Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 180

178
is in part synonymous with the name Grey Stage (Graue
Stufe) introduced hy Pjeturss (1905) and assumed hy him
to be of Pleistocene age. But the stress laid on the grey colour
of the fresh basalts is quite misleading, as we have indicat-
ed, and on this basis the occurrence of the group has been
assumed to he much more general than is the case. In my
studies in the Eyjafjörður area after 1935 I recognized that
there are nearly always fresh grey basalts at high elevations,
although they are not to be distinguished from the lower rocks
in other respects. Similarly, at Steingrímsfjörður the Eocene
basalts become quite fresh and light-grey, and are devoid of
infillings, above a certain elevation. This is clearly related
to the possibilities of warm groundwater to circulate in the
rocks at the time of the formation of the infillings.
Quite similar results have been obtained by Walker (1960)
in extensive studies of zeolite zones (nearly horizontal) in the
dipping hasalts of the Eastern Fjords in Iceland. Walker finds
that, irrespective of stratigraphy, the basalts become fresh
and grey at the highest elevations. This led him to assume
the other extreme: that there is no separate group at the top
of the Plateau which could be stratigraphically distinguished
from the main mass. We have here partly come to a similar
result. Between the lowest cold climate beds in the Borgar-
fjörður (Ok) area and the supposedly Oligocene lignite at
Sleggjulækur there is no angular unconformity. Similarly,
in Stóradalsfjall at Ljósavatnsskarð and in Skessuskálarfjall
there is no clear unconformity between our Young Plateau
Basalts and the lower hasalts. On the other hand an uncon-
formity is found at Stóruvellir and in the Esja area. And
the difference in the sediments and often in the volcanic
rocks is clear. Primary hreccias are very common in the
upper rocks while they are nearly absent in the lower ones.
Thus a distinction of an upper part of the Plateau basalts
seems justified, but the name Grey Stage is not well chosen
and should he abandoned.
The Young Plateau Basalts have a wide extension at the