Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 42

42
and a topmost normal group containing especially the frag-
mental rocks.
We shall here relate some observations in this area.
The hut Öldumóðuskáli stands on a reverse lava. But 100 m
west of the hut is the edge of a normal lava of columnar and
kubbaberg structure that rests on the reverse one. Between
the two, seen at the öldumóðukvísl about 1 km south of the
hut, is seen grey-brown conglomerate. On the normal lava,
a little west of the hut, is found a remnant of a reverse lava.
2—3 km farther southwest, i.e. south of Öldumóðuflá, is
reverse basalt at the base, but a little higher, in the slope of
Thjófahæðir at about 570 m, we find normal kubbaberg. In
the southeast slope of this spur, at Thjófakvísl (580 m), we
find also normal mixed kubbaberg and columnar basalt. This
is the base of the topmost normal group and it is thus of the
same character as the lower young rocks. But soon we meet
the predominance of the fragmental rocks, in Svínafell and
along the Thjófakvísl. Svínafell (713 m) is a tuff hill; in
a pass (650 m) on its west side we find tuff containing large
bombs. At Tröllagil, on the south side of Svínafell the tuff
overlies a normal lava (650 m) but the contact is not seen.
On the south side of the gully is seen pillow lava. Near the
mouth of Tröllagil (610 m) there is normal porphyritic grey
basalt resting on fine sandstone and a fine grey conglomerate.
The topmost group thus contains flatlying kubbaberg and
columnar lavas, as well as pillow lavas and sand layers up
to an elevation of at least 650 m, while higher the fragmental
products of explosive volcanism become dominant. Farther
east, Helgufell belongs to the normal group; it consists of
breccia over grey, fine-porphyritic basalt. Also the hills
Sauðafell and Áfangafell seem to belong to it and normal
basalt comes down to 460 m in Kolkuhóll.
Going farther west from the hut we find fresh grey reverse
basalt in Birnuhöfði (581 m). One km farther south, at the
same elevation, we have reverse primary breccia, but above
this rises a scarp (613 m) of normal lava, the base of the