Ogallala formation

Ogallala Group or Formation (Miocene) at surface, covers 63 % of this area. Silt, sand, sandstone, gravel and conglomerate. Predominantly interfingered fine- to coarse grained, poorly sorted, arkosic, fluvial deposits of light-gray, light-olive-gray, and grayish-green calcareous silt and sand, and locally poorly consolidated conglomerate, sandstone, and siltstone.

2. Altitude of the base of the Ogallala formation. 3. Generalized geologic sections A-A' and B-B''. 4. Approximate saturated thickness of the Ogallala formation, 1958. 5. Approximate altitude of the water table, 1958. 6. Approximate depth to water in the Ogallala formation, 1958. 7. Approximate saturated thickness of the Ogallala formation priorThe Ogallala was deposited by coalescent, low-gradient, wet alluvial fans that headed in mountains to the west. Geometry and depositional facies of the Ogallala Formation in Texas north of the 33 rd parallel have been determined from outcrop studies and drillers' log descriptions. Averaging techniques compensated for the variability of drillers ...The Ogallala Aquifer is the largest aquifer in the United States and is a major aquifer of Texas underlying much of the High Plains region. The aquifer consists of sand, gravel, clay, and silt and has a maximum thickness of 800 feet. Freshwater saturated thickness averages 95 feet. Water to the north of the Canadian River is generally fresh ...Deposits of the Ogallala Formation lie to the north and cast of the buried ridge, while deposits of the ancestral Pecos River (variously 2. 09/18/2003 08:37 505-830-9528 FRAMATOME AW' MtAIO r&K- It .1 mapped as "Cenozoic Basin Iill, Gatufia Formation, or Ogallala Formation) lie to the south andThe Ogallala Formation is the principal geologic unit in the High Plains aquifer in eastern Colorado and New Mexico. The Ogallala generally consists of an unconsolidated and poorly sorted sequence of gravel, sand, silt, and clay. Moderately to well-cemented zones within the Ogallala are resistant to weathering and form ledges in outcrop areas.Expert Answer. Answer:- The elevation of the South Pla …. Previous 14 UNIVERSITY OF KANSAS PALEONTOLOGICAL CONTRIBUTIONS COLORADO PIEDMONT (South Platte Drainage) + HIGH PLAINS Pleistocene a Recent 6020 feet Cedar Point (near Limon) Ogallala Earliest Piocene fm. E е V a t i o Pawnee Ck. fm Miocene n White River fm. Oligocene White R. fm ...

Ogallala Aquifer, Texas By R. F. Brown andW. S. Keys Abstract Four recharge tests were conducted by injecting water from playa lakes through wells into the Ogallala Formation. Injection was by gravity flow and by pumping under pressure. At one site, 34-acre feet of water wasFour recharge tests were conducted by injecting water from playa lakes through wells into the Ogallala Formation. Injection was by gravity flow and by pumping under pressure. At one site, 34-acre feet of water was injected by gravity and produced a significant increase in yield of the well. At a second site, gravity injection of only 0.58 acre-foot caused a significant decrease in permeability ...You might have music files on a music CD that you would also like to have on an mp3 player. Or, you might have a collection of older CDs that you would like to convert into a more modern format. Either way, this process is easy.the Ogallala Formation of Miocene age and overlying hydraulically connected Quaternary deposits, if present. Northwestern Nebraska, south central South Dakota, and southeastern Wyoming: the fractured upper part of the Brule Formation or the Arikaree Group.the Ogallala Formation underlying irrigated cropland and (b) if agricultural land-use practices affect water quality. Results from Figure 2. Areal photograph of irrigated cropland overlying the Ogallala Formation, Central High Plains aquifer. the reconnaissance study will be used to determine whether a full-scale land-use study is warranted.Elsewhere the Niobrara is overlain disconformably by the Ogallala Formation (Miocene and Pliocene) at a contact that truncates the formation from west to east, or by unconsolidated Quaternary deposits. The main part of the Niobrara outcrop lies in northcentral and western Kansas, and underlies the eastern edge of the High Plains physiographic ...

