潮汐周期在潮坪沉积中的记录

选择平静天气泥质潮滩相对淤积期进行现场直接观测每个潮周期的沉积物特征。结果表明潮汐层偶的厚度变化与大小周期潮差旋回性变化密切相关。原始数据平滑后曲线更清晰地展示出大小潮周期，反映随机的非潮汐因素的影响可以通过地定的数学方法予以去除。现代潮坪观测表明潮汐沉积可以记录潮汐能量呈周期性变化的特性，因此，可通过研究保存较完整的潮汐韵律层的层偶组来提取古潮汐信息。但这种蕴含潮汐信息的韵律层可能只局限于一些基本不受风浪影响的沉积环境，而在长江三角洲开敞型泥质潮坪难以保存。

Tidal Cycles Recorded in Tidal- flat Deposits

Field observation on the mudflat is carried out to examine the relation of sedimentary features with tidal cycle during calm-weather when mudflat experiences continuous accumulation.The result shows that the variation of tidal-couplet thickness is closely related to the changes of tidal energy in neap-spring cycles.The smoothing curves of couplet-thickness variation distinctly display neap-spring tidal periodicities.Thus,random non-tidal factor effect can be filtered out by numerical methods.Modern tidal-flat observation shows that tidal deposits can continuously record the periodicities of tidal energy,so paleo-tidal cycles can be extracted from couplet-thickness variation of well-developed tidal rhythmites.However,tidal rhythmites potential for paleo-tidal cycle study are probably restricted to some wave-protected environments.Tidal flat surrounding the Changjiang Delta exposed to wave impact is not an ideal site for tidal-rhythmite preservation.