南海北部陆坡神狐海域峡谷地貌形态特征与成因

FEATURES OF CANYON MORPHOLOGY AND THEIR ORIGIN IN THE SHENHU AREA,NORTHERN SLOPE OF THE SOUTH CHINA SEA

  • 摘要: 利用多波束水深及高分辨率数字单道地震测量手段,对南海北部陆坡神狐海域进行了精细地形和浅部地层结构探测,认为研究区存在4条海底峡谷及3条槽谷。其外形呈喇叭型或直线型,规模不等,长度为8~25 km,宽度为1.5~4 km,下切深度最大可达175 m。研究区浅地层自下而上可划分为U1和U2两套层序。地层总体上以高频、强振幅、中-高连续、平行-亚平行反射地震相为主,但在峡谷区层序U2则以杂乱或低连续反射为特征。在详细分析峡谷与槽谷地貌形态及浅地层地震反射特征的基础上,对其成因进行了初步分析,研究表明神狐海域浅地层发育与天然气水合物有关的BSR及滑塌体,水合物的分解导致地层滑塌并发生塌陷,在NW向构造以及底流冲刷共同作用下,最终形成本区形态各异的峡谷及槽谷地貌。其形成时间推测为第四纪,属幼年期阶段。

     

    Abstract: Detailed interpretation of morphology and shallow stratigraphic structure were carried out base on high-resolution multi-beam water depth data and single-channel seismic profiles. Three canyons and four channels were recognized in the study area. The bird view of the shape and length of the canyons or channels vary greatly in a range of 8~25km long, 1.5~4 km wide, with a maximum incised depth up to 175 m. The shallow strata of the study area can be divided to two parts from bottom to top:namely U1 and U2 respectively. The seismic reflection in general is characterized by a high frequency, strong amplitude, medium-high continuation, and parallel to sub-parallel pattern. However, the reflection in the canyon is chaotic with low continuation or even discontinued. The research result indicates that slumping was well developed in the sequence U2 in the canyons area, which has close relationship with the occurrence of gas hydrate. The canyons or channels were initially formed by the decomposition of gas hydrate and further developed under the control of NW trend faults and the erosion of bottom current. The canyons and channels were formed in Quaternary according to its shape and stratigraphic position. The results may contribute to the study of oceanic morphology and the exploration of gas hydrate in the region.

     

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