My initial "Oklahoma Blog" centered on the eastern one-third of Oklahoma, home of deciduous trees, Mississippian and Pennsylvanian rocks, coal mines, a coastal plain, large lakes, the Ouachita and Ozark Mountains, and the lead-zinc mines. In this Blog I move further west where the middle third of the state is dominated by exposures of late Pennsylvanian and Permian rocks, many of which are red in color. The Panhandle region has exposures of dinosaur-containing Mesozoic rocks along with a Tertiary cover and a few basalt flows. Interrupting this logical sequence of rocks are two interesting “mountain” regions—the Arbuckle Mountains south of Oklahoma City and the Wichita Mountains in the southwest near Lawton---subjects for my next Blog.
Geologic map of Oklahoma (from Oklahoma Geological Survey). Note the light blue streak (Permian) trending north-south through the state.
Physiographic regions of Oklahoma (courtesy Oklahoma Geological Survey). A the Arbuckle Mountains, W the Wichita Mountains, RB, the Permian redbeds, HP, the High Plains. Compare with map above.
A more detailed province map of central Oklahoma (courtesy of Oklahoma Geological Survey).
To better understand the geology and related landforms of Oklahoma, readers should keep in mind above maps.
The sandstone cuestas (Spanish for cliffs) region has gently dipping, to the west, sandstone layers protecting underlying, slope-forming shale layers. The sandstone of the province is late Pennsylvanian in age and was formed as flowing rivers carried sand and other sediments into deltas and estuaries of an ocean. These sandstone hills are quite scenic with a somewhat distinct flora and fauna and extend into Kansas as the Chautauqua Hills. The dipping beds of the cuestas are associated with the large Ozark dome to the east. I have collected some nice tree-fern fossils in the northern reaches of the province but mostly I just visited the area for the scenic beauty and camping, noting the old-growth forests of post oak and blackjack oak with blooming redbuds in the spring.
In Kansas, the Flint Hills are one of the major physiographic provinces in the state (trending north-south) and provide a unique landscape of native tallgrass prairie in a rocky and hilly terrain with major relief (at least for the plains states). In Oklahoma this province is known as the Limestone Hills (also The Osage or the Limestone Cuestas) and only extend about one-third of the way south. The Flint Hills/The Osage have marine early Permian rocks exposed and are quite fossiliferous. I have not collected in the Osage but have pulled hundreds/thousands of fossils from the Flint Hills in Kansas. For 20 plus years I took my undergraduate invertebrate paleontology class to the Flint Hills and students routinely collected over 100 different species from Permian rocks.
Cartoon showing configuration of continents at the end of the Paleozoic Era. Note how Africa and South America collided with North America and produced the Appalachian and Ouachita Mountains. Public Domain map.
The later Permian represents the end of the great Paleozoic seaway in the U.S. where marine waters that had covered parts/most of the continent since the late Precambrian were receding and drying. Plate activity had moved continents world-wide so that a single large continent, Pangaea, was formed and, except for continental margins, marine waters receded from the (current) North American continent. The later Permian represented the culmination of the Appalachian-Ouachita Orogen where Gondwana was attached/sutured to (current) North America. As the Permian seas were drying and receding the continent experienced restricted circulation waters and widespread deposition of halite and other “salts” and gypsum. In addition, wind and fluvial (stream) deposits containing grains of iron-rich minerals later “rusted” and created the color in the widespread redbeds trending north-south through the center of the state. As these beds extend north into Kansas they are known as the Red or Gyp Hills. I have examined the gypsum, anhydrite, and dolomite but found them rather uninteresting as mineral specimens and “left them in place.”
Now, I have to admit that my experience with the central Oklahoma redbeds essentially has been driving I-35 south to the Arbuckles or Texas Cretaceous! About the only prospecting accomplished has been to look for the barite roses. Of course, I suppose these concretions are the best-known mineral in this part of the state.
Barite rose collected near Norman from Permian Garber Formation. Width of left single rose ~3.5 cm.
