Leó Kristjánsson and Ágúst Guðmundsson
Paleomagnetic studies in Skarðsheiði, South-Western Iceland. Jökull 50, 33-48, 2001.

We have mapped a well-exposed composite profile through the lava pile in the western part of the Skarðsheiði mountain, and made detailed laboratory measurements of paleomagnetic remanence directions in oriented samples from 92 lava sites from this profile. The lower 55 lavas or so consist of a partially recorded normal-polarity zone, overlain by a thick reverse-polarity zone. The latter which includes a series of porphyritic lavas, was named R5 by Einarsson (1957). The upper part of our profile contains a normal-polarity sequence of about 20 flows (N5 of Einarsson) and a partially recorded reverse zone. Franzson (1978) and others have correlated the R5-N5 boundary with a similar boundary in the Akrafjall mountain and with the transition between the Gilbert and Gauss geomagnetic chrons. We have also sampled 29 lavas in two shorter profiles farther east in Skarðsheiði, at the boundary between the R5 and N5 polarity zones. We confirm the observations of Wilson et al. (1972) and Kristjánsson and Sigurgeirsson (1993) that several lava flows with transitional directions occur at this boundary at the northern side of the mountain. Only a few such flows are found on the south slopes of Skarðsheiði. At least three short geomagnetic excursions are recorded in the R5 zone. The lava flows are good material for paleomagnetic direction measurements, although hydrothermal alteration has affected the lowest part of the composite profile. Their average direction is quite similar to the axial dipole field as expected. Thermomagnetic tests on several samples indicate that they are not very suitable for paleointensity studies.

Trausti Einarsson: Magneto-geological mapping in Iceland with the use of the compass. Adv. Phys. (Phil. Mag. Suppl.) 6, 232-239, 1957.

Hjalti Franzson: The structure and petrochemistry of the Hafnarfjall-Skardsheidi central volcano and the surrounding basalt succession. Ph.D. thesis, University of Edinburgh, 264 pp, 1978.

R.L. Wilson, N.D. Watkins, T. Einarsson, T, Sigurgeirsson, S.E. Haggerty, P.J. Smith, P. Dagley and A.G. McCormack. Paleomagnetism of ten lava sequences from south-western Iceland. Geophys. J.R. astr. Soc. 29, 459-471, 1972.

Leó Kristjánsson and Magnús Sigurgeirsson: The R3-N3 and R5-N5 paleomagnetic transition zones in SW-Iceland revisited. J. Geomag. Geoel. 45, 275-288, 1993.