The Holocene climatic optimum in Korea: Evidence from wetland records

• The Chollipo and Pyeongtaek areas changed simultaneously during the Holocene.
• The reasons for environmental change are hydrological factors.
• Sea level rise is relevant to environmental change in coastal areas.
• The discrepancy between Korean and Chinese sea levels needs further study.

Three wetland sediment sections from two different locations (core CL-4 in the Chollipo area, and trenches HS and HY in the Pyeongtaek area) in west-central Korea yield crucial information on the timing and spatial pattern of century-scale climatic changes and subsequent surficial responses during the Holocene. In the Chollipo area, a lake environment developed from 7360 to 5000 calibrated years before present (cal. yr BP), the deposition of organic materials increased from 5000 to 2600 cal. yr BP, and peatland have formed since 2600 cal. yr BP. In the Pyeongtaek area, fluvial sediment was deposited prior to about 7000 cal. yr BP. From 7000 cal. yr BP onward, thick peat sequences started to develop. These two patterns of surficial responses to climate change through the Holocene are different from one another. While this might be due to the dissimilarity in geomorphic conditions, the approximate simultaneity of the environmental changes in the two areas shows that they both can be correlated with major climatic changes. Two such areas that have undergone major changes indicate that the hydrological factors including precipitation and strength of water flow were most responsible for the landscape and geomorphic evolution. The upward trend in relative sea level also played a primary role for environmental change in the coastal areas.