The iconic PDF: a digital document file format developed by Adobe in the early 1990s. PDFs are very useful on their own, but sometimes it’s desirable to convert them into another type of document file. This is easy to do with the right soft...Oct 20, 2023 · Ogallala formation. Calcareous grit or soft limestone, sandy clay, and sand, with basal conglomerate at many places. Of late Tertiary (Pliocene?) age. Thickness 150 to 300 feet. Unconformably underlies EQUUS beds and unconformably overlies Arikaree formation. Extends from Kansas and Colorado far into Nebraska. The northern boundary of the Raton section is placed somewhat indefinitely at the northern limit of the area injected by igneous dikes. The eastern boundary of the Raton section is at the eastern margin of the lavas of Mesa de Maya and adjoining mesas, where lava-capped outliers of Ogallala Formation are separated from the Ogallala of the High Plains only by the canyon of Carrizo Creek.The hydraulic gradient in the Ogallala Formation is approximately 12 feet per mile across the county. Aquifer tests indicate an average permeability of about 900 gpd per square foot. With an assumed porosity of 30 percent, the average velocity of the ground water is calculated to be v = (900 x 12) / (395 x 30) = 0.9 foot per day, or

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Ogallala Formation in Denver Basin. Hanna Formation (Paleocene) at surface, covers 5 % of this area Brown and gray sandstone, shale, conglomerate, and coal; giant quartzite boulders near Medicine Bow Mountains.Aeolian processes, also spelled eolian, [1] pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets ). Winds may erode, transport, and deposit materials and are effective agents in regions with sparse vegetation, a lack of soil moisture and a large ...When it comes to job searching, having a great resume is key. A resume is your first impression to potential employers, and it’s important to make sure that you’re presenting yourself in the best possible light. One way to ensure that your ...A special concern of ts repoxt is detrna:6on of the local characteristics of the Ogallala formation and other shallow permeable strata, as expressed in ex geologic seting and the storage and Unsmission of water. Many citizens are concerned vwith te protection of the Ogallala aquiferThe Ogallala Formation is the only named rock unit of Neogene ("Tertiary") age recognized in Kansas. The unit was originally named by Darton (1899) from exposures in western Nebraska. Zeller (1968) placed the Ogallala Formation in the Pliocene Series/Epoch; however, more recent work suggests the Ogallala is mostly Miocene and earliest Pliocene ...

Skip to Main ContentMost of the Ogallala sits in these clay formation areas. In fact, the aquifer is almost stagnant. Water from one zone doesn't move to another zone. ... "The Ogallala is a mined aquifer, different areas have different capacities and life spans," Woomer said. "Our area is drawing water at a higher rate than it is recharging. It's not ...upper Tertiary Ogallala Formation (containing Ogallala aquifer) Cretaceous formations (containing Edwards-Trinity [Plateau] aquifer); Triassic Dockum Group (containing Dockum aquifer) Permian formations (containing Rustler aquifer, Capitan Reef Complex aquifer, and Roswell Basin aquifer system) Figure 1.Ogallala Group or Formation (Miocene) at surface, covers < 0.1 % of this area. Silt, sand, sandstone, gravel and conglomerate. Predominantly interfingered fine- to coarse grained, poorly sorted, arkosic, fluvial deposits of light-gray, light-olive-gray, and grayish-green calcareous silt and sand, and locally poorly consolidated conglomerate ...Formation of both the Gulf of Mexico and the Rocky Mountains is part of continuing global deformation. The Atlantic Ocean is widening as Europe and North America separate, while the Pacific Ocean basin is closing as the North American plate and Asia converge. ... Extensive stream-laid sand and gravel deposits, which contain the Ogallala aquifer ...The aquifer is formed by sand, gravel, clay, and silt, and has a maximum thickness of 800 feet, according to the Texas Water Development Board. Its freshwater- ...Niobrara Chalk was weathered and opalized in the Valentine phase of the Ogallala Formation. The Niobrara Formation / ˌnaɪ.əˈbrærə /, also called the Niobrara Chalk, is a geologic formation in North America that was deposited between 87 and 82 million years ago during the Coniacian, Santonian, and Campanian stages of the Late Cretaceous.An extensive saline plume (> 250 km2) within the regionally important unconfined aquifer in the Neogene Ogallala Formation overlies the Panhandle oil and gas field in the Southern High Plains ...

Ogallala Formation (Pliocene) at surface, covers 61 % of this area. ... Includes Ogallala and Laverne Formations of Pliocene age and younger deposits of Pleistocene age. Locally the units are tightly cemented by calcium carbonate; other places, they are very poorly consolidated and nearly free of cementing materials. Thickness ranges from 0 to ...