There are several instances where minerals, mostly calcite, barite, and selenite gypsum, have formed clusters of crystal “roses” or sand crystals. In some case the roses are formed from “pure” minerals, with maybe an encrustation of sand grains, such as the selenite roses (Desert Roses) from St. David, Arizona (see Blog Feb. 4, 2013). However, in parts of northwestern Nebraska the selenite roses have been replaced by chalcedony.
In other cases the mineral solution carries along sand-size grains from the host rock as inclusions. London (2008), in an article in The Mineralogical Record, noted that “roses are mineral specimens, not rocks, because the shapes of rocks are indeterminate, whereas the shapes of minerals are determined by a combination of forms and habits derived from the interplay of crystal structure and environment of growth.” Each of the petals of the rose are individual barite crystals. The Oklahoma roses are due to the “intergrowth of crystals of barite…into a cluster of divergent blades… The rose-like concretions incorporated the iron-stained quartz sand grains and thus acquired the red color of the host Garber Sandstone” (Tulsa Geoscience Center, 2012). The Oklahoma Geological Survey (London, 2009) noted that “the best explanation for the roses is that deep basinal groundwater containing barium and reduced sulfur species (sulfide) migrated upward along fractures and porous layers into the Garbar Sandstone. Upon reaching an aerated region, the sulfur in the groundwater was then oxidized from sulfide to sulfate, leading to the precipitation of barite.”
Barite roses were designated as the official “State Rock” in 1968. It seems unfortunate that no mineralogist (or so it seems) told Governor Bartlett and the legislature that barite roses are minerals, as opposed to rocks. But, life goes on!
In Kansas, the red to orange barite roses are similar except they have been collected from the Cretaceous Kiowa Formation (see Blog July 23, 2013) derived from barium-rich solutions in the underlying Permian rocks.
Barite Rose collected many years ago near the hamlet of Bavaria, Kansas, in Cretaceous rocks. Width ~6 cm.
Calcite sand crystals are similar to the barite roses except the form takes on the shape of calcite crystals. I suppose the most famous locality for collecting these latter crystals has been Rattlesnake Butte in South Dakota (now off-limits see Blog Jan. 9, 2014) although some crystals have started to come from Wyoming (see Blog Dec. 17, 2011).
The further west one goes in Oklahoma, the less time I have spent in the region other than traveling south to the Wichita Mountains or to southwestern Texas where my son attended a university. A long time ago (my favorite phrase) I did take my students to: 1) Alabaster Caverns State Park; and 2) the Great Salt Plains. The cave is formed in Permian age massive gypsum and is a solution cavity. In my home state of Kansas a few miles to the north, there are large sinkholes such as Big Basin that are related to subsurface dissolution of similar age gypsum and halite. At one time, before collapse, a large natural bridge near Sun City was 35 feet wide, 55 feet long, and 12 feet above stream level. In addition, there are at least 117 gypsum caves in Barber County (Kansas Geological Survey, 2013).
The second place that we visited was the well-known Great Salt Plains near the Arkansas River to dig and collect selenite gypsum crystals--there is both a state park and a federal wildlife refuge and collecting is on the refuge and hours/days etc. are posted. Check ahead before you drive to collect!
|Big Basin is a sinkhole south of Dodge City, Kansas. Permian halite and gypsum beds in the subsurface have dissolved allowing the surficial Ogallala Formation to collapse.|
As it appears to me, the salt plains are essentially a playa with incoming fresh water, at times, but without an outlet. The original source of the salt and gypsum are beds in the underlying Permian rocks---as noted above, the great Paleozoic seaway was receding and drying and evaporation of brine waters left behind a number or different minerals. In the playa, the saline- and gypsum-infused groundwater is usually a few inches to to few feet below the surface. If the groundwater reaches the surface for a short duration but then evaporates a crust of halite forms while the gypsum crystals form below the surface. These selenite crystals at the salt plains are sort of a chocolate brown to orange color due to minor amounts of iron oxide used as a coloring agent. What makes the crystals unique is that they have included tiny sand grains and these grains are in the shape of a hourglass! Some crystals are covered by a thin layer of sand while others are quite transparent and the included sand grains are clearly observed. According to all references I could locate, this is the only locality in the world where this hourglass inclusion occurs. I don’t have the slightest idea “why” and it appears that other geologists are also “stumped” at the shape of the inclusions. At times the crystals are solitary, sometimes they are twinned (penetration twins common), and many times are in clusters. A gazillion of these crystals have been collected since they are “for sale” in virtually every rock/mineral shop, and in the rock and mineral shows. But they are also fun to collect if you don’t mind getting a little muddy during the process.
