Because the relations among post-Devonian, pre-Morrowan units (Woodford, Sycamore, Caney, Godddard, and Springer) in southern Oklahoma apparently are conformable, previous reports on this complex area have attributed any interruption of the normal succession of these strata to faulting. In the Madill-Aylesworth area of Marshall and Bryan Counties, Oklahoma, the writers found a systematic pattern at the base of the Goddard Formation such as would be formed by deep erosion of a pre-Springeran anticline. Thick sections of Goddard are found in off-structure positions and in a belt presumed to occupy a deep valley along the axis of the old anticline. Detailed cross sections and reconstructions to an Early Pennsylvanian datum indicate the presence of an axial valley more than 2 500 feet deep (cut largely in Simpson and Arbuckle) between strike ridges formed by the limbs of the anticline. Confirmation of this interpretation is seen in the localization of sandstone accumulations over presumed topographic highs on the buried erosion surface. There may be a relation between the postulated erosional episode and the boulder beds of the Johns Valley Shale (Ouachita province).