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天津以东,宝坻、丰南县城向南直至海边的低洼平原,其沉积相表明全新世中期以来始终是个滨海湿地环境,分布有宽阔平坦的淤泥质海滩。它和滦河三角洲砂质平原共同构成渤海湾北岸的海岸带。 全新世以来,海平面逐渐上升,至全新世中期,大约距今6000多年海进曾到达最大范围,淹没海拔4米多的高程。嗣后,稳定海面逐渐退落。到距今2000年左右,早已成陆的滨海平原再次受海水入侵,使多处较大规模的高2.5—3米以上的战国至西汉文化遗存被海积物覆盖,或使3000年前的陆相草炭和粘土层被海岸沙堤(沙丘)超覆沉积。
The sedimentary facies of the low-lying plain south of Tianjin, Baodi, Fengnan county southward to the seafront indicates that since mid-Holocene it has always been a seashore wetland environment with broad and flat muddy beaches. It and the Luan River Delta sandy plains constitute the northern coast of the Bohai Bay coast. Since the Holocene, the sea level has gradually risen to the mid-Holocene, about 6000 years ago Haimai has reached the maximum range, submerged altitude of 4 meters above sea level. Subsequently, the steady sea gradually receded. Until about 2000 or so, the long-established coastal plain has again been invaded by seawater, causing many large-scale Warring States 2.5 to 3 meters above sea level to be covered by marine sediments or by land The facies of peat and clay were overburden by coastal sand embankments (sand dunes).