Penetrating twin hourglass selenite with sand inclusions. Length ~4.0 cm. In 2005 Oklahoma designated hourglass selenite as the official State Crystal.
Along the Cimarron and Canadian Rivers a hummocky terrain of both grass covered (stabilized) and active sand dunes is found. Most of the dune fields are on the north side of the rivers as a southern wind blows sand- and silt-size grains from the current alluvium and the older terrace deposits. These dune fields are similar to the large fields on the north side of the "big bend" of the Arkansas River.
I have always had an interest in history, and especially of western U.S history between ~1800 (Lewis and Clark) to ~ 1890 (Wounded Knee). This was a time of great conflict between representatives of the federal government and the Native Americans. Since I grew up in Ottawa County Kansas I have been particularly interested in the summer of 1868 when Southern Cheyennes and some of their allies raided settlements along the Saline and Solomon rivers (I grew up fishing in these rivers) killing several Caucasian settlers. Partially as a result of these raids General Phillip Sheridan, Commander of the U.S. Army’s Department of Missouri, an area of over a million square miles between the Rocky Mountains and the Mississippi, decided to conduct a winter campaign against the “insurgents.” In this manner he hoped to destroy food stores and horses along with people and housing at a time when the Native Americans were usually semi-permanently camped for the winter. In late 1868 Sheridan sent Lt. Colonel George A. Custer on a winter mission to subdue the Southern Cheyenne in western Oklahoma. At the ensuing battle or massacre (I will not get into that argument) on November 27, 1868, Custer destroyed the village of, and killed, the Cheyenne Peace Chief Black Kettle at an encampment along the Washita River in the redbed plains of far western Oklahoma. If readers ever get a chance, take a side trip and visit the national monument.
About where the Panhandle “hooks on to” the main segment of Oklahoma the Plains Border section of the Great Plains Physiographic Province ends and the large High Plains section begins. At one time in the late Tertiary the Ogallala Formation (Group) extended from the Rocky Mountains (the source for its sediments) eastward to the Missouri River and beyond. However, uplift to the west, and erosion by rivers on all sides, has essentially left the High Plains as an island, one that is capped by the Ogallala Formation. Today the High Plains extend from the Pine Ridge Escarpment along the South Dakota-Nebraska border south to the breaks at the Edwards Plateau in Texas. The western boundary is situated at the eroded breaks along the mountain front (such as the Colorado Piedmont). In the east the formation feathers and thins and the High Plains end. Most people know about the High Plains as being the source of the rapidly depleting Ogallala Aquifer. Exposures of the Ogallala Formation are common in the Panhandle.
A very unique geological area is located in the far western Panhandle of Oklahoma and much geology is preserved in Black Mesa State Park and the surrounding area along the Cimarron River where rocks from the Triassic to Recent are well-exposed. Triassic and Jurassic rocks in the Great Plains are relatively rare east of New Mexico and Colorado as are Cenozoic volcanics. However, a nice section of of the Triassic Dockum Group and the overlying Entrada and Morrison Formations of Jurassic age crop out in the area. Of additional interest are the remains of dinosaurs, both body fossils and ichnofossils (dinosaur tracks), from the Morrison. Most people with even a slight interest in natural history usually associate dinosaur fossils with places like Dinosaur National Monument and the Cleveland-Lloyd Quarry in Utah, and Canon City and Dinosaur Ridge in Colorado. However, an Oklahoma geologist by the name of Willis Stovall collected thousands of dinosaur bones from the Morrison around Black Mesa in the late 1930’s and early 1940’s. Today most of these fossils reside in the Sam Noble Oklahoma Museum of Natural History.
