THE SWEDISH VARVE CHRONOLOGY
De Geer applied the term varve (Swed. varv) to the annual coarse-fine layers in sediment deposited in proglacial lakes in Sweden and elsewhere. The layers were produced by the annual melt-water sequence with rapid melting and discharge in summer depositing coarse sediments, versus slow settling of fine-grained material during the winter months.
By counting and comparing many exposures of these sequences, brought above sea level by isostatic rebound, De Geer and his colleagues produced a master chronology for Sweden, which De Geer then applied to other regions of the world, including South America (Argentina). The basis for the "teleconnection," as De Geer coined the word, was GLOBAL CLIMATIC CHANGE.
The first varve series to be developed were of late glacial age. Eventually, a system was developed in which the late-glacial varves were given negative numbers and postglacial varves positive ones, with the "Zero Varve" the boundary between late-glacial and postglacial time. New series were "dated" by correlating their varve sequence with the master chronology, shown below.
REFERENCE: De Geer, Gerard. 1940. Geochronologia Suecica Principles. Kungl. Svenska Vetenskapsakademiens Handlingar Tredje Serien. Band 18, No. 6, pp. 1-367.