A sedimentary bed, layer, or sequence of layers deposited in a body of still water within a year's time, and usually during a season, by the melting of glaciers and is used in determining the age of geological formations and in archaeological dating, especially in northern Europe. These annual deposits are found in river and lake beds near glaciers, reflecting the fluctuation of the flow of water during periods of freezing and melting and especially useful in measuring recent Pleistocene geological events. Swedish pioneer Baron Gerard de Geer discovered in the late 19th century that these could be counted and correlated or linked over long distances, which gave him a timescale of 12,000 years and fixed the end of the Ice Age at about 10,000 years ago.