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Annual layer thickness varies as weather patterns that control meltwater and sediment input to the lake vary from year to year.Long term thickness changes reflect changing patterns of sedimentation resulting from such things as changes in sediment sources and distribution patterns, climate change, and vegetation patterns on the land adjacent to the lake.Ice cores are claimed to have as many as 135,000 annual layers.Yet airplanes of the Lost Squadron were buried under 263 feet of ice in forty-eight years, or about 5.5 feet per year. The GISP2 ice core: Ultimate proof that Noah's flood was not global. In Sweden, varve sequences may be calibrated by simply counting varves because the youngest varves are historic and come up to the present.The count of varves back from the present then gives an estimate of the absolute age of the sediment provided that the varve sequence does not have any gaps or the lengths of gaps can be estimated precisely.To assemble a glacial varve record at an outcrop, overlapping cores can be matched or spliced according to thickness patterns and intra-annual features seen in specific varves.Shown here are matching varve cores from the lower part of a varve section at Newbury, VT in the Connecticut Valley.
Throughout this web site the terms varve record, varve series, and varve chronology are used to denote varve sequences of different hierarchical status.
To construct a varve record in glacial lacustrine sediment the thicknesses of annual layers are counted and measured to formulate a time scale of varve years and corresponding varve thickness.
The block of sediment shown here is from the deposits of Lake Vermont, a late Pleistocene glacial lake that occupied the Champlain Valley of New York.
The advantage that varves have over other sediments is that they have tremendous precision of a year and in some cases down to the level of seasonal layers within a varve if intra-annual stratigraphy shows a consistent separation of seasonal features.
Correlation of glacial varve records from place to place is generally based on the matching of the pattern of varve thickness change and not absolute thickness, which varies widely for a single varve year across a lake or region.