Geomagnetic secular variation from Holocene lake sediments of Sorø Sø, Denmark

Abstract

A record of geomagnetic secular variation for the last 7500 years has been obtained from three cores of lake sediment from Sorø Sø in Denmark. The time-scale has been derived from six radiocarbon age determinations on one of the cores. Variations in geomagnetic declination and inclination agree well with those found in a previous study using sediments from another Danish lake, Skanderborg Sø, some 120 km from Sorø Sø. A correlation with the record from the U.K. has been made, but with age differences of up to 1000 years, which are attributed to the dating errors inherent in the radiocarbon method when applied to lake sediments in both the U.K. and Danish sediments. The virtual geomagnetic pole path since 7500 BP appears to have had periods of both clockwise and anticlockwise motion of 1000-year duration, where the looping is open, interspaced with shorter periods of ∼ 500 years in which the geomagnetic behaviour is more irregular. It is suggested that this indicates a possible regularity in the pattern of field behaviour during the Post Glacial.