Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 15

15
isolated patches in Belgsárfjall and Bakkaselsíjall between
heights of about 700 and 850 m.
This distribution of the young group indicates extensive
erosion, but also that the group took part in the blockfaulting
of the area which, as the smooth erosional forms of the sur-
I' I i LUJ.LLÍJLXUI1,1)1. II.'IL
1 I i i_ i_L L I II I I I I I
I I i i 'i I I i i i i i > i i i i i
7~T i i I il
I I I I l i I I Ml
m
1 l 1 > i i ÍÍJJJ.
irrrTi ) i )i i i
1 II II ll II
i n n i 11
- 2 O O bri. -
Fig. 5. Section at S in Fig. 4.
face of these mountains show, took place before the Older
300 m stage. The same story is also told by the occurrence
of a small isolated patch of Young rocks much farther north,
in Skessuskálarfjall (Figs. 4 and 5), discovered by Líndal
(1942).
In the north facing wall of the cirque Skessuskál we see
about 15 lavaflows in a 150 m high section. Between the lavas
are mostly scoriae. From the foot of the wall I was not able
with a field glass to see any discordance, any grey conglo-
merate or any other sign of Young rocks, but on reaching
the edge they were immediately evident: a typical grey,
moraine-like conglomerate covered by one lava flow. The lava
has a globular and glassy breccia structure near the base, pos-
sibly caused by flow into water, but higher it is normal basalt.
It contains numerous star-like phenocrysts which distinguish
it very clearly from the other basalts in the section, as does
also its remarkable freshness. This lava has normal magne-
tization. These Young rocks occur only in a stretch of the
wall about 200 m wide which is bounded by faults on both
sides. On the east side the block containing the Young rocks
has been thrown down relatively 20—30 m, while the throw
on the other side could not be estimated. The surface of the
mountain is very smooth and no trace of the displacements