Neogene sequence stratigraphic architecture of the Nile Delta,Egypt: A micropaleontological perspective     

《Marine and Petroleum Geology》2017

The sequence stratigraphic architecture of the Neogene section from the subsurface Nile Delta is resolved based on exceptionally well-preserved microfossils from the offshore NDOB-1 borehole. The architecture is configured on bathymetry variations and statistical parameters as deduced from the relative abundance of foraminiferal associations. The statistical parameters include ratios of planktic versus benthic foraminifera, and cluster and correspondence analysis of the twelve most commonly used benthic foraminiferal genera as proxies of water depths. The combination of cluster and correspondence analysis was employed to decipher the evolution and dynamics of the basin and the mechanisms that controlled the deposition of Neogene sequences in the Nile Delta region. Four basic environmental settings were recognized: 1.) a middle to outer neritic eutrophic setting, 2.) a middle to outer neritic mesotrophic setting, 3.) an outer neritic to upper bathyal mesotrophic setting and 4.) an upper bathyal mesotrophic setting.Eight stratigraphic sequences were identified in the Neogene Nile Delta section. Three sequence in the Miocene (MSeq1, MSeq2 and MSeq3), three in the Pliocene (PSeq1, PSeq2 and PSeq3) and two in the Pleistocene (PtSeq1 and PtSeq2). These sequences are systematically measured and described in terms of time, space and water bathymetry. The sequence boundaries and flooding surfaces were dated using high-resolution microfossil biochronology and stratigraphic index markers. Individual sequences and boundaries were correlated with international and local sequence stratigraphic models. The new sequence stratigraphic model established here provides age calibrated surfaces for inter-basinal correlations and opens new avenues for hydrocarbon reservoir exploration.  相似文献   

High-resolution sequence stratigraphy of clastic shelves V: Criteria to discriminate between stratigraphic sequences and sedimentological cycles     

《Marine and Petroleum Geology》2017

In contrast to high-frequency sequences driven by high-magnitude relative sea-level changes, those controlled by short-term, minor relative sea-level and/or sediment supply changes may be difficult to discriminate from sedimentological cycles (i.e., bedsets) unrelated to shoreline shifts, especially in case of limited outcrop exposures. In fact, meter-scale, fully shallow-marine high-frequency sequences and typical meter-scale bedsets may share a similar, simple facies succession documenting either an upward increase or decrease of event beds. It is therefore necessary to define a set of criteria that allows to discriminate between thin high-frequency sequences and bedsets, based on sedimentological, stratigraphic, micropaleontological, mineralogical and diagenetic data. In particular, the sedimentological and stratigraphic criteria that aid discriminating between high-frequency sequences and bedsets include: 1) occurrence of environmental changes across bounding surfaces; 2) occurrence of water-depth changes across bounding surfaces; 3) physical appearance of bounding surfaces and associated substrate-controlled ichnofacies; 4) lateral extent of bounding surfaces; 5) presence of condensed deposits; 6) cycle thickness; 7) recognition of a set of clinoforms in a regressive shoreface-shelf succession. Moreover, the formation of wave-ravinement surfaces in the shoreface is usually associated with an increase in the percentage of benthic micro-foraminifera specimens documenting energetic conditions, and in the abundance of heavy minerals. Extensive cementation may also be found just below and/or above transgressive surfaces. However, the integration of more than one of the above criteria is necessary to reliably discriminate between sequence stratigraphic surfaces (and therefore high-frequency sequences) and bedset boundaries, the latter being only related to changes of energy level and/or local sediment supply without shoreline shifts. This work is essential to correctly reconstruct the sequence stratigraphic framework of a given succession and to interpret the factors that controlled the cyclicity.  相似文献   

Effect of seismic sequences in reinforced concrete frame buildings located in soft-soil sites     

《Soil Dynamics and Earthquake Engineering》2014

On September 19 and 20, 1985, two strong subduction interface earthquakes struck Mexico City leading to a large stock of damaged, or even collapsed, reinforced concrete (RC) building structures located in soft soil sites of the former lake-bed zone. The aim of this study is to gain further understanding on the effects of soft-soil seismic sequences on the seismic response of RC framed-buildings. This investigation employed artificial sequences since only two real sequences were gathered during the 1985 earthquakes. The nonlinear response, in terms of peak and residual lateral inter-story drift demands of four RC buildings having 4, 8, 12, and 16 stories, was evaluated. Results show that the relationship of the damaged period of the building (i.e. period of the building after the mainshock) to the predominant period of the aftershock, which is a measure of its frequency content, has a significant impact in the building response.  相似文献   

2013年甘肃岷县—漳县交界Ms6.6地震序列双差定位研究     

王未来  吴建平  房立华  来贵娟 《地震地磁观测与研究》2014,35(5):29-32

利用甘肃遥测台网2013年7月22日至9月22日的震相观测报告,对2013年7月22日07时45分甘肃省岷县漳县交界Ms 6.6地震的地震序列进行双差定位研究.结果表明,地震序列呈北西向分布,与临潭宕昌断裂的走向基本一致,地震分布长度约10 km.震源深度剖面显示断层面向西南倾斜,浅部倾角较陡,深部略缓,表现为“铲形”逆冲断层的特征.余震区存在一条向西南延伸的余震带,与发震断层相交成y字型,推测可能是逆冲推覆构造中常见的反冲断层.  相似文献   

