The Blanco Formation, originally named the

Blanco Canyon Blanco Canyon is a canyon located in the U.S. state of Texas. Eroded by the White River into the Caprock Escarpment on the east side of the Llano Estacado, the canyon runs for in a southeasterly direction, gradually widening from its beginning ...

Beds, is an early

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

of clay, sand, and gravel whitened by calcium carbonate cementation and is recognized in

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

and

Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...

. After the Ogallala had lain exposed for some time since the

Neogene The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...

, developing a thick

caliche Caliche () is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, ...

petrocalcic horizon under the surface, deposition of sand and gravel by wind and east-flowing streams resumed to lesser extent during the early

Pre-Illinoian The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma (million years ago). North America As the oldest stage in t ...

glaciation cycles of the

. As the weathering and erosion of the exposed Ogallala, rich in calcium carbonate, contributed heavily to the formation, the resulting material is white (

blanco Blanco (''white'' or ''blank'' in Spanish) or Los Blancos may refer to: People *Blanco (surname) Fictional characters *Blanco, a hobbit in J. R. R. Tolkien's Middle-earth * Blanco Webb, character in the BBC sitcom ''Porridge'' * El Blanco, albin ...

). This gave the name to

, which in turn is the type locality for the Blanco Formation. In Texas, the unit covers the extent of the

Llano Estacado The Llano Estacado (), sometimes translated into English as the Staked Plains, is a region in the Southwestern United States that encompasses parts of eastern New Mexico and northwestern Texas. One of the largest mesas or tablelands on the North A ...

, attaining a thickness of . Exceptionally flat, it is conjectured that the limestone beds in the Texas region formed within broad, shallow lakes. The Blanco Formation is recognized in Kansas where it attains a maximum thickness of over . In much of its extent in Kansas, the Blanco is buried under deep Pleistocene

loess Loess (, ; from german: Löss ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loess or similar deposits. Loess is a periglacial or aeolian ...

and soil deposits and a certain amount of knowledge of the unit comes from well drilling. While the whole of the unit is clay, sand, and gravel, the lower part of the unit is coarser material and the upper part is finer and plastic, with enough distinction to identify two members. In Kansas, the upper member is named Fullerton and the lower is named Holdrege for their respective correspondence with the

Fullerton Formation Fullerton may refer to: Places Australia * Fullerton Cove, New South Wales Canada * Cape Fullerton, Nunavut India * Fullerton Securities, a financial planning and wealth management product company United States * Fullerton, California, a city ...

and

Holdrege Formation Holdrege is a city in Phelps County, Nebraska, United States. The population was 5,495 at the 2010 census. It is the county seat of Phelps County. The Nebraska Prairie Museum is located in Holdrege. History Holdrege was established in 1883 whe ...

that are identified in

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the southwe ...

. The Blanco is not recognized as a unit in Nebraska.

References

Geologic formations of Texas Geologic formations of Kansas {{Kansas-geologic-formation-stub

See also

References