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Comparative morphosedimentary framework of small subtropical islands offshore Kuwait
Marine Geology ( IF 2.9 ) Pub Date : 2020-07-22 , DOI: 10.1016/j.margeo.2020.106294
Ilya V. Buynevich , Duncan M. FitzGerald , Abdalla Z. Al-Zamel , Mohammad A. Al-Sarawi

Five small islands offshore of the State of Kuwait in the northern Arabian Gulf (Miskan, Awhah, Kubbar, Qaruh, and Umm Al-Maradem) occur in differing structural settings and have evolved in a dynamic environment of shifting fluvial depocenters, fluctuating Holocene sea level, and variable tidal conditions. As a first step in reconstructing the origin and evolution of the islands, bathymetric charts, historical photographs, topographic profiles, and sediment samples were used to investigate their geomorphology and sedimentary environments. The subaerial portion of the islands varies in area from 0.04 to 0.57 km2. The plan-shape ellipticity ranges from nearly circular (0.10) to oval-shaped (0.54). The northern two islands (Miskan and Awhah) experience mesotidal conditions and are situated on a shallow platform (<5 m below mean sea level), which is part of a larger Failaka Island structure. In contrast, the three southern sites have a microtidal regime and sit atop small isolated platforms of aggrading perched reef origin, which descend steeply to more than 20–30 m depth within 3 km of the islands. Topographic profiles indicate that island interiors are composed of beach-ridge sets, whereas modern shoreline consists of segments of beachrock platforms alternating with depositional salients and flying spits in areas of longshore transport convergence. The proportion of total shoreline length represented by exposed beachrock varies from 4 to 46%. Beach sediments consist of very coarse to medium sand and variable sorting, primarily due to the degree of attrition of bioclastic material. A simple conceptual model is proposed to describe the general evolutionary trajectory of end-member islands. Both their accretion during the Late Holocene sea-level stillstand and decadal-scale persistence of sediment transport convergence sites (salients) suggest a morphosedimentary stability of the islands in the near future.



中文翻译:

科威特近海小亚热带岛屿的比较形态沉积框架

阿拉伯湾北部科威特州近海的五个小岛(Miskan,Awhah,Kubbar,Qaruh和Umm Al-Maradem)发生在不同的结构环境中,并在河流沉积中心变化,全新世海平面变化的动态环境中演化,以及各种潮汐条件。作为重建岛屿的起源和演变的第一步,使用了测深图,历史照片,地形图和沉积物样本来研究其地貌和沉积环境。岛屿的空中部分面积从0.04到0.57 km 2。平面形状的椭圆率范围从接近圆形(0.10)到椭圆形(0.54)。北部的两个岛屿(Miskan和Awhah)经历了中生度条件,并位于浅平台上(低于平均海平面以下5 m),该平台是较大的Failaka岛结构的一部分。相比之下,南部的三个地点具有潮汐作用,位于栖息的珊瑚礁起源的孤立的小平台之上,这些平台陡峭地下降到离岛3 km之内超过20–30 m的深度。地形图表明,岛屿内部由海滩山脊构成,而现代海岸线则由海滩岩平台的各部分组成,这些沉积岩在长岸交通汇聚区域交替着沉积凸出物和飞蝇。裸露的滩石所占海岸线总长度的比例从4%到46%不等。滩涂沉积物包括非常粗糙至中等的沙子和可变的分类,这主要是由于生物碎屑材料的磨损程度所致。提出了一个简单的概念模型来描述端部成员岛的一般演化轨迹。全新世晚期海平面静止期的增生和沉积物运移收敛点(盐)的年代际持续性都表明该岛在不久的将来会形成形态沉积。

更新日期:2020-07-22
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