| 钱塘江下切河谷充填及其层序地层学特征 |
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| 引用本文： | 张桂甲,李从先.钱塘江下切河谷充填及其层序地层学特征[J].海洋地质与第四纪地质,1995,15(4):57-68. |
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| 作者姓名： | 张桂甲 李从先 |
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| 作者单位： | 同济大学海洋地质系 |
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| 摘 要： | 钱塘江口是世界著名的强潮型河口湾。平面上呈典型的喇叭状，具明显的三分性：上部的正常河流段、中部的河口湾漏斗、下部的口门带。据沉积作用和沉积相组合，钱塘江河口湾的形成及其发育可以分为四个阶段：（１）末次冰期（２００００－１５０００ａＢ，Ｒ）──下切河谷形成；（２）冰后期早期海侵（１５０００－７５００ａＢ，Ｐ．）─－河口湾充填；（３）最大海侵（７５００－６０００ａＢ．Ｐ．）──海湾形成；（４）海面相对稳定期（６０００ａＢ．Ｐ．至今）──河口湾发育。其间形成了一套完整的海退－海侵进积旋回沉积层序。下切河谷底部的厚度异常的河床相砂砾层，从形成阶段上看，可以分为两个阶段，早期是河流下切的滞留沉积，晚期是基面抬升河流加积作用形成，它们的界限即为初次海泛面。加积作用形成的河床相砂砾层，有别于滞留沉积作用形成的河床相砂砾层，前者具加积副层序组合、向上变细的正粒序，且形成的地质年代较晚。
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| 关 键 词： | 钱塘江 河口湾 下切河谷体系 层序地层学 |
THE INFILLING OF THE INCISED QANTANG RIVER PALEOVALLEY AND ITS SEQUENCE STRATIGRAPHIC CHARACTERISTICS |
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| Zhang Guijia Li Congxian.THE INFILLING OF THE INCISED QANTANG RIVER PALEOVALLEY AND ITS SEQUENCE STRATIGRAPHIC CHARACTERISTICS[J].Marine Geology & Quaternary Geology,1995,15(4):57-68. |
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| Authors: | Zhang Guijia Li Congxian |
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| Abstract: | The Qiantang River Estuary is a world-famous tidal-dominated eatuary which canbe zoned into three sections:(1)upper normal river section,(2)midd1. estuarine funnel,and(3)lower estuarine mouth.The formation of the estuary can be divided into fourstages:(1)last glaciation(2000-15000a B.P.)formation of the incised paleovalley,(2)early postglacial transgression(15000-7500a B.P.)-infilling of the paleovalley,(3)maxi-mum transgression(7500-6000aB,P,)-formation of the bay, and(4) highstand period(6000a B,P,to present )-development of the estuary.Correspondingly,a regressive-transgressive progradational sedimentary sequence,including SB,LST, TST and HST,was formed in the incised paleovalley.The fluvial-channel gravelly sands of anomousthickness at the bottom of the valley are composed of early lag sediments deposited dur-ing river incision and later aggradational sediments resulting from the base-level risingand the boundary between the two is the initial flooding surface.The latter distinguishesitself from the former in its aggradational parasequence assem blage,up-fining sedimen-tary sequence and relatively later formation. |
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| Keywords: | Qiantang River Estuary incised paleovalley fluvial gravel sandinitial flooding surface |
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