共查询到20条相似文献，搜索用时 29 毫秒
1.
N. S. Meadows 《Geological Journal》2006,41(1):93-122
The existing stratigraphic nomenclature applied to the Early and Middle Triassic Sherwood Sandstone Group in NW England has resulted from more than 150 years of geological investigation, but is characterized by a lithostratigraphic system that is insufficiently flexible to allow for variations in lithology and sedimentary facies within a continental depositional system. A revised well correlation based on the detrital mineralogical and chemical composition of the Ormskirk Sandstone Formation in four offshore wells, that is then extended to provide near‐basin‐wide well correlations using a regional shale marker, confirms previously suggested but unproven diachroneity at the top of the Sherwood Sandstone Group. It also reveals the presence of incised valleys filled by stacked amalgamated fluvial channel sandstones and cut into previously deposited aeolian and sandflat sequences as well as older fluvial channel sandstones. The combination of well correlations indicates that the valleys were incised by a fluvial system flowing NW from the Cheshire Basin into the East Irish Sea Basin and then west towards the Peel and Kish Bank basins. The stratal geometry of the upper part of the Sherwood Sandstone Group is suggested to conform to models of climatically mediated alternations of fluvial degradation and aggradation in response to changes in the relationship between sediment flux and stream discharge. This model is supported in the Sherwood Sandstone Group by climatically driven variations in the non‐channelized facies which record upward wetting and drying cycles that can be locally tied to fluvial incision surfaces, and suggest a hierarchy of at least three levels of climatic cyclicity recorded within the sedimentary succession. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
2.
The Miocene marine molasse of Digne is thought to have been deposited in a structural embayment with a gulf-like morphology. This gulf was closed toward the alpine front and opened on to the Rhodano-Provençal gulf, part of the Tethys. The outcrop of Auribeau, located on the northern margin of the gulf of Digne, displays a conspicuous vertical record of different tidal cyclicities indicating the importance of tidal dynamics on the Miocene marine molasse deposits. For the first time these tidal cyclicities are analysed from a vertical section (deposited by vertical accretion) and these are similar to the cyclicities described from megaripples or sand waves (deposited by lateral accretion). By means of thickness measurements and time series analysis, four main tidal cyclicities have been recognized: (1) the diurnal cyclicity (as it exists in the Atlantic Ocean); (2) the semi-lunar month cyclicity of neap to spring; (3) the lunar month cyclicity of neap, high spring, neap to low spring and (4) the semi-annual cyclicity of solstice to equinox. 相似文献
3.
S.B. Kelly 《地学学报》1992,4(5):578-584
Hydrographically closed basins are sensitive to environmental change at all scales, the influence of climate being particularly strong. Some Devonian basins contain non-marine successions which appear to represent the deposits of such basins. Climatic fluctuations may be recorded by sediments in the form of Milankovitch band cyclicity. Two novel records of climatically related cyclicity are discussed. Well 12/13-1 in the North Sea penetrates a fine-grained Old Red Sandstone succession which is thought to be comparable to the largely lacustrine Middle Devonian deposits of the Orcadian Basin which outcrop onshore. The gamma ray log through the Devonian interval reveals periodic large peaks which correlate with U-rich, fine-grained intervals deposited during periods of greatest lake expansion. The peaks are cyclical; power spectrum of the gamma ray data reveal periodicities of c. 8 and 40 m, which are thought to correlate with the 21,000 yr (precession) and 100,000 yr (eccentricity) Milankovitch cycles. The Sherkin Sandstone Formation of the Munster Basin, SW Ireland, is a thick (> 1000 m) succession of largely alluvial deposits which were deposited by a terminal fan network. Detailed analysis of channel body sandstones and sedimentary structures contained within them reveals a cyclical variation in the dimensions of the bedforms camed by the channels. The same cyclicity is evident in the proportion of channel deposits. This variation reflects fluctuations in palaeodischarge, probably related to climatic variation. The main cycles are approximately 130 m thick; spectral analysis reveals two further strong periodicities at approximately 36 and 55 m. Estimated sediment accumulation rates suggest that the cycles represent periods of the order of lo4 years. It is proposed that the longer cycles reflect the 412,000 yr orbital eccentricity cycle and that the shorter cycles are either harmonics or components of the 100,000 yr eccentricity cycle. 相似文献
4.
