九州四万十帯，古第三系日向層群のデュープレックス構造と赤・緑色珪質泥岩

The Paleogene Hyuga Group of the NE Miyakonojo and Aradani Areas in Kyushu consists of sandstone-dominated formation, mudstone-dominated formation, and chaotic formation. They are altemately repeated by originally low-angled thrusts, and probably form duplex structures. The duplexes of the Hyuga Group are in most cases hinterland-dipping duplex. The fundamental structure of the Paleogene Shimanto Terrane in Kyushu is characterized by low-angled nappe structures with stacked duplexes, in which duplexes lie one above the other, similarly to those of the Cretaceous Uchinohae Formation. Red and green siliceous mudstones of Middle Eocene age occur along major thrusts as thrust sheets of 40 to 80 m thick. The siliceous mudstones, which are considered to be hemipelagic sediments, were subducted, and formed thrust sheets during underplating. The siliceous mudstones were probably situated in the decollement horizons, but were not flowed as a lubricant layer.