This aquifer was named the Ogallala aquifer after the Ogallala Sioux Indians, who once inhabited the region The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to …The upper Tertiary Ogallala Formation contains the Ogallala (High Plains) aquifer, which is the major source of water for agricultural and domestic use on the Southern High Plains of Texas and New Mexico. Locally, perched aquifers overlie the Ogallala aquifer. This study, based on outcrop and subsurface data, provides a regional stratigraphic ...However, its crown jewel is the Scotts Bluff National Monument, an 800-foot-high natural rock formation offering stunning North Platte River vistas, immersive country, and cityscapes, including the equally iconic Chimney Rock. ... Ogallala View of Front Street in Ogallala, Nebraska, via YULIYAPHOTO / Shutterstock.com.Ogallala Formation White River Fm Lower part Cgl Brule Fm Chadron Fm White River Group Precambrian rocks Lance Formation Fox Hills Sandstone Pierre Shale Belle Fourche Shale Greenhorn ... Formation Formation Fort Union Formation Formation Adobe Town Mbr Laney Member Green River Fm Cathedral Bluffs Tongue Green Battle Spring …Four recharge tests were conducted by injecting water from playa lakes through wells into the Ogallala Formation. Injection was by gravity flow and by pumping under pressure. At one site, 34-acre feet of water was injected by gravity and produced a significant increase in yield of the well. At a second site, gravity injection of only 0.58 acre-foot caused a significant decrease in permeability ...Ogallala formation often sits directly on top of consolidated sediments, which are more than 250 million years old. In Cimarron and western Texas counties, a younger formation of shale and sandstone called the Dockum group overlies the redbed. Other formations, including the Dakota Sandstone and Morrison Formation, also are found in the OklahomaThe Ogallala Formation varies both in depth and in water reserves per unit of surface area. In 1977, of the total 3.04 bil­ lion acre-feet available, 2.3 billion acre-feet (77 percent) were located in Nebraska, where the saturated depth ranged from less than 100 feet to 1200 feet. Approximately 8 percent wasThe Ogallala Formation ranges in thickness from a few meters to more than 90 m. The formation was deposited on an erosional surface exposing rocks of Cretaceous age and was itself eroded after deposition, partially accounting for the changes in thickness.

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Biggest by far, the Ogallala aquifer underlies most of western Kansas and makes up the bulk of the High Plains aquifer in all eight states. It consists mainly of the Ogallala Formation, a geologic unit that formed from sediment eroded off the uplifting Rocky Mountains.Four recharge tests were conducted by injecting water from playa lakes through wells into the Ogallala Formation. Injection was by gravity flow and by pumping under pressure. At one site, 34-acre feet of water was injected by gravity and produced a significant increase in yield of the well. At a second site, gravity injection of only 0.58 acre-foot caused a significant decrease in permeability ...In Nebraska, this and possibly some underlying beds are assigned to the Kimball Member of the Ogallala Formation by Condra and Reed (1959). The characteristic feature of the Ash Hollow Member is the mortar beds; grayish-orange-pink pebbly sand and silt firmly cemented by calcium carbonate or locally opal and forming many resistant ledges ...When you’re searching for a job, your resume is one of the most important tools you have to make a good impression. But with so many different resume formats available, it can be hard to know which one is right for you.Moss opal is found in the Ogallala Formation and contains inclusions of various iron minerals. The stone's inclusions resemble moss's small collection of branching tendrils. Some refer to moss opal as "dendritic opal" because the inclusions could be called dendrites. The most common iron mineral present in moss opal is manganese oxide.Courage, experimentation, voices needed to drive change The Ogallala Aquifer's future requires not just adapting to declining water levels, but the involvement of a wide range of participants comfortable with innovation who will help manage the situation and drive future changes. That was the message heard by more than 200 participants from across eight statesBase of Ogallala Formation: Top of Trinity Group : Top of Dockum Group : Base of Dockum Group : Comments: Points are locations where observations (such as surface and borehole geophysical data and drillers logs) were used to help develop hydrogeologic unit surfaces of the tops and bases of the gridded model. Data Source: Teeple and others, 2018.The Oklahoma Panhandle and adjacent areas in Texas, Kansas, Colorado, and New Mexico have prospered because of the development of supplies of fresh water and of oil and gas. The Ogallala and, in places, Cretaceous rocks produce fresh water for irrigation, public supply, and domestic and stock use through approximately 9,000 irrigation and public supply wells and a large but undetermined number ofWestern Trails. 144 miles / US 26 and State 92 from the Wyoming border to Ogallala. Pioneers would have come across the same towering formations and pine-shaded bluffs on this route as drivers encounter today. Get out of your “wagon” and explore: Storied sites, picturesque trails and sparkling lakes await your discovery.is located along a paleo-channel of the Ogallala formation (locally known as the Slaton Channel) approximately 48.3 km (30 miles) southeast of Lubbock, TX. In an attempt to beneficiate the 25.4-mm (1-in.) concrete aggregate product, a log washer was installed in the processing line to liberate and remove fines (clay) from the finished product.How Long Ago Was The Ogallala Aquifer Formed? Advertisements. The principal sediments and rocks of the aquifer range in age from 33 million years old to sediments being deposited today, but the majority is less than 12 million years old. Much of the aquifer is composed of the Ogallala Group or Formation. ….

