Stratigraphy and structure of Devonian fluvial sediments,western Beara Peninsula,south-west Ireland     

Andrea James  John R. Graham 《Geological Journal》1995,30(2):165-182

A stratigraphic and structural summary of 5 km of Upper Devonian strata of south-west Beara, part of the Munster Basin, south-west Cork is presented. Five formations are recognized on the basis of lithofacies geometries and associations. The lowest Caherkeen Formation comprises rapidly alternating sheet-like, plane-bedded, low-angle, cross-bedded sandstones and laminated, rippled or desiccated mudrocks. The incoming of thin lenticular sandstone packages, commonly with high-angle cross-bedding, distinguishes the overlying Eagle Hill Formation. The succeeding Reen Point Formation comprises thicker bedsets of plane-bedded, low-angle and high-angle cross-bedded sandstones, separated by thick, massive mudrocks. Intraformational breccias and calcareous nodular siltrocks are distinctive features. The Tholane Formation is characterized by thick massive red-green mudrocks and a general absence of coarser grained lithologies. This sequence was deposited in a terminal fluvial fan in a basin characterized by decreasing subsidence rates and gradient with time. The overlying Toe Head Formation represents the deposits of a fluvial coastal plain. It has siltrocks that are predominantly green, often with preserved fish and plant debris. There is a relative absence of high-angled cross-bedded sandstones and an abundance of flat-laminated and inclined parallel-laminated sandstones. The structure of the Beara Peninsula comprises a WSW plunging anticlinorium with a single cleavage formed during the Variscan orogeny. Evidence from locally transecting cleavages and from mapping indicates dextral transpression. Development of the three main fault trends was contemporaneous with the folding. The well-known copper mineralization of the Allihies area is associated with east-west fault trends, a pattern observed elsewhere in the western Munster Basin. Basement involvement during both basin development and deformation is likely, but is difficult to test.  相似文献   

海相泥页岩沉积过程研究进展     

李一凡  魏小洁  樊太亮 《沉积学报》2021,39(1):73-87

随着全球页岩油气勘探开发的不断深入,海相泥页岩作为非常规油气沉积学的重要研究对象之一,其沉积特征及沉积过程日益引起学者们的关注,并在岩相分类、沉积过程解释及层序地层划分方面取得了显著进展.海相泥页岩的岩相划分已达到厘米—毫米尺度,其命名原则主要考虑结构(粒度)、层理及矿物成分等特征,结构方面着重参考砂级、粗泥级和细泥级...  相似文献   

SediNet: a configurable deep learning model for mixed qualitative and quantitative optical granulometry     

Daniel Buscombe 《地球表面变化过程与地形》2020,45(3):638-651

I describe a configurable machine-learning framework to estimate a suite of continuous and categorical sedimentological properties from photographic imagery of sediment, and to exemplify how machine learning can be a powerful and flexible tool for automated quantitative and qualitative measurements from remotely sensed imagery. The model is tested on a dataset consisting of 409 images and associated detailed label data. The data are from a much wider sedimentological spectrum than previous optical granulometry studies, consisting of both well- and poorly sorted sediment, terrigenous, carbonate, and volcaniclastic sands and gravels and their mixtures, and grain sizes spanning over two orders of magnitude. I demonstrate the model framework by configuring it in several ways, to estimate two categories (describing grain shape and population, respectively) and nine numeric grain size percentiles in pixels from a single input image. Grain size is then recovered using the physical size of a pixel. Finally, I demonstrate that the model can be configured and trained to estimate equivalent sieve diameters directly from image features, without the need for area-to-mass conversion formulas and without even knowing the scale of one pixel. Thus it is the only optical granulometry method proposed to date that does not necessarily require image scaling. The flexibility of the model framework should facilitate numerous application in the spatiotemporal monitoring of the grain size distribution, shape, mineralogy and other quantities of interest of sedimentary deposits as they evolve, as well as other texture-based proxies extracted from remotely sensed imagery. © 2019 John Wiley & Sons, Ltd.  相似文献   

Distinction between the Storegga tsunami and the holocene marine transgression in coastal basin deposits of western Norway     

