Rit (Vísindafélag Íslendinga) - 01.07.1962, Síða 183

181
Up to this time absolute sea-level was about 300 m above
the present.
With the uplift began the modelling of the present topo-
graphy. Two valley generations with a base-level of 250—
300 m above present sea-sevel can be recognized. During the
first was formed a smooth topography with shallow valleys
the clearest vestiges of which are found in the northern part
of the area between Skagafjörður and Eyjafjörður. During
the second the upper parts of the same valleys were deepened
very considerably and flat graded floors were formed. The
main difference between the two valley generations must be
sought in different climates, the second generation corre-
sponding to increased precipitation.
After a eustatic drop of sea-level to about 100 m above the
present, an event assumed to mark about the beginning of the
Pleistocene, the larger valleys were again graded and a pro-
minent strandplane was formed, whose remnants are wide-
spread. The lavas of Skagi, of reverse magnetization, rest on
this strandplane. The maintainance of this rock terrace in
Iceland, and a similar one in Norway, is considered a proof
that a Lower Pleistocene shoreline has in all essentials sur-
vived the vicissitudes of the Pleistocene in glaciated countries.
Its level and the fact that it is as old as the last period of
reverse geomagnetic polarity, is taken as a stong indication
that it corresponds to the Lowest Pleistocene Sicilian shore-
line in the Mediterranean area. It is probable that the Mi-
lazzian interglacial shoreline is left in about 50 m high gra-
vel terraces in Eyjafjörður. The 250—300 m base-level is on
this background and for more reasons considered to be Plio-
cene. Hence the general tuff-breccia layer is of Tertiary age,
probably Upper Pliocene.
Lavas of normal and reverse polarity are found to have
flowed within some valleys on the 250—300 m floors. We
then find at least 2 magnetic groups between the peneplane
and the valley formation, at least further 2 within the high
level valleys, and 2 at the lower, truely Pleistocene levels.