Abstract
The Plio-Pleistocene Kobiwako Group is a typical fluvio-lacustrine formation located at Lake Biwa, Japan. However, the stratigraphy of the lowermost part of this group contained inaccuracies. In this study, 33 tephra beds were examined to correct the stratigraphy and to investigate possible correlations among these beds and with other widespread tephras. As a result, six correlated tephra beds corrected the lowermost part of the group. A subsequent reassessment of the stratigraphy indicates that this group was formed at ca. 4.4 Ma in the eastern part of the area, and slightly later in the western part, due to constraints imposed by the terrain during this period.
