Upon the Silurian slate and limestone of the Kristiania
district follows a series of sandstone, mostly reddish, not separately
marked on the map. Only some very few and ill preserved
fossils have been-found therein, probably this sandstone is Devonian,
corresponding to the «Old Bed» of the British Islands. The rest
of the supposed Devonian of Norway forms four areas on the
west coast to the north of Bergen. Fossils are absent here.
If we draw a line from the southernmost point of Norway,
Lindesnes, to the North Cape, such a line divides, in a broad
way, the Scandinavian peninsula into two parts, which are very
different in so far as the .area to the east has not been subject
to mountain-making compression to any considerable extent since
the beginning of the Cambrian period. We may call it «The
Scandinavian-Finnish plateau»; I t is, upon the whole, a flat and
low but uneven land, in which the Gulf of Bothnia occupies a
shallow basin. The south-eastern part of Southern Norway belongs
to this plateau.
To the west of the above-mentioned line we have «The Western
Scandinavian Mountain Region»’, where the earth’s crust has
greatly been contorted since the Silurian period. The Cambro-
Silurian rocks have been altered by this folding process, and the
underlying Archaean has been squeezed into them and has also
been altered.
The consequence is, that in many cases it is difficult to
separate the altered Cambro-Silurian from the Pre-Cambrian rocks.
An additional difficulty is, that not folding alone but also overthrusts
of enormous extent seem to have played a role in the
construction of the mountain regiom The highest part of the
Scandinavian peninsula is the district to the east of the inner
part of the Sognefjord, the Jotun mountains. Masses of gabbro,
which has existed before the folding process and has been acted
upon by it, are here predominant and constitute the rock of the
highest peaks.
While the Cambro-Silurian rocks of the Kristiania district are
chiefly shales and limestones, and in the Sparagmite area chiefly
sandstones, in the Trondhjem area which comprises the country
to the south and east of the Trondhjemsfjord, the Cambro-Silurian
has quite another aspect, as great volcanic activity characterised
the Cambro-Silurian period in these parts. Deposits of great
thickness occuring here were probably originally composed of basic
volcanic ashes and lava-streams. The rocks are’principally finegrained
and more or less schistose rocks of a greenish colour due
to the presence of chlorite or hornblende in microscopical • or
almost microscopical grains. Acid tuffs may also have been thrown
out of the ancient volcanoes, but it is more difficult to point out
rocks which have been formed of these. Deep seated eruptives
occur as metamorphic granite and gabbro, also a great number of
dykes altered by pressure. The ordinary sedimentary deposits inter-
stratified with the volcanic rocks show by their nature that they,
as a. rule, have been formed in shallow water. Beds of conglomerate
attain considerable thickness. The clay-slate has in several
areas been converted into mica schists. Limestone, which is generally
altered into marble is often interstratified with the schists.
Fossils are found in some places in the Trondhjem region. They
belong to the upper part of the Cambrian and to the Silurian,
but these fossilbearing localities are too few to give us more than
a very limited account of the succession of rocks in this great
area. Fossils are also found at very few places in the. altered
Cambro-Silurian of the western part of Southern Norway.
The Cambro-Silurian northwards from the Trondhjem region
is even less known. Some few traces of crinoid stems have been
found. Beds of limestone and dolomite attaining considerable
thickness occur in some places on the coast of Northern Norway.
These deposits are now beginning to be worked for marble, and
it is hoped that an industry of considerable importance may develop.
Some very pretty " varieties consist of pressed conglomerates of
limestone fragments showing different shades of red.
Some interesting ore-deposits occur in the region described.
They, consist of pyrites sometimes containing a small percentage
of copper, making it valuable as a copper ore. The Boros . Coppermine
has been worked for two hundred years, while Sulitjelma
Coppermine (somewhat north of the Polar circle) has been worked
only a few years but has developed quickly. The ores occur as
rather pure lenticular masses in schists. These masses attain such
a very great length in proportion to their thickness that they
assume the form of sedimentary strata and they have even been
regarded by several geologists as having been formed by some
sort of sedimentation in a similar way to bog iron ore. But it
has been pointed out, on the other hand, that they always occur
in the immediate neighbourhood of masses of altered gabbro. They