CoachA reflection termination is the end of a reflection against another. Onlap: an initially horizontal reflection ends against a surface that rises more steeply, the younger beds lapping onto an older slope. Downlap: an inclined reflection ends down-dip against a gentler surface, as the toes of prograding beds rest on the floor of a basin. Toplap: inclined reflections end up-dip against an overlying surface, with little erosion, as the tops of prograding beds meet the level of the sea. Erosional truncation: reflections end up-dip against an overlying surface that cuts them, an unconformity.
