Gerard De Geer pioneered the study of glacial varves, and coined the term "geochronology." He was the professor of Ernst V. Antevs and several other prominent early twentieth-century geomorphologists. By 1912 De Geer and his associate Ragnar Liden had produced an approximate count of the annual deposits made by melting ice. The similarity of these annual deposits to the annual rings led De Geer to communicate, beginning in ca. 1918, with A. E. Douglass, the tree ring scientist at the University of Arizona. In 1920 De Geer visited the United States to study the varves of New England. In the figure at the left he is shown sampling varves at the Essex locality.

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.