Acta naturalia Islandica - 01.02.1946, Síða 56

50
TRAUSTI EINARSSON
ments of brown translucent glass, opaque glass, ancl a relatively few
very small fragments of crystals.
As to the coarse structureless conglomerate I can see no reason
why it should necessarily be interpreted as a moraine, although at
a glance it looks like one. In my view it is most probably a
volcanic product, extruded as a mixture of fragmental material and
it reminds us of the British necks.
We now follow the edge of the escarpment eastwards to a point
a short distance east of the highest point of the escarpment.
The interesting section here found is most probably the one ob-
served by J. Líndal (l.c.). Beneath several basaltic lavas there is the
following series of varied sediments of a total thickness of about
40 m. (Fig. 10).
Fig. 10. — Main sediments in southern side of Ljósvatnsskarð.
1. Fine-grained brown breccia. The thin section (443) is very
interesting. It shows large fragments of brown sideromelan, heavily
charged with phenocrysts of plagioclase and olivine, and a great
abundance of microlites. These fragments are embedded in an abun-
dant base of compact, somewhat fractured sideromelan of a lighter
colour and, remarkably enough, this glass is wholly devoid of pheno-
crysts and microlites. It is clear, both from the fractured condition