Varve dating

SYNONYMS OR RELATED TERMS: chronology CATEGORY: technique DEFINITION: The process by which an archaeologist determines dates for objects, deposits, buildings, etc., in an attempt to situate a given phenomenon in time.

, in which figures in solar years (often with some necessary margin of error) can be applied to a particular event.

CATEGORY: geology DEFINITION: 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.

During the summer, melting accelerates, melt-water streams flow faster and carry more material.

The supply of sediment to the ice-marginal lake varies with the season.

CATEGORY: person DEFINITION: Swedish geologist, originator of the varve-counting method used in geochronology, first published in a paper entitled, A Geochronology of the last 12 000 years".

De Geer observed that lake beds consist of couplets of laminated sediments (varves) light-colored silt layers alternating with strata of darker clay.

Broad correlations between the glaciation schemes in different parts of Europe and North America exist.As the climate warmed, the glaciers retreated, the ice melted, and the sea-level rose.The ice also deposited various forms of boulder clays, and banks of debris at the sides and ends of glaciers, known as moraines.The land is subject to erosion and deposition by this process, which occurred repeatedly during the Quaternary; the process modifies landscapes and affects the level of ocean basins.These periods of colder weather are also called glacials, and the warmer periods between them interglacials.Such varve chronologies have been built up for Scandinavia and are used to date the retreat of the Weichselian ice-sheet.

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