长江三角洲南翼第四纪沉积层序及其与古环境演变的耦合

为研究长江三角洲南翼第四纪地层划分及其与古环境演变的耦合关系,对长江三角洲南翼的第四系BZK02孔(孔深322. 1 m,取芯率大于96%),进行沉积物粒度、孢粉和微体古生物分析,结合岩性地层讨论了上新世以来钻孔揭示的孢粉组合、古环境演化、沉积层序和古气候特征。结果表明,研究区上新世以来经历了多次环境变化,孢粉类型鉴定133种,有孔虫鉴定17属29种,介形类鉴定7属8种。钻孔自下而上揭示岩性第四纪沉积地层依次为上新统嘉兴组一段(299. 8～322. 0 m)、早更新统嘉兴组(160～299. 8 m)、中更新统前港组(87. 3～160. 0 m)、晚更新统东浦组(72. 0～87. 3 m)、晚更新统宁波组(18. 6～72. 0 m)、全新统镇海组(0～18. 6 m)。古环境演化主要表现为上新世以残积坡、河流沉积为主,气候温冷偏湿;早更新世以河流相、河湖相沉积为主,气候经历温暖湿润-寒冷干燥变化的2个旋回;中更新世早期为河流-滨海相沉积,气候温暖湿润,晚期为河湖相沉积为主,气候温凉干燥;晚更新世以河湖、潮坪、河口沉积环境为主,气候经历温暖湿润-温暖偏干-温暖偏湿-寒冷干燥变化;全新世以浅海相、河湖相、湖沼相沉积环境,气候特征早期为干冷,晚期温暖偏干。

Quaternary sedimentary sequence of the southern Yangtze River Delta and its coupling with paleoenvironmental evolution

The sediment granularity, sporopollen and micropaleontology analysis of quaternary BZK02 bore (depth: 322.1 m, core-taking rate > 96%) of the south wing of Yangtze River delta has been carried out in this paper. It discusses the sporopollen assemblage, sedimentary environment evolution, sedimentary facies and paleoclimate characteristics revealed by bore since the Pliocene, and studies the quaternary stratigraphic division and paleoenvironment. The results showed that since the Pliocene, 133 species of sporopollen, 29 species of foraminifera, 7 genera and 8 species of foraminifera had been identified. Bore reveals that the lithologic quaternary strata are in turn the first member of Jiaxing formation (299.8-322.0m), the Jiaxing formation of early Pleistocene (160-299.8 m) and the Qiangang formation of middle Pleistocene (87.3-160.0m). The late Pleistocene Dongpu formation (72.0-87.3m), the late Pleistocene Ningbo formation (18.6-72.0 m) and the new Pleistocene Zhenhai formation (0-18.6 m). The evolution of paleoenvironment is mainly represented by residual slope, fluvial deposition and warm, cold and wet climate. In the early Pleistocene, fluvial facies and lacustrine facies were the main deposits, and the climate experienced two cycles of warm, humid, cold and dry changes. In the early middle Pleistocene, river-shore marine facies was deposited, the climate was warm and humid, the late period was dominated by fluvial and lacustrine facies, and the climate was warm, cool and dry. The late Pleistocene was dominated by river and lake, tidal flat and estuary sedimentary environment. The climate experienced warm and humid, warm and dry, warm and wet, cold and dry. The sedimentary environment of the Holocene is shallow sea facies, river and lake facies, lake and marsh facies, and the climate is dry and cold in the early stage and warm and dry in the late period.