江苏建湖庆丰海相全新世剖面的古生态学研究与古环境恢复

PALEOECOLOGICAL STUDY AND PALEOENVIRONMENTAL RECONSTRUCTION OF THE HOLOCENE MARINE SECTION IN QINGFENG, JIANHU COUNTY, JIANGSU PROVINCE

对沉积物的后生改造及化石保存状况的研究表明,庆丰海相全新世剖面的宏体化石群落属原地或准原地埋藏,包括植物化石(炭化木)、动物遗迹化石(潜穴)和动物遗体化石(贝壳)基本可反映生活群落面貌。炭化木主要由灌木残体构成。动物潜穴多为垂直圆管,示间歇暴露环境。贝类可依生态类型分为四个组合:篮蛤-珠带础螺组合,为广生境的潮间带底栖游移类群;缢蛏-青蛤组合,为广生境喜污类群,底埋生活于潮间带;大连湾牡蛎-日本棱蛤组合,为狭生境喜洁类群,底表固着生活于潮间带中下部至潮下带上部;篮蚬-环棱螺组合,为淡水半咸水类群。这些组合构成了水动力较弱、化学介质非正常的潮间泻湖-海湾群落。依群落的纵向演替,可将环境演变进一步划分为五个阶段。即滨海泥沼阶段、泻湖阶段、海湾阶段、滨海低地阶段和淡化泻湖阶段。这五个阶段与本地区全新世以来的海面变化及环境变迁紧密相关。

Studies on fossil preservation and postdepositional change show that macrofossil communities on the Holocene marine section in Qingfeng, including plant remains (carbonized wood),an-imal traces (burrows) and remains (shells), are autochthonic or Para-autochthonic. They reflect basically the main features of the biocoenose. Carbonized wood is composed mainly of the remains of bushes. Burrows are always vertical and deep tubes, which indicates intermittent exposure. Shells can be distinguished into four assemblages according to their ecotypes: 1. Aloidissp. -Tympanotomus cingulata assemblage, the dominant assemblage here, composed of eurytopic, small body species with a intertidal crawling life;2. Sinonovacula constricta- Cyclina sinensis assemblage, composed of eurytopic, large body species with a intertidal buried, especially in foulmud, life ;3. Ostrea talienwhanensis - Libitina japonica assemblage, composed of stenotopic, clear-water species which attach in middle- lower intertidal or upper subtidal; 4. Corbicula -Bellamya assemblage, freshwater or brackish species. Communities formed by these assemblages indicate generally a lagoon-bay environment with relatively weak hydrodynamic and anomolous chemical medium. The process of environmental evolution can be fruther divided into five stages according to the vertical succession of the communities. These are coastal swamp stage, developing lagoon stage, bay stage, coastal lowland stage and desalinated lagoon stage, which are closely related to the Holocene regional sea level change and coastal environmental evolution.