Acta naturalia Islandica - 01.02.1946, Blaðsíða 17

ORIGíN OP THE BASIC TUFFS OF ICELAND
11
G. Bárðarson in his Icelandic text book of
geology10) accepts the main conceptions
of Thoroddsen that the Palagonite Forma-
tion fills a gap in a sunk central zone of the
old basalt plateau. Fig. 1 which is reproduced
from his book, shows his and Thoroddsen’s
scheme.
The distribution of the Basic Tuffs in the
areas where they are most prominent is ex-
tensively dealt with by Thoroddsen in his
“ísland”, and is shown on his geological map.
As to the “Basaltformation”, it must be re-
membered, however, that Thoroddsen did not
accomplish more thali a few ascents of its
high mountains and his knowledge of it was
bound to be rather fragmentary. Thoroddsen
points out that layers of “Palagonite breccia”
are occasionally embedded in the „Basalt-
formation”. In reality such material is very
common in the “Basaltformation”. The result
is that Thoroddsen’s and Bárðarson’s views
as to the relation between a Palagonite
Formation and a Basalt Formation are far
from the truth.
The picture envisaged by the present
author will be presented in the concluding
chapter. —
The origin and nature of the Basic Tuffs
have always been one of the main problems in
Icelandic geology and it has occupied some
well-known scientists such as v. Waltershau-
sen. R. Bunsen and A. Penck.
Sartorius v. Waltershausen, who brought
the matter up for discussion, ascribed the
formation to submarine chemical alteration
of basaltic volcanic ashes, through which a
brown or yellow substance, the palagonite
should be formed.
On the other hand, it was clearly expressed
Fig. 1. — Geological structure of Iceland according to G. G. Bárðarson. An E—W section looking south. 1. Older Ba-
salts. 2. Lignite. 3. The Younger Basalts. 4. Pliocene of Tjörnes, covered with hasalt. 5. The palagonite Formation
with intercalated layers of basalt and dolerite, filling the supposed great gap across the centre of the country. 6. Sur-
face lavas. 7. A dome and young lavas of dolerite.