The neotropical loess is made of silt or silty clay. The quaternary sediments consist of clay, silt, and several grades of sand and gravel. Windborne silt contributes to the total deposit of sediments. Mixtures of sand, silt and less than 40% clay are called loam. Deposits of this windblown silt are known as loess. The soil composition typically contains sand, silt and clay. The freshwater is usually found in deposits of gravel, silt, and sand. The soil consists of several metres of alluvium or silt deposited by the Seine. Silt and clay contribute to turbidity in water. Sedimentary rock composed mainly of silt is known as siltstone. Langlade County has a soil rarely found outside of the county called Antigo silt loam. The lost soil fills rivers and reservoirs with silt. It is defined by size, being finer than gravel and coarser than silt. Other species can dig into bottom silt or sand until they are completely buried. This area of deposited clay, silt or sand is known as a playa.