Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 31

31
255 m. Fresh basalt, reverse magnetization.
270— Brown conglomerate, 10 m thick, covered by a lava
of columnar and kubbaberg structure. Reverse mag-
netization.
410— Brown soft sandstone covered by a reverse lava.
At the gully B the old basalts reacb to about 310 m. They
are very much split and in part decomposed by weathering
(can be crushed with the fingers). Yet, no infillings are seen.
They have normal magnetization, where testing is possible.
A dyke is cut off at the surface of the basalts. On this rest
about 90 m thick sediments, best seen at the head of the
gully and in the west side. They consist nearly exclusively
of brown sandstone and fluviatile conglomerates, a clear delta
formation. Cross-bedded sandstone at the top seems to be of
eolian origin. At the head of the gully we find this section,
from above:
Fine sandstone. Then a 10—12 m thick delta formation,
consisting of alternating layers of sand and coarser river gra-
vel, with a dip of nearly 40° W or a little south of west. The
gravel is smooth and well rounded down to grades of 2—3 mm
but below 1 mm the grains (basalt and glass) are mostly an-
gular. There are many different varieties of basalt and scat-
tered pebbles of rhyolite, and glass grains are not uncommon.
The brown colour is due to a coat of iron oxides around each
grain. At some places there are fractures into which higher
members have crept or been squeezed. The covering sand
and a layer with numerous rhyolite pebbles, which must
have existed in a soft state when the fracture was formed,
have crept or have been pushed into it. Possibly the fracture
is due to sagging in the steep advancing delta front.
These layers rest on a much coarser fluviatile gravel with
a common block size of 20—30 cm, but also with blocks of
up to 1 m in diameter. Finer gravel of 3—8 cm fills the spa-
ces between the blocks but there is hardly any sand or clay.
The layer is 6—7 m thick and nearly horizontal. It rests on
a 1 m thick grey conglomerate with a moraine-like appear-