渤海海域新近系长期被认为属于冲积河流相沉积, 然而近年勘探成果表明, 渤海海域渤中凹陷、黄河口凹陷新近系广泛存在浅水湖泊沉积, 其中还发现了一种优质储集体———浅水三角洲砂体。笔者从古生物组合、泥岩特征、岩电特征、砂岩百分含量、砂岩粒度特征、沉积构造等方面证实了渤海新近纪存在浅水湖泊沉积。在河流入浅湖处则发育浅水三角洲, 可以从沉积层序、沉积微相类型等方面加以识别。浅水三角洲不同于经典的Gilbert 型三角洲, 有其自身的特点, 表现为垂向上相序不连续; 骨架砂体为分流河道砂体; 河口坝厚度较薄; 前缘相带十分宽广; 砂体具条带方向性; 三角洲形态表现为鸟足状等。

The sedimentary facies of Neogene in Bohai Sea area used to be considered as fluvial facies over a long time. Results of exploration in recent two years indicate that shallow lake is widely developed in the Neogene in Bozhong Sag and Huanghekou Sag in Bohai Sea area, in which a kind of excellent reservoir is also found—shallow water deltaic sand bodies. It is proved that the shallow lake exists in the Neogene in Bohai Sea area by the evidence of paleontological assemblages, characteristics of mudstone, litho-electric relationship, sand percentage, sand grain size, sedimentary structure. Shallow water delta is developed in the river mouth around the shallow lake which can be identified with sedimentary sequence and types of sedimentary facies. Being different from the classical Gilbert delta, shallow water delta is with thinner mouth bar and broadly spread sheet sands, and displays that the facies sequence is discontinuous in vertical direction, and the matrix sand bodies are distributary channel sand bodies. The type of the shallow water delta is fluvial-dominated delta.