Limitations of sequence stratigraphic correlation between marine and continental deposits: a 3D experimental study of unconformity-bounded units

Experiments have been carried out in a model basin 16 × 1·2 × 0·9 m to address the effect of base‐level and discharge changes on actively growing alluvial‐shoreline wedges. Two distinct types of erosive surfaces were investigated: one produced by base‐level fluctuations in the coastal zone and the other by discharge and supply fluctuations in the upstream alluvial basin. In the first experiment, three similar base‐level cycles were simulated keeping sediment supply and basin tilting constant within each cycle, and changing discharge from one cycle to the next. In the second experiment, rises and falls of base level were instantaneous and discharge changes were in phase (high discharge linked to high water levels in the basin). In the third experiment, base level and discharge changed gradually, at different rates and they were out of phase, resembling a typical glacio‐eustatic cycle in which sea‐level rises and falls are linked to increased and decreased discharge, respectively. The resulting stratigraphy of the alluvial to deltaic sedimentary wedge was analysed in terms of the development of unconformities and the evolving depositional geometry. An intervening decoupled zone between parts of the model basin dominated by alluvial processes and that at the coastal zone is identified. Within this decoupled zone, unconformities in the alluvial succession tend to vanish basinward, and base‐level generated coastal unconformities disappear landward. The two types of unconformity can be generated at different times during a glacio‐eustatic cycle, and it is thus erroneous to correlate them, even though they may appear to form a continuous surface. Unconformities within the modelled stratigraphy do not constitute time lines nor do they consistently separate younger from older beds, as they require a significant time to form and they have thick sedimentary packages as depositional correlatives. The experiments also support a fourfold division of sequences, showing the development of a significant sedimentary package during base‐level falls.     

Simultaneous operation of opposing reaction mechanisms: The influence of matrix heterogeneity on post-kinematic garnet crystallization in an inverted metamorphic sequence

Metapelites from the inverted Barrovian sequence in the Sikkim Himalaya (northeast India) are shown to be largely continuous with respect to their bulk rock compositions, microstructures and pressure–temperature–time–deformation (P–T–t–D) histories. However, the upper garnet–lower staurolite zone demarcates a region of microstructurally anomalous post-kinematic garnet populations contained within strongly segregated matrices. The different microstructures within samples from this region cannot be attributed to differences in their thermobarometric histories or bulk compositions, but are instead interpreted to represent an otherwise unexposed level of the Daling Group that is now exposed along a post-metamorphic thrust splay. These heterogeneous samples contain several discrete garnet populations that progressively crystallized with increasing P–T. Garnet populations that experienced the most protracted growth now form complex polycrystals that exhibit crystallographically controlled and morphologically irregular interfaces adjacent to micaceous and quartzofeldspathic domains respectively. Electron backscatter diffraction indicates that these polycrystalline garnet structures contain numerous coalesced porphyroblasts that are structurally uncorrelated across their grain boundaries. However, a crystallographically preferred orientation at the polycrystal scale is interpreted to derive from epitaxial crystallization of early-formed garnet porphyroblasts on precursor mica. Later-nucleated porphyroblasts within polycrystals preferentially concentrated towards quartzofeldspathic domains, with the overall nucleation distribution likely controlled by a complex interplay between chemical heterogeneities, strain partitioning and epitaxial crystallization. The subsequent growth of these polycrystals was equally spatially heterogeneous; it was moderated by differences in the efficiency of grain boundary transfer between quartzofeldspathic and micaceous domains that precluded thin section-scale chemical equilibration. In contrast to samples from Sikkim containing more typical porphyroblastic populations in continuous and disseminated matrices, heterogeneous availability of garnet-forming components within this strongly layered matrix is shown to have resulted in grain-scale variations in growth rates and the spatial juxtapositioning of interface-controlled microstructures and locally equilibrated chemical compositions with those that were transport controlled.     

鄂尔多斯盆地中东部奥陶系马家沟组马五6亚段硬石膏产状类型与成因*

鄂尔多斯盆地中东部奥陶系马家沟组马五₆亚段硬石膏产状类型多样,基于系统的宏观与微观岩石学分析,识别并区分出星散状(A1型)、纹层状(A2型)、致密块状(A3型)、结核状或团块状(A4型)、鸡雏状或角砾状(A5型)等硬石膏产状类型。单井高频旋回和微相分析表明,马五₆亚段发育与潮坪、潟湖、鲕粒滩、砂屑滩、微生物丘等有关的5种高频向上变浅序列,硬石膏的产状类型、产出位置和分布形式等与向上变浅序列有很好的耦合关系。A1型和A2型硬石膏发育于高频向上变浅序列的下部和中部,主要与膏云质或云膏质潟湖相关,属于潟湖相原生化学沉积成因。A3型硬石膏分布于高频向上变浅序列的上部,受膏质潟湖控制,也属于原生化学沉积成因。经典的结核状硬石膏(A4-1)呈随机分布形式产于潮坪沉积序列,为成岩期交代作用或者膏化作用成因,与传统萨布哈交代成因的膏质结核相似。A4-2型硬石膏主要出现在颗粒岩和微生物岩中,主要由富含CaSO₄的下渗卤水在溶蚀孔洞中沉淀形成;A5型硬石膏发育于向上变浅序列的上部和顶部,与高频暴露有关,为准同生期以溶蚀—充填为主的岩溶改造成因。发育完整的单个高频旋回,大致经历了高频快速海侵早期、高频快速海侵晚期至缓慢海退早期、高频缓慢海退晚期和高频海退末期暴露4个演化阶段,形成了与之耦合的海相碳酸盐岩与硬石膏共生序列。这些认识将对马家沟组沉积古环境的再认识具有重要的参考意义。     

