云贵地区二叠系瘤石灰岩的成因   总被引：3，自引：0，他引：3  

金振奎  冯增昭 《岩石矿物学杂志》1994,13(2):133-137

云南东北部及贵州北部的二叠系中广泛发育了瘤石灰岩（亦称眼球石灰岩）。瘤石灰岩由颜色较浅、较纯净的石灰岩瘤和颜色较深、泥质含量较高、微缝合线发育密集的包层组成。组成瘤和包层的石灰岩类型一致,为生屑石灰岩、生屑质灰泥石灰岩、含生屑灰泥石灰岩或灰泥石灰岩。本次研究认为,瘤石灰岩是压溶成岩作用的产物,不是某种沉积环境的标志  相似文献   

Chemostratigraphy of the Ediacaran basinal setting on the Yangtze platform,South China: Oceanographic and diagenetic aspects of the carbon isotopic depth gradient          下载免费PDF全文

Seishiro Furuyama  Akihiro Kano  Yoko Kunimitsu  Tsuyoshi Ishikawa  Wei Wang  Xin‐chun Liu 《Island Arc》2017,26(5)

The Ediacaran Yangtze platform in South China, which represents depositional settings ranging from coastal to basinal, provides valuable information for understanding climate changes and animal evolution during the Ediacaran Period. Although the shallower settings have been investigated, research on the basinal sections has been limited. This has hampered efforts to establish stratigraphic correlations and understand the oceanographic setting of the Yangtze platform. In this paper, the chemostratigraphy of a basinal section at Fengtan, Hunan Province, is reported based on analyses of stable carbon isotope profiles in carbonates (δ¹³C_carb), organic matter (δ¹³C_org), total organic carbon, ⁸⁷Sr/⁸⁶Sr ratios, and Mn, Rb, and Sr concentrations. The basinal section of the Doushantuo Formation, which is represented at Fengtan, provides data supporting regional correlations and oceanography. Three intervals in the Doushantuo Formation are correlated with the Three Gorges: (i) a negative δ¹³C_carb anomaly with stable δ¹³C_org values and altered ⁸⁷Sr/⁸⁶Sr ratios in the lower section can be correlated to the boundary between Doushantuo Members 2 and 3 (Interval A); (ii) a relatively high δ¹³C_carb anomaly with unaltered ⁸⁷Sr/⁸⁶Sr ratios (up to 0.7086) in the middle section corresponding to the lower part of Doushantuo Member 3 (Interval B); and (iii) a negative δ¹³C_carb anomaly with lowered δ values in the upper section can be correlated to the long interval of negative δ¹³C_carb (Interval C). The Gaskiers glaciation is likely represented in Interval A, and Interval C corresponds to the Shuram excursion reported for other Ediacaran localities. Our correlations confirm the depth gradient of δ¹³C_carb in the Yangtze platform and imply that reductive conditions prevailed in the basinal section from the Early to Middle Ediacaran. Under such conditions, anaerobic degradation of organic carbon or methane perturbed the inorganic carbon isotopic compositions and was at least partly responsible for the depth gradient of δ¹³C_carb.  相似文献   

RESEARCH PROGRESS ON LUMINESCENCE DATING OF ROCK SURFACES AND ITS APPLICATION          下载免费PDF全文

LUO Ming  CHEN Jie  LIU Jin-feng 《地震地质》2017,39(1):183-192

There are many examples of exposed or buried rock surfaces whose age is of interest to geologists and archaeologists. Luminescence dating is a well-established method of absolute chronology which has been successfully applied to a wide range of fine-grained sediments from hundreds of years to several hundred thousand years. Optical stimulated luminescence (OSL) has been recently proposed as a new method to date these rock surfaces (Laskariset al., 2011; Sohbatiet al., 2012a; Chapotet al., 2012; Pedersonet al., 2014; Sohbatiet al., 2015; Freieslebenet al., 2015). The basic principle is that luminescence signal of rock surface will soon decay when the rock is exposed to sunlight. When the rock surface is turned to be buried side, the OSL signal begins to accumulate again. With the variation of residual luminescence with depth, it is possible to estimate exposure and burial history of the rock. This article describes briefly the different luminescence dating methods for rock surfaces, its progress, application examples and present problems. For instance, Sohbatiet al. (2011) studied the depth dependence of the bleaching of the IRSL signal from granitic rocks, Laskaris and Liritzis (2011) proposed a mathematical function to describe the attenuation of daylight into rock surfaces, Sohbatiet al. (2012a) developed their model to include the environmental dose rate, Sohbatiet al. (2012b) overcame the problem of parameter estimation by using a known-age road-cut sample for calibration, Sohbatiet al. (2012c) further developed the OSL surface exposure dating model by including the simultaneous effect of daylight bleaching and environmental dose rate, and so on. These studies indicate that OSL dating method for rock surface can be applied widely to studies of geological and geomorphological evolution, archeology and Quaternary tectonic activity.  相似文献   

