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东沙海底峡谷是南海东北部峡谷群中最西边的一条大型峡谷,其研究对于深入理解晚新生代南海东北部峡谷群的成因、沉积输移机理、台西南前陆盆地及台湾造山带的演化等具有重要意义.综合利用多道反射地震和多波束海底测深数据,研究东沙海底峡谷的地貌、沉积特征及成因.结果表明,东沙海底峡谷是一条陆坡限定型峡谷,它发源于东沙群岛东部上陆坡区,自NWW往SEE方向于水深3000 m处汇入台湾浅滩南峡谷,全长约190 km,平均宽度10 km.根据地震层序分析,在峡谷充填沉积物中识别出了11个层序界面,解释为峡谷的古下切侵蚀面.地震相分析表明,该峡谷及有关沉积主要表现为平行上超充填、杂乱充填、丘状发散和迁移波状等地震相类型,分别解释为浊流或其他重力流沉积与半远洋沉积的交互、滑坡或碎屑流及峡谷底部滞留沉积、浊流溢流形成的天然堤,以及发育于天然堤或峡谷口外海底扇上的沉积波.ODP1144孔合成记录层位标定表明,东沙海底峡谷的发育大致始于中更新世约0.90 Ma.东沙海底峡谷最先形成于现今峡谷中游的上段,随着浊流或其他重力流不断的下切侵蚀,峡谷顺陆坡而下逐渐向海盆方向延伸,同时在溯源侵蚀作用下逆坡向陆架破折带方向延伸至现今峡谷头部.上述11个地震层序界面的年代大致可以与全球低海平面期进行对比,表明海平面变化是控制东沙海底峡谷多期下切-充填的重要因素.综合分析认为,东沙海底峡谷的成因与台湾隆升及台西南前陆盆地的发育这一大的区域构造背景有关,但没有证据表明东沙海底峡谷的形成与断裂、岩浆活动等存在直接联系.陆坡重力搬运过程(包括滑坡及浊流)对东沙海底峡谷的形成演化具有重要影响.
The study of the East Shashi canyon is one of the largest canyons in the northeastern South China Sea. The study is of great help in understanding the genesis of the canyon group in the northeastern South China Sea, the sediment transport mechanism, the evolution of the Taiwan-Southwest foreland basin and the Taiwan Orogenic Belt Is of great importance.Using multi-channel seismic reflection and multi-beam submarine sounding data, the study of the geomorphology, sedimentary characteristics and causes of the Dongsha submarine canyon.The results show that the submarine canyon is a limited canyon slope, which originated in the eastern part of the Dongsha Islands The slopes are imported from the NWW to the SEE at a depth of 3000 m into the southern canyon of Shoal, Taiwan with a total length of 190 km and an average width of 10 km.According to the seismic sequence analysis, 11 sequences were identified in the canyon sediments Which is interpreted as the ancient undercut erosion surface of the canyon.The analysis of seismic facies shows that the canyon and related sediments are mainly characterized by seismic facies such as hyperfill, miscellaneous filling, mound divergence and migrating wavy in parallel, which are respectively interpreted as turbidity or other Interaction between gravity flow sedimentation and semi-oceanic sedimentation, landslide or debris flow and sediment deposition at the bottom of canyon, natural dike formed by turbidity overflow, However, the sedimentary waves on the submarine fan outside the dike or canyon.ODP1144 pore-scale calibration shows that the development of the Dongsha submarine canyon roughly starts from the Middle Pleistocene about 0.90 Ma. The Dongsha submarine canyon first formed in the upper reaches of the present canyon, The turbidity stream or other gravity flow continued undercut erosion, along the slope gradually down the slope to the basin direction, and at the same time under the retrograde erosion to the continental shelf shelf collapse zone direction extends to the head of the current canyon above 11 seismic sequence The age of the interface can be compared with the global low sea level period, which shows that the sea level change is an important factor in controlling the multi-period undercut-fill in the Dongsha submarine canyon.A comprehensive analysis shows that the origin of the Dongsha submarine canyon is related to the uplift of Taiwan and the southwestern front of Taiwan However, there is no evidence that there is a direct correlation between the formation and fracture of the Dongsha submarine canyon and the magmatic activities, etc. The process of gravitational transportation (including landslides and turbid currents) on the formation and evolution of the Dongsha submarine canyon has the following features Significant influence.