In addition, some of the Quartermaster [strata] have [ripple marks] on their surfaces. These features are common in certain [sedimentary rocks] and were formed when the surface of a bed of [sediment] was agitated by waves or currents. The size, shape, and cross section of the ripple marks can be used to tell whether the marks were produced by waves or currents. The ripple marks in the Quartermaster appear to have been formed by the action of waves on a shallow sea floor.
A number of interesting geologic features in the canyon have been formed in part in the Quartermaster [Formation]. These include the multi-hued Spanish Skirts ([fig. 26]), the Devil’s Slide ([fig. 35]), Capitol Peak ([fig. 32]), and Catarina Cave ([fig. 27]). The latter is a rather unusual cave in that it has developed in a large mass of landslide debris divided by projecting bedrock of the Spanish Skirts. The cave has been formed by suffosian, a process whereby water enters the landslide debris on the upper slopes and follows buried channels in the landslide removing [rock] debris as it passes through. The flood water exits at the base of the landslide by means of Catarina Cave. The plan of the cave closely resembles the drainage patterns of surface gullies.
Tecovas [Formation].—
[Rocks] of the Triassic System ([fig. 6]) are well represented in Palo Duro Canyon and consist of the Tecovas and Trujillo [Formations]. These formations are part of the Dockum Group of Late Triassic age.
Having a total thickness of about 200 feet, the Tecovas (which is named from exposures found on Tecovas Creek in Potter County, Texas) consists largely of multicolored [shales]. Also present are thin layers of soft [sandstone], which are disseminated throughout the shales, and a more prominent bed of white sandstone, which marks the middle of the [formation]. The Tecovas shales overlie the Quartermaster Formation, and the lower zone of lavender, gray, and white shales forms a relatively smooth slope that is easily distinguished from the steeper slopes of gullied red-and-white-banded shales beneath them ([fig. 12]).
Fig. 10. Chemical reactions in certain of the red Quartermaster [shales] have produced reduction halos ([p. 19]) which give the [rocks] a polka-dot appearance.
Fig. 11. This boulder, located near the foot of Triassic Peak along the Sad Monkey Railroad track, exhibits the cross-bedding typical of the Trujillo [sandstones].
But the contact zone between the Tecovas and Quartermaster [shales] involves more than a mere change in color. Here is one of the missing “chapters” in the geologic history of the canyon, for part of the Late [Permian] record and all of the record of Early and Middle Triassic time are missing from the geologic column. Such gaps in the column are represented by unconformities in the [rocks]. Here the [unconformity] is an ancient erosional surface between the Tecovas [Formation] of Late Triassic age and the Late Permian Quartermaster Formation, and there are many millions of years of earth history represented in this missing “chapter” in the geologic story of Palo Duro Canyon. During this vast span of time, thousands of feet of [sediments] were probably deposited, converted into rock, and then later removed by erosion.