As noted above, all of the rocks which crop out in Palo Duro Canyon are
sedimentary in origin. They represent four different geological periods:
the Permian, Triassic, Tertiary, and Quaternary (fig. 12).
Although these rock formations differ considerably in composition and
age, they do not tell the whole geologic story of the area. Long spans
of geologic time are not represented by rock units because the region
was undergoing erosion or no sediments were being deposited during
certain portions of geologic time. Rocks that had formed during one
geologic period were removed by erosion during a later period. Thus,
segments of the geologic record were destroyed or never recorded. For
this reason, much of the geologic history of the Palo Duro area is
unrecorded and must be inferred from fragmentary evidence borrowed and
pieced together from adjacent areas. Even so, an interesting story can
be assembled from the rocks that remain in the canyon today.
In general, the following descriptions of the formations exposed in Palo
Duro Canyon State Park follow the procedure that most geologists use in
presenting the results of their geologic investigations. The more
distinctive characteristics of the rock units are described in order
that they may be more easily recognized, and the ways in which the rocks
were formed are also considered. With this background it is then
possible to review the geologic history recorded in the bedrock of the
canyon. A simplified geologic map is presented in figure 7; this shows
the distribution of the major rock types in the canyon. The reader will
find it helpful to refer to this map when reading the descriptions of
the various formations.