Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 38

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Víðidalur of essentially its present shape, as was assumed
by Líndal.
The flora of Bakkabrúnir (Líndal 1939) shows the relative
percentage: Alnus (viridis) 43%; Betula 35%; Salix 22%
and in addition modern plants. This compares with the flora
of the lower part of the Breiðavík sediments in Tjörnes,
which are of upper Pliocene or lowest Pleistocene age, de-
pending on definition.
In the northern part of Víðidalur the long ridge Björg—
Nesbjörg consists of fresh young kubbaberg of dark dense
basalt of normal magnetization. It is probably cut by an ero-
sion level at 120—165 m, although the ridge is too narrow
to show this without doubt.
Borgarvirki is a castle-like small remnant of a single co-
lumnar horizontal lava of reverse magnetization, resting on
a layer of fresh river gravel at a height of 150 m. The gravel
rests on westwards dipping old basalts. This is possibly a
remnant of the strandplane stage, somewhat disturbed by
tectonic movement.
5. HoltavörSuheiði. The Young rocks are found at Holta-
vörðuheiði and sections are seen in several gullies around the
Heiðarsporðsá as well as at Hrútafjarðará. At the latter lo-
cality, in the south wall of the gully, where the river turns
from a westerly to a northerly course, we find the section
shown in Fig. 20:
1. Old basalt.
2. Light-pink claystone with seams of lignite.
3. Fine-grained hard sandstone.
4. Lava of reverse magnetization.
5. Black sandstone (% m).
6. Lava of reverse magnetization.
7. Scoriae.
8. Kubbaberg of reverse magnetization.
9. Columnar lava of reverse magnetization.
The group of young lavas is quite fresh. Rather large stems
of fossil wood are found in the scree below 4). They must