Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 181

179
upper Fljótsdalur and Jökuldalur in Eastern Iceland but the
contact with the lower hasalts is here not clear. Further, the
group extends to Vopnafjörður and Thistilfjörður where it
rests discordantly on steeply dipping rocks. At its base are
the lignites of Vopnafjörður-Jökuldalur (Jux 1960).
In all this area from Thistilfjörður to Fljótsdalur the gently
inclined group is cut by a peneplane on which rest the large
amounts of tuff-breccia which in one word may be called
Hólsfjöll tuff-breccia. Several magnetic groups are here found
in the Young Plateau Basalts but the stratigraphy has not
yet been fully worked out, and will not be considered fur-
ther here.
We next move to the mountainous area west of Bárðar-
dalur. Here the Young Plateau Basalts are thin and occur
only in isolated patches. This is a result of the peneplanation
following upon some vertical displacements.
But in the lower area south of Skagafjörður and Húna-
vatnssýsla the Young Plateau Basalts have a wide extension.
From here they stretch to the south and west, consisting
of 4 magnetic groups in the Stórisandur area, and disappear-
ing at a height of about 700 m under thick and extensive
masses of fragmental rocks in the Central country. They re-
appear in the Hreppar—Gullfoss area with 5 magnetic groups
on one hand and in the Ok-Esja area with the correspond-
ing groups on the other. In the latter area they reach a thick-
ness of about 1000 m. The lowest groups in the Ok area are,
as far as can be seen, conformable with the supposedly Oligo-
cene lignite at Sleggjulækur. But the topmost groups, which
have a slight southeast dip, are unconformable with the lower
groups. It would seem likely that the Young rocks in Middle
Northern Iceland correspond to these upper groups rather
than to the lower ones in the Ok as well as in the Plval-
fjörður and Hreppar areas.
The conglomerates, so common in the Young Plateau Ba-
salts, are indicative of much wetter conditions than seem
to have obtained in the lower parts of the Plateau. At the