baselap

onlap

terminations

A base-discordant relation in which initially inclined strata terminate downdip against an initially horizontal or inclined surface. (Mitchum, AAPG Memoir 26)

References
Mitchum Jr., R.M., 1977. Seismic stratigraphy and global changes of sea level. Part 11: glossary of terms used in seismic stratigraphy. In: Payton, C.E. (Ed.), Seismic Stratigraphy––Applications to Hydrocarbon Exploration, vol. 26. A.A.P.G. Memoir, pp. 205–212.