Transgression of Oklahoma and Kansas began in Dresbachian (early Late Cambrian) time. Precambrian and Cambrian basement rocks were peneplaned prior to submergence, but scattered monadnocks remained. Greatest relief was in northeast Oklahoma where two large uplands consisted of hills with as much as 1,800 ft of relief. These produced an archipelago which gradually was reduced in size during each successive transgression; several peaks remained as islands through Roubidouxian (mid-Early Ordovician) time.

Dresbachian seas overlapped basement only in eastern Kansas, eastern Oklahoma, and along the axis of the southern Oklahoma geosyncline. Some sand deposition occurred in northwest Kansas. Late Dresbachian withdrawal of the sea was rapid and widespread.

Regression prevailed during Franconian time except in the geosyncline. Youngest Franconian carbonates in western Missouri indicate a return of transgressive conditions.

Deep Trempealeauan transgression inundated all but north-central Kansas and the highest Oklahoma islands. Emergence followed.

Ordovician seas overlapped all older strata, finally submerging the last remnants of the Precambrian basement.

Lines of pinchout, facies change, and overlap produced potential stratigraphic traps, best shown by "worm's eye" maps. Precise delineation depends on time-stratigraphic correlation which is most difficult to achieve in these sparsely fossiliferous, lithologically similar formations.