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    南海海盆东南部大型深水浊积扇体系及其成因的构造控制

    The large deep-water turbidity fan system in southeastern South China Sea Basin: Formation and tectonic constraint

    • 摘要: 运用近年来海洋地质调查工程获取的最新地质地球物理数据,在南海海盆东南部水深2000~3800 m区域,发现中中新世到第四纪多期大型浊积扇沉积体系,揭示了南海南部深海沉积作用及沉积演化过程。该浊积扇体系以沉积物波、水道充填、海底扇、块体流等沉积体为主,总体上由海盆东南部向海盆中央呈扇形推进,推进距离为150~ 260 km,从老到新规模和结构不断变化,蕴含了丰富的海平面变化信息。垂向上浊流沉积层层叠置发育,形成厚层的浊积砂体。海底水道十分发育,水道砂体底部呈“V”型展布,由南向北延伸,揭示出物源主要来自礼乐滩及北巴拉望区域。该浊积扇的形成明显受到构造控制,与中中新世以来礼乐滩—巴拉望岛的隆升和晚中新世以来的岩浆活动密不可分。浊流发育位置处于南海东南部陆缘和深海平原之间,是陆源物质由浅海输送到深海平原的重要机制,构成南海南部“源-汇”沉积体系的重要环节。

       

      Abstract: A large turbidite fan system was found from southeastern South China Sea basin through the latest multi-channel seismic profiles in the regional geological and geophysical measurement data set. This fan system occurred in the water depth from 2000 m to 3800 m of the present sea level, with forward northwest direction to the central basin edge 150-260 km in length. The fan system was interpreted to have been formed from middle Miocene to Quaternary with series of turbidite fan sequences, mainly composed of sediment waves, channel filling, submarine fans, and mass flows. In time scale, from the early to late stage, the size and architecture of fan system were constantly changing, underlying valuable information of sea level change, depositional process and tectonic evolution. In spatial scale, the turbidite sand bodies were formed by the superimposed layers of turbidite flow sediments. The channels were well developed on the seabed within this fan system. The bottom of the channel sand bodies are distributed on "V" shape in panel, extending from south to north, revealing mainly sources from Liyue Bank and north Palawan Island area. The turbidite fan's formation was obviously controlled by tectonic movement, on the one hand related to the uplift of Liyue Bank-Palawan Island since the middle Miocene and, and on the other hand related to magmatic activity since the late Miocene. The turbidite current mechanism occurred in the transition of continental margin to abyssal plain in the southeast of the South China Sea, driving particles transportation from shallow sea to deep basin. This new interpreted large turbidite fan system presents an important linkage of "source-to-sink" sedimentary system, and benefits to revealing deep-sea sedimentary evolution process in the South China Sea.

       

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