The Amagase duplex, discovered in the southeastern Tamba Belt within the Amagase Broken Formation, resembles a Foreland-Dipping Duplex (FDD). The outcrop surface of this duplex displays numerous traces of fluidized conglomerate and sandstone. The outcrops we encountered show duplex structures, multiple decollements, and other features such as jumps, underplating, and typical accretionary features in the area. The apparent morphology of this duplex is as follows: the roof and floor thrusts are connected to form a lateral Y-shaped structure at the western end. Two bag-shaped structures (Horse-Set) occupy the inner Y. The ramps show an apparent dip to the west at an angle of 20° to 30° toward the floor thrust at the confluence. The hanging wall of this duplex is significantly disturbed near the front edge, and both the roof thrust and hanging wall exhibit ramp anticlines with flat tops. Many traces of fluidization (or liquefaction) were observed between the horses at the front edge, and traces of fluidization among the horses on the front edge of Horse-Set A were formed by excess pore pressure caused by shear stress from the hanging wall. A detailed investigation into the duplex’s morphology has revealed features consistent with FDD, leading us to classify it as having this structure. During the survey, a duplex was found between the horses of Horse-Set B and its lower part, indicating a composite structure is present. Moreover, based on the Wulff net's reconstruction, the FDD is accreted to land meanderingly.
