Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 118

116
vatn) this is a fresh unporphyritic, normally polarized coarse
pillow lava, xnerging upwards into a layer of pillow-breccia
with much glass matrix (2—3 m). The dolerite comes 40 m
above the lake, but the contact is hidden. From here north
along the mountain the main wall, largely hidden, is much
higher, and rising, but lower there are steps in which appa-
rently the same pillow breccia is found as that in Vatnsheiði.
However, the outcrops are bad. Only at the north corner a
pretty clear section is seen, beginning at about 120 m and
reaching the summit at 317 m, Fig. 59. The lower part of this
section is made of coarse tuff with fine stratification. There
are no whole bombs, and basalt fragments with remnants of
glass coating are at least extremely rare. We are concerned
with sediments consisting of pumice and other porous and
light basalt fragments, as well as glass fragments. The frag-
ments are equidimensional and subangular. This material
must have been transported rather far from the origin, pro-
bably by wind, and it can be considered as certain that the
layers were originally nearly horizontal. In the lowest and
northemmost spur (1) of the wall they still have a slight
(northern) dip. But in the main part (2) they form a sharp
bend where the dip is up to 70° north on the north side, turn-
ing over to 40° south. The layers are much fractured at the
crest of the bend. The south facing layers have been lost on
the north side; they consist of a coarse breccia which has
been formed by breaking up or deep weathering of the under-
lying hard tuff, and was rehardened before the bending
process.
Above this is a layer (3) of very much altered breccia,
closely similar to the Silfurberg material (Ingólfsfjall). The
lower contact is not seen, but the altered layer is covered by
a horizontal unaltered brown tuff (4), 2m thick. It is of a
secondary origin and similar to (2). Now there is a cover of
a lava flow (5) (normal pol., unporphyritic, 2—3m thick).
Above the lava the tuff layers are continued (6), and from
the fine-structure of the clay strata it seems clear that this is