Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 8

8
wards the end of the Younger 300 m stage rest on river gra-
vel close to the 300 m level and fall into one to three magne-
tic groups. Thus in Stóradalsháls (háls = low ridge) on the
west side of Blöndudalur there are three groups: reverse, nor-
mal, reverse. A lava left on Sólheimaháls is normal and be-
longs prohably to the normal group of Stóradalsháls which
obviously is older than RUj .1) But also in another way it is
seen that the lava on Sólheimaháls is older than RU1? for al-
ready at the close of RUX the larger valleys, among them no
doubt the Langidalur, bordering the Sólheimaháls, had been
eroded to the level of the strandplane. It is also very clear in
the case of a normal lava resting on river gravel at 300 m in
Höskuldsstaðanúpur, that it must be older than RUX for the
same reason. The groups in Stóradalsháls show that the
Younger 300 m stage was fully developed at the time of NU2
and RU2 or earlier. Where to place the topmost reverse
group of Stóradalsháls is uncertain. If it belongs to the period
RU, which extended to the close of the strandplane stage,
this period must have been very long. It is quite possible,
therefore, that the topmost group of Stóradalsháls is older
than RUX.
In spite of the local appearance to the contrary I shall, for
reasons seen later, keep open the possibility that the just
mentioned lavas are in reality older than the valleys. The
argumentation, however, remains unchanged, that the lavas
of Sólheimaháls and Höskuldsstaðanúpur flowed before the
strandplane stage and must be older than RUx. In this case
we have no certain lavas from the 300 m stage and palaeo-
magnetism is of no immediate further aid in dating this stage.
The valley erosion at the Younger 300 m and the strand-
plane stages has destroyed most signs of older morphologic
a) In the following I shall denote by NUi, RUi, NU2, RU2 etc. the uni-
versal series of geomagnetic periods or the corresponding magnetic groups;
by Nj, Ri, N2, R2 etc. a regional series, and by n1? rj, n2, r2 etc. a local
series.