The Sankoty aquifer is an aquifer in the U.S. state of Illinois that provides groundwater to a number of communities in northwestern and central Illinois. It is an unconsolidated deposit lying in a bedrock valley formerly occupied by the ancestral Mississippi River.

Type locality

The sand which forms the Sankoty aquifer was named after a railroad siding near

Peoria, Illinois Peoria ( ) is the county seat of Peoria County, Illinois, United States, and the largest city on the Illinois River. As of the United States Census, 2020, 2020 census, the city had a population of 113,150. It is the principal city of the Peoria ...

in 1946 by Leland Horberg. The

legal description A land description location of the written words which delineate a specific piece of real property. Also known as a "Legal Description". In the written transfer of real property, it is universally required that the instrument of conveyance (deed ...

given by Horberg in identifying the type locality for the Sankoty sand is T9N, R8E, Section 15 ( Peoria County, Illinois).

Lithology and stratigraphy

The Sankoty sand is an unconsolidated deposit within a bedrock valley formerly occupied by the ancestral Mississippi River. It is classified as a member of the

Banner Formation The Banner Formation is a Carboniferous period geologic formation in northern Elko County, Nevada. It is composed of conglomerate, sandstone, and limestone and was formed in connection with the Antler orogeny. ;Fossils It preserves fossils dati ...

and occupies the same stratigraphic position as the Mahomet sand. The Sankoty sand has distinctive characteristics that are readily recognized in sample cuttings. In its most typical aspect, the Sankoty is composed of 70 to 90 percent quartz grains of which 25 percent or more are pink, rounded, and polished. The texture is usually medium-grained but varies from silty fine sand to coarse gravelly sand.

Groundwater occurrence

The Sankoty sand is one of the most extensive aquifers in the state. It frequently is thick and is typically found below elevations of 520 to 530 feet above sea level. It has been used as a water source in the Peoria area since at least 1892. By 1909, it was observed that groundwater levels at the North Field in Peoria fluctuated with the river stage in the

Illinois River The Illinois River ( mia, Inoka Siipiiwi) is a principal tributary of the Mississippi River and is approximately long. Located in the U.S. state of Illinois, it has a drainage basin of . The Illinois River begins at the confluence of the D ...

. The Sankoty aquifer extends beyond the width of the Illinois River valley and occurs beneath the uplands. In these locations, it is frequently confined by clayey deposits of glacial till (which may include other sands). Consequently, the groundwater may occur under confined (

artesian Artesian may refer to: * Someone from the County of Artois * Artesian aquifer, a source of water * Artesian Builds, a former computer building company * Artesian, South Dakota, United States * Great Artesian Basin, Australia * The Artesian Hotel ...

) conditions. Groundwater pumping has altered historical groundwater flow in the Sankoty aquifer. The flat geography of the area leads to groundwater flows that are perpendicular to the Illinois River; however, municipal groundwater pumping in the Peoria, Illinois area and to a lesser degree agricultural pumping elsewhere over the aquifer has led to numerous cones of depression.

References

''Groundwater in the Peoria Region''. Horberg, Leland, Max Suter, and T.E. Larson, 1950 Illinois State Water Survey, Bulletin 39, Champaign, IL 128 p. ''Water Resources in Peoria-Pekin District''. Buswell, A.M, 1940 Illinois State Water Survey, Champaign, Bulletin 33, IL 114 p. {{Aquifers Geology of Illinois Aquifers in the United States