Rit (Vísindafélag Íslendinga) - 01.07.1962, Síða 160

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absent and possibly they never covered this part of the tuff-
breccia heap. It is at any rate clear that the Ok lavas have
never been thick on the northem slope. It is also likely that
the same applies to the other sides, for the characteristic por-
phyritic Ok lavas have a very short extension towards the
south. In Flókadalur, as far west as Steðji, is found a lava
flow which must have originated in Ok or in its neighbour-
hood, but it does not belong to the porphyritic lavas.
It would seem that the tuff-breccia of Ok formed originally
a flat cone and that it was built up between the flank moun-
tains Oköxl, Fanntófell, and Lyklafell which are erosional
remnants of older tuff-breccia masses.
A late stage in the volcanic activity of the Ok area is re-
presented by the Bræðravirki breccia ridge which is about
2 km long and has a relative height of less than 20 m. A sec-
Fig. 85. Section through the Bræðravirki breccia ridge.
tion through the ridge is shown in Fig. 85. On a coarse wea-
thering layer on the porphyritic Ok lavas is a general yellow-
brown eolian layer, 10—20 cm thick. The Bræðravirki vol-
canic breccia was pushed through these layers and we find
them much distorted and mixed with the breccia. The figure
shows a core C of the weathering and eolian material within
the volcanic breccia B. It seems possible that the emption
was sub-glacial.
Summing up, we have gained important new insight in
this area. It is much clearer here than in Hvalfjörður or