摘要
通过分析时间序列的卫片资料、4m高的露头剖面的沉积学和元素地球化学特征,研究钱塘江涌潮河段的滩槽冲淤变化规律、涌潮沉积特征和沉积层序.涌潮河段河道宽浅,受径流与潮流相互作用强烈,冲淤频繁且剧烈,滩槽演替存在约20a的周期,与流域年代际洪、枯期转变有关.在滩槽叠置的垂向层序中,底部为河槽、低潮滩相的厚层块状砂质沉积,发育各种变形沉积构造,为典型的涌潮沉积;顶部为高潮滩相的潮汐韵律沉积,发育典型的潮汐成因的双黏土层、大小潮周期;二者之间的中潮滩相呈渐变过渡.C-M图和概率累计曲线可较好地区分涌潮沉积与潮成砂、泥质沉积.涌潮沉积层Si/Al、Zr/Al、Ti/Al等元素比值较高,而潮汐韵律层Fe/Al、Mn/Al等元素比值较高,这与它们的赋存方式和水动力分异有关.Si、Zr和Ti主要见于石英和重矿物中,因此在强水动力沉积层中富集;而Fe、Mn易被黏土矿物吸附,在水动力较弱的中高潮滩富集.
Sedimentary features of tidal-bore deposits, evolution and resultant sedimentary sequence of main channel and tidal flat in the Qiantang Estuary are studied in detail by analyses of time-series satellite photos, and sedimentological and geochemi- cal characters of a 4 m high crop. The wide and shallow channel at the bore-affected reach shifts rapidly under intense interac- tion of tidal flow and river runoff. There is channel evolution cycle of 20 years linked to the decadal alterations of dry and wet periods in the catchment. On the vertical facies association of tidal channel-flat system, the lower section is a typical tidal-bore deposit at the main channel and the lower tidal flat, characterized by thick massive sandy beds with well developed soft- sediment deformation structures. The upper section is tidal rhythmite at the higher tidal flat, typical of mud couplets and spring-neap tidal cycles of tidal origin. The middle tidal-flat facies bears both sedimentary features of tidal-bore deposits and tidal rhythmite. C-M diagram and probability cumulative curve are useful to differentiate tidal-bore deposits from tidal sandy/ muddy deposits. There is a general trend of higher ratios of Si/A1, Zr/A1 and Ti/A1 in tidal-bore deposits, and Fe/A1 and Mn/ A1 in tidal rhythmites, which is mainly related to elemental behavior and selected sorting of hydrodynamic. Elements of Si, Zr and Ti majorly present in quartz and heavy minerals are therefore abundant in the higher energy depositional environment, while Fe, Mn elements which can be easily adsorbed by clay minerals are consequently enriched in the lower energy sedimentary environment.
出处
《地球科学（中国地质大学学报）》
EI
CAS
CSCD
北大核心
2014年第3期261-270,共10页
Earth Science-Journal of China University of Geosciences
基金
国家自然科学基金(Nos.41076016
41276045)
中国地质调查局海保工程专项(No.GZH201100203)
中央高校基本科研业务费专项资金
关键词
钱塘江
涌潮沉积
沉积物
粒度分析
XRF岩心无损探测
地球化学
Qiantang River
tidal-bore deposit
sediments
grain-size analysis
XRF nondestructive core scanning
geochemistry.
