Rit (Vísindafélag Íslendinga) - 01.07.1962, Síða 159

157
lowest visible lava in this group. Direction of striae W 35° N.
It is most likely that these isolated remnants all belong to
the Bæjarfell group.
The summit of Búrfell is formed by one reverse thick
kubbaberg lava separated by sediments from the dipping
Fig. 84. Lava cap on Búrfell.
Plateau lavas, Fig. 84. The lava seems to be quite horizontal,
although a dip of 2—3° SE might perhaps be difficult to detect.
At any rate this lava is possibly younger than the Bæjarfell
group. It seems likely that it corresponds to the Grímmanns-
felI-Skálafell group, while the Bæjarfell group, just as N2
and n2 in Hreppar may be considered as a final Plateau group.
Retuming to Ásgil the Bæjarfell group is covered by a
moraine at 400 m and hereon, probably on an essentially
horizontal plain, rests a thick heap of normal kubbaberg,
primary breccia, and a thick layer of primary tuff. The tuff
can he traced far up along the slope and in Deildargil it
forms a layer from 600 m to over 900 m (Vinnumanna-
hnúkur). It is rather clear that the natural surface of this
tuff forms very closely the present slope of the mountain.
This slope was first covered with a thick weathering mantle,
especially solifluction material (easternmost branch of Ásgil),
then by a moraine and finally by the high-porphyritic lavas
from the Ok crater. From this it appears clear that we can
separate two volcanic stages in Ok. In the first was produced
a flat pile of tuff-breccias and this stage might be thought to
be older than the main valley erosion as the material is re-
stricted to levels above 400 m. In the second, much later, ap-
peared the shield-volcano, producing a relatively thin cover of
lavas which have been lost in wide outskirt areas. In a con-
siderable area on both sides of Deildargil the Ok lavas are