鄂尔多斯盆地马家沟组准层状岩溶角砾岩特征及其成因*

鄂尔多斯盆地奥陶系马家沟组广泛发育岩溶角砾岩,结构特征复杂。近期研究发现,这些角砾岩的组构和分布特征难以能单纯地用经典的风化壳岩溶模式解释,各类角砾岩的成因机理值得进一步探究。文中基于大量岩心及薄片观察,对苏里格气田东区奥陶系马家沟组上组合不同层位角砾岩进行归纳和判识,明确其空间展布和序列结构特征,分析形成机理。研究发现: (1)根据成因与发育环境,苏格里气田东区奥陶系马家沟组上组合角砾岩可划分为5类,分别是近原地解离角砾岩(B1)、近地表堆积角砾岩(B2)、洞穴堆积角砾岩(B3)、洞顶(壁)碎裂角砾岩(B4)和坍塌角砾岩(B5),它们具有纵向多层叠置、横向可对比的“准层状”特征; (2)不同类型角砾岩的纵向配置和演化与周期性的向上变浅沉积序列和暴露溶蚀有关,共归纳为3种类型,即B1主发育型、B2-B3-B4组合发育型、B5主发育型; (3)准层状角砾岩形成于早成岩期,受控于古地貌起伏背景下的高频海平面变化,由暴露溶蚀透镜体横向迁移连片和纵向多旋回叠置而成。研究结果不仅有助于了解鄂尔多斯盆地马家沟组多样化的岩溶角砾岩特征与成因,也为白云岩早成岩期岩溶研究提供了新的素材。     

金坛储气库阜宁组四段含盐层系沉积特征及成盐模式

为了解决金坛储气库的安全平稳运行及下一步开发建设等问题,在综合利用岩心、薄片、测井、地震以及分析化验等资料的基础上,对该区含盐层系沉积特征、控制因素及沉积模式进行了研究。结果表明：阜宁组四段含盐层系发育石盐岩、硫酸盐岩、碳酸盐岩、泥岩、粉砂岩5种岩石类型,具有6种层理构造和2种化学成因构造;沉积时气候干旱炎热,盐度较高。研究区含盐层系在测井上表现为箱形、钟形、齿形、漏斗形及平直形5种形态,地震上表现为平行状、杂乱丘状、舌形孤立状3种反射特征;含盐层系属于盐湖沉积,可识别出中心膏盐岩、过渡带碳酸盐岩、边缘带砂泥岩3种亚相及7种微相,含盐层系在不同层序内部沉积特征和分布规律各异,沉积中期高位体系域盐岩厚度最大;古地貌控制含盐层系沉积微相类型和分布特征,水体开放程度控制沉积序列演化和岩性组合,湖平面变化控制含盐层系岩石类型和发育规律。研究区存在局限型和广覆型两种成盐模式,湖盆中心的低洼区域为下一步开发建设的有利区域。     

Integration of Sequence Stratigraphic Analysis and 3D Geostatistical Modeling of Pliocene–Pleistocene Delta,F3 Block,Netherlands

This research is focused on the analysis of the sequence stratigraphic units of F3 Block, within a wave-dominated delta of Plio–Pleistocene age. Three wells of F3 block and a 3D seismic data, are utilized in this research. The conventional techniques of 3D seismic interpretation were utilized to mark the 11 surfaces on the seismic section. Integration of seismic sequence stratigraphic interpretation, using well logs, and subsequent 3D geostatistical modeling, using seismic data, aided to evaluat...     

Biostratigraphy,Microfacies, Sedimentary Environments and Sequence Stratigraphy of the Late Devonian–Carboniferous Deposits at the Anarak Section,Central Iran

The Late Devonian–early Carboniferous deposits of the Anarak section in northeastern Isfahan, Central Iran, evaluated based on conodont biostratigraphy, sedimentary environment and sequence stratigraphy. According to the field observations, five lithological units were identified. Investigating the conodont fauna of the Late Devonian–Carboniferous(Mississippian–Pennsylvanian) deposits of Bahram, Shishtu, and Qaleh(Sardar 1) formations in Anarak section led to the identification of 67 species of ...     

无碰撞区跳频/时序列理论界与设计

跳频(时)序列分析与设计是跳频(时)扩频通信系统的核心技术.无碰撞区跳频序列是近年新出现的一个研究方向,现已成为通信领域的研究热点.对无碰撞区跳频序列的理论界及其设计进行深入研究,导出无碰撞区跳频序列的一些本质属性;讨论无碰撞区跳频序列集周期汉明相关函数的理论界,揭示几个理论界之间的关系,给出这些理论界等价的条件.提出最优无碰撞区跳频序列的一般构造方法.利用该构造方法,可以产生任意长度的最优无碰撞区跳频序列集.并且,任意一个最优无碰撞区跳频序列集,都可以由一般构造方法产生.     

基于同源数据的序列比例尺地图综合缩编平台建设

如何维护更新数据是"数字城市"建设中面临的重要问题,而构建基于同源基本大比例尺数据连续化生产序列小比例尺数据,对多尺度城市空间数据进行纵向一体化管理的软件平台成为数据更新维护的关键。研究以基于同源数据的序列比例尺地图综合缩编平台建设为对象,主要从地图综合知识库形式化表达、地图综合流程决策控制机制、构建开放式地图综合软件系统构架体系、高效地图综合算子设计等方面进行重点阐述。此研究建设的软件平台已在广州市大型多尺度空间数据库快速构建中得到成功应用。