Greinar (Vísindafélag Íslendinga) - 01.01.1976, Blaðsíða 136

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Fig. 7: The present state of the Jórukleif fault. Heights in meters above sea-level.
A: looking NE; 1-2 = breccia- and lava parts of the western dolerite formation.
3 = unporphyritic basaltic subaquatic breccia, to such a degree intergrown with
more or less stooping blocks of the dolerite that the eruption is considered simulta-
neous with the initial faulting. 4 = strand terrace with well rounded pebbles of
basalt up to 6 or 7 cm in diameter, resting on plagioclase coarse-porphyritic breccia
4a. At the lake (about 103 m), the dolerites 2 crop out, up to 8-15 m above the
lake level, in part directly covered by the unporphyritic breccia 3a, corresponding
to 3, but largely by basaltic sediments formed at the shore of the lake during a
150 m stand of its level. B: looking SW; 2 = dolerite, s = fine-grained sediment,
3 = the unporphyritic breccia, 4 = dolerite blocks, 5 = filling of a fissure,
6 = vertical slickensides. None of the details of Fig. 7 are mentioned in (16).
ated at the crossing of major fractures. The case for true point
eruptions as a cause of the shields is then fairly strong. It is on
this basis that we suggested in a) that Skjaldbreidur is due to the
crossing of conjugate fractures; the Sandey line may then have
continued to the NE as a volcanically inactive line, until it cros-
sed the Thverfell line. If so, magma was present at depth all along
that continuation of the Sandey line, it only needed a path to the
surface. The valley volcanoes, and not less the dolerite shields,
suggest the idea that there was a wide magma layer, although it
only led to volcanism where the stress field created special funnels
for it to the surface.