今天是2017年11月18日

钱塘江河口涌潮河段滩槽演替与沉积层序

DOI:10.3799/dqkx.2014.025

作者:涂俊彪,范代读,尚帅,陈玲玲,张悦

联系地址:同济大学海洋地质国家重点实验室,上海200092

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.犆犕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.

关键字: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

Evolution and Sedimentary Sequence of Tidal Channel-Flat System at Bore-Affected Reach of the Qiantang Estuary

Author:Tu Junbiao, Fan Daidu, Shang Shuai, Chen Lingling, Zhang Yue

Author Address:State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092,China

Abstract: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 analuses of time-series satellite photos,and sedimentological and geochemical characters of a 4m high crop.The wide and shallow channel at the bore-affected reach shifts rapidly under intense interaction of tidal flow and river runoff.There is channnel 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/Al,Zr/Al and Ti/Al in tidal-bore deposits,and Fe/Al and Mn/Al 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 absorbed by clay minerals are consequently enriched in the lower energy sedimentary environment.

Keyword:Qiantang River;tidal-bore deposite;sediments;grain-size analysis;XRF nondestructive core scanning;geochemistry

 

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作者简介:涂俊彪(1989-),男,硕士研究生,海洋地质学专业

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