Stein Bondevik  John Inge Svendsen  Jan Mangerud 《第四纪科学杂志》1998,13(6):529-537

Many coastal lakes were inundated by both the Storegga tsunami (7000 ¹⁴C yr BP) and the mid-Holocene sea-level rise (the Tapes transgression) in western Norway. The tsunami eroded lake bottoms and deposited graded and/or massive beds of sand, rip-up clasts, and coarse plant material. By contrast, when the rising sea entered the lakes, it deposited only gyttja, silt and fine sand, without causing much erosion of the underlying lake sediments. Storegga tsunami deposits in some coastal lakes were interpreted previously as ordinary marine sediments from the Tapes transgression. Our reinterpretation of these deposits shows that the transgression maximum phase was reached after 6500 yr BP, more than 1000 yr later than previously inferred for the coast of Sunnmøre. The new data cannot be combined in a shoreline diagram without showing the 6000 yr BP and 7000 yr BP shorelines as slightly warped. © 1998 John Wiley & Sons, Ltd.  相似文献   

The Late Devensian glaciation of the eastern Lleyn Peninsula,North Wales: evidence for terrestrial depositional environments     

Geoffrey S. P. Thomas  David K. Chester  Peter Crimes 《第四纪科学杂志》1998,13(3):255-270

The glacial deposits of the eastern Lleyn Peninsula record the advance, coalescence and subsequent retreat and uncoupling of Welsh and Irish Sea ice-sheets during the Late Devensian cold stage. During advance a thick sheet of basal diamict was deposited over much of the area, and during retreat and uncoupling, which occurred after 14.5 ka, the eastern part of the area was dominated by the formation of a large sandur system draining from the retreating margin of the Irish Sea ice-sheet. Subsequent stages of retreat are marked by a series of arcuate cross-valley moraines formed either by ice-contact deposition during stillstand or by structural deformation during minor snout oscillation. In the western part of the area sedimentation was controlled by a series of dead-ice ridges running parallel to the retreating ice-margin and this led to the development of a complex assemblage of localised depositional environments including ice-front alluvial fans, marginal sandur troughs and pro-glacial lake basins, all formed under supraglacial ice-marginal conditions. No evidence of glaciomarine deposition is recorded. © 1998 John Wiley & Sons, Ltd.  相似文献   

沉积学数据库建设与沉积大数据科学研究进展：以Macrostrat数据库为例     

蒋璟鑫  李超  胡修棉 《高校地质学报》2020,26(1):27-43

沉积岩(物)是构成地球表层的主要岩石类型。自地质学诞生以来,地质学家已经积累了海量的沉积学相关研究数据,国内外也相继涌现出Macrostrat等以整合沉积学、地层学相关数据为主的优秀数据库。随着沉积学、地层学、古生物学、地球化学、地质年代学、地球观测等学科数据的快速增长,数据整合分析技术的重大突破,从全球视野研究深时沉积过程变为了可能。文章介绍了国际沉积相关数据库的总体建设情况,并深度剖析美国Macrostrat数据库的结构及其创新工作模式,旨在为深时数字地球(Deep-Time Digital Earth,DDE)计划建设多学科、多尺度、多层次、共享开源的大数据库提供借鉴和参考;在此基础上,剖析了若干应用大数据思维开展的重要科研实例。  相似文献   

地震沉积学在不同沉积相和储集层研究中的应用^*     

徐兆辉  胡素云  王露  赵文智  曾洪流 《古地理学报》2020,22(4):727-743

地震沉积学包括地震地貌学和地震岩性学,应用前景广阔。针对玛湖凹陷克拉玛依组碎屑岩、川中地区龙王庙组碳酸盐岩和嘉陵江组混积岩3种不同岩性的沉积环境开展研究,探讨了地震沉积学在3种环境下沉积相与储集层研究的应用效果。研究发现,玛湖凹陷克拉玛依组发育冲积扇和河流相,点坝储集层孔渗条件好,产能优于扇缘储集层。川中龙王庙组碳酸盐岩沉积受控于同沉积走滑断裂,白云岩厚储集层分布在磨溪构造斜坡区。川中嘉二下亚段自西南向东北从陆相经海陆过渡相和局限蒸发相变为海相,有利于储集层发育的白云岩岩相位于中部的局限蒸发相附近。3个实例研究中除了使用相位旋转、地层切片和分频3种传统技术之外,还利用了主因子分析和RGB融合2项新技术。研究结果较理想,表明地震沉积学在定性重建沉积相和定量预测储集层方面应用效果显著。  相似文献   

