Paleomagnetic observations on Late Quaternary basalts around Reykjavík and on the Reykjanes peninsula, SW-Iceland

Abstract

This paper reports paleomagnetic remanence directions from Late Quaternary lava units in the Reykjavík area and on the Reykjanes peninsula. In Reykjavík, samples were collected at about 30 sites in the interglacial “gray basalts” in the hope offinding unusual directions which might help in stratigraphic mapping in this region as well as documenting the behaviour ofthe geomagnetic field. The directions in these lavas are tightly grouped which indicates that the lavas were emplaced in a short time interval (<50 kyr?). One instance was found ofa geomagnetic excursion, which probably occurred early in this volcanic phase. On Reykjanes, emphasis was on sampling lavas which might exhibit directions similar to the “Skálamælifell geomagnetic excursion”. Lava sequences erupted during this excursion, ofabout 43 kyr age, were previously found to cover a few isolated areas in the region northeast ofGrindavík. Their presence has already been ofvalue in studies of local geomorphologic activity. The current work has since 1990 resulted in minor modifications in a map ofthe main areas covered by the excursion sequences, and one new area was found. Several lava flows erupted during an excursion ofthe geomagnetic field (possibly the Skálamælifell one) were sampled in mt. Fagradalsfjall.