潮滩沉积环境与岩相对比研究

潮滩沉积是海陆交互作用的产物,形成于海岸坡度平缓、有丰富的细粒泥沙供应,以潮流动力为主的低能海岸环境,尤以河-海作用活跃的边缘海环境最为发育。潮滩沉积以粉砂为主,由于涨落潮流往复循环,潮滩具有动力、沉积、地貌与生物群体的分带现象。因海平面涨落与波浪参与的扰动筛选,导致潮滩沉积中的粗粒沉积物含量及微地貌形态的变化。这些因素反映于潮滩沉积相中具有下列特点:粉砂与粘土质交互叠置的页状层理;原始沉积层自下向上,粒径组成逐渐变细;下部的粉砂质层具有波痕、鱼刺状或丘状的交错层理、透镜体与扰动结构,或潮水沟堆积的镶嵌沙体;上部淤泥质层中具有草根、龟裂、虫管与钙质填充物、泥砾、泥块等。将现代潮滩沉积与南京钟山北麓下三叠统的黄马青组砂页岩,以及海口马村的下更新统湛江组粘土、粉砂岩进行对比,据泥沙粒径、矿物组合与含量,盐度,特别是薄互层理,虫管与钙质填充,泥裂块,波痕与交错层理等多项对比,均具有极好的相似性,表明该两组岩层为古潮滩沉积。

Study on Tidal Flat Environment and It's Sedimentary Facies Comparative

Sedimentary facies of tidal flat indicate that coastal environment is characterized by gentle coastal slope, predominant tidal dynamics, and with plenty of fine grain (silt) sediment supply. The comparative study of sedimentary facies has shown high level agreement between present tidal flat and ancient fine textural sedimentary rocks of the middle Triassic Huangmaqing Formation in Purple Mountain of Nanjing, and Zhanjiang Formation of early Pleistocene Period in Haikou. Besides the similarity in nature of grain size probability diagram, palosalinity and Brackish paleontology group among the three sedimentary series, the major character of the rocks is the Zonation features with typical structures as rhythmic thick thin laminal of silty and clayey sediments, with ripples, herring bone shaped or dune shaped cross beddings in the lower sandy sections, and polygon structures or desiccated clay cracks, clay pebbles, worm tubes or calcic concretions in the upper muddy sections. These series of sedimentary facies reflect a lower energy environment of land sea interaction along coastal shallow sea.