河流相砂体精细描述在西湖凹陷某气田的应用     

张锡楠  程超  鞠颢  黄启彰 《中国地质调查》2020,7(5):25-32

西湖凹陷某气田钻井资料少,传统陆上利用多井点资料描述河流相储层展布的方法不适用该气田。前人关于该区为浅水三角洲平原分流河道沉积、储层横向上连片分布的认识过于宏观,不能指导气田的开发生产。研究从已钻井资料出发,充分利用海上高分辨率三维地震资料对河流相储层横向识别精度高、单一河道边界刻画清晰的特点,开展地震沉积学研究和单河道精细解释,识别出4期目的层单河道砂体,形成横向上逐渐向东迁移摆动、纵向上相互叠置的沉积演化模式。这一认识指导了地质模型优化,解决了生产井动静储量差异矛盾,能够有效指导气田开发生产。在海上少井条件下,利用地震沉积学方法进行河流相砂体精细描述的方法有较强的适用性。  相似文献   

Shallow-water deltaic clinoforms and process regime     

Piret Plink-Björklund 《Basin Research》2020,32(2):251-262

Utilizing two outcrop data sets with dip direction exposures of shallow-water (tens of meters) deltaic clinoforms, this paper quantifies sedimentary facies proportions and clinoform lengths and gradients, and links process regimes to delta clinoform dimensions. Both data sets are from foreland basins, the Cretaceous Chimney Rock Sandstone of the Rock Springs Formation from the US Western Interior, and the Eocene Brogniartfjellet Clinoform Complex 8 of the Battfjellet Formation from the Central Basin of Spitsbergen. Sedimentary facies indicate presence of both river- and wave-dominated clinothems in each data set. Facies characteristics and distribution implies that river-dominated clinothem progradation was primarily driven by deposition from weak hyperpycnal flow turbidity currents across the clinoforms, and minor slumps. Wave-dominated clinothems were constructed by wave processes rather than alongshore currents, and are also progradational subaerial clinoforms, with one exception, where the formation of a compound subaqueous clinoform set indicates erosion and sediment bypass above the wave base. Sediment distribution and lithological heterogeneity in the river-dominated clinothems is controlled by individual hyperpycnal flow events or mouth-bar collapse events, and thus by self-organization and minimal reworking that results in a heterogeneity that is difficult to predict (high entropy). The efficient reworking of river-derived sediments in wave-dominated clinothems results in predictable lithological sediment partitioning (low entropy). Clinoform dimension analyses show that although of similar sediment caliber, river-dominated clinoforms in both data sets are on average 3–4 times steeper and 3–4 times shorter than the wave-dominated clinoforms, with mean gradients of ca 4 degrees and ca 1 degree, respectively, and mean lengths of 150–230 m and 640–760 m. These results require corroboration from additional data sets, but do suggest that river- and wave-dominated delta clinoforms are likely to have distinct downdip extents (lengths) and gradients for given clinoform heights. Clinoform shape can thus be a method for differentiating ancient river- vs. wave-dominated deltaic clinoforms, in addition to their sedimentary facies, biogenic features and sandstone maturity, and helpful when incorporated into reservoir models.  相似文献   

建立辫状河储层地质模型的露头调查———以张家口地区为例   总被引：2，自引：2，他引：0  

伍涛  王德发 《现代地质》1998,12(3):394-400

摘 要　 根据储层沉积学原理‚对张家口地区辫状河砂体的成因进行分析‚划分出3级层次 界面和6种岩石相类型‚对沉积、成岩作用与储层物性的关系进行了探讨。指出：沉积作用 是影响砂体物性的主要因素‚成岩作用对物性的改造受沉积作用控制;砂岩物性和粒度中值 及泥质含量密切相关‚胶结物对孔隙度有一定影响‚对渗透率影响较弱。各次洪泛事件的能 量大小控制了有利储集带的分布。最后建立了辫状河砂体的一维和二维储层地质模型。  相似文献