江苏弶港潮汐沉积

The Tidal Sedimentation in Jianggang, Jiangsu

港潮坪为开阔海型潮坪，正规半日潮在近岸浅滩平均潮差为３．１４ｍ。据平均高、低潮线可将潮汐沉积相划分为潮上带、潮间带（含高、中、低潮坪）、潮下带三个亚相带。沉积物的结构特征表现为自低潮坪向潮上带粒径变小和分选性总体变差的一般规律。各亚相带一般各具特怔性构造，并表现为有序演变的带状系列。潮坪内放射状大潮沟发育，并对沉积结构、构造、韵律产生干扰。底栖动物对潮汐沉积干扰较小。

The Jianggang tidal ,sedimentaryly belongs to openmarine tidal flat of which the average tidal is about 314m in the shoal near coast. According to the average maximum and minimum tidal line, the tidal sedimentary facies can be divided into subtidal zone, intertidal zone (including high, middle, low tidal flat) and supratidal zone. From low intertidal flat to supratidal zone, the average grain size of sediments is fining and badly sorted. On the subtidal zone, gently wavy alternating coarse silt or fine sand layers characterized by tidal bundles are well developed. On the low intertidal flat, the laminated sand and smallscale ripple crossbedding are found. The middle intertidal flat is thickly interlayered with fine sandcoarse grained silt beddings. The high intertidal flat is characterized by welldeveloped thininterlayerd sandy coarse siltcoarse silt beddings.Due to rapid sedimentation, the organisms have time to rework themselves before buried, the net rate of bioturbation is less than 10%. On supratidal zone, coarse silt and fine silt consist uneven wavy bedding penetrated by hadophilous plant stems and roats. The channels in Jianggang tidal flat are exceptionally developed. The lateral migrating rate of channels is about 120mm per year. Owing to rapid Shifting of channels, the sedimentary textures and structures paralleling the shoreling have been interfered in large areas.