Baron Gerard de GeerDied 23 Jul 1943 at age 84 (born 2 Oct 1858).Gerhard (Jakob), Friherre De Geer (Baron) was a Swedish geologist, originator of the varve-counting method used in geochronology. A varve is a seasonal coarse-fine layer of clay deposited in still water.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. The method he devised of counting of layers in glaciers was good for dating back to 18,000 years. Although only accurate to that time, it was useful for studies of the Ice Age.Image: In 1920 De Geer visited the United States to study the varves of New England; he is shown sampling varves at the Essex locality. |
