Reconstructing paleohydrological conditions using pore water in low-permeability lake bottom sediment cores from Lake Kasumigaura during a Holocene

Abstract

In order to reconstruct paleohydrological conditions, whole-core drilling samples of low-permeability clay from Holocene lakebed sediment in Lake Kasumigaura in Japan were taken at Sites K-1 and K-2. By assessing the water quality of the extracted pore water and the diatomic fossils from the cores, paleohydrologic condition was investigated. The results of these investigations revealed that the paleo-brackish water component remained in the pore water. Pore water is composed of the mixing by three end-member components: paleo-sea water, surface water, and regional groundwater. But the ratios of residual paleo-brackish water differed between Sites K-1 and K-2. Site K-1, which is close to the lakefront, was affected by local groundwater as well as surface water, while Site K-2, some way distant from the lakefront, was unaffected by the regional groundwater. Brackish water from the period of sedimentation remained in the sediment column at Site K-2.