Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 110

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very clearly that to the north of Ingólfsfjall there must have
existed relatively higher terrain.
Rather gradually, in the present section, the primary cha-
racter of these layers becomes more predominant as we come
higher and we have finally a very thick tuff-breccia contain-
ing here and there larger basalt masses, but I have not at-
tempted to differentiate it further. But the thick coarse breccia
below the sediments can be traced northwards as far as Kaga-
gil. On the east side of this gully can be distinguished a high-
er member: a thick formation of tuff-breccias dipping 15—22°
south.
It should be added that in the present area many fractures
are seen that have the same trend as the present westem wall
of Ingólfsfjall. The trend of the wall is marked by faults and
this applies also to the slope farther north, from Svartagil
to Stóri Háls.
Partly these walls are the result of displacements but nor-
mal erosion, guided by the faults, has had very great influence
in shaping of this landscape. At Miðmundagil on the north
side of Ingólfsfjall the upper group falls to lower levels in
steps and the older group is not seen.
The stratigraphically important distinction of an older
and younger group in Vörðufell and Ingólfsfjall can also be
made in the mountains northwest of Ingólfsfjall, at least as
far as Reykjadalur. The older group forms the lower part of
Reykjafjall as I have described elsewhere (Einarsson 1951).
Here an erosion surface cuts the displaced lower rocks, appa-
rently including the group n,. A moraine, probably m2, co-
vers the plain and is overlaid by the fresh breccia n2. The
erosion plain, however, dips here considerably southwards.
It rises nearly to 400 m in Self jall and Klóarfjall, where the
upper group is rather thin, and southeast of Reykjafell it
falls down nearly to the lowland, where we can trace the
lower reverse breccia beyond the main road near farm Vellir.
This shows that the mountains are uplifted relative to part of
the lowland, although large parts of the latter are due to later