Figure 9. Well-log structural cross-section in the Jennings, Oklahoma, area, along the en echelon Whitetail fault trend (Figure 1), showing a narrow graben that is known to have developed during parts of Middle and Late Pennsylvanian. The Desmoinesian interval is 25% (100 feet) thicker than it is on the upthrown block on the west. Numbers along the faults give cumulative stratigraphic displacements, which decrease upward. Vertical exaggeration required to illustrate detail.