Sedimentary characteristics and main controlling factors of coastal shallow sea in the Pearl River Mouth Basin

Neogene Zhujiang Formation in Zhusan Depression of Pearl River Estuary Basin is an important oil-bearing series, but it lacks the coastal shallow sea environment of Zhujiang Formation in Qionghai Bulge The systematic study of sedimentary characteristics restricts the further exploration in this area. With the guidance of sedimentology and the full use of core, drilling, logging and seismic data, the sedimentary characteristics, sedimentary evolution and controlling factors of the first member of the Miocene Zhujiang Formation in the study area of the eastern dip end of the Qionghai Bulge in the Pearl River Estuary Basin are studied. The results show that: ① The research area develops coastal and shallow sea sediments, which can be further divided into nearshore sandbar sediments, nearshore sandbar lateral margin sediments, nearshore mud sediments, offshore sandbar sediments, offshore sandbar lateral margin sediments, and shallow sea mud sediments. ② The central part of the research area is characterized by the development of nearshore sandbar deposits, nearshore sandbar lateral margin deposits, nearshore sandbar deposits, and nearshore sandbar lateral margin deposits. The sandbar lateral margin is surrounded by sediment around the sandbar periphery and is distributed in an NE-SW direction, parallel to the coastline. ③ From bottom to top, there is a transition from coastal sedimentation to shallow sea sedimentation, with continuous stacking of sand bodies in the southwest and northeast. The scale first decreases and then increases, and the thickness of mudstone increases. The middle sand body is thin, and the edges are thick. ④ The main controlling factors include paleogeomorphology, sea level rise and fall, provenance, wave and current action, etc.The paleogeomorphology controls the sedimentary environment, the relative sea level controls the type of facies belt, the provenance supply controls the size of the sand bar, and the wave and current control the shape of the sand body.