat aggradation punctuated by the rapid expansion and contraction of perennial lakes. The sandy facies occur as single, decimetre-scale sedimentation units or as two or more stacked sedimentation units up to 1 m thick. These record sheet floods across ephemeral floodplains. 相似文献
11.
四川会理 会东及邻区中元古界昆阳群 ,由下而上可分为力马河组、凤山营组和天宝山组 ,与古元古界河口群为不整合接触 ,其代表年龄值为 1 70 0± 1 0 0Ma～ 1 2 0 0± 1 0 0Ma。对这套地层的沉积学研究 ,前人涉及甚少。笔者在野外考察和室内分析的基础上 ,对其沉积相和沉积环境进行了详细的研究。初步认为研究区的中元古界昆阳群可分为 7种沉积相 ,进而探讨了该区的沉积演化历史。 相似文献
12.
D.M.D. James 《Sedimentary Geology》1983,34(1):21-40
The sedimentology of the Drosgol Formation is summarised in terms of nine sedimentary facies with particular attention given to the pebbly mudstones and major arenites. Sedimentary facies, geometry and palaeocurrents suggest the interpretation of the major arenites as inner-fan channel deposits locally preserving their levees. The lower less-organised part of the formation suggests a slope-base environment with small-scale channelling, slumping and development of mass-flow deposits. A new definition of the upper boundary of the formation is proposed and map references are given to key localities. 相似文献
13.
Facies and Architecture of a Carboniferous Grounding-line System From the Guandacol Formation, Paganzo Basin, Northwestern Argentina 总被引：1，自引：0，他引：1
New outcrops of Middle Carboniferous glacigenic deposits found in the Guandacol Formation (western Paganzo Basin) are described in this paper. The study locality of Los Pozuelos Creek (northwestern Argentina) includes coarse-grained diamictites, rhythmites, laminated pebbly mudstones and shales that represent an expanded column of the Gondwanic glaciation in this region. Thirteen lithofacies recorded at the measured section have been grouped into three facies associations. Facies Association I is composed of coarse-grained massive and stratified diamictites (lithofacies Dmm, Dms, Dmg, Dcs), laminated siltstones with dropstones (Fld) and interstratified sandstones and mudstones (Fl, Sr). These rocks represent both tillites and resedimented diamictites closely associated to small water bodies where laminated siltstones with dropstones and stratified sandstones and mudstones were deposited. Facies Association II comprises couplets of matrix-supported thinly bedded diamictites (Dmld) and laminated mudstones with dropstones (Fld). This facies association results from the combination of three different processes, subaqueous cohesionless debris flows, coeval rainout of ice-rafted debris and settling of fine-grained particles from supension. Finally, Facies Association III is made up of laminated mudstones without dropstones, thin marl levels and scarce fine- to very fine-grained sandstones. This assemblage clearly suggests sedimentation in a deep marine environment below the wave base.The architecture of the glacigenic deposits has been investigated using photomosaic panels. The geometry of the depositional bodies and facies suggest that Los Pozuelos Creek outcrops exhibit a well preserved three-dimensional example of a grounding-line system. In particular, three different subenvironments of a morainal bank were interpreted: a bank-front, a bank-core and a bank-back. The bank-front assemblage is characterized by coarse-grained, mainly resedimented, diamictites grading laterally to prograding clinoforms composed of interbedded matrix-supported thinly bedded diamictite and mudstones. The bank-core assemblage is formed by a stacking of coarse-grained diamictites where at least five major erosional surfaces, bounding four multistory diamictite bodies, can be recognized. Finally, the bank-back assemblage corresponds to discontinuous intervals of striated lodgement till, and coarse-grained resedimented diamictites showing important post-depositional deformation. The retrogradational stacking of the morainal banks indicate an overall glacial retreat and a glacioeustatic sea-level rise. Erosional surfaces at the base of each morainal bank suggest intervening short term episodes of ice advance.The new data presented here confirm the existence of "true" tillites in western Paganzo Basin and suggest several (at least four) pulses of glacial advance and retreat during the Namurian glaciation in the region and permit a more refined interpretation of the glacial deposits in the Huaco area. 相似文献
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The role of wave reworking on the architecture of storm sandstone facies, Bell Island Group (Lower Ordovician), eastern Newfoundland 总被引：2，自引：0，他引：2
