Quaternary glacial varves of Ragunda

De Geer built up a varve chronology from Skåne to Jämtland in central Sweden, a year-by-year chronology of glacial retreat for the Late-glacial period (De Geer, 1912). This chronology was not only the most precise and accurate geological timescale of its day, it was the first absolute time-scale, showing the exact record of the end of the last ice age. His research showed that it took 1073 years for the land-ice to retreat from Stockholm to Ragunda in central Sweden, a distance of 500 km. Later, in 1940, he published his major and classic scientific paper, the Geochronologia Suecica Principles, in which he presented the full Swedish Time Scale, a floating varve chronology for ice recession from Skåne to Jämtland. As varves as such are found in many geological environments, the varve chronology system has with time proven to be of wider use and importance. Along with new dating methods, like radiocarbon dating, the system has during the twentieth century been both challenged and improved. The full plethora of De Geer’s ideas on varve chronology for global correlation have not stood the test of time, but the essence of the method has proven a solid tool for modern geological science.