南海北部神狐陆坡限制型滑塌体特征及成因机理

Characteristic and Formation Mechanism of the Frontally Confined Landslide in Shenhu Slope,Northern South China Sea

滑塌体是深水沉积的重要组成部分,研究滑塌体沉积有助于揭示深水沉积过程。利用高精度多道地震资料,首次在南海北部神狐陆坡段发现了规模逾千平方千米的限制型滑塌体,它在顺坡滑塌时,未能超越下坡地层的围限,突然终止于下坡未变形地层中,因此陡冲斜坡两侧的地震相特征发生截然的变化。滑塌体整体呈楔形,内部呈杂乱反射,前端存在逆冲断层以及挤压褶皱。由于顺坡滑塌距离较短,因此与非限制型滑塌体相比,限制型滑塌体内部地层连续性较好。结合神狐滑塌体地震反射特征并通过与世界典型滑塌体的对比,可知滑塌体的厚度、地形坡度二者共同控制了神狐滑塌体的发育类型,前端地形突起对其发育没有影响。

Landslides constitute important aspects of deepwater sediment fill;and the study of the landslide does much help unveiling the deposition process in deepwater settings.Using the high resolution multichannel seismic profiles,the frontally confined landslide is firstly discovered in Shenhu slope of the Northern South China Sea,of which distribution area is over 1 000 km2.The landslide undergoes a restricted downslope translation and does not overrun the undeformed downslope strata,so the seismic facies features are definitely different in the two sides of the ramp.With the internally chaotic reflection,the landslide is externally wedge shaped and the impressive fold and thrust develop in the toe domain of the landslide.Comparing with the frontally emergent landslide,the continuity of the frontally confined landslide sediment is better for the shorter downslope transport distance.Combined with the seismic reflection features of the slide and the comparison among the Shenhu landslide and the worldwide landslides,the type of the landslide is determined by the thickness of the slide and the slope angle,but the positive landform-Yitong shoal has no effect on the Shenhu landslide＇s evolution.