Stacked shallow marine cycles in the Lower Ordovician, Bell Island Group, of Bell Island, Newfoundland, show upward thickening and upward coarsening sequences which were deposited on a storm-affected shelf. In the Beach Formation each cycle has a facies sequence comprised, from base to top, of dark grey mudstones, light grey mudstones, tabular sandstones and mudstones, lenticular sandstones and mudstones, and thick bedded lenticular sandstones, reflecting a progressive increase of wave orbital velocities at the sediment surface. The mudstones and tabular sandstones reflect an environment in which the sea floor lay in the lower part of the wave orbital velocity field and in which tempestites were deposited as widespread sheets from weak combined flow currents. The lenticular sandstones in the succeeding facies are wave reworked sands, commonly lying in erosional hollows and having erosional tops and internal hummocky cross-stratification. Planar lamination is relatively uncommon and sole marks are mainly absent. In this facies oscillatory currents were dominant and accumulated sand in patches generally 10–30 m in diameter. The facies formed on the inner shelf where the oscillatory currents generated by storm waves had powerful erosional effects and also determined the depositional bedforms. Mud partings and second-order set boundaries within sandstone beds are believed to separate the products of individual storms so that many lenticular sandstone beds represent the amalgamation of several event beds. This interpretation has important implications for attempts to estimate event frequency by counting sandstone beds within a sequence and for estimates of sand budgets during storm events. The thick bedded lenticular facies appears to have been formed by erosion of the mud beds between the lenticular sands, leading to nearly complete amalgamation of several lenticular sand bodies except for residual mud partings. In the overlying Redmans Formation the process of amalgamation progressed even further so that nearly all the mud partings were removed, resulting in the formation of thick bedded tabular sandstones. Sequence stratigraphic analysis of the cyclical sequence suggests that the cycles were eustatically controlled. The rising limb of the sea level curve produced only the dark grey mudstone part of the cycle while the remainder of the cycle was deposited on the falling limb. There is a gradational but rapid facies transition from the tabular to the lenticular sandstone facies which is interpreted as occurring at the inflexion point on the falling limb. The thick bedded facies of the Beach Formation and the thick bedded tabular facies of the Redmans Formation represent periods of maximum sea level fall. The stacked cycles in the Beach Formation are interpreted as an aggradational, high frequency sequence or parasequence set bounded at the top by a sequence boundary and succeeded by the three aggradational parasequences of the Redmans Formation. The recognition of storm facies with sandstone beds of very different bed length has important implications for the reservoir modelling of such facies. 相似文献
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The Karoo Supergroup in Madagascar is subdivided into three lithostratigraphical units: the Late Carboniferous-Early Permian Sakoa Group; the Late Permian-Middle Triassic Sakamena Group; and the Triassic-Early Jurassic Isalo Group. The Sakamena Group is fairly well exposed in the southern Morondava Basin, where it is approximately 4000 m thick. The Sakamena Group is separated from the Sakoa Group by an angular unconformity. The Lower Sakamena Formation is characterised by two major facies associations: (1) interbedded muddy conglomerates and coarse sandstones; and (2) interbedded sandstones and mudstones, which were deposited in a rejuvenated rift setting by coarse-grained fluvial systems and debris flows on the rift margins. In the Vatambe area, facies represent fandelta deposition in a saline lake or tongue of the ocean. The Middle Sakamena Formation comprises three major facies: (1) laminated mudstones and sandstones; (2) sandstones; and (3) mudstones. The Middle Sakamena facies were deposited by low gradient meandering streams and in shallow lakes. The Upper Sakamena Formation was deposited in similar environments, except that it is comprised predominantly of red beds. The Isalo Group consists predominantly of coarse-grained sandstones (up to 6000 m thick). These sandstones were deposited by braided streams with the coarse detritus derived from a structural uplift in the east. 相似文献
17.
