Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 7

7
lescence of valleys even broad plains were formed. At the
same time a broad strandplane was eroded; within the Eyja-
fjörður this strandplane or rock terrace was at many places
2—3 km hroad.
It seems clear that the new valley erosion was much in-
fluenced hy glacial meltwaters (Einarsson 1959 b).
At the mouth of the Skagafjörður, hasalt lavas covered the
strandplane; the earlier lavas have reverse magnetic polarity
(lavas of Skagi and Málmey), the younger normal polarity
(Skagi, Thórðarhöfði, Hrolleifshöfði, Drangey), which gives
a lower limit for the age of the strandplane.
The last turnover of the magnetic field of the earth, from
the reverse to the normal sense, took place in the early or
middle Pleistocene, perhaps before the Sicilian stage. Where
to put the magnetic turnover in the scheme of Alpine glacia-
tions is still a matter of debate. Some authors would put it
before Giinz while others put it closer to Mindel. Bout (1960),
in a thorough work on the Villafranchian of Velay, puts the
magnetic turnover even after Mindel. In any case the forma-
tion of the strandplane would seem to belong to the begin-
ning of the Pleistocene. The cover of the strandplane in Skagi
consists, from below upwards, of grey sandstone and conglo-
merates, possibly in part of glacial origin, then a general
layer of brown, probably windblown sandstone, then 3 lava
flows with reverse magnetization, two of which seem to have
been separated by a lowland glaciation, and finally a lava
with normal magnetization. If this lowland glaciation, at lat-
est, corresponds to Mindel, the brown sandstone might corre-
spond to the Giinz-Mindel interglacial and the base of the
sediments might correspond to Gunz. In any case it seems
extremely likely that the strandplane is of early Pleistocene
age, while the inferred influence of glacial meltwaters in
eroding the larger valleys, corresponding to the strandplane
base level, suggests still earlier Pleistocene time.
I propose to speak of the strandplane stage or the 100 m
stage. The lavas that seem to have flowed at or rather to-