The Ogallala Formation was named by Darton (1899) from a locality in southwestern Nebraska that he later (1920) referred to as Ogallala Station. Elias (1931, 1932, 1935, 1942) made detailed studies of the Ogallala in western Kansas and described fossil endocarps, nutlets, and anthoecia from the formation while Lugn (1938, 1939) studied the ...Ogallala Formation is composed of sediments eroded from the ancestral Rocky Mountains by streams and wind. The dominant mode of deposition was by braided streams that coalesced to form broad alluvial fans (Gutentag and others, 1984). The Ogallala Formation consists of semi-consolidated layers ofWhen you write academically, you will research sources for facts and data, which you will likely include in your writing. Using this information will require that you cite your sources. Your instructor may require Harvard referencing format...The Ogallala formation is characterized by the deposition of the substance of limestone and quartizite. View answer & additonal benefits from the subscription Subscribe. Related Answered Questions. Explore recently answered questions from the same subject. Q: The accompanying diagram is a cross-section of a hypothetical area. Place the lettered ...Ogallala Formation (Pliocene) at surface, covers 25 % of this area. CIMARRON- Generally semiconsolidated clay, silt, sand, gravel, and caliche 0 to 400 feet thick. BEAVER- Interbedded sand, siltstone, clay, gravel lenses, and thin limestone. Caliche common near surface but occurrence is not limited to the surface.In cooperation with the North Plains Groundwater Conservation District (NPGCD), the U.S. Geological Survey collected and analyzed water-quality samples at 30 groundwater monitor wells in the NPGCD in the Texas Panhandle. All of the wells were completed in the Ogallala Formation of the central High Plains aquifer. Samples from each well were collected during February-March 2012 and in March 2013.the Ogallala Formation of Miocene age and overlying hydraulically connected Quaternary deposits, if present. Northwestern Nebraska, south central South Dakota, and southeastern Wyoming: the fractured upper part of the Brule Formation or the Arikaree Group. Eastern Nebraska and south central Kansas: Quaternary depositsOgallala Formation (Pliocene to Miocene) at surface, covers 0.3 % of this area. Ogallala Formation. Doxey Formation or Doxey Shale (Late Permian) at surface, covers < 0.1 % of this area. WOODWARD- "Doxey Formation"- Red brown shale and siltstone, with greenish-gray calcareous siltstone at base. Exposed thickness is 30 feet, with top eroded.ally eastward drainage, on which the Ogallala Formation and equivalents was deposited. The Ogallala underlies the High Plains Surface, the highest and oldest geomorphic surface preserved in this region. It has been completely eroded along some parts of the western margin of the region (e.g., the Colorado Piedmont), but Ogallala formation, Jul 7, 2023 · Unconformably overlies Valentine Formation of Ogallala. Glass shards, from Swallow and Davis ashes in lower part of Ash Hollow Formation, yielded Ar/Ar ages from about 11.5 to 12.2 Ma (citing C.C. Swisher, III, 1992, Univ. California-Berkeley PhD dissert.). Fossils. , The Ogallala Formation of Miocene/Pliocene age is present over a large area of the Great Plains in the central US. The formation is composed of mostly clastic material eroded and transported ..., Ogallala Aquifer - The Ogallala Aquifer (oh-guh-LAH-luh) is a shallow water table aquifer surrounded by sand, silt, clay, and gravel located beneath the Great Plains …, The Ogallala, or High Plains, Aquifer is a porous body of complex sediments and sedimentary rock formations that conducts groundwater and yields significant quantities of water to wells and springs., The best known of the Plains aquifers is the Ogallala, which was named in the 1890s by N. H. Darton of the U.S. Geological Survey. Together with several smaller hydraulically connected formations that with it comprise the Great Plains Aquifer, the Ogallala covers some 177,000 square miles, across which the aquifer is draped like a blanket., The fossil seeds from the Ogallala formation (Pl. 8, 9; Fig. 4) may be divided into three major, stratigraphically significant