Gerard de Geer - de Geer's Discovery of Varves

De Geer's Discovery of Varves

De Geer graduated from Uppsala University in 1879, after joining the Swedish Geological Survey the previous year, and began what was to be his life's work studying the late Quaternary deposits and landforms of southern Sweden. De Geer's early studies of raised beaches, used to reconstruct glacio-isostatic sea level changes, and his mapping of glacial moraines to reconstruct the extent of the last Scandinavian ice sheet and its pattern of deglaciation (the particular type of moraine he studied is now referred to as De Geer moraine), were well received. However, De Geer is most famous for discovering varves and pioneering their use in geochronology.

During fieldwork in 1878, De Geer noticed that the appearance of laminated sediments deposited in glacial lakes at the margin of the retreating Scandinavian ice sheet at the end of the last ice age, closely resembled tree-rings. In his best known work Geochronologia Sueccia, published in 1940, De Geer wrote "From the obvious similarity with the regular, annual rings of the trees I got at once the impression that both ought to be annual deposits" (1940, p. 13).

While this observation was not new, De Geer was the first geologist to exploit its potential application. De Geer called these annual sedimentary layers varves and throughout the 1880s further developed his theory, publishing a brief outline of his discovery in 1882, which he followed with a presentation to the Swedish Geological Society in 1884. It was not until 1910, at the International Geological Congress, that De Geer's pioneering work reached the wider international scientific community.