One particular dinosaur collected by Stovall from near Black Mesa was designated in 2000 as the State Fossil of Oklahoma. Saurophaganax maximus is a large theropod (meat-eating) maybe 50 feet in length and 17+ feet tall. It is most likely related to the allosaurs, the dominant theropods of the Morrison. A cast of a front claw is shown below.
Terminal phalanx or claw of Saurophaganax maximus (cast replica).
I once participated in a field trip to the area, mainly to examine the exposures of Cretaceous rocks. This section is very similar to the Cretaceous rocks in Kansas, the big difference being the aerially widespread exposures in Kansas compared to quite limited outcrops in Oklahoma. The oldest Cretaceous units are the Cheyenne Sandstone, a fluvial sandstone (mostly), overlain by the marine Kiowa Shale. The latter formation is quite interesting is that it contains a “southern” assemblage of invertebrate fossils. That is, marine waters invaded the continent from the south and the resulting rocks contain fossils normally associated with Gulf Coast Cretaceous rocks in Texas.
Marine waters then retreated south and the mostly non-marine (wind, stream, delta, estuary) Dakota Formation was deposited. Some units in the formation contain dinosaur tracks (similar to Dinosaur Ridge in Colorado).
The widespread Western Interior Seaway (WIS) is represented in Oklahoma by the Graneros and Greenhorn Formations (calcareous shales and limestones) overlying the Dakota. Invertebrate fossils such as coiled ammonites and straight-shelled baculites, along with inoceramid bivalves, are abundant. The WIS had marine waters transgressing from both the north and the south and the resulting northern fauna is completely different from fossils found in the Kiowa Shale.
Image of Mesa de Maya and Black Mesa, Colorado, New Mexico and Oklahoma. Image © Google Earth.
One of the best known structures in south-central/southwestern Colorado is the Raton Mesas starting near Trinidad and continuing eastward along the Colorado-New Mexico state line where thick (~800 feet) late Tertiary basalt flows (~3.5--9.0 Ma) cap the Poison Canyon Formation (Tertiary: Paleocene) and hold up the topography. The area, including Barella Mesa and Johnson Mesa, is often referred to as the Raton-Clayton Volcanic Field since the basalt extends as far east as Clayton, New Mexico. Near Trinidad, Fishers Peak (9626 feet) is the highest point in the United States east of I-25. Further east on the plains, “near” Tobe, and Walt’s Corner, Colorado, is an isolated, but related, mesa termed Mesa de Maya where 400-500 feet of basalt cover the Ogallala Formation at an elevation of around 6500 feet. The Mesa continues south and eastward as Black Mesa and actually extends into the Oklahoma Panhandle where at 4973 feet it is the highest point in Oklahoma. Suneson and Luza (1999) believe the age of the capping basalt flow at Black Mesa is ~5 Ma.
For additional reading see:
Publications, many available as PDF files, of the Oklahoma Geological Survey at: www.ogs.ou.edu.
Neil Suneson, 2010, Petrified Wood in Oklahoma: The Shale Shaker, v 60, no.6.
Common Fossils of Oklahoma, Sam Noble Museum: www.commonfossilsofoklahoma.snomnh.ou.edu
Oklahoma Crystal Collecting: www.brightok.net/~rockman/
Anonomous, 2013, Red Hills: Rocks and Minerals: Geofacts, Kansas Geological Survey.
London, D., 2008, The Barite Roses of Oklahoma: the Mineralogical Record.
London, D., 2009, The Barite Rose; State Rock of Oklahoma: Oklahoma Geological Survey.
Tulsa Geoscience Center, 2012, Barite Rose: Our State Rock: www.tulsageosciencecenter.org
Suneson, N. H. and K. V. Luza, 1999, A Field Trip Guide to the Geology of the Black Mesa State Park Area, Cimarron County, Oklahoma: Oklahoma Geological Survey Open-file Report OF4-99.