Robin John Bailey 《地学学报》2009,21(5):340-351
Cyclostratigraphy postulates that the stratigraphic record cyclically encodes the periodic orbital forcing of terrestrial insolation, thus providing a time calibration. Regular cycles are sought using spectral analysis of lithological data series, but there are inherent ambiguities in this method. It may detect more cyclicities than conventional orbital forcing allows, but only those with the closest correspondence to estimated orbital frequencies are used for time calibration. Irregular cycles are subjectively defined in terms of non-rhythmic repetitions of facies. The calibrations assume that they record the spatially distorted sedimentary effects of orbitally forced periodicity in insolation. The null hypothesis that such non-rhythmic repetitions are autogenic, rather than orbitally forced, cannot, however, be rejected. Both types of cyclicity conform to an 'expected universe' where orbital forcing is reliably and recognisably encoded in the stratigraphic record. Neither form of cyclicity rules out the presence of hiatuses; thus, even if orbital in origin, neither can provide dependably refined, orbitally scaled, time calibration. 相似文献
5.
对珠江口盆地珠一坳陷惠州凹陷北部HZ0811井和惠陆低凸起HZ1811井中中新世-上新世的韩江组、粤海组和万山组自然伽马测井曲线进行频谱分析和小波分析, 识别出显著的米兰柯维奇沉积旋回.通过对短偏心率旋回进行高斯带通滤波, 建立了HZ0811井和HZ1811井的"浮动"天文年代标尺.两口井的万山组、粤海组和韩江组分别记录了35个、56个和64个短偏心率旋回, 据此估计出万山组沉积时限约为3.5 Ma, 粤海组沉积时限约为5.6 Ma, 韩江组沉积时限约为6.4 Ma.根据天文年代标尺计算出HZ0811井和HZ1811井韩江组-万山组的沉积速率, 结果表明沉积速率变化显示出明显的1.0 Ma和0.4 Ma的旋回性, 可能与长偏心率周期(1.0 Ma和0.4 Ma)控制的海平面变化有关. 相似文献
6.
The Early Permian Warchha Sandstone is well preserved in subsurface in the Potwar Basin and the Punjab Plain of Pakistan. However, this succession is only exposed in the Salt Range, and within this region, only a modest number of the many outcrops are of sufficient quality to enable the preparation of lateral and vertical log profiles. From the subsurface, data from five wells drilled in the Salt Range and Potwar Basin have been analysed. Although they are of restricted coverage, these subsurface data — which take the form of gamma ray logs and well cuttings — provide a valuable addition to the outcrop dataset of the Warchha Sandstone as they provide useful information about vertical textural changes, type and thickness of bedding and the nature of sandbody contacts with underlying strata. Overall, the Warchha Sandstone succession is composed of repeated fining-upwards cycles indicative of a meandering fluvial succession. Sub-components of each cycle are themselves classified into six subsurface sedimentary facies. Through comparison with outcropping parts of the succession, the origin and significance of these subsurface facies can be related to specific architectural elements within the meandering fluvial system responsible for generating the Warchha Sandstone succession. 相似文献
7.