groups: (1) seeds that occur in the Valentine member, represented in Kansas by a single species of grass, Stipidium commune; (2) a large assortment of grasses and other herbs characteristic of the Ash Hollow member ..., Ogallala Formation CIMARRON- Generally semiconsolidated clay, silt, sand, gravel, and caliche 0 to 400 feet thick. BEAVER- Interbedded sand, siltstone, clay, gravel lenses, and thin limestone. Caliche common near surface but occurrence is not limited to the surface. Caliche accounts for most of the white color in the Ogallala., Aug 4, 2011 · Stratigraphy. The Ogallala of northern Kansas meets all the stated requirements of a formation (Ashley and others, 1933). Although it contains a wide range of lithologic types, it is essentially a continuous blanket of alluvium that may be regarded as "homogeneous in its heterogeneity"; it is considered a conformable sequence, as the multitude ... , Ogallala Formation (Pliocene) at surface, covers < 0.1 % of this area. CIMARRON- Generally semiconsolidated clay, silt, sand, gravel, and caliche 0 to 400 feet thick. BEAVER- Interbedded sand, siltstone, clay, gravel lenses, and thin limestone. Caliche common near surface but occurrence is not limited to the surface., The High Plains aquifer includes all sediments from the base of the Ogallala Formation to the potentiometric surface. The saturated thickness in Oklahoma ranges from more than 400 feet to less than 50 feet. Natural recharge to the aquifer from precipitation occurs throughout the area but is extremely variable. Dryland agricultural practices ..., The chemical composition and TDS content (800 to 2,200 mg L-1) of water from five Tertiary Ogallala Formation groundwater wells in the study area is comparable to other groundwaters from the Southern High Plains aquifer. Groundwaters from the Triassic Dockum Group Santa Rosa (δ7Li range of +21 to +23) are isotopically distinct from waters from ..., The chemical composition and TDS content (800 to 2,200 mg L-1) of water from five Tertiary Ogallala Formation groundwater wells in the study area is comparable to other groundwaters from the Southern High Plains aquifer. Groundwaters from the Triassic Dockum Group Santa Rosa (δ7Li range of +21 to +23) are isotopically distinct from waters from ..., The iconic PDF: a digital document file format developed by Adobe in the early 1990s. PDFs are very useful on their own, but sometimes it’s desirable to convert them into another type of document file. This is easy to do with the right soft..., The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota. Water from rains and melting snows has been accumulating in the Ogallala for the past 30,000 years. Estimates indicate that the aquifer contains enough water to fill Lake Huron, but ..., Ogallala Formation: Ogallala Silicified Sediment AKA: Ogallala Chert: Ranges from a buff to a reddish color or gray. Quartz inclusions form speckles in the material. Northern Texas: Ogallala Formation: Owl Creek Black Chert Edwards Chert variation: Ranges from a dark gray to black, small white speckles may be present. Central Texas, OgallalaFormation,Texas BureauofEconomicGeology TheUniversityofTexasatAustin Austin,Texas 78712 W.L.Fisher,Director 1980 by StevenJ.Seni Preparedforthe U.S.DepartmentofEnergy underContractNumber DE-AC97-80ET-46615, The Ogallala geological formation of the American Midwest is home one of the most vital water sources for American agriculture—the High Plains aquifer. Commonly referred to as the Ogallala aquifer, it covers an area of 174,000 square miles across eight states and holds over 978 trillion gallons of fresh water. The aquifer, Pliocene Ogallala Formation of Trego County, Kansas may be referable to Regina. PERTINENT LITERATURE. General accounts of the four species are in Wright and Wright (1957), Emst and Barbour (1989) and Emst and Emst (2003). Important life history studies include those of Hall (1969), Branson and Baker (1974), Franz, The Ogallala aquifer is a sandstone formation that underlies some 583,000 square kilometers of land extending from northwestern Texas to southern South Dakota. Water from rains and melting snows has been accumulating in the Ogallala for the past 30,000 years. Estimates indicate that the aquifer contains