Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 3

INTRODUCTION.
The present paper has developed in later years out of the
studies of rock magnetism which I began in 1953 in colla-
boration with Th. Sigurgeirsson. By 1956 we had mapped
the magnetic groups of the Plateau Basalts in Middle West-
em Iceland, especially the Hvalfjörður area, and a succes-
sion of 15 magnetic groups, corresponding to as many periods
of polarity of the geomagnetic field, had been found. In addi-
tion, a profile in the Plateau Basalts in Eastern Iceland had
been studied, rendering about 30 magnetic groups, and by
studies in Snæfellsnes and Tjörnes a correlation with the
main Lower Pleistocene and Pliocene marine shell-bearing
deposits had been attempted. The results were presented at
an International Conference on Rock Magnetism in London
in 1956 and in several papers (Einarsson & Sigurgeirson
1955, Sigurgeirson 1957, Einarsson 1957 a & b).
For the series of magnetic groups in the Hvalfjörður-
Borgarfjörður area the notations N1? Rl5 N2, R2 etc. had been
introduced. These were meant as local notations only, not
implying for instance that R2 corresponded necessarily to
the last but one period of reverse polarity of the geomagne-
tic field. But we did, implicitly at least, assume that Nj and
Rx corresponded to the two last magnetic periods, the Pleisto-
cene ones. On the other hand there was no doubt in my mind
that a gap in the record had to be assumed at one or two
places below Rx.
In the years after 1956 I have continued the magnetic-
geological mapping and Sigurgeirsson has collected samples