Although plots of pressure versus depth are useful for understanding the hydrodynamics of ground-water systems, they can be difficult to interpret. Data plotted from a confined aquifer may reflect underpressuring because the aquifer is isolated from hydrostatically pressured aquifers (depth intercept is greater than zero) or because there is potential for downward flow within the aquifer (pressure-depth gradient is less than hydrostatic).

Pre-Pennsylvanian rocks in the Palo Duro Basin include (1) basal transgressive marine Cambrian(?) sandstones deposited over Precambrian basement, (2) overlying Lower Ordovician dolomites of the Ellenburger Group that formed when shallow seas covered much of the North American continent, and(3) Mississippian limestones and dolomites deposited when the area was inundated again after middle Paleozoic uplift and erosion. A generally similar stratigraphic sequence exists in the adjacent Dalhart and Hardeman Basins.