downlap

offlap

onlap

toplap

truncation

The terminations expressed by strata within depositional sequences is used to discriminate the location of the depositional setting of a systems tract and/or from one sequence geometry to another. Terms expressed in this diagram include truncation, toplap, offlap, onlap and downlap. The movies to the left capture how these various geometric relationships are connected to rates of sedimentaion and changing base level.