Mineral magnetic characterization of sediment sources from an analysis of lake and floodplain sediments in the catchments of the Old Mill reservoir and Slapton Ley,South Devon,UK     

I. D. L. Foster  J. A. Lees  P. N. Owens  D. E. Walling 《地球表面变化过程与地形》1998,23(8):685-703

Research on suspended sediment transport in the catchments of the Old Mill reservoir and Slapton Lower Ley, South Devon, has attempted to discriminate changing catchment sources on the basis of downcore variations in the mineral magnetic properties of lake, reservoir and floodplain sediments. Here, we examine these downcore variations and also explore the variability in catchment sources and the influence of topographic controls on mineral magnetic signatures of topsoils and subsoils. Particle size controls on the mineral magnetic signatures are explored by an analysis of a fractionated sediment sample, whilst the possible impact of diagenesis is assessed by an examination of the Mn profiles in the lake and reservoir sediments. From this analysis it is evident that the mineral magnetic signatures of well sorted floodplain deposits are more likely to reflect the particle size composition of the transported material. By contrast, the mineral magnetic record in the sediment of Slapton Ley appears to be most strongly influenced by dissolution of magnetic minerals. The sediment of the Old Mill reservoir provides the only suitable record for the application of a simple mixing model which is developed in order to quantify changes in the relative contribution of topsoil and subsoil through time. The research has important implications for attempting to reconstruct sediment sources in highly eutrophic lakes and emphasizes the uncertainty in the application of simple mixing models. © 1998 John Wiley & Sons, Ltd.  相似文献   

冀中孙虎地区含油气系统埋藏史研究   总被引：6，自引：1，他引：6  

褚庆忠 《地球学报》2000,21(3):306-312

孙虎地区是华北油田油气勘探的一块“硬骨头” ,长期勘探未获较大突破。本文运用近年来国内外石油地质界广泛流行的含油气系统理论[1～5] 对这一勘探薄弱地区的埋藏史进行了研究 ,在恢复剥蚀厚度及压实的基础上 ,做出了各埋藏史图 ,并划分了埋藏史类型 ,在此基础上探讨了埋藏史与油气的关系。这对正确划分孙虎地区的含油气系统 ,指导油气勘探具有重要作用。  相似文献   

Diagenesis of the Gully Oolite (Lower Carboniferous), South Wales     

Alison Searl 《Geological Journal》1989,24(4):275-293

Deposition of the Gully Oolite was locally interrupted by emergence and a regionally extensive palaeosol is present at the top of the unit. Early diagenetic phases include isopachous, fibrous submarine cements, nonluminescent vadose cements, and mixing zone dolomite. Subsequent nonferroan phreatic cements are non- to dully luminescent and in restricted vertical intervals predate significant compaction. More usually, however, phreatic cements postdate extensive overpacking of allochems. Ooid isotopic composition (δ¹⁸O=-7·80° to -3·10° and δ¹³C = -2·38° to +3·28°) is similar to that of associated phreatic cements and the data suggest that the bulk of ooid stabilization and cementation occurred within meteoric groundwaters. The extensive allochem overpacking appears to have occurred during the first few tens of metres of burial and intergranular macroporosity was eliminated prior to deep burial. Fracturing of the Gully Oolite during the Hercynian Orogeny and subsequent post-orogenic uplift led to localized dolomitization, several generations of calcite veins, and the restricted occurrence of ¹⁸O depleted cements in inter- and intragranular microporosity. Some of the veins clearly relate to Triassic exhumation of the Carboniferous Limestone, but others may be related to post-Mesozoic uplift and erosion of South Wales. Fracture-associated dolomitization may have occurred within a large-scale post-orogenic groundwater system, with Mg²⁺ being supplied through the release of deeply buried diagenetic brines.  相似文献   

