America's Volcanic Past
|"Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits." -- Excerpt from: Brantley, 1994|
Volcanic Highlights and Features:
|[NOTE: This list is just a sample of various Oklahoma features or events and is by no means inclusive. All information presented here was gathered from other online websites and each excerpt is attributed back to the original source. Please use those sources in referencing any information on this webpage, and please visit those websites for more information on the Geology of Oklahoma.]|
The oldest known rocks in Oklahoma are Precambrian
granites and rhyolites formed
1.05 - 1.35 billion years ago; pre-existing rocks were altered,
destroyed, or consumed by
igneous or metamorphic activity.
Much later, during the early and middle parts of the Cambrian Period, a different
group of thick granites, rhyolites, gabbros, and basalts formed in
southwestern and south-central Oklahoma. Heat and fluids given off by the
Cambrian magmas changed an older group of
sedimentary rocks into metamorphic rocks.
Precambrian and Cambrian igneous rocks underlie all
of the State and are the floor or "basement" upon which younger rocks rest.
The Interior Plains:3
Ouachita-Ozark Interior Highlands:3
The ancient, eroded mountains of the Ouachita-Ozark Highlands stand surrounded by the nearly flat-lying sedimentary rocks and deposits of the Interior and Atlantic Plains provinces. Unlike the relatively young rocks that characterize neighboring provinces, the rocky outcrops that make up the core of the Ouachita-Ozark Highlands are Paleozoic age carbonate and other sedimentary rocks that were originally deposited on the sea floor. In the Ouachita Mountains these ancient marine rocks are now contorted by folds and faults. These rocks closely match deformed strata found today in the Marathon Mountains of Texas and the southern Appalachians -- strong evidence that the Ouachita-Ozark Highlands were once part of a mighty folded, uplifted mountain range that stretched from the Appalachians Highlands to the northeast through Texas to the southwest.
The Atlantic Plain:3
The Atlantic Plain is the flattest of the provinces. It stretches over 2,200 miles in length from Cape Cod to the Mexican border and southward another 1000 miles to the Yucatan Peninsula. The Atlantic plain slopes gently seaward from the inland highlands in a series of terraces. This gentle slope continues far into the Atlantic and Gulf of Mexico, forming the continental shelf. This region was born during the breakup of the supercontinent Pangea in the early Mesozoic Era.
Precambrian and Cambrian Igneous Activity
(greater than 500 million years ago):1
Cambrian, Ordovician, Silurian, and Devonian
Sedimentation (570 to 365 million years ago:1
Mississippian and Pennsylvanian Sedimentation
(365 to 290 million years ago):1
Pennsylvanian Mountain Building (330 to 290 million
Permian Red Beds and Evaporites (290 to 250 million
Triassic, Jurassic, and Cretaceous Sedimentation
(250 to 65 million years ago):1
Tertiary Period (65 to 1.65 million years ago):1
Quaternary Period (1.65 million years ago to recent):1
|Oklahoma's Volcanic Rocks|
Rocks of every geologic period crop out in Oklahoma. Nearly 99 percent of all outcropping rocks are of sedimentary origin: the remainder are 1) igneous rocks, mainly in the Wichita and Arbuckle Mountains; 2) metamorphic rocks in the eastern Arbuckle Mountains; 3) and mildly metamorphosed rocks in the core of the Ouachita Mountains. Most of the outcropping rocks in Oklahoma are of sedimentary origin, and they consist mainly of shale, sandstone, limestone, and gypsum. These sedimentary rocks typically are 2,000-10,000 feet thick in the northern shelf areas, and they increase sharply to 30,000-40,000 feet thick in the deep basins of the south. These sedimentary rocks contain most of the States' mineral resources, including petroleum, coal, water, and most of the nonfuel minerals. Sedimentary rocks rest upon a "basement" of igneous and metamorphic rocks that underlie all parts of the State.
Crushed-stone and building-stone resources include limestone, dolomite, granite, and rhyolite; other major construction resources are cement (made from limestone and shale) and the extensive sand and gravel deposits along modern and ancient riverways.
Oklahoma's Volcanic Ash Deposits:1
Other important industrial minerals in Oklahoma include clays and shales (to make brick and tile), and tripoli and volcanic ash (abrasive and/or absorbent materials).
Granite exposed in the Arbuckle Mountains in Johnston County is 1.4 billion years old. It is the oldest rock exposed between the southern Appalachians and the Rocky Mountains. The Arbuckle Mountains are an area of low to moderate hills in south-central Oklahoma. They contain a core of Precambrian granite and gneiss formed about 1,300 million years ago; in the western Arbuckles, Precambrian rocks are overlain by at least 5,000 feet of Cambrian rhyolites formed about 525 million years ago. Most of the Arbuckles consist of 15,000 feet of folded and faulted limestones, dolomites, sandstones, and shales deposited in shallow seas from Late Cambrian through Pennsylvanian time (515 - 290 million years ago). Folding and uplift of the mountains occurred during several mountain-building episodes in the Pennsylvanian Period.
