REFERENCE:
De Geer, Gerard. 1940. Geochronologia Suecica Principles. Kungl.
Svenska Vetenskapsakademiens Handlingar Tredje Serien. Band 18,
No. 6, pp. 1-367.
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.
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.