Geology of the Canadian River Valley

View from Fritch Fortress of the Canadian Breaks on a sunny day with blue skies.
View of the Canadian Breaks from Fritch Fortress

NPS Photo

Lake Meredith National Recreation Area and Alibates Flint Quarries National Monument are located in the Texas Panhandle along the rugged Canadian River Breaks. Millions of years of erosion have carved a series of canyons, mesas, and draws through a landscape of relatively flat plains. The geology in this area tells a fascinating story of almost 300 million years.
 
Permian Redbeds with green grasses and plants. The skies are blue.
Exposed Permian Red beds at Harbor Bay

NPS Photo

Permian Period:

The exposed geology of Lake Meredith and Alibates dates back almost 300 million years during the Permian period. During this time, the Earth underwent numerous changes in climate, which produced several different rock and mineral deposits. The red and white rock layers (formations) were deposited approximately 260 million years ago during the Permian Period. During this period, the Texas Panhandle was located near the equator and was part of the supercontintent Pangaea.

These sandstones, siltstones and mudstones, along with interbedded layers of gypsum and dolomite, are known as Permian red beds for their age and predominate red to burnt orange colors. These unique red beds were deposited near the sea that extended up from the south. Massive amounts of salt and other evaporite minerals were also included in these sediments. The Permian reds beds in Lake Meredith National Recreation Area consists of three different formations, identified as the Whitehorse Sandstone, Cloud Chief Gypsum, and Quartermaster Formation. These Red beds are colored by small amounts of iron oxides and clay minerals. The sandstones, siltstones and mudstones erode easily and expose the beautiful red rounded hills.

 
Permian Redbeds with green grasses and plants. The skies are blue.
Permian red beds exposed near Alibates

NPS Photo

Red Beds

In colder periods, polar ice caps grew larger and the receding water moved this area above sea-level. Rivers and streams dominated the region and meandered across the Texas Panhandle. These water features lost energy and deposited hundreds of feet of shale, sandstone, and mudstone.

The oldest rocks found on the surface in the Panhandle of Texas are the Permian red beds and can be found throughout both parks. These rocks occupy a considerable part of the Great Plains from southern Kansas across Oklahoma and Texas as far as New Mexico and Arizona, and outcrop along the eastern flank of the Rocky Mountains as far north as the Black Hills of South Dakota.

These “Beds” aquired their red coloration from the metallic minerals in the rocks which have rusted. These rocks are relatively soft and can erode one grain at a time from rain and flash flooding. Similar to making a cake, the first or oldest layers are found on the bottom, with younger layers above them. This oldest layer of geologic cake is found at the base and sides of the Canadian River Breaks.

 
Dolomite boulders on a mesa overlooking the lake
Large pieces of dolomite rock on a mesa near Lake Meredith

NPS Photo

Dolomite

Our next layer of geological cake revealed warming temperatures around the Earth during the late Permian Age, 260 million years ago. The warming temperatures melted ice in the Polar Regions, causing the oceans to rise and placed this area below sea-level. This transition can be observed in the thinner layer of Alibates Dolomite, a gray colored rock found on the mesa tops throughout both parks.

Dolomite is formed from the organic material (plankton, shelled animals, algae, corals) in a shallow sea. This sea stretched from the Arctic Ocean near Alaska, covering the interior of Canada and the United States before connecting to the Pacific Ocean in Mexico.

Organisms that created the dolomite were preserved as fossils within the rock. Due to its hardness, the dolomite resisted erosion. The dolomite acted as a “caprock” and slowed the erosion of the softer red beds, resulting in the rugged mesas around Lake Meredith and Alibates Flint Quarries. When the underlying rock eventually erodes, the dolomite fractures into numerous white boulders found on the sides of mesas.

 
Gypsum near Plum Creek with Permian red beds below and grass growing on top
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 from on the Alibates Flint Quarries tour.
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
Ogallala formation near Cedar Canyon

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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.

 
Several flint pieces showing the  many colors of Alibats flint:  grey, blue, dark red, and white.
The many colors of Alibates Flint

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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 on a sunny day with blue skies.
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.

Last updated: May 28, 2020

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Fritch, TX 79036

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