Near bottom acoustic detection of canyon Mousse layers in the South China Sea

In cruises of the R/V Tansuo Yihao 12, in order to measure the reflection properties of deepsea surface sediment in the South China Sea,a reflection survey of near bottom surface sediments was carried out via a highfrequency sub-bottom profiler(110 kHz) mounted on the Shenhai Yongshi manned deep-submergence vehicle in the continental slope canyon of Qiongdongnan basin in the northern South China Sea with 2 m operating height and 1578 m diving depth.Sediment profile images showed that there existed five layers in 2 meters sediment below the canyon surface,so-called Mousse layers.The average reflection strength of Mousse water-sediment surface was-11.86 dB with standard deviation 2.51 dB.The average particle size in situ samples is 7.2 μm and the reflection coefficient of water-sediment surface,as well as the particles size,showed the Mousse surface was muddy sediment.Mousse layers located in the corner of continental slope canyon and the sediment in Mousse layers mostly came from current transport.Sediments from current transport in different periods settled down to forming the typical Mousse layers in the special geographical environment.We first obtain the high resolution profile images of Mousse layers and it help the research of multi-layers in the surface sediment and its acoustics properties.Meanwhile,for a large amount of sediment transport and gather into the Mousse layers,it has important research value for marine sedimentary history.