The characteristics and genesis of bottom cyclic steps in the Lingshui Sag of Qiongdongnan Basin

Cyclic steps, as a kind of bedforms on the deep sea bottom, are one of the hot research spots in deep sea geology nowadays. Based on the 285 km² of 3D seismic data collected from the Qiongdongnan Basin, the characteristics of cyclic steps, such as the wavelength, wave height, length of lee side, length of steep side, angle of lee side and angle of steep side, as well as their forming mechanisms are carefully analyzed in this paper. The study area is located on the upper slope (2°～14°), with a NE-SW channel of 6.5 km in width and 35 m in depth. Cyclic steps are developed on both inner and outer sides of the channel, with wavy patterns on profile. Wavelength (20～160 m) increases, while wave height (4～10 m) decreases with depth, the length of the leeward side (20～140 m) is longer than that of the windward (10～40 m), the leeward side is gentle (0.05°～0.06°), but windward side steep (0.1°～0.35°). It is suggested that most of the cyclic steps be formed by the deposition of a continuous and stable turbidity current.