enough water to fill Lake Huron, but ..., Brule Formation. The Brule Formation was deposited between 33 and 30 million years ago, roughly the Rupelian age ( Oligocene ). [2] It occurs as a subunit of the White River Formation in Nebraska, Colorado, North Dakota, South Dakota, and Wyoming . It is a sequence of fine grained clastic rocks ( claystones, mudstones, siltstones) interbedded ..., The Oklahoma Panhandle and adjacent areas in Texas, Kansas, Colorado, and New Mexico have prospered because of the development of supplies of fresh water and of oil and gas. The Ogallala and, in places, Cretaceous rocks produce fresh water for irrigation, public supply, and domestic and stock use through approximately 9,000 irrigation and public supply wells and a large but undetermined number of, Pawnee Buttes - Ogallala Formation (GC1EHCK) was created by Me & Bucky on 7/25/2008. It's a Other size geocache, with difficulty of 2, terrain of 2.5. It's located in Colorado, United States. This EarthCache is found on the Pawnee National Grassland, a part of the Arapaho & Roosevelt National Forests and Pawnee National Grassland, and is ..., The present study defines the western limits of the Ogallala Formation (upper Tertiary) and documents the late Cenozoic geology of the region including fragmentary deposits of …, Dec 28, 2006 · The northern boundary of the Raton section is placed somewhat indefinitely at the northern limit of the area injected by igneous dikes. The eastern boundary of the Raton section is at the eastern margin of the lavas of Mesa de Maya and adjoining mesas, where lava-capped outliers of Ogallala Formation are separated from the Ogallala of the High Plains only by the canyon of Carrizo Creek. , The Ogallala Formation is Neogene in age; Paleogene rocks do not occur in Kansas. This paper outlines Neogene ("Tertiary") nomenclature changes to Zeller (1968) that are now formally adopted by the Kansas Geological Survey (KGS). Lithostratigraphy of the Ogallala Formation, Late Miocene (10 to 7 Ma ago) floras from five geographically distinct sites in the Ogallala Formation are described and compared: the Poison Ivy and Russ's floras from Nebraska, the Minium and ..., Wilson said 80-90% of the water used in the Ogallala aquifer region goes to irrigation. That averages out to about 2.5 billion gallons a day, pumped up and sprayed on crops. It can’t go on like that forever. Estimates show that if pumping trends continue, more than two-thirds of the water under Kansas will be gone within 40 years., Symposium papers describe elements of the stratigraphy, biostratigraphy, hydrology, and geomorphology of the Ogallala and Blackwater Draw Formations. CONTENTS Introduction Acknowledgments Depositional facies of the Miocene-Pliocene Ogallala Formation, northwestern Texas and eastern New Mexico, by T. C. Gustavson and D. A. Winkler, You might have music files on a music CD that you would also like to have on an mp3 player. Or, you might have a collection of older CDs that you would like to convert into a more modern format. Either way, this process is easy., Neogene Ogallala Formation underlies much of the North American High Plains region and is composed chie fl y of fl uvial and eolian sediments consisting of interbedded conglomerate, sandstone ..., Keith County is a county in the U.S. state of Nebraska.As of the 2020 United States Census, the population was 8,335. Its county seat is Ogallala.. In the Nebraska license plate system, Keith County is represented by the prefix 68 (it had the sixty-eighth-largest number of vehicles registered in the county when the license plate system was established in 1922)., The Ogallala formation in Texas is the southernmost extension of the major water-bearing unit underlying the physiographic province of North America. It was named in 1898 by N.H. Darton for the town of Ogallala, Nebraska, near where the formation was discovered., The Ogallala Formation is a late Miocene to early Pliocene unit which forms the cliffs and ledges at the very top of the canyon. It is composed of sandstone, siltstone, and conglomerate eroded from a late Cenozoic uplift of the Rocky Mountains , and is separated from the lower Trujillo Formation by a disconformity , representing a long hiatus.