Depositional processes on oceanic island shelves – Evidence from storm‐generated Neogene deposits from the mid‐North Atlantic
Depositional processes on oceanic island shelves – Evidence from storm‐generated Neogene deposits from the mid‐North Atlantic
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大洋岛架上的沉积过程——来自北大西洋中部风暴生成的新近纪沉积物的证据
DOI：
10.1111/sed.12055
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发表时间：
2013
期刊：
影响因子：
3.5
通讯作者：
ÁvilaS.
中科院分区：
文献类型：
--
作者：
MeirelesR;QuartauR;RamalhoR;RebeloA;MadeiraJ;ZanonV;ÁvilaS.
海洋岛屿--如中北大西洋的亚速尔群岛--周期性地暴露在大风暴中，这些风暴往往会沿着沿着重新移动和运输海洋沉积物，并进入更深的环境。这种破坏性事件产生了被称为风暴岩的沉积物，其特征反映了它们形成时的高度动态环境。然而，来自海洋岛屿的风暴岩在文献中很少描述，并且对影响海洋岛屿架的风暴相关沉积动力学知之甚少。因此，大洋岛屿风暴岩沉积物的地质记录可以提供关于在大风暴期间和之后在岛架上发生的沉积物再流动、搬运和沉积过程的宝贵信息。在圣玛利亚岛（亚速尔群岛），一系列新近纪风暴岩沉积物因持续的火山活动而被纳入岛屿的建筑物中（因此得以保存），后来因隆起和侵蚀而暴露。由于它被当代沿海熔岩三角洲覆盖，因此可以推断沉积时的水深，这是一个很好的案例研究，可以深入了解岛架沉积的神秘过程。沉积学、古生物学、岩相学和古水深信息使这些沉积物的沉积环境得以重建。该序列典型的特征风暴岩（或连续风暴岩）形成atca 50米深，在陡峭，充满活力的开放的岛屿架，并与大量的沉积物再动员的证据从近岸到中间或外部的货架。作者声称，风暴事件引起的跨大陆架运输是沉积物沉积的主要过程，沉积物沉积作用于受到高能环境影响的陡峭和狭窄的大陆架，例如公海火山岛的岛架。
Oceanic islands – such as the Azores in the mid‐North Atlantic – are periodically exposed to large storms that often remobilize and transport marine sediments along coastlines, and into deeper environments. Such disruptive events create deposits – denominated tempestites – whose characteristics reflect the highly dynamic environment in which they were formed. Tempestites from oceanic islands, however, are seldom described in the literature and little is known about storm‐related sediment dynamics affecting oceanic island shelves. Therefore, the geological record of tempestite deposits at oceanic islands can provide invaluable information on the processes of sediment remobilization, transport and deposition taking place on insular shelves during and after major storms. In Santa Maria Island (Azores), a sequence of Neogene tempestite deposits was incorporated in the island edifice by the ongoing volcanic activity (thus preserved) and later exposed through uplift and erosion. Because it was overlain by a contemporary coastal lava delta, the water depth at the time of deposition could be inferred, constituting an excellent case‐study to gain insight on the still enigmatic processes of insular shelf deposition. Sedimentological, palaeontological, petrographic and palaeo‐water depth information allowed the reconstruction of the depositional environment of these sediments. The sequence typifies the characteristics of a tempestite (or successive tempestites) formed atca50 m depth, in a steep, energetic open insular shelf, and with evidence for massive sediment remobilization from the nearshore to the middle or outer shelf. The authors claim that cross‐shelf transport induced by storm events is the main process of sediment deposition acting on steep and narrow shelves subjected to high‐energetic environments, such as the insular shelves of open‐sea volcanic islands.
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DOI：
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