南海海盆盆西峡谷的形态与结构及形成演化

盆西峡谷是南海中建南盆地中东部的一条大型峡谷，整体呈NW向，水深介于2 850~4 300 m，全长约188 km，宽为1.5~14.5 km，起始于中建南盆地，延伸到西南次海盆，对其进行形态、结构和形成演化的研究，为后续西南次海盆浊积扇的研究奠定了基础，对深入了解浊流沉积物的搬运模式提供科学依据.利用高分辨率多波束测深、单道和多道地震的最新资料，研究盆西峡谷的形态特征和结构及形成演化，结果表明盆西峡谷具有"分段性"特征，剖面形态从WN向ES依次表现为上段U型、中上段V型、中下段下V上U型和下段U型4段形态；上段以沉积作用为主，发育多期下切河道充填沉积，厚度可达1 200 m；中上段以侵蚀-沉积过渡作用为主，发育浊积水道砂体；中下段以冲刷作用为主，发育内堤岸和块体流沉积；下段发育块体流和滑塌体沉积.研究表明，盆西峡谷的形成受古地貌条件、侵蚀-沉积作用、海平面变化、构造运动和岩浆活动等多方面的影响，其中侵蚀-沉积作用、断裂活动和海平面变化为主控因素.揭示出盆西峡谷沉积演化可分为3个演化阶段:中中新世的峡谷蕴育阶段、晚中新世的峡谷侵蚀-充填阶段和上新世-第四纪的峡谷"回春"阶段. 

Morphology and Structure and Evolution of West Basin Canyon,South China Sea

The west basin canyon is a large cayon in the middle east of the Zhongjiannan basin in South China Sea. It appears to be NW direction, the depth of water is 2 850-4 300 m, and the length of it is about 188 km, the width is 1.8-14.5 km. It begins within the Zhongjiannan basin, and extends to the southwest sub-basin. The study of it provides a basis for the study of turbidite fan in the southwest sub-basin, and also provides scientific basis for deep understanding of the transportation model of turbidy currents. Based on the latest data of high resolution multi-beam depth sounding, single channel and multichannel seismic, this paper studies the morphological characteristics and structure and evolution of the west basin canyon. The results show the "segmentation" characteristics of the west basin canyon, including four stages:U type upper segment, V type middle upper segment, V bellow U type middle lower segment and U type lower segment, from the northwest to the southeast. The upper segment is mainly because of sedimentation processes, the infill of the multiphase incised valley reaches a thickness of 1 200 m; the middle-upper segment is mainly controlled by erosion-deposition, which leads to the formation of the turbidite sandstone body; the middle-lower segment is mainly controlled by erosion, which leads to the formation of the embankment and the mass flow deposit; the mass-flow and slip block deposited within the lower segment. The formation of the west basin canyon is influenced by palaeogeomorphology, erosion-deposition, sea-level change, tectonic movement, and magmatic activity, and the main controlling parameters are erosion-deposition, fault activity and sea-level change. The sedimentary evolution of the west basin canyon can be divided into 3 stages:the Middle Miocene canyon breeds stage, the Late Miocene sea canyon erosion and filling stage, the Pliocene-Quaternary canyon "rejuvenation" stage.