Holocene environmental changes in Lixiahe area

Abstract：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. Then the vegetation change and palaeoclimatic and palaeoenvironmental variations in the area since 10 ka BP 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.