Acta naturalia Islandica - 01.02.1946, Blaðsíða 48

42
TRAUSTI EINARSSON
a remote resemblance to the polished surfaces left by the late Quater-
nary glaciation in this country.
If this lava surface was filecl by a glacier, that glacier must have
been thin or ineffective and to assume a general glaciation of the
country on account of such glacial work is in my opinion impossible.
But there is a further fact to be taken into account which is decis-
ively against glacial action. This is the extra-ordinary contact of the
conglomerate and the lava. The conglomerate does not touch directly
the lava surface, but there is left an open space of 4—5 mm between
them. Out of the conglomerate protrude small pebbles and on these
as on innumerable pillars rests the conglomerate.
This peculiar contact is hardly
that of a moraine and its bed-
rock, but it is on the whole not
easily understood. It seems the
most probable theory that an ori-
ginally high temperature of the
mud might in some way be the
cause (a layer of steam?).
Cortg-conz ercíúe
Fig. 6. — Lower contact of cong'íome-
rate at Glymur. See text.
Thus, as far as I am able to
see, Pjeturss’ interpretation of these conglomerates in Austurgil and
at Glymur is not convincing. The interpretation pays no attention
to the composition of the matrix of the conglomerates or to the accom-
panying volcanic products, or the peculiar contacts. On the other hand
it stresses too far the occurrence of scratched pebbles as indicative of
glacial action. And as to the striated floor, other possible agencies
such as wind erosion, the erosion of a volcanic blast (note that at
Glymur the flow direction of the lava is that of the striae), and of
the mudflow itself, are left out of consideration.
There is no conclusive proof of glacial action; on the contrary,
there are many factors against such an interpretation.
General aspects of this area. The mountains- at the head of Hval-
fjörður are, if we leave for the present Hvalfell and Botnssúlur out
of consideration, eroded out of an extensive plateau, built up of
slightly eastward dipping layers. This piateau is built up of al-
ternating layers of grey fine-grained, porous porphyritic basalt la-
vas, beds of glassy tuffs, the glassy fragments sometimes showing
no sign of longer transport, sometimes being probably wind blown,