Numerous elongated mounds and channels were found at the top of the middle Miocene strata using 2D/3D seismic data in the Liwan Sag of Zhujiang River Mouth Basin (ZRMB) and the Beijiao Sag of Qiongdongnan Basin (QDNB). They occur at intervals and are rarely revealed by drilling wells in the deepwater areas. Origins of the mounds and channels are controversial and poorly understood. Based on an integrated analysis of the seismic attribute, palaeotectonics and palaeogeography, and drilling well encountering a mound, research results show that these mounds are dominantly distributed on the depression centres and/or slopes of the Liwan and Beijiao sags and developed in a bathyal sedimentary environment. In the Liwan and Beijiao sags, the mounds between channels (sub) parallel to one another are 1.0–1.5 km and 1.5–2.0 km wide, 150–300 m and 150–200 m high, and extend straightly from west to east for 5–15 km and 8–20 km, respectively. Mounds and channels in the Liwan Sag are parallel with the regional slope. Mounds and channels in the Beijiao Sag, however, are at a small angle to the regional slope. According to internal geometry, texture and external morphology of mounds, the mounds in Beijiao Sag are divided into weak amplitude parallel reflections (mound type I), blank or chaotic reflections (mound type II), and internal mounded reflections (mound type III). The mounds in Liwan Sag, however, have the sole type, i.e., mound type I. Mound type I originates from the incision of bottom currents and/or gravity flows. Mound type II results from gravity-driven sediments such as turbidite. Mound type III is a result of deposition and incision of bottom currents simultaneously. The channels with high amplitude between mounds in the Beijiao and Liwan sags are a result of gravity-flow sediments and it is suggested they are filled by sandstone. Whereas channels with low-mediate amplitudes are filled by bottom-current sediments only in the Beijiao Sag, where they are dominantly composed of mudstone. This study provides new insights into the origins of the mounds and channels worldwide.

利用2D / 3D地震数据，在珠江口盆地荔湾凹陷和琼东南盆地北郊凹陷中中新世地层顶部发现了许多细长的丘陵和河道。它们每隔一段时间发生一次，很少在深水区的钻井中被发现。土墩和沟渠的起源是有争议的，人们对此知之甚少。在对地震属性，古构造和古地理以及遇到丘陵的钻探井进行综合分析的基础上，研究结果表明，这些丘陵主要分布在荔湾凹陷和北the凹陷的凹陷中心和/或斜坡上，并发育于海相沉积岩中。环境。在荔湾凹陷和北郊凹陷之间，彼此平行的河道（子）之间的土丘宽1.0–1.5 km和1.5–2.0 km，高度为150–300 m和150–200 m，分别从西向东直线延伸5–15 km和8–20 km。荔湾凹陷的丘陵和河道与区域斜坡平行。但是，北jia凹陷的丘陵和河道与区域斜坡成小角度。根据丘的内部几何形状，质地和外部形态，将北郊凹陷的丘分为弱振幅平行反射（I型丘），空白或混沌反射（II型丘）和内部丘状反射（III型丘）。但是，荔湾凹陷的丘具有唯一的类型，即I型丘。I型丘起源于底部水流和/或重力流的切口。II型土墩是由重力驱动的沉积物（例如浊石）形成的。Ⅲ型丘是同时沉积和切割底部电流的结果。北郊凹陷和荔湾凹陷凹陷之间的高振幅通道是重力流沉积的结果，建议它们被砂岩填充。而中振幅低的河道仅在北jia凹陷以底流沉积物填充，那里主要由泥岩组成。这项研究为世界各地的土丘和沟渠的起源提供了新的见解。