The Middle Miocene Kotambetsu Formation consisting of turbidite and related coarse clastic sediments, attains to 2,000 meters in thickness. Conglomerates in this formation are channel-fill deposits with normal or inverse type graded-bedding and clast fabrics. The clast fabrics are characterized by inclining orientation of the long axes to the bedding plane. Analysis of the sedimentary structures suggests that the coarse clastic sediments of the Kotambetsu Formation were transported by the sediment gravity flows of turbidity currents
