南海北部台湾峡谷“蛟龙号”第140潜次沉积物特征及其沉积过程指示意义

Sedimentary characteristics and processes revealed by the push cores of the 140th dive of DSV "Jiaolong" in the Taiwan Submarine Canyon, Northern South China Sea

  • 摘要: 海底峡谷沉积物来源、输运机制和沉积过程的研究一直是深水沉积体系研究的关键,也是近年来深海浊流沉积研究中的热点问题。对“蛟龙号”第140潜次在南海北部台湾峡谷中段3个站位获取的沉积物短柱的粒度、有孔虫和黏土矿物进行综合分析,结果表明3个短柱上部均以粒度较细、变化较小并含半深海—深海环境的底栖有孔虫为特征的半深海沉积,下部以粒度明显变粗、含有较多浅水种底栖有孔虫的浊流沉积为主。AMS14C测年结果显示该浊流沉积形成于约150aBP,表明台湾峡谷中段有典型的近现代浊流活动。此外,黏土矿物组成表明研究区正常半深海沉积与浊流沉积物源主要来自台湾,其次为珠江和吕宋岛的碎屑沉积物。

     

    Abstract: Transportation and deposition of sediments in submarine canyons are critical for understanding the deep-sea processes and environments, particularly the turbidity currents. In this paper, three push cores, collected from three sites in the middle reaches of the Taiwan Submarine Canyon during the 140th dive of Chinese DSV (Deep Submersible Vehicle) "Jiao Long", are analyzed for sediment characteristics, sources, and depositional processes. The upper parts of the push cores are dominated by homogeneous fine-grained sediments signified by a typical hemipelagic-pelagic benthic foraminifera assemblage. In contrast, the lower parts consist of coarse-grained sediments and assemblages of "shallow-water" benthic foraminifera typically occur in coastal or shelf areas. Their depositional characteristics suggest a down-slope transportation most likely by turbidity currents along the canyon. AMS14C dating indicates that the turbidite was formed approximately 150 cal.aBP, and the clay mineral compositions suggests a kind of hemipelagic-pelagic and the turbidite deposits with sediment sources dominantly from the Taiwan island and partly from the Pearl River and Luzon Island.

     

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