MORE Arbuckle Mountains:1
The Arbuckle Mountains are an area of low to moderate hills in south-central Oklahoma. They contain a core of Precambrian granite and gneiss formed about 1,300 million years ago; in the western Arbuckles, Precambrian rocks are overlain by at least 5,000 feet of Cambrian rhyolites formed about 525 million years ago. Most of the Arbuckles consist of 15,000 feet of folded and faulted limestones, dolomites, sandstones, and shales deposited in shallow seas from Late Cambrian through Pennsylvanian time (515-290 million years ago). Folding and uplift of the mountains occurred during several mountain-building episodes in the Pennsylvanian Period. The complex mountain area probably was never more than several thousand feet above the surrounding plains and seaways. Relief in the area now ranges from 100 to 600 feet, and the highest elevation, about 1,415 feet, is in the West Timbered Hills, about 9 miles west-southwest of Davis. Although the relief in this mountain area is low, it is still impressive because it is six times greater than any other topographic feature between Oklahoma City and Dallas, Texas. Two significant features in the mountains are the deep road cuts on Interstate 35, and the "tombstone topography." The road cuts are as much as 156 feet deep and provide spectacular exposures of rock units that are of strong interest to geologists, partly because they yield great amounts of oil and gas and other mineral and water resources throughout the southwestern United States. "Tombstone topography," which looks like rows of tombstones in a field, results from differential weathering and erosion of alternating layers of hard and soft limestone that dip steeply into the ground. Important scenic sites in the Arbuckle Mountains are the Chickasaw National Recreation Area, Turner Falls, Price Falls, and the Arbuckle Wilderness Park. The Arbuckles contain the most diverse suite of mineral resources in Oklahoma: limestone, dolomite, glass sand, granite, sand and gravel, shale, cement, iron ore, lead, zinc, tar sands, and oil and gas; all these minerals are, or have been, produced commercially.
|Black Mesa State Park|
Black Mesa State Park:1
Black Mesa State Park in Cimarron County includes the highest point in Oklahoma at 4,973 feet above sea level. This point is on a basal lava flow that is less than 5 million years old. The lava flow came from a volcano located in southeastern Colorado.
Black Mesa, in the northwest corner of the Oklahoma Panhandle is the highest point in the State; it has an elevation of 4,973 feet. It is not a mountainous area, but is a plateau that rises about 600 feet above the adjacent Cimarron River and North Carrizo Creek. The Oklahoma portion of Black Mesa is 0.5 - 1 mile wide and 3 miles long; it is the erosional remnant of a finger-like basaltic lava flow extruded from a volcano in southeast Colorado. The lava flow occurred during late Tertiary (Pliocene) time, about 2.4 million years ago, and it occupied what was then a broad valley. Since Tertiary time, the local topography has been reversed; less-resistant sandstone and shale uplands that were adjacent to the basalt flow have been deeply incised by the Cimarron River system, whereas the resistant basalt, that once occupied a valley, now stands high above the surrounding terrain. Black Mesa and Black Mesa State Park are located 3 miles northwest of Kenton and about 30 miles northwest of Boise City.
|Quartz Mountain State Park|
Quartz Mountain State Park - Wichita Mountains:1
The southern part of Oklahoma tried to split (rift) away from the northern part of Oklahoma about 550 million years ago, but failed. Some of the evidence for this attempted split is found in the granites of southern Oklahoma, like those at Quartz Mountain State Park. The attempted rift resulted in a zone of weakness in the Earth's crust that was exploited by rising magma. Some of the magmas erupted at the surface; other magmas cooled beneath the surface forming the Wichita Mountains granites.
|Volcanic Ash Deposits|
Volcanic ash was once mined for abrasives in Beaver, Hughes, and Okfuskee Counties. Some of the ash was blown by the wind from Mount Mazama (in Oregon, where only Crater Lake now remains of the volcano) and from volcanoes in Yellowstone National Park, Wyoming, and northern New Mexico. The volcanoes erupted thousands to hundreds of thousands of years ago.
The Wichita Mountains in southwest Oklahoma consist mainly of granite, rhyolite, and other igneous rocks emplaced during the Cambrian Period of geologic time, about 525 million years ago. The southern part of Oklahoma tried to split (rift) away from the northern part of Oklahoma about 550 million years ago, but failed. Some of the evidence for this attempted split is found in the granites of southern Oklahoma, like those at Quartz Mountain State Park. The attempted rift resulted in a zone of weakness in the Earth's crust that was exploited by rising magma. Some of the magmas erupted at the surface; other magmas cooled beneath the surface forming the Wichita Mountains granites.
MORE Wichita Mountains:1
The Wichita Mountains in southwest Oklahoma consist mainly of granite, rhyolite, and other igneous rocks emplaced during the Cambrian Period of geologic time, about 525 million years ago. They are flanked, on the northeast, by thousands of feet of folded and steeply dipping marine limestones and other sedimentary rocks deposited during Late Cambrian and Ordovician time (515-425 million years ago). The mountains were created during the Pennsylvanian Period (330-290 million years ago) due to 20,000 feet of local uplift of the Earth's crust; the uplift was accompanied by weathering and erosion, so the mountains probably never towered more than 3,000-5,000 feet above the surrounding plains and seaways that had covered Oklahoma. At present, the relief (the difference in elevation between hilltops or mountain summits and the nearby lowlands or valleys) generally ranges from 400 to 1,100 feet, and the highest elevation is about 2,475 feet above sea level on an unnamed peak 4 miles east-southeast of Cooperton. Mt. Scott is the best-known peak; its summit (2,464 feet), which can be reached by car or bus, commands the most spectacular view of the Wichita Mountains. Much of the mountain area is in the Wichita Mountains National Wildlife Refuge and the Fort Sill Military Reservation; other significant sites in the Wichitas are Quartz Mountain State Park and Great Plains State Park. Important mineral resources produced in the area are granite, limestone, and sand and gravel. The mountains have been prospected (with only limited success) for gold, silver, copper, lead, zinc, aluminum, and iron ores; oil and gas have been produced from sedimentary rocks that surround the mountain area.
1)Oklahoma Geological Survey Website, 2001, 2002
2) Kenneth S. Johnson, Oklahoma Geological Survey, 1997, Mountains, Streams, and Lakes of Oklahoma: Information Series #1, February 1997
3) USGS/NPS Geology of the Parks Website, 2001
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