Sedimentary facies of the Tetori Group in the Shiramine, Ishikawa Prefecture

The Mesozoic Tetori Group, exposed in the Shiramine area of Ishikawa Prefecture, is characterized by nonmarine deposits unconformably overlying the Hida Metamorphic Rocks. Sedimentological investigation of the upper part of the Akaiwa Formation (the upper part of the Tetori Group) recognized seven sedimentary facies (channel floor, sand bar, plane beds, crevasse splay, flood plain, vegetated swamp, and soil) and seven cycles; each of them generally appears fining upwards.
Stratigraphy of the upper part of the Akaiwa Formation shows a graded change from a gravely fluvial system (the lowest cycle) to a sandy meandering river system (the upper cycles). Nodular calcretes found from the soil facies indicate that the climate was once arid during sedimentation of the upper part of the Akaiwa Formation. However, it is inconsistent with well development of coal seams and carbonaceous mudstone.