Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 22

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between these and the horizontal young rocks is clear. At
550 m we find a grey moraine-like conglomerate, about 4 m
thick. The upper part consists of brown sand with sparse
pebbles and is probably of eolian origin. This sediment is
covered by porphyritic grey basalt and all the young rocks
in this spur (reverse magnetization) are porphyritic, in con-
trast to the uppermost old basalts here. The total thickness
of the Young basalts is here 160—170m.
3. The spur between Vestari-Jökulsá and Svartá. The en-
tire spur above a level of 500 m consists of the Young basalts
(reverse magnetization). On the west side, above the mouth
of Selá, we see the lower contact at 520 m. The lowest lava
rests on these sediments (from below): morine-like material;
2m coarse river gravel; 10—30 cm fine sandstone; (locally)
10 cm fine gravel. Total thickness of Young rocks 80—100 m.
At this place the Young lavas have a very slight south-
wards dip. They occur on the west side of Svartá at Polla-
lækur in the form of kubbaberg at a height of 460 m. Rela-
tively late faultlines cutting the spur (direction N25°W)
show up clearly in the landscape.
To these is possibly connected a faint postglacial eruption in the
Svartárdalur, evidenced by a very small lava flow. The spot is on the
east bank of the Svartá river 350 m above sea-level, 1.8 km south from
the deserted farm ölduhryggur. Above this place we can for a long di-
stance follow a 8—10 m thick gravel terrace along the river. The topmost
part of this terrace is formed of very coarse gravel, with boulders up to
1 m in diameter. The lava, hardly more than 20—30 m across, rests on
this coarse gravel on the bank of the river. It is partly covered with river
gravel. The lava is probably early post-glacial in age. It appears not to
have been noticed earlier.
4. Hellisás—Stapar. In connection with the sediments at
the base of the Young rocks just described the remnants of
similar sediments that form ridges and hills on a 7 km long
stretch between Stapar and the farm Lýtingsstaðir in Tungu-
sveit in southern Skagafjörður should be considered. In the
2.5 km long Hellisás the sediments have a thickness of about
100 m, reaching from about 150 to 250 m elevation but only