Geology of the Canadian River Valley

View of the Canadian Breaks from Fritch Fortress

NPS Photo

Lake Meredith is located along the rugged Canadian River Breaks where years of erosion has carved canyons and mesas through the valley.

 

Exposed Permian Red Beds at Harbor Bay

NPS Photo

Permian Period:

The exposed geology of Lake Meredith dates back almost 300 million years during the Permian period when the Earth underwent numerous changes in climate, which produced several different rock and mineral deposits. The red and white rock layers were deposited approximately 260 million years ago during the Permian Period.

The Permian Red Beds consist of three different formations: the Whitehorse Sandstone, Cloud Chief Gypsum, and Quartermaster Formation. The Red Beds get their color from small amounts of iron oxides and clay minerals. The sandstones, siltstones, and mudstones eroded and exposed red hills.

 

Permian Red Beds exposed near Alibates

NPS Photo

Permian Red Beds

The oldest rocks throughout Lake Meredith are the Permian Red Beds. These geological features occupy the Great Plains from Kansas, Oklahoma, Texas, New Mexico, and Arizona. Outcroppings can be found along the eastern flank of the Rocky Mountains as far north as the Black Hills of South Dakota.

The red beds acquired their red coloration from the metallic minerals in the rusted rocks. These rocks are relatively soft and can erode one grain at a time from rain and flash flooding. Like making a cake, the first or oldest layers are on the bottom, with younger layers above them. The oldest layer is at the base and sides of the Canadian River Breaks.

 

Large pieces of dolomite rock near Lake Meredith

NPS Photo

Dolomite

A sea once stretched from the Arctic Ocean near Alaska, covering the interior of Canada and the United States before connecting to the Pacific Ocean in Mexico. The earth began to warm during the late Permian Age, 260 million years ago, warming temperatures that melted ice in the Polar region. When the oceans began to rise, the Texas Panhandle region fell below sea-level. This change is visible in the thinner layer of Dolomite, a gray-colored rock found on the mesa tops at Lake Meredith.

Dolomite formed from organic material such as plankton, shelled animals, algae, and corals. Organisms that created this rock became preserved as fossils within the rock. Due to its hardness, Dolomite resisted erosion. The Dolomite acted as a “caprock” and kept the softer red beds from dissolving, resulting in the rugged mesas around Lake Meredith. When the underlying rock eventually eroded, Dolomite fractured into the large white boulders around the lake.

 

Gypsum near Upper Plum Creek

NPS Photo

Gypsum

Sea-levels fluctuated as the climate changed many times throughout the Permian Period. When sea-levels dropped during colder periods, saltwater was trapped in low lying basins. As water evaporated in the basin, salt and organic material were left behind. Over time, this material formed beds of gypsum within the Permian red beds. Gypsum outcrops can be found at Dolomite Point and Plum Creek.

Today, when water flows over these gypsum layers, salt dissolves from the rock and is carried with the flowing water. If you have ever wondered why the Canadian River has a salty taste, it is due to Texas and New Mexico gypsum beds. When these gypsum beds dissolve in water, the rocks above can collapse into new voids, creating chimneys and depressions on the surface. A chimney can be located near Dolomite Point at Lake Meredith National Recreation Area.

 

Fossilized algae located on the Alibates Flint Quarries Trail

NPS Photo

Fossils and Petrified Wood

Fossils are a fantastic resource for geologists to discover what conditions were millions of years ago. Within the dolomite, thin layers of fossilized algae can be observed. Algae needs sunlight to carry out photosynthesis for survival. Geologists have assumed the saltwater, where the dolomite formed, must have been shallow because the algae needed sunlight to survive. Another geological clue is present in the fossilized coral polyps found in shallow waters.

Petrified wood can be found along the Canadian River in the Southwest section of Lake Meredith National Recreation Area. This ancient wood is found in Triassic rocks. Geologists have been able to link this wood to petrified wood from the Chinle Formation of Petrified Forest National Park in Arizona.

 

Missing History

Rocks from the end of the Permian Period until about 12 million years ago are not found in most areas of Lake Meredith and Alibates Flint Quarries. At many rocky sites across America, a 550 million-year-old rock sits on top of rock that has existed as long as 3 billion years. There is nothing in between and it seems time periods have been wiped from Earth. This mystery is called the Great Unconformity. Some geologists and researchers believe a massive cataclysmic event happened in Earth's history. Rocks in our parks were deposited during the Permian period, however were later removed by erosion and the geologic history was erased. The geological record for that time interval is missing and still remains a mystery to this day. To find rocks from the Triassic Period, travel to the Southwest section of Lake Meredith. Rocks from the Ogallala formation can be found near Cedar Canyon.

 

Ogallala formation near Cedar Canyon

NPS Photo

Pliocene Epoch:
Ogallala Formation

Some of the youngest rocks found in both parks is the Ogallala Formation. This formation is composed of rounded river rocks and sediments ranging from sand-sized to hand-sized. The Ogallala Formation originated from the Rocky Mountains of Colorado and New Mexico. This formation covered portions of the Great Plains, extending from central Texas to southern South Dakota. These rocks filled in valleys and covered mesas. In some areas, outside of the park, this formation became over 500 feet thick.

 

The many colors of Alibates Flint

NPS Photo

Alibates Flint

Alibates flint is found on the tops of mesas and is multi-colored. This special flint is known as agatized dolomite, or chert. The minerals in the dolomite have been replaced with quartz crystals from silica-rich water. The quartz crystals are small and can't be seen with a microscope. These crystals create the steel-like hardness of Alibates flint. The variety of colors in the flint is due to the trace elements and minerals found in the original dolomite. The silica-rich water in the dolomite can turn fossils into Alibates flint. When cracks or voids in the dolomite developed, the quartz crystals became larger. These larger crystals make poor quality flint for stone tools. Indigenous people discarded the “garbage” and used the best quality stones for their tools.

There are three primary theories of the source of the silica-rich water. The first theory is an eruption of the Yellowstone super-volcano around 675,000 years ago provided silica in ash. A three-foot bed of Yellowstone ash can be found in several locations around Lake Meredith. When rain fell on the ash, some of the ash dissolved into a silica-rich solution. A second theory is a silica rich material was brought here during the Ogallala Formation. A third theory is Alibates Flint formed the same time as the original dolomite. In each case, Alibates flint filled the cracks and completely replaced portions of the dolomite. This geological process is complex and would require perfect conditions to form the flint. Alibates flint formed along a small section of the Canadian River Breaks in a very specific area.

 

Canadian River flowing along Mullinaw Trail

NPS Photo

Quaternary – Present

Around 2.6 million years ago, the last Ice Age began and brought high-moisture to the area, providing more energy to local rivers. Instead of the rivers meandering and dropping sediments, they carved through the rocks forming canyons. The Canadian River has carved out more than 200 feet of rock creating the Canadian River Breaks. Numerous side canyons and mesas (breaks) were carved from the underlying Permian rock as high-volumes of water cut its way through the main canyon and river valley.

The geology of the Canadian River is fascinating and also beautiful. The north central part of the Panhandle of Texas is traversed by the Canadian River, which rises in the mountains of New Mexico. The river runs over a sandy bed varying in width from a half mile to more than a mile. The Canadian River is constantly shifting,excavating sand in one place and depositing it in another.