Greinar (Vísindafélag Íslendinga) - 01.01.1935, Síða 89

87
reach as high up at this time as when the sand strata
overlying the moraine in Háubakkar were formed,
which in my opinion took place earlier in the intergla-
cial period, while the land was raised up afterwards.
As I mentioned before, Dr. Helgi Péturss considered
that the interglacial shell-strata in Fossvogur were
younger than the shell-strata in Elliðaárvogur, and we
might therefore expect the fossil-stratum at Gelgju-
tangi to be from the same interglacial period as those
at Fossvogur. J. Áskelsson draws the conclusion
from the composition of the strata at Fossvogur that
the lower strata were formed while the sea was grow-
ing deeper (transgression phase), but the topmost lay-
ers while the sea was growing shallower (regression
phase). According to this view we might expect that
the fossiliferous stratum at Gelgjutangi was from the
latter part of the period when the Fossvogur strata
were formed, but the sand-strata which lie above the
moraine at Elliðaárvogur from the middle of this period.
This indicates that there was considerable variation
as to the extent to which the land sank at different
places in this country. The sand-stratum at Elliðaár-
vogur, which is now about 4 metres higher above sea-
level than the corresponding strata at Fossvogur, would
then have been at least 15—20 metres higher if they
are to be considered as contemporaneous formations,
the one in very shallow water, but the other at a con-
siderable depth. Yet the Fossvogur strata are only 3
kilometres to the south-west of Háubakkar.
Although the Gelgjutangi strata and the Fossvogur
strata might well be from the same interglacial period,
yet I believe that period to have been so long that there
is no need for there to be any question of exactly con-
temporaneous formations, and for this reason it would
be premature to conclude from them that such differ-
1) Nokkur orð um skeljalögin í Fossvogi. Náttúrufræðingur-
ínn, Reykjavík 1933, p. 84.