Dating glacier layers

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.

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.Varve sequences allow us to fix very precisely in varve years the age of any fossil or sediment feature found in the varves or the varve age of any event that may be tied to the varve sequence.Sediment features found in varve sequences include abnormally thick sandy beds marking flood events and volcanic ash beds.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.