Glutenite reservoirs are characterized by strong heterogeneity, large thickness, complex rock fabric, and low maturity in terms of structure and composition, which makes the division of sedimentary periods an arduous task. This restricts the exploration and development of oil and gas fields in glutenite reservoirs. Wireline logging signals, which contain rich geological information and record the sedimentary cycle of the strata, are sensitive to changes in the lithologic interface. Moreover, the formation microscanner image (FMI) method provides a complete lithologic profile of the formation and intuitively identifies sequence boundaries, unlike cores and conventional well logs. By integrating mathematical tools based on time–frequency analysis technology of multiscale wavelet transform and FMI as the geological constraint, a sensitive logging curve was selected to delineate the sedimentary cycles of a glutenite reservoir. Optimization of wavelet decomposition parameters was conducted by employing Morlet as the wavelet base, and the scale factors were screened by the direct power spectrum method. Taking the glutenite reservoirs of the Baikouquan Formation in the MA131 well block of the Mahu Sag as the research object, the sedimentary periods of the glutenite body of well MA15 were divided under seismic constraints. The results indicated that the abrupt interface of the wavelet coefficient curve of different scale factors closely corresponded to the interface of sedimentary cycles at distinct levels. This demonstrates the effectiveness of the proposed method. Subsequently, the dynamic time warping algorithm was employed for automatic stratigraphic well correlation. It is concluded that the proposed technique eliminates the overdependence on traditional methods, such as geological and well stratification information, as well as possessing superiority with regard to high precision, better flexibility, and convenient operation.
相似文献8.
应用频谱分析技术对测井物理参数记录的沉积旋回在深度域的变化进行了研究,发现沉积速率变化对沉积旋回波长、旋回谱系的组合样式和连续性具有明显的影响。数字模拟实验研究结果表明,在深度域对测井数据进行递进扫描的频谱分析图中,旋回波长和旋回谱系的终止面和转换面,指示沉积速率突变界面,对应地层间断面或沉积体制转型的位置和深度,这是我们识别旋回层序界面的标志,这一结论在深海钻孔中得到了验证。文中详细地介绍了从测井曲线数据中提取沉积旋回信号的数据处理方法和流程,提出根据原始测井曲线建立的极值曲线,可以检测到最明显的旋回波长为10 m级的频谱信号,这一层级的旋回层序界面,可以作为区域等时对比的基准。文中以川西上三叠统须家河组为例,根据自然伽马测井曲线的频谱分析,讨论了旋回层序界面在解决地震层序界面标定中的实用价值。 相似文献
9.
Identification of sharp and discontinuous lithological boundaries from well log signal stemming from heterogeneous subsurface structures assumes a special significance in geo-exploration studies. Well log data acquired from various geological settings generally display nonstationary/nonlinear characteristics with varying wavelengths and frequencies. Modelling of such complex well-log signals using the conventional signal processing techniques either fails to catch-up abrupt boundaries or at the best, do not provide precise information on insidious lithological discontinuities. In this paper, we have proposed a new wavelet transform-based algorithm to model the abrupt discontinuous changes from well log data by taking care of nonstationary characteristics of the signal. Prior to applying the algorithm on the geophysical well data, we analyzed the distribution of wavelet coefficients using synthetic signal generated by the first order nonstationary auto-regressive model and then applied the method on actual well log dataset obtained from the KTB bore hole, Germany. Besides identifying the formation of layered boundaries, the underlying method also maps some additional formation boundaries, which were hitherto undetected at the KTB site. The results match well with known geological lithostratigraphy and will be useful for constraining the future model of KTB bore hole data. 相似文献
10.
11.
碳酸盐岩测井层序识别方法研究——以塔中隆起卡1地区奥陶系为例 总被引：1，自引：0，他引：1
进行碳酸盐岩高分辨率的测井层序识别,建立精细等时地层格架,对碳酸盐岩油气勘探开发具有重要的意义。碳酸盐岩颗粒的大小和圆度不能明显地反映水动力作用的过程和能量;成岩作用往往增强储层非均质性,减弱原生沉积旋回性。这些特征使测井曲线对岩性变化与物性好坏的对应关系变差,测井曲线旋回性减弱,测井响应成为多因素作用的综合结果,划分层序所主要依据的沉积旋回特征隐藏在综合响应之中。测井层序识别的关键是多测井参数综合判定泥岩成因,剔除成岩作用后期改造等因素的响应信息,提取对层序划分有用的原生沉积特征信息。通过自然伽马、自然伽马能谱、FMI、地层倾角、双侧向电阻率等测井参数的综合应用,可以较好地识别碳酸盐岩中泥岩成因类型、不整合面,突出原生沉积旋回特征,在塔中隆起卡1地区奥陶系识别出三种泥质成因、两类层序界面。层序分析结果和缝洞统计规律对比表明:较高的泥质含量不利于溶蚀作用的发生;层序对溶孔的纵向分布有着显著的控制作用,而对裂缝的分布影响较弱。 相似文献
12.
