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Contourite depositional system after the exit of a strait: Case study from the late Miocene South Rifian Corridor, Morocco
Sedimentology ( IF 2.6 ) Pub Date : 2021-04-25 , DOI: 10.1111/sed.12882
Wouter de Weger 1 , Francisco Javier Hernández‐Molina 1 , Olmo Miguez‐Salas 2 , Sandra de Castro 1 , Miguel Bruno 3 , Domenico Chiarella 1 , Francisco Javier Sierro 4 , Graham Blackbourn 5 , Mohamed Amine Manar 6
Affiliation  

Idealized facies of bottom current deposits (contourites) have been established for fine-grained contourite drifts in modern deep-marine sedimentary environments. Their equivalent facies in the ancient record however are only scarcely recognized due to the weathered nature of most fine-grained deposits in outcrop. Facies related to the erosional elements (i.e. contourite channels) of contourite depositional systems have not yet been properly established and related deposits in outcrop appear non-existent. To better understand the sedimentary facies and facies sequences of contourites, the upper Miocene contourite depositional systems of the South Rifian Corridor (Morocco) is investigated. This contourite depositional system formed by the dense palaeo-Mediterranean Outflow Water. Foraminifera assemblages were used for age-constraints (7.51 to 7.35 Ma) and to determine the continental slope depositional domains. Nine sedimentary facies have been recognized based on lithology, grain-size, sedimentary structures and biogenic structures. These facies were subsequently grouped into five facies associations related to the main interpreted depositional processes (hemipelagic settling, contour currents and gravity flows). The vertical sedimentary facies succession records the tectonically induced, southward migration of the contourite depositional systems and the intermittent behaviour of the palaeo-Mediterranean Outflow Water, which is mainly driven by precession and millennial-scale climate variations. Tides substantially modulated the palaeo-Mediterranean Outflow Water on a sub-annual scale. This work shows exceptional examples of muddy and sandy contourite deposits in outcrop by which a facies distribution model from the proximal continental slope, the contourite channel to its adjacent contourite drift, is proposed. This model serves as a reference for contourite recognition both in modern environments and the ancient record. Furthermore, by establishing the hydrodynamics of overflow behaviour a framework is provided that improves process-based interpretation of deep-water bottom current deposits.

中文翻译:

海峡出口后的轮廓沉积系统:来自晚中新世南里菲亚走廊的案例研究,摩洛哥

已为现代深海沉积环境中的细粒等高岩漂移建立了底部流沉积(等高岩)的理想相。然而,由于露头中大多数细粒沉积物的风化性质,它们在古代记录中的等效相很少被识别。与等高岩沉积系统的侵蚀要素(即等高岩通道)有关的相尚未正确建立,露头的相关沉积物似乎不存在。为了更好地了解等高岩的沉积相和相序列,研究了南里夫安走廊(摩洛哥)的上中新世等高岩沉积系统。由致密的古地中海流出水形成的等高岩沉积体系。有孔虫组合用于年龄限制(7.51 到 7. 35 Ma)并确定大陆坡沉积域。根据岩性、粒度、沉积结构和生物成因结构,已识别出九个沉积相。这些相随后被分为五个与主要解释的沉积过程(半远洋沉降、等高流和重力流)相关的相组合。垂直沉积相序列记录了等高岩沉积系统的构造诱导、南移和古地中海出流水的间歇性行为,主要受岁差和千年尺度气候变化驱动。潮汐在亚年尺度上对古地中海出流水进行了大幅度调整。这项工作展示了露头泥质和砂质等高岩沉积的特殊例子,通过这些例子,提出了从近端大陆坡、等高岩通道到其相邻等高岩漂移的相分布模型。该模型可作为现代环境和古代记录中等高线识别的参考。此外,通过建立溢流行为的流体动力学,提供了一个框架,以改进深水底部洋流沉积物的基于过程的解释。
更新日期:2021-04-25
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