Topset beds overlie foreset beds in a prograding delta. As the delta builds into open water, the stream extends the channel to the edge of the delta, and as a result, coarser material is deposited.
Images
Section through a lake delta Leet, L. D., S. Judson, and M. E. Kauffman.
Physical Geology.
Prentice-Hall, Inc., Englewoods Cliff, New Jersey, 1982.
