Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 138

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breccia and pillow lavas. Although outcrops are not
good it is possible that this thick mass could he divided
into smaller elements but this has not been attempted.
The basalts below the breccia have a general dip of 2°
north, and the breccia layer as a whole seems to have been
tilted in the same way.
The main volcanic hiatus is no doubt between (1) and (3).
Below we have much split and infilled basalts while a re-
gular succession of fresh rocks starts with (3). The upper
rocks form Sámsstaðafjall and are seen also to occur below
rhyolite in Skeljafell, but an unbroken link with Stangarfjall
is not seen. Unless there is here a major displacement, the
dipping younger rocks in Búrfell fit very well with the lower
part of Stangarfjall. The great difference in the state of al-
teration may perhaps be due to rhyolite intrusions of which
none are seen in Búrfell.
At the southwest end of Heljarkinn the deep gully of Grjótá
cuts through the deeper layers below rx and n2 in Heljarkinn.
We have here the section shown in Fig. 69:
(1) Thick altered dark-brown fine sediment, secondary (?).
(2) Rhyolite, probably a lava flow.
(3) Moraine.
(4) Basalt lava of faint reverse magnetization.
(5) Rhyolite.
(6) Reverse basalt lava.
(7) Thick yellowish sandstone.
(8) Thick rhyolite layer.
These rocks are, south of Grjótá at about 470 m, covered
by one much fresher reverse lava which clearly corresponds
to r1? while the lower rocks correspond most naturally to r3.
This thin remnant of rx extends as a narrow crest southwest
to Geldingadalsfjall, where also a fresh normal group, n2, is
left in between rx and r3. Here r3 consists mainly of a thick
primary basalt breccia.
Below r3 we find here an extensive normal group which we
shall call n4. Selklettar, Skriðufell, and the most of Hagafell