Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 81

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in one way or another over the edge of the slope, but later
lavas flowed over the scree and down the slope.
The slope formation was later cut by a number of dykes
and other small intrusive bodies.
The layers seen in Stórkonugil are not part of the near-
horizontal primary tuff-breccia formation; they are a young-
er peripheral formation deposited at a fault in the main for-
mation. The following picture can now be envisaged:
The core of Ármannsfell belongs to the main Súlur tuff-
breccia and was thrown down at the main fault line which
runs along the eastem wall of Súlur, and as part of a much
larger subsided block. At this time Ármannsfell and Gagn-
heiði probably did not rise markedly above their surround-
ings within the graben. Later a new fault was formed near
the east side of the present Ármannsfell and an eastern block
sunk farther, so that here a steep slope was formed. Before
this movement dolerite lavas (of normal polarity) had been
poured out within the graben and debris from these lavas
was now cleared over the edge of the new slope and new
lavas also found their way into this slope.
It is possible that the new graben was slowly filled up,
both by advancing scree and lavas as well as by volcanic
activity within the graben itself (cf. Hrafnabjörg below).
After a long period of erosion of the surface of the Ármanns-
fell block this surface was covered with eolian sediments
which indicate that the block did not at that time rise mar-
kedly above its surroundings. There was then also further
explosive volcanic activity from which lapilli and finer ash
fell over the Ármannsfell area. Only after this, or at least
later than the eolian sediments, a new tectonic cycle set in.
During this the present mountains Gagnheiði, Ármannsfell,
as well as Lágafell and Mjóufell were uplifted by several
hundred metres. This took place before the last glaciation,
even long before that time, to judge from the thick mantle
of weathering — covered by a hard moraine — which covers
the present slopes of Ármannsfell.