缅甸睡宝盆地A井区古近系碎屑岩储层成岩作用与孔隙演化     

朱光辉  谢楠  李毓丰  金英爱 《海洋地质译丛》2010,(4):26-31

首次分析睡宝盆地A井区古近系成岩演化序列并提出其储层处于中成岩A1-A2期,此成岩阶段有利于次生孔隙的保护。研究区古近系储层成岩演化序列具有特殊性：第一期胶结作用为硅质胶结,早于机械压实作用或者同时进行,强烈的机械压实作用使得孔隙度减小15%,此后第二期碳酸盐胶结作用占主导,镜下统计两期胶结作用的减孔量为4%~6%;渐新世受到挤压构造运动和表生成岩作用的双重影响,紧临渐新统不整合面以下的储层由于碳酸盐胶结物溶解而形成次生孔隙。2009年中海油新钻井地处冲起构造,后期的这种构造变形对始新统及其以下的核部地层产生侧向挤压形成构造压实效应,原始孔隙遭到更多的破坏,而对渐新统起到构造托举的作用,可以减缓上覆沉积物的静岩压实效应。成岩演化序列的特殊性和多期构造运动使得古近系储层物性出现差异,总结储集性好的储层并分析其成因机制,对睡宝盆地下一步勘探具有重要指导意义。  相似文献   

Nested intrashelf platform clinoforms—Evidence of shelf platform growth exemplified by Lower Cretaceous strata in the Barents Sea     

Ivar Midtkandal  Thea Sveva Faleide  Jan Inge Faleide  Sverre Planke  Ingrid Anell  Johan Petter Nystuen 《Basin Research》2020,32(2):216-223

Two nested clinoform set types of different scales and steepness are mapped and analysed from high-resolution seismic data. Restoration of post-depositional faulting reveals a persistent pattern of small-scale, high-angle clinoforms contained within platform-scale, low-angle clinothems, showing a combined overall progradational depositional system. The large clinoforms lack a well-defined platform edge, and show a gradual increase in dip from topset to foreset. A consistent recurring stratal pattern is evident from the architecture, and is considered a result of interplay between relative sea-level change and autocyclic switching of sediment delivery focal points that brought sediment to the platform edge. This un-interrupted succession records how intra-shelf platforms prograde. Quantitative clinoform analysis may assist in determining the most influential depositional factors. Post-depositional uplift and erosion requires restoration with re-burial to maximum burial depth. Backstripping, decompaction and isostatic correction was performed assuming a range of lithologic compositions, as no wells test the lithology. Nearby wells penetrate strata basinward of the clinoforms, proving mudstone content above 50%, which in turn guide restoration values. Typical restored platform heights are 250–300 m, with correspondingly sized platform-scale clinoform heights. Typical large-scale clinoform foreset dip values are 1.3°–2.4°. Small-scale clinothems are typically 100 m thick, with restored foreset dip angles at 4.4° - > 10°. The results suggest that intrashelf platform growth occurs in pulses interrupted by draping of strata over its clinoform profile. The resultant architecture comprises small-scale clinoforms nested within platform-scale clinothems.  相似文献   

Simple parameterisations for describing N and P diagenetic processes: Application in the North Sea   总被引：1，自引：0，他引：1  

Nathalie Gypens  Christiane Lancelot 《Progress in Oceanography》2008,76(1):89-110

  相似文献   

Soil-zone microfabrics in calcrete and in desiccation cracks from the upper Jurassic purbeck formation of dorset     

Julian E. Andrews 《Geological Journal》1988,23(3):261-270

Soil-zone microfabrics, alveolar-septal structure, needle-fibre calcite, and calcans are described from horizontal calcrete layers, stringers, and infillings in vertical desiccation cracks from an Upper Jurassic limestone in the Lower Purbeck Formation of Dorset. These calcrete palaeosols occur in an oolitic limestone (the Hard Cap) which represents former evaporitic lagoonal to carbonate mudflat environments. The calcretes occur 6-10 cm below the Great Dirt Bed, a former rendzina soil with rooted tree remains. Desiccation cracks and vugs formed in the oolitic sediment before Great Dirt Bed times. After formation of the Great Dirt Bed, soil-water rich in dissolved CaCO₃ preferentially flowed through natural conduits in the underlying sediment, namely the desiccation cracks and vugs. Calcrete precipitated in these cracks and vugs around decaying plant roots, and probably, during more arid (evaporative) climatic periods. These palaeosol microfabrics are among the first to be described from the British Jurassic and were probably preserved due to the semiarid Lower Purbeck climate where rapid oxidation of organic matter limited the amount and strength of carbonic acid generation, thereby limiting extensive dissolution of early formed soil-zone carbonate. Early diagenetic cementation of the sediment also aided microfabric preservation by sealing off soil-zone structures from subsequent diagenetic fluids.  相似文献