摘要
应用800多口钻孔及文献资料，讨论了中国沿海滦河扇三角洲、长江三角洲和珠江三角洲及钱塘江河口湾4个地区的下切河谷体系，这些皆为丰沙河流形成的河口三角洲。这些河口三角洲地区的下切河谷为长形或扇形，长数十至数百千米，宽数十千米，深40-90m。河口三角洲地区的下切河谷相序可分为4种类型，即FS-Ⅰ，FS-Ⅱ，FS-Ⅲ和FS-Ⅵ。可以将这4类相序自海向陆排成一个理想序列：FS-Ⅰ位于海岸线附近，FS-Ⅳ位于河口三角洲的顶部，显示海的影响逐渐减弱，陆相作用逐渐增强。下切河谷层序可分为海侵和海退序列。海侵序列的厚度占下切河谷层序的50％以上，体积占60％～70％。海侵序列是在海平面上升过程中，溯源堆积依次叠置而成的，其下部的河床相是在溯源堆积能到达、而涨潮流未能到达的下游河段产生的，往往不含海相微体化石和潮汐沉积构造。在海侵序列中未见区域上可对比的侵蚀面，表明冰后期海平面上升速率的变化、甚至小幅下降也未留下统一的侵蚀记录。下切河谷中的海退序列由河口湾充填及三角洲进积而成，其进程是各不相同的：长江古河口湾先被强潮河口湾相、后由三角洲相所充填，河口湾也经历了由强潮型向中潮型的转变；滦河扇三角洲和珠江三角洲，其古河口湾则被河流相和三角洲相所充填；钱塘江河口湾正被强潮河口湾相所充填。
Four incised-valley systems including the Luanhe fan-delta, the Changjiang delta, the Qiantangjiang estuary, and the Zhujiang delta in China, are discussed based on over 800 drilling-holes. These incised vallies are elongated or fan-shaped and with tens to hundreds of kilometers in length, tens of kilometers in width and 40 -90 m in depth. Four facies assemblages （FS-Ⅰ , FS-Ⅱ , FS-Ⅲ and FS-Ⅵ） are distinguished in the incised-valley sequences. An ideal incised-valley sequence may include all four types, with FS-I near the coastline region and FS-Ⅵ at the top of the deltas, which indicates a decreasing marine influence and an increasing terrestrial effect. The Late Quaternary incised-valley sequence inthese deltas and the estuary areas may be distinguished into transgressive and regressive succesions. The thickness of the transgressive succession make up more than 50% of the total thickness of the entire sequence and the transgressive sediment volume constitutes approximately 60% - 70% of the total. The transgressive succession of the incised-valley sequences was formed by retrogressive aggradation during sea level rising. The fluvial-channel facies in the transgressive succession, was formed in the river reach where the retrogressive aggradation extended but the flood tidal currents did not arrive. It usually contains no marine microfossils and tidal sedimentary structures. A regionally comparable erosional surface is not found in the transgressive succession of the incised-valley sequence, which means there is no erosional record resulting from the fluctuations of the postglacial sea level rising rate or even minor sea level fall. The regressive succession in the incised-valley sequences was developed as the estuary was filled and delta pro- graded. The Changjiang paleo-estuary was filled by strong tidal facies and then by deltaic facies, and the tidal regime in it was changed from macro-tidal to meso-tidal process. In the Luanhe fan-delta and the Zhujiang delta areas, the paleo-estuaries were fille
出处
《古地理学报》
CAS
CSCD
2008年第1期87-97,共11页
Journal of Palaeogeography：Chinese Edition
基金
国家自然科学基金(批准号:40276018)
国家海洋局908项目(批准号:908-02-02-05)资助的课题
关键词
中国沿海
晚第四纪
河口三角洲
下切河谷
沉积层序
coastal zone of China, Late Quaternary, estuary and delta, incised-valley, sedimentary sequence
