By Natalie Bright
The Caprock, the surface across the Texas Panhandle, is a flat, treeless expanse resistive to erosion. Where rivers cross these Great Plains and spill over the edge to the lower elevations, erosion can create chasms. As is the case of the Prairie Dog Fork of the Red River, which created the geological formation of Palo Duro Canyon, located south of Amarillo. Over millions of years the river has eroded down, dropping the floor by 800 feet.
“It is a burning, seething cauldron, filled with dramatic light and color”.
I think artists find our Palo Duro Canyon so pleasing to paint because the layers are compliments of each other. Right next to the purple layers, is the complementing yellow shale. The Yellow shale is oxygen rich swamp deposits as opposed to the anoxic blue shale below. The off-white, or grey sandstone at the top of the Canyon is the Trujillo sandstone, or white sandstone of the Caprock.
The very top, is the white sandstone of the Ogallala, which is our major water aquifer. Here the Ogallala is exposed at the surface. The purple and grey gravels of the Sierra Grande uplift washed down to mix with the sand giving us our major fresh water aquifer for this area.
The grey or white bed layers are actually volcanic ash from the formation of Yellowstone National park that drifted to settle in our area. How do geologists know it is Yellowstone ash? Through testing of the chemical compound, every volcanic eruption has a particular signature and chemical make-up unique to that one particular incident.
Murky, blue shale was deposited in this environment. The inland sea evaporated, transitioning into the Triassic swamp mud. With rivers flowing through the area and cutting into the bright red Permian, the mixture of the Blue shale with the Permian red beds resulted in the purple shale layers seen just above the Permian-Triassic contact.
There is evidence of the depositional environment of a sea floor. This is not the massive ocean covering the earth at the time, but a small inland sea – hot, stagnate, evaporate left white gypsum in the sea bed resulting in the gypsum rich layers you can see in the Canyon walls. At the bottom of the Canyon, the dark red is the top of the Permian, and right above that is the Triassic.
Mankind brought their own color as evidenced by rock art, bedrock mortars, points, metal weapons, and other artifacts left behind. The Clovis and Folsom peoples hunted mammoth and giant bison about 12,000 years ago. The deep chasm, abundant wildlife and flowing river provided shelter and resources for the Apache, Comanche and Kiowa.
In 1876 Charles Goodnight drove 1,600 Longhorn cattle to the canyon, and formed the famous JA Ranch along with his English partner, John Adair. The ranch grew to 100,000 head of cattle and most of the canyon belonged to the JA. The state purchased the land in 1933 and opened the park in 1934. Containing 28,000 acres, Palo Duro Canyon is the second largest park in the state parks system.
Today Palo Duro Canyon State Park is a unique place to picnic, hike, and explore.
Resource: C.M. Bright, Geologist
Photo Credit: Natalie Bright