猪苗代湖盆の起源と地史的変遷  [in Japanese] Origin and geohistory of the Inawashiro Lake Basin, Northeast Honshu, Japan  [in Japanese]

The Inawashiro Lake Basin is the largest lake basin in the Ohu Range, a back-bone in Northeast Honshu, Japan. The late Quaternary stratigraphy in and around the basin was synthesized from available age data obtained by botanical biostratigraphy, magnetostratigraphy, tephro-chronology and isotopic geochronology. The late Quaternary strata were divided into six zones which are distinguished by characteristics of sedimentary facies, thickness, stratigraphic relations and microbiofacies. The formation of the Inawashiro Lake Basin began with the rapid subsidence of a restricted area of the Ohu Range in the middle of the Last Glacial Age, followed by the opening of a narrow, graben-like basin. The basin was rapidly filled with freshwater which had a miximum depth of more than 100 meters and which spread over a wide area. Local uplift and the decline of water level began at about 35,000 years ago, local uplift continuing to be distinctive at about 20,000 years ago. During the latest period of the Last Glacial Age (about 10,000 years ago), local uplift associated with faulting, was most intense. The sediments, which consist of coarse grained matter, increased in quantity during the latest period of the Last Glacial Age and the early half of the Holocene.