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Facies variebility and depositional processes of storm deposits

风暴沉积物相变化与沉积过程

基本信息

批准号：
08640579
负责人：
MAEJIMA Wataru
金额：
$ 1.34万
依托单位：
Osaka city University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08640579/
关键词：
storm deposits sedimentary facies wave base shelf upper shoreface shallow marine bar shoreface recovery 相変化ストーム波浪限界深度陸棚堆積物村岡累層複合流

项目摘要

Facies variability of storm deposits and its response to differentiation of strorm processes in upper shoreface to shelf environments were studied in the Miocene Muraolka Formation, Togane Formation and Misaki Group in southwestern Japan, and the preservation potential of storm and non-storm processes in a shallow marine environment was evaluated.The facies spectrum in the Muraoka storm deposits reveals that the storm beds were originated by waning combined-flows across the storm-wave base. Storm-induced currents deposited sand under significant oscillatory water-motion in a shallow depth. Offshore down slope, the oscillatory component of a flow rapidly diminished due to increasing water depth, whereas the unidirectional component was still intense enough to transport sand. The depositional current further transported and deposited finer sediments into deeper water below the storm-wave base.Within the succession of the Muraoka shelf deposits, thick sandstone beds tend to be covered by … More thick mudstones. Such couplets represent sedimentation controled by sand availability. Powerful currents generated by extraordinary storms carried considerable volumes of sand away from the coast and resulted in sand-starved condition for some long periods. During these periods, sand availability on the stormy shelf was extremely low, and storm events were seldom recorded in the shelf deposits.The shoreline deposits in hte Togane Formation provides an example of storm erosion and recovery stage deposition in an upper shoreface environment. Backwash action of storm waves or storm-enhanced rip currents awept sediments into the shoreface and emplaced coarse materials as a lag on the erosion surface produced in the peak stage of a storm. During the declining and following stage of storms, long-period awells reworked much of the sediment previously transported offshore and returned them onshore in the form of migrating sand bars.Shallow marine bar deposits in the Misaki Group predominantly records storm processes. However, storms were seldom responsible for sand accumulation. Rather, sand transport and deposition were basically controled by fluvial discharge from the river mouth. Storm waves reworked were basically controled by fluvial discharge from the river mouth Storm waves reworked bar sands almost completely, and fluvial-influenced sedimentation records were mostly unpreserved. Less

本文研究了日本西南部中新世Muraolka组、Togane组和Misaki群风暴沉积的相变化及其对上滨-陆棚环境中构造过程分异的响应，对村冈风暴沉积物的相谱分析表明，风暴床是由浅部海洋环境中的风暴和非风暴过程共同作用形成的，流经风暴波的底部风暴引起的水流沉积砂下显着的振荡水运动在一个较浅的深度。离岸下坡时，由于水深增加，水流的振荡分量迅速减小，而单向分量仍然足以输送沙子。沉积流进一步将较细的沉积物输送并沉积到风暴浪底以下的深水中。在村冈陆棚沉积物的继承范围内，厚的砂岩层往往被 ...更多信息厚泥岩这种对偶体代表了由砂的可利用性控制的沉积作用。特大风暴产生的强大水流将大量的沙子从海岸带走，导致长时间的沙子匮乏。在这些时期，风暴架上的砂的可用性非常低，风暴事件很少记录在货架deposit.The海岸线沉积物在hte Togane Formation提供了一个例子，风暴侵蚀和恢复阶段的沉积在上滨面环境。风暴波或风暴增强的离岸流的反洗作用将沉积物扫入滨面，并将沉积的粗物质作为风暴高峰期产生的侵蚀面上的滞后物。在风暴的衰减和后续阶段，长时间的水井改造了以前被输送到海上的沉积物，并将它们以迁移砂坝的形式返回陆地。然而，风暴很少造成沙子堆积。泥沙输移和沉积基本上受河口径流控制。风暴波的改造作用基本上受河口径流的控制，风暴波几乎完全改造了拦门沙，河流作用的沉积记录大多未保存下来。少