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Sedimentology and stratigraphic architecture of a fluvial to shallow-marine succession: The Jurassic Dhruma Formation, Saudi Arabia
Journal of Sedimentary Research ( IF 2.0 ) Pub Date : 2021-07-31 , DOI: 10.2110/jsr.2020.077
Bassam Alshammari 1, 2 , Nigel P. Mountney 1 , Luca Colombera 1 , Mohammed A. Al-Masrahy 2
Affiliation  

The interaction of fluvial, tidal, and wave processes in coastal and paralic environments gives rise to sedimentary successions with highly varied styles of facies architecture; these are determined by the morphology and evolutionary behavior of the range of coastal sub-environments, which may be difficult to diagnose in subsurface sedimentary successions with limited well control.This study presents depositional models to account for stratigraphic complexity in a subsurface fluvial to shallow-marine succession, the Middle Jurassic Dhruma Formation, Saudi Arabia. The study achieves the following: i) it examines and demonstrates sedimentary relationships between various fluvial, nearshore, and shallow-marine deposits, ii) it develops depositional models to account for the stratigraphic complexity inherent in fluvial to shallow-marine successions, and iii) it documents the sedimentology and the stratigraphic evolutionary patterns of the lower Dhruma Formation in the studied area of Saudi Arabia. The dataset comprises facies descriptions of 570 m of core from 14 wells, 77 representative core thin sections, 14 gamma-ray logs, and FMI image logs from 4 wells. These data are integrated with quantitative information from > 50 analogous systems from a wide range of modern and ancient settings, stored in a relational database. Stratigraphic correlations reveal the internal anatomy of the succession.Facies associations are representative of fluvial channels, intertidal flats, pedogenically modified supratidal flats or floodplains, river-influenced tidal bars, weakly storm-affected shoreface and offshore-transition zones, storm-dominated delta-front and prodelta settings, and an open-marine carbonate-dominated shelf. These sub-environments interacted in a complex way through space and time. The vertical succession of the studied interval records an overall transition from coastal-plain deposits at the base to marine deposits at the top. As such, the succession records a long-term transgressive, deepening-upward trend. However, this general trend is punctuated by repeated progradational events whereby coastal sand bodies of fluvial, wave, and tidal origin prograded basinward during stillstands to fill bays along a coastline. The nature of juxtaposition of neighboring sub-environments has resulted in a sedimentary record that is highly complex compared to that generated by morphologically simple shoreface systems that accumulate more regularly ordered stratal packages.

中文翻译:

河流到浅海层序的沉积学和地层结构:沙特阿拉伯侏罗纪 Dhruma 组

沿海和近海环境中河流、潮汐和波浪过程的相互作用产生了具有高度不同的相结构样式的沉积层序;这些是由沿海亚环境范围的形态和演化行为决定的,在井控有限的地下沉积序列中可能难以诊断。本研究提出了沉积模型,以解释地下河流到浅层的地层复杂性。海洋演替,中侏罗世 Dhruma 组,沙特阿拉伯。该研究实现了以下目标:i) 它检查并证明了各种河流、近岸和浅海沉积物之间的沉积关系,ii) 它开发了沉积模型以解释河流到浅海序列中固有的地层复杂性,iii) 它记录了沙特阿拉伯研究区域下 Dhruma 组的沉积学和地层演化模式。该数据集包括来自 14 口井的 570 m 岩心的相描述、77 个代表性岩心薄片、14 个伽马射线测井和来自 4 口井的 FMI 图像测井。这些数据与来自各种现代和古代环境的 50 多个类似系统的定量信息相结合,并存储在关系数据库中。地层相关性揭示了演替的内部解剖结构。相协会代表河流河道、潮间带、土壤改造的潮上滩或泛滥平原、受河流影响的潮汐带、受风暴影响较弱的岸面和近海过渡带、风暴主导的三角洲-前端和 prodelta 设置,和一个开放的海洋碳酸盐为主的架子。这些子环境通过空间和时间以复杂的方式相互作用。研究区间的垂直序列记录了从底部的沿海平原沉积物到顶部的海洋沉积物的整体过渡。因此,该演替记录了长期的海侵、深化的上升趋势。然而,这一总体趋势被反复的进积事件打断,在这些事件中,河流、波浪和潮汐起源的沿海砂体在静止期间向盆地进积,以填充沿海岸线的海湾。相邻亚环境并置的性质导致沉积记录与由形态简单的滨面系统产生的沉积记录相比非常复杂,这些系统积累了更规则有序的地层组合。这些子环境通过空间和时间以复杂的方式相互作用。研究区间的垂直序列记录了从底部的沿海平原沉积物到顶部的海洋沉积物的整体过渡。因此,该演替记录了一个长期的海侵、深化的上升趋势。然而,这一总体趋势被反复的进积事件打断,在这些事件中,河流、波浪和潮汐起源的沿海砂体在静止期间向盆地进积,以填充沿海岸线的海湾。相邻亚环境并置的性质导致沉积记录与由形态简单的滨面系统产生的沉积记录相比非常复杂,这些系统积累了更规则有序的地层组合。这些子环境通过空间和时间以复杂的方式相互作用。研究区间的垂直序列记录了从底部的沿海平原沉积物到顶部的海洋沉积物的整体过渡。因此,该演替记录了长期的海侵、深化的上升趋势。然而,这一总体趋势被反复的进积事件打断,在这些事件中,河流、波浪和潮汐起源的沿海砂体在静止期间向盆地进积,以填充沿海岸线的海湾。相邻亚环境并置的性质导致沉积记录与由形态简单的滨面系统产生的沉积记录相比非常复杂,这些系统积累了更规则有序的地层组合。研究区间的垂直序列记录了从底部的沿海平原沉积物到顶部的海洋沉积物的整体过渡。因此,该演替记录了长期的海侵、深化的上升趋势。然而,这一总体趋势被反复的进积事件打断,在这些事件中,河流、波浪和潮汐起源的沿海砂体在静止期间向盆地进积,以填充沿海岸线的海湾。相邻亚环境并置的性质导致沉积记录与由形态简单的滨面系统产生的沉积记录相比非常复杂,这些系统积累了更规则有序的地层组合。研究区间的垂直序列记录了从底部的沿海平原沉积物到顶部的海洋沉积物的整体过渡。因此,该演替记录了长期的海侵、深化的上升趋势。然而,这一总体趋势被反复的进积事件打断,在这些事件中,河流、波浪和潮汐起源的沿海砂体在静止期间向盆地进积,以填充沿海岸线的海湾。相邻亚环境并置的性质导致沉积记录与由形态简单的滨面系统产生的沉积记录相比非常复杂,这些系统积累了更规则有序的地层组合。深化上升趋势。然而,这一总体趋势被反复的进积事件打断,在这些事件中,河流、波浪和潮汐起源的沿海砂体在静止期间向盆地进积,以填充沿海岸线的海湾。相邻亚环境并置的性质导致沉积记录与由形态简单的滨面系统产生的沉积记录相比非常复杂,这些系统积累了更规则有序的地层组合。深化向上的趋势。然而,这种总体趋势被反复的进积事件打断,在这些事件中,河流、波浪和潮汐起源的沿海砂体在静止期间向盆地进积,以填充沿海岸线的海湾。相邻亚环境并置的性质导致沉积记录与由形态简单的滨面系统产生的沉积记录相比非常复杂,这些系统积累了更规则有序的地层组合。
更新日期:2021-08-01
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