越後平野の地盤環境 Ground Environment of the Echigo Plain, Niigata, Japan
1. As a result of analyzing many records of drilling in the Echigo Plain, the late Quaternary deposits overlying the burried terrace gravels can be subdivided into three formations: the Nishikanbara Formation, the Shirone Formation, and the Kurotori Formation, in ascending order.<br>2. The Shirone Formation is lithologically subdivided into lower, middle, and upper members. The middle unit consists mainly of silt and clay under marine environments. The upper unit consists of two major lithofacies: sand dune deposits along the coast and lagoon deposits of silt in the inland area. The former was formed by the invasion of warmer current into the Japan Sea 7, 000-8, 000yrs BP.<br>3. From the viewpoint of subsurface geology of the late Quaternary deposits, the Echigo Plain can be subdivided into several types of ground. The ground types are the most important evidence of environmental interactions between nature and human agencies and ground movement, such as earthquake disasters and land subsidence causing groundwater withdrawal.
第四紀研究 35(3), 259-270, 1996-07-31
Japan Association for Quaternary Research