Channel-levee complexes, terminal deep-sea fan and sediment wave fields associated with the Toyama Deep-Sea channel system in the Japan Sea
Channel-levee complexes, terminal deep-sea fan and sediment wave fields associated with the Toyama Deep-Sea channel system in the Japan Sea
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DOI：
10.1016/s0025-3227(97)00137-0
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发表时间：
1998-05
期刊：
影响因子：
2.9
通讯作者：
T. Nakajima;M. Satoh;Y. Okamura
中科院分区：
文献类型：
--
作者：
T. Nakajima;M. Satoh;Y. Okamura
富山深海道（Toyama Deep-Sea Channel， TDSC）是日本裂谷边缘最突出的深海道之一。该研究首次基于高分辨率和气枪地震反射剖面以及沉积物岩心揭示了整个TDSC系统的过程和形态。该水道起始于富山湾，经富山海槽（中新世裂谷）延伸750公里，至中新世大和和日本弧后盆地。TDSC系统的沉积物来自日本北部阿尔卑斯山脉，通过狭窄大陆架上的支流峡谷，这些支流峡谷直接与河流相连，即使在海平面高的时候也是如此。在富山海槽和大和盆地中，河堤复合体与河道接壤，在日本盆地中，河道为富山扇的末端提供补给。富山海槽边界的堤防伴随着堤岸上的浊积平原，而大和盆地的堤防则以突出的泥沙波为特征。富山扇由河槽-堤复合体组成，上游为泥沙波，河槽末端为叶状。河道-扇体系的走向和形态主要受盆地形态的控制。在狭窄细长的富山海槽中积聚了由浊积流沉积而成的厚片状沉积物，而在更开阔的盆地中则形成了广泛的堤岸和富山扇。沉积物的分布和随之形成的河道-堤防复合体的形态也受科里奥利力和离心力的控制。右面堤防的优先发展归因于北半球的科里奥利力倾斜效应。在河道蜿蜒的环形或弯曲处的离心力导致水流剥离，导致堤防在外部弯曲处形成。泥沙波的分布、形式和方向与推断的溢流浊流的范围和方向一致，并与相应的堤防生长相一致。沿TDSC发育曲流、阶地、堤防塌陷和裂缝展等河流状特征。与其他海底通道不同，曲度似乎是由基岩结构而不是由山谷坡度控制的。河道崩裂在TDSC系统中未被记录。近1ka来，上叶碎屑沉积活跃，表明近期泥沙通过河道进行了活跃的搬运。然而，在全新世期间，第四纪演替期间在沟槽斜坡上发育的切割和填充支流中，沉积物的搬运可能已经停止，在沟槽的东部边缘，一个相对较宽的陆架将峡谷与河流分开。
The Toyama Deep-Sea Channel (TDSC) in the Japan Sea is one of the most prominent deep-sea channels in rifted margins. This study revealed the course and morphology of the entire TDSC system for the first time, based on high-resolution and air-gun seismic reflection profiles, and sediment cores. The channel starts from Toyama Bay and extends for 750 km through the Toyama Trough, a Miocene rift, to the Miocene Yamato and Japan back-arc basins. The TDSC system is fed with sediment from the Northern Japan Alps, through tributary canyons on the narrow shelf, which are directly connected with rivers, even during sea-level highstands. Levee complexes border the channel in the Toyama Trough and Yamato Basin, and in the Japan Basin, the channel feeds the terminal Toyama Fan. Levees in the confines of the Toyama Trough are accompanied by an over-bank turbidite plain, whereas levees in the Yamato Basin are characterized by prominent sediment waves. Toyama Fan consists of a channel-levee complex with sediment waves in the upstream part and of lobes at the channel end. The course and morphology of the channel-fan system are primarily controlled by basin morphology. Thick, sheet-like sediments, deposited from ponded turbidity currents, have accumulated in the narrow, elongate Toyama Trough, whereas extensive levees and the Toyama Fan have formed in the more open basins. Distribution of sediments and consequent morphology of the channel-levee complexes are also controlled by Coriolis and centrifugal forces. Preferential development of the levees on the right-hand side is attributed to Coriolis-force tilt effects in the Northern Hemisphere. Centrifugal forces at the meander loops or bends of the channel result in flow stripping, causing levees to build on the outer bends. The distribution, form and orientation of sediment waves are consistent with the extent and direction of inferred spill-over turbidity currents, and with consequent levee growth. Fluvial-like features such as meanders, terraces, levee slumps and a crevasse splay are developed along the TDSC. Unlike other submarine channels, sinuosity seems to be controlled by bedrock structures rather than by valley slopes. Channel avulsion has not been recorded in the TDSC system. Active clastic deposition on the uppermost lobe during the past 1 ka suggests recent active sediment transportation through the channel. Sediment transportation, however, may have ceased during the Holocene in the cut- and fill-tributaries developed in the Quaternary succession on the slope to the trough, where a relatively wide shelf separates canyons from rivers in the eastern margin of the drainage area.