Paleosecular Variation of Direction and Intensity from Two Pliocene-Pleistocene Lava Sections in Southwestern Iceland

Abstract

Two lava sections in southwestern Iceland were revisited; sectoin IG of Kristjánsson et al. (1988) of Brunhes chron age and section K of Wilson et al. (1972) of early Matuyama chron age. Paleodirections obtained from 22 laves at the former section do not seem to have averaged out the secular variation completely because of their small angular standard deviation, and this suggests rapid accumulation of the lavas. The latter section consists of 29 lavas and contains the Gauss to Matuyarna transition near its base. The time interval during which the laves at this section were erupted also seems to be short, judging from the small directional dispersion. Thelliers' paleointensity method was also applied to the samples from this section. A characteristic low paleointensity was obtained from the transitional lava flow. However, low paleointensities were also obtained from the lavas which erupted some time after the transition, and which record directions close to those of an axial geomagnetic dipole.