The stratigraphy of the lower-middle Miocene Kuma Group of Shikoku, southwestern Japan, was re-examined on the basis of geological field observations of the previously defined Shimosakabatoge Formation and the Tomishige Formation. The redefined Kuma Group consists of, in ascending stratigraphic order, the Furuiwaya Formation, composed mainly of clasts of Sambagawa metamorphic rocks, and the Myojin Formation, mainly sandstone and granite clasts. The lithofacies of the Shimosakabatoge Formation and its depositional age, as deduced from its clasts and the ages of igneous rocks that intrude the formation , suggest it is part of the Furuiwaya Formation. The previously proposed stratigraphy of the Kuma Group, in which the Tomishige Formation was placed at the top of the group, is questionable. The relationships between the Kuma Group and the lower Eocene Hiwadatoge Formation is revealed as an unconformity.

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