In Kansas and throughout the northern midcontinent area,
excepting parts of Oklahoma and Arkansas, definition of the
lower limit of Pennsylvanian rocks is one of the most evident in
the rock succession (Fig. 3). Not only are the types of
sedimentary rocks on opposite sides of the boundary very
dissimilar generally, but there is evidence of pre-Pennsylvanian
erosion of the underlying strata and varyingly prolonged break
in sedimentation. The basal Pennsylvanian rocks rest on
different parts of the Mississippian succession, from high in
the system down to the bottom-most beds, and at many places,
both at the outcrop in Missouri and in the subsurface of Kansas
and Nebraska, the Pennsylvanian overlaps on to pre-Mississippian
rocks. The oldest Pennsylvanian deposits in most of this
territory are clearly much younger than rocks classed as
belonging to the system elsewhere. Accordingly, there is no
problem in marking the base of Pennsylvanian strata in the
Kansas region. Figure 3. Diagrammatic east-west section of r