Abstract: Taking the north sag in the Melut Basin in South Sudan as a case, researches were carried out based on regional geology, cores, logging data, grain sizes and seismic facies, which showed that the Paleogene Yabus Formation is a shallow-water delta facies developed in the weak rifting period of the northern sag. In?uenced by rifting activities and lake water level, the upper and lower members of the Yabus Formation have different sedimentary characteristics of shallow-water deltas. During the sedimentary period of the lower member, basin tectonic activities were weak, and the lake water was shallow, so distributary channels of the shallow-water delta plain were widely developed. During the sedimentary period of the upper member, rifting activities were intensive, and the lake water became deep, so there developed widely distributed shallow-water delta frontal sediments and local coastal shallow lake sediments. The underwater distributary channels, distributary mouth bars and other sand bodies may form structural-lithologic traps controlled by faults. The research results are of great signi?cance for continuously estimating the potential and ?nely exploring in the mature exploration areas in the northern sag of the Melut Basin.