Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 158

156
Fig. 83. Section of the spur between Lambá and Geitá.
Explanation in the text.
Geitá and Lambá. At Lambá we have then the section shown
in Fig. 83. In the lower wall we have the reverse basalts (1),
the sediments (2) and the Bæjarfell group (3) cut by an
erosion slope (4). On this slope is a remnant (5) of the high-
porphyritic, shieldvolcano-type Ok lavas. This isolated occur-
rence shows on the one hand considerable erosion of the Ok
lavas, on the other hand it proves the existence of the valley
slope at the time of the Ok eruption.
The main layers in the lower part of Bæjargil extend west-
ward and form the Húsafell mountain and are clearly equi-
valent to the Valagil normal group. The reverse group r3 is
also found west of Húsafell at several places. The dip is vari-
able, 9—10° SE near Húsafell but 5° SE above Augastaðir.
There is a number of faults which are sometimes confusing
but the occurrence of the two dipping Plateau groups here
is undoubted.
At 350 to 400 m these Plateau groups are cut by an ero-
sion horizon and covered by hard sediments which contain
considerable amounts of rhyolite. This is natural as rhyolites
have been cut. On this horizon at Ásgil we get much fresher
basalt lavas and kubbaberg of normal polarity and slight dip,
about 3° SE. Similarly there are just west of Valagil several
hills, Giljahnúkar and Auðsstaðahnúkur, representing rem-
nants of such a group, fresh basalts of normal polarity, with
a dip of 2—3° SE. In the northemmost Giljahnúkur (442 m)
we have fresh kubbaberg on top, then grey basalt lava, thin
light-brown sandstone, grey basalt lava, 6—7 m grey moraine
resting at about 385 m on the glacially striated surface of the