通过研究构造背景、野外露头、岩性组合、沉积构造、古生物特征和测井曲线特征,分析和总结鄂尔多斯盆地白垩系洛河组至环河华池组沉积相、相带分布范围和沉积特征。洛河组主要沉积了冲积扇相、风成沉积相、辫状河相和沙漠相;而在环河华池组主要沉积了湖相、三角洲相、曲流河相及风成砂岩夹层。平面上沉积相带的变化规律性较强,由盆地边缘的冲积相、冲积—河流相砾岩向盆内渐变为河流相—滨浅湖—半深湖相泥岩。沉积特征受构造运动影响和沉积相带控制,洛河组是从山缘向盆地内砂岩厚度迅速变薄、尖灭;环河华池组岩性变化表现为北粗南细、东粗西细,在北部砂体呈现东薄西厚,东北向西南增厚,在南部砂体呈近南北向展布,东薄西厚,南薄北厚。 相似文献
13.
The growth and subsequent dissolution of salts on or within sediment may alter sedimentary structures and textures to such an extent that it is difficult to identify the depositional origin of that sediment and, as a result, the sediment may be misinterpreted. To help to overcome such problems with investigating ancient successions, results are presented from a comprehensive study of the morphology and fabrics of three large areas of modern salt flats in SE Arabia: the Sabkhat Matti inland region and the At Taf coastal region, both in the Emirate of Abu Dhabi, and the Umm as Samim region in Oman. These salt flats are affected by tidal‐marine, alluvial and aeolian depositional processes and include both clastic‐ and carbonate‐dominated surficial sediments. The efflorescent and precipitated salt crusts in these areas can be grouped into two main types: thick crusts, with high relief (>10 cm) and a polygonal or blocky morphology; or thin crusts, with low relief (<10 cm) and a polygonal or blister‐like appearance. The thin crusts may assume the surface morphology of underlying features, such as ripples or biogenic mats. A variety of small‐scale textures were observed: pustular growths, hair‐like spikes and irregular wrinkles. Evolution of these crusts over time results in a variety of distinctive sedimentary fabrics produced by salt‐growth sediment deformation, salt‐solution sediment collapse, sediment aggradation and compound mixtures of these processes. Salt‐crust processes produce features that may be confused with aeolian adhesion structures. An example from the Lower Triassic Ormskirk Sandstone Formation of the Irish Sea Basin demonstrates how this knowledge of modern environments improves the interpretation of the rock record. A distinctive wavy‐laminated facies in this formation had previously been interpreted as the product of fluvial sheetfloods modified by soft‐sediment deformation and bioturbation. Close inspection of laminations seen in core reveals many of the same sedimentary fabrics seen in SE Arabia associated with salt crusts. This facies is the product of salt growth on aeolian sediment and is not of fluvial origin. 相似文献
14.
南海深海沉积物花粉记录的快速气候波动事件 总被引：10，自引：2，他引：8
本文根据１７９４０柱状样花粉研究结果,分析了南海末次冰期以来千年尺度气候波动事件,并利用频谱分析方法得到南海深海沉积物花粉记录的气候变化的周期。本文研究认为,这种千年级准周期的气候波动可能与高纬度地区的亚米兰科维奇准周期性事件进行对比;它也可能反映了Ｅ１Ｎｉｎｏ－ＳｏｕｔｈｅｒｎＯｓｃｉｌｌａｔｉｏｎ(ＥＮＳＯ)系统较长周期的变化,其形成和演化机制仍待进一步探讨。 相似文献
15.