贵州瓮福磷矿床含磷岩系沉积层序的划分     

李守能  程鹏林 《贵州地质》2005,22(1):26-30

应用层序地层学的概念和方法,从沉积特征研究入手,对该区的含磷岩系——洋水组划分出5个沉积层序(旋回),结合层序界面及层序的归纳描述,确定了层序类型,并认为洋水组是一套海进体系域中由一系列低级别退积型沉积层序(旋回)组成的高级层序(Ⅰ级))。  相似文献   

苏德尔特构造带贝14块兴安岭群层序地层分析          下载免费PDF全文

张君龙  司英华  汪爱云 《地质找矿论丛》2009,24(3):237-242

以层序地层学理论为指导,利用岩心、测井、地震资料相结合的分析手段,建立了苏德尔特构造带贝14块兴安岭群的层序地层等时格架,将兴安岭群划分为3个三级层序和短期中期基准面旋回。分析了个层序的主要构型及其成因,认为盆地由断陷向凹陷转化,沉积速率也随之降低,盆地各层序的厚度由厚变薄。兴安岭群内部层序界面多为沉积间断,不同沉积时期的岩性、物性以及沉积物叠置关系具有明显的韵律性变化。层序发育明显受构造活动的控制,幕式构造活动是构成层序主要构型的成因。  相似文献   

Dynamic responses under the excitation of pulse sequences   总被引：6，自引：3，他引：3  

戴君武  Mai Tong  George C.Lee  齐霄斋  白文婷 《地震工程与工程振动(英文版)》2004,3(2):157-169

This paper studies the dynamic responses of SDOF system under pulse-dominant excitations. The purpose of the study is to prepare for scrutiny of some near-field pulse-dominant ground motions and their potential to cause structural damage. Extending the single pulse dynamics, we consider the effect of pulse sequences. This kind of excitation was particularly obvious in some of previous earthquakes such as Northridge (1994) and Chi-Chi (1995). Based on the duration,peak and rise and decay era of the main pulse as well as its relationship with the predecessor and successor pulses, we propose a classification for the pulse sequences. Consequent studies have been carried out for acceleration, velocity and displacement response spectra of the main pulse with either a predecessor or a successor pulse. The analysis also includes general response behaviors in different fundamental period segments and special aspects of response at certain points (e.g., the corresponding peak points).  相似文献   

中国上石炭统滑石板阶   总被引：5，自引：0，他引：5  

张遴信  王志浩  周建平 《地层学杂志》2004,28(1):18-26,34

滑石板阶一名最初见于项礼文等 ( 1980 )的文章 ,阶名源自同名岩石地层单位——滑石板组 ,典型剖面位于贵州省盘县县城以东约 30 km的滑石板村。岩性以浅灰色厚层灰岩为主 ,局部夹白云岩 ,厚 315 .4 6 m。底界以化石 Pseudostaffella antiqua的始现为标志 ,顶界止于化石 Profusulinella priscoidea带之底。滑石板阶包含 2个带 Pseudostaffella antiqua- P. antiqua posterior带和 Pseudostaffella composita- P. paracompressa带 ;2个菊石带Reticuloceras guizhouense带及 Branneroceras branneri- Grastrioceras cf. cumbriensis带 ,还包含腕足类 Choristitesmansuyi- Plicatifera chaoi组合带。牙形刺仅在下部找到 ,归属于 N eognathodus symmetricus带。滑石板阶大致相当于国际地层表中的巴什基尔阶 ( Bashkirian)中部  相似文献   

内蒙迪彦庙地区寿山沟组地层研究          下载免费PDF全文

宋鹏  王丰翔  李英杰  张红晨  贺秋利  于灵艳 《山东国土资源》2013,29(10)

内蒙迪彦庙地区早二叠世寿山沟组地层发育良好,岩性相对稳定,变质、变形程度较低,是研究区范围内早二叠世地层层序研究的理想地区。该课题逐层实测了寿山沟组剖面,从剖面的岩性地层入手,着重分析了迪彦庙地区早二叠世的岩性组合特征、基本层序、沉积旋回特征;同时根据古生物化石类型和组合,推断该区域形成的地质时代和沉积环境。研究表明：寿山沟组剖面厚度为9598.98m,根据岩性和粒度的大小,可分3个岩段：一段为滨浅海浅海陆棚沉积;二段、三段为一套浊流沉积岩系,发育特征性浊流沉积构造,为典型的复理石建造。  相似文献   

接收台阵、震源阵的传递函数与双聚束法的初步研究     

郝春月  牟磊育  郑重  张爽 《地震地磁观测与研究》2012,33(5):79-87

根据汶川地震序列,选出距离合适、波形相关性较好的事件作为震源阵,联合永久台阵(那曲、和田台阵),进行震源阵与固定台阵组合研究,计算其台阵响应.结果表明,地震序列可以形成震源阵,按照地震台阵的特殊方法进行研究,可以提高信噪比,为揭示地下精细结构提供条件.  相似文献