Currently, Palo Duro Canyon State Park is visited by approximately 300,000 visitors each year and is one of the State’s more popular recreational and scenic areas. REGIONAL SETTING Palo Duro Canyon State Park is located in the Panhandle of Texas (fig. 5) approximately 13 miles east of Canyon on State Highway 217 (_see_ fig. 7). It is about 12 miles south and 8 miles east of Amarillo via Ranch Road 1541 which intersects State Highway 217. The park includes more than 15,000 acres of Palo Duro Canyon, a complexly dissected area which spreads into Randall, Armstrong, and Briscoe counties. More specifically, the Palo Duro area is situated on the Llano Estacado or High Plains area which comprises approximately 20,000 square miles of Texas and New Mexico (_see_ fig. 5). Generally speaking, the Llano Estacado is a high isolated plateau or broad mesa, rising above the surrounding rolling plains in a nearly flat, island-like mass. On the west, southwest, and south, the Llano Estacado is bounded by the valley of the Pecos River, while its eastern escarpment is drained by the headwaters of the Red, Brazos, and Colorado Rivers. The rim of Palo Duro Canyon is formed by the Eastern Caprock Escarpment. Caprock is the term used to describe a massive layer of calcareous rock which supports the High Plains surface (_see_ p. 26). Because it is more resistant to forces of erosion than the softer, underlying more or less horizontal strata, the caprock forms an abrupt, precipitous escarpment at the edge of the High Plains. With the exception of the resistant caprock, however, the surficial deposits on the High Plains are for the most part unconsolidated sediments. The Llano Estacado is essentially devoid of native trees and is characterized by a sparse, but uniform, covering of grasses. The surface rocks are of Tertiary and Quaternary age (_see_ geologic time scale, fig. 6) and have a general easterly to southeasterly slope of about 9½ feet per mile. In the vicinity of Palo Duro Canyon, rocks of Late Cenozoic age are directly underlain by Permian and Triassic formations. These Permian and Triassic rocks, which are discussed elsewhere in this publication, are not normally exposed except in deeply eroded areas such as the canyon. [Illustration: Fig. 5. Generalized geologic map of the Texas Panhandle showing location of Palo Duro Canyon.] _Showing:_ Q & T Pleistocene and Pliocene undifferentiated Trdo Dockum Group (Triassic) P Permian undifferentiated THE GEOLOGIC STORY THE CANYON’S ROCKS AND MINERALS