Mass movements in small canyons in the northeast of Baiyun deepwater area, north of the South China Sea
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Mass movements in small canyons in the northeast of Baiyun deepwater area, north of the South China Sea LI Xishuang1, LIU Lejun1, LI Jiagang2, GAO Shan1, ZHOU Qingjie1, SU Tianyun1 1 The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China 2 Research Center of China National Offshore Oil Corporation, Beijing 100027, China
Received 11 March 2014; accepted 17 October 2014 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2015
Abstract
The process of mass movements and their consequent turbidity currents in large submarine canyons has been widely reported, however, little attention was paid to that in small canyons. In this paper, we document mass movements in small submarine canyons in the northeast of Baiyun deepwater area, north of the South China Sea (SCS), and their strong effects on the evolution of the canyons based on geophysical data. Submarine canyons in the study area arrange closely below the shelf break zone which was at the depth of –500 m. Within submarine canyons, seabed surface was covered with amounts of failure scars resulted from past small-sized landslides. A complex process of mass transportation in the canyons is indicated by three directions of mass movements. Recent mass movement deposits in the canyons exhibit translucent reflections or parallel reflections which represent the brittle deformation and the plastic deformation, respectively. The area of most landslides in the canyons is less than 3 km2. The trigger mechanisms for mass movements in the study area are gravitational overloading, slope angle and weak properties of soil. Geophysical data indicate that the genesis of submarine canyons is the erosion of mass movements and consequent turbidity currents. The significant effects of mass movements on canyon are incision and sediment transportation at the erosion phases and fillings supply at the fill phases. This research will be helpful for the geological risk assessments and understanding the sediment transportation in the northern margin of the SCS. Key words: mass movement, geophysical data, trigger mechanism, submarine canyon, north of the South China Sea Citation: Li Xishuang, Liu Lejun, Li Jiagang, Gao Shan, Zhou Qingjie, Su Tianyun. 2015. Mass movements in small canyons in the northeast of Baiyun deepwater area, north of the South China Sea. Acta Oceanologica Sinica, 34(8): 35–42, doi: 10.1007/s13131-015-0702-z
1 Introduction Submarine canyons develop widely in the shelf break zones and their adjacent slopes (Shepard, 1965; Harris and Whiteway, 2011) and they were important passages for sediments transportation and energy exchange from the shelf to the deep water (Inman et al., 1976; Shepard, 1979; Hickey et al., 1986; Xu et al., 2002; Puig et al., 2003; Canals et al., 2006; Allen and Durrieu De Madron, 2009; Vangriesheim et al., 2009; Pierau et al., 2011). As the important sedimentary processes in canyons, mass movements and their consequences are not only the main factors of the formation of canyons (Shepard, 1981; Krast
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