Peter H. Feldhausen 《Mathematical Geology》1970,2(2):113-129
Ordination is a multivariate technique developed by plant ecologists which has proven effective in the interpretation of paleoenvironments.
It allows gradational relationships among samples to be depicted in contrast to other quantitative techniques which classify
samples into discrete groups. In this study, ordination is used to interpret textural data for 62 bottom samples taken from
the Cape Hatteras, North Carolina, continental margin. The ordination suggests the existence of six sedimentary facies that
are similar to those obtained by cluster analysis using a dendrograph display. The facies represented are: littoral sands
and outer-shelf shelly sands; inner-shelf sands; outer-shelf sands and silts; outer-shelf slope silts; and two highly biogenic,
deep-water silt and clayey silt facies with similar characteristics. The facies are related in a qualitative manner to the
environmental processes operating off Cape Hatteras.
Chicago Bridge Technical Paper No. 5139. 相似文献
18.
加水热模拟中深湖与煤系泥岩地化特征比较 总被引：2，自引：0，他引：2
通过深湖泥岩和煤系泥岩的加水热模拟研究认为,在热模拟实验过程中,深湖泥岩和煤系泥岩显示不同特征,并且其演化有差别。深湖泥岩利于液态原油的生成,并且转化率高于煤系泥岩。深湖泥岩残余可溶有机质饱和烃含量高于煤系泥岩,非烃含量则低于煤系泥岩。深湖泥岩胶质 /沥青质和饱芳比均随温度升高而降低,而煤系泥岩的胶质 /沥青质随温度升高有增加趋势,其饱芳比的变化则不大或有降低趋势。深湖泥岩的Tmax难以指示演化阶段,其干酪根碳同位素值明显轻于煤系泥岩,它们的值均随温度的升高而变重。 相似文献
19.
贵州平坝白垩纪地层及沉积特征 总被引：1，自引：0，他引：1
通过对平坝一带区域地质的调查,认为这套白垩系砾岩、紫红色泥岩为山麓—河湖相沉积,是燕山期构造控制的山前盆地沉积。在紫红色泥岩中首次发现介形类Ｔａｌｉｃｙｐｒｉｄｅａｓｐ．、Ｔ．ｌａ－ｔｉｏｖａｔａ、Ｃｙｐｒｉｓｓｐ．,证明其属上白垩统扎佐组,而不是侏罗系。根据沉积学研究将其划分为４种沉积类型,并圈定了各类型空间展布。砾岩,砂岩属碎屑流沉积产物,而紫红色泥岩为湖相沉积,两者在很大程度上属同时异相沉积。 相似文献
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塔西南白垩系发育,可分为上、下两统。下白垩统克孜勒苏群可分4段,多以陆相沉积为主,富含棕红色砂砾岩夹少许砂岩、粉砂岩、泥岩和砾岩。上白垩统英吉沙群为海陆相并存,库克拜组可分2段,常见泥岩、膏岩和海相化石;乌依塔格组多为红色泥岩、泥质粉砂岩夹砂岩;依格孜牙组多见灰岩、白云质灰岩,富含海相化石;吐依洛克组为棕红色泥岩、石膏和砂、砾岩,含海相化石。通过勾勒9个岩性单元的沉积相展布,分析昆仑山前白垩纪的沉积环境演化过程。克孜勒苏群西区多为陆相快速堆积,东区远离陆源为三角洲和滨岸沉积,具有宽泛的冲积扇—辫状河三角洲相分布。库克拜组总体显示为辫状河三角洲—潮坪相变的过程;乌依塔格组以潮坪为主;依格孜牙组表现为碳酸盐岩台地—台地边缘的演化;吐依洛克组为宽广潮坪。 相似文献