Baron Gerard Jacob De Geer (20 November 1858 – 24 July 1943) was a Swedish geologist who made significant contributions to Quaternary geology, particularly geomorphology and geochronology. De Geer is best known for his work on varves. In 1890 De Geer was the first to apply the name Ancylus Lake to the Baltic paleolake discovered by Henrik Munthe. He subsequently participated the protracted scientific controversy surrounding this lake. Biography Baron Gerard Jacob De Geer comes from a well-known Swedish aristocratic family of Brabant origin, who had emigrated to Sweden in the early seventeenth century. His family included prominent industrialists and politicians. His father Louis and older brother Gerhard Louis served as the Prime Minister of Sweden. Gerard Jacob was born on October 2, 1858 in Stockholm in the family of Baron Louis Gerhard de Geer, at that time the first Minister of Justice in the Swedish government, and Carolina de Geer, née Countess Wachtmeister. Since 1869 he studied at primary school, and since 1873 - at the Stockholm gymnasium. In 1877, de Geer entered Uppsala University. In May 1879 he graduated and received a Bachelor of Arts degree. In 1878, De Geer became an employee of the Geological Survey of Sweden, initially freelance, then, since 1882, as an assistant to a geologist, and since 1885, a full-time geologist. At this time he started to study the late Quaternary deposits and landforms of southern Sweden. In 1897, he left his job in the geological service for the position of professor of general and historical geology at Stockholm University. In 1882, on the recommendation of Otto Martin Torell, de Geer participated in the Swedish expedition to Spitsbergen as part of the first International Polar Year as a staff geologist. This marks the beginning of many years of research on the modern glaciation of the Svalbard archipelago: in total he took part in six expeditions to Svalbard (1882, 1896, 1899, 1901, 1908 and 1910). Gerard de Geer remained a lecturer at the Department of Geology at the University of Stockholm from 1897 to 1924. At the university, he served as rector (1902-1910) and vice-chancellor from (1911-1924). In addition, De Geer was a member of the Swedish Parliament from 1900 to 1905. The pinnacle of de Geer's scientific career can be considered the receipt of the presidency of the X International Geological Congress, held in Stockholm in 1910. At first he took part in