The Sankoty aquifer is an aquifer

Aquifer

An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...

 in the U.S. state of Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

 that provides groundwater

Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

 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

Mississippi River

The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...

.

Type locality

The sand

Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...

 which forms the Sankoty aquifer was named after a railroad siding near Peoria, Illinois

Peoria, Illinois

Peoria is the largest city on the Illinois River and the county seat of Peoria County, Illinois, in the United States. It is named after the Peoria tribe. As of the 2010 census, the city was the seventh-most populated in Illinois, with a population of 115,007, and is the third-most populated...

 in 1946 by Leland Horberg. The legal description given by Horberg in identifying the type locality

Type locality (geology)

Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....

 for the Sankoty sand is T9N, R8E, Section 15 (Peoria County, Illinois

Peoria County, Illinois

Peoria County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 186,494, which is an increase of 1.7% from 183,433 in 2000. Its county seat is Peoria....

).

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 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

Quartz

Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of 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 100 feet (30.5 m) 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

Illinois River

The Illinois River is a principal tributary of the Mississippi River, approximately long, in the State of Illinois. The river drains a large section of central Illinois, with a drainage basin of . This river was important among Native Americans and early French traders as the principal water route...

. 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 aquifer

An artesian aquifer is a confined aquifer containing groundwater under positive pressure. This causes the water level in a well to rise to a point where hydrostatic equilibrium has been reached. This type of well is called an artesian well...

) conditions.