里下河地区全新世自然环境变迁

Holocene environmental changes in Lixiahe area

在区域地质调查项目进行过程中,以几个典型地质剖面和钻孔为基础,讨论了里下河区域全新世地层的分布规律,研究了地貌分布特征;探讨了全新世古植被、古气候与古环境变迁以及历史时期自然环境变化特征。里下河地区全新世自然环境变迁经历了4个重要的阶段:(1)10～7.5 kaBP,以湖沼发育为主,海水曾经影响到本区;(2)7.5～4.0kaBP,海水入侵本区,自然环境以潮滩、滨浅海、潟湖等为主,最大海侵甚至可到达运河以西地区,但里下河仍然有部分地区未被海水淹没;(3)4.0 kaBP～1128 AD,海水全面后退,岸线在范公堤一线曾做长时间停留,形成西冈贝壳砂堤,断续分布,海水时常影响西部地区;(4)1128 AD以来,由于黄河南泛夺淮入海,改变了里下河地区的地表水系,苏北滨海平原迅速向海推进,此后里下河地区远离海水的影响。

During the performance of the regional geological survey project, the authors, based on several typical geological profiles and drill holes, discussed the distribution regularity of Holocene strata and studied the distribution characteristics of landform in Lixiahe area. palaeoenvironmental variations in the area since 10 ka BP Then the vegetation change and palaeoclimatic and were analyzed and investigated. According to the results obtained, the natural environment changes in Holocene in Lixiahe area went through four stages： （1） From 10 to 7.5 ka BP, lakes and swamps were widely distributed, and some parts of the area were affected by the sea water. （2） From 7.5 to 4.0 ka BP, a transgression occurred in this area, and the natural environment was mainly composed of tidal flat, shallow marine foreshore and lagoons. The greatest transgression could reach the area west of the Great Canal, but a part of the area was not influenced by this transgression. （3） From 4.0 ka BP to 1128 AD, the regression occurred, the coastline stayed for a long time along the Fangong embankment, and the shell bar of Xigang was formed. Consequently, the west part of Lixiahe area was often impacted by the sea water. （4） From 1128 AD, because the Yellow River captured the Huaihe area, the surface water system in Lixiahe area changed, and the shoreline in the area withdrew continuously eastwards. Since then, the area has not been impacted by the sea water again.