对济阳坳陷中生代沉积特征的综合研究, 初步提出一套改造型残留盆地沉积相研究方法, 强调从野外露头、岩芯、岩屑录井、测井、人工地震和盆地结构6个方面进行沉积相综合研究, 并与研究区周围地层沉积特征、岩芯沉积相识别、沉积相垂向演化、测井相、地震相和沉积体系分布研究相结合。其中最核心的技术是平衡剖面及地震约束下的连井剖面沉积相纵横向研究。研究认为济阳坳陷在中生代由多个时而分割时而相连的湖盆组成, 主要发育冲积扇相、河流相、扇三角洲相、三角洲相、湖泊相及沼泽相。 相似文献
16.
测井信息用于层序地层单元划分及对比研究综述 总被引：5，自引：0，他引：5
测井曲线是载有地层沉积旋回信息的信号,运用测井信息划分层序地层单元及地层对比研究自开始以来已取得了长足进步,从定性的分析、识别发展到现在可半定量、定量提取不同级别的沉积单元界面及进行层序地层对比,更进一步克服了地质学家手工划分层序中人为因素的影响,进而也推进了层序地层学研究的定量化发展。岩性突变、沉积韵律是影响其测井响应及曲线形态的两个重要因素,测井响应对沉积单元界面上下岩性的类型及粒度的不同而产生的声、放、电性质的变化,是利用测井信息划分沉积单元界面的基础。随着层序地层学研究的深入,沉积单元界面识别及层序地层对比的测井研究将向更深层次、更定量化的方向发展,短周期及超短周期沉积旋回的测井曲线形态内部特征提取及划分、层序地层智能动态匹配对比的方法研究将是今后开展研究的新方向。 相似文献
17.
18.
在陆源碎屑岩地层的沉积记录中,测井曲线上一个砂泥岩旋回可以采用正弦波进行描述,测井曲线幅度的高低反映旋回粒度大小的变化,旋回波长则是度量旋回厚度的标尺。本研究表明,测井曲线变化幅度与其平均值之差计算的累积残差曲线,是识别沉积体系、判别旋回层序界面的一个有效图解方法。根据数值模拟实验,证实对于任意一个级次的旋回复合波系,累积残差曲线的正半波和负半波曲线分别对应低频旋回的向上变细和向上变粗的沉积序列,正半波和负半波曲线的转换点位置对应旋回层序界面的深度。同时,引进测井曲线的频谱分析和滤波方法,可以划分沉积旋回的级别,进而研究沉积旋回变化形式的驱动机制。文中以柴达木盆地东部地区仙3井为例,根据测井数据计算的累积残差曲线,说明了划分低频和高频旋回层序的方法和流程,讨论了旋回幅度、波长变化与沉积环境和沉积速率的关系。 相似文献
19.
Geophysical well-log (bore-hole) data facilitate understanding of the physical properties of the subsurface formations as a function of depth measured in a well. In the present study, the wavelet transformation technique was applied to the well-log data of three wells in the Bombay High oil field, India, in order to identify depths to the tops of oil and/or gas formation zones (pay zones). Continuous wavelet transformation (CWT) was performed on gamma-ray, resistivity, neutron porosity and velocity log data sets in order to determine the space-localization of the oil and/or gas formation zones. The choice of a mother wavelet is important and largely depends on the data under investigation. We have applied a variety of wavelets to the different log data sets to not only identify the depths to the tops of formation zones, but also to determine the optimum wavelet that best characterizes the pay zones. On examination of scalogram plots of each log corresponding to each wavelet for their better resolution in identifying the formation boundaries, we have found that the scalograms corresponding to the Gaus1 wavelet appeared to give the best resolution in identifying the depths of pay zones in all the well-log data sets of all three wells. To further validate the above observation, a histogram analysis of CWT coefficients is made. This showed that, of all the wavelets considered for the present study, Gaus1 wavelet is the most appropriate and optimum for determining the space-localization of pay zones in all the well-log data sets considered in the present study. The depths of pay zones estimated from scalogram plots of logs agree well with those provided by the Oil and Natural Gas Corporation Ltd., India. 相似文献