If we draw, a line along tlie Hardangerfjord and continue it eastward
to Lake Mjosen, we have on its southern side a great Archaean
region in which gneiss and foliated granite are prevalent rocks.
Telemarken is. a province in southern Norway. A peculiar
series of Archaean ròcks, the Telemarken series, occurs in it and
in the adjacent region to the north of it. Many of the rocks
here are obviously clastic such as conglomerates, sandstones and
clayslates, but besides these rocks crystalline schists as gneiss,
granulite, hornblende schist also occur. The strata are folded and
often traversed by granitic dykes.
Kongsberg «the King’s mountain» is a celebrated mining town
about two hundred and fifty years old, one of the few places in
the world where native silver is the chief ore. The silver, which
sometimes occurs in good crystals, besides' other minerals, has
made the mine well known among mineralogists. A peculiar relation
existing between the ore in the veins and the «country» rock
has been a puzzle to the students of ore-deposits for more than
a century. The region consists of vertical strata, striking north
and south, of gneiss, quartz schists and mica schists. In two
bands lying in the line of stratification, the ròcks contain grains
and small patches of pyrites and other sulphurets. The rocks
assume a rusty appearance where the pyrites occurs, and the
bands can by that character be followed on the surface without
difficulty. The silver-bearing veins run across the stratification
in an east and west direction. The veins are vertical fissures
filled with different minerals, chiefly calcite. The silver occurs in
paying quantities only where the veins intersect the pyrites-
bearing bands of the «country» rock. No satisfactory explanation
has as yet been given for this remarkable fact. I t has been
suggested that the pyrites increases the electric conductivity of
the rock and that currents of electricity passing thròugh these
bands have precipitated the silver from solutions circulating in
the fissures, which have become the. veins.
A great Norite region occurs in the vicinity of Ekersund in
the south-west. Some varieties contain titaniferous iron-ore as-a
constituent and in a few "places such ore is concentrated to dykelike
or vein-like masses which have been worked for, mining purposes.
. From a theoretical point of view this occurrence has been
of interest as showing an instance of ore-deposits formed in an
eruptive way by differentiation within an eruptive mass.
CAMBRIAN, SILURIAN AND DEVONIAN.
We can form only very uncertain opinions about the condition
of the earth during the' first long division of its history,
the Archaean period. The oldest remains of organic life have
been preserved in the rocks formed during the Cambrian period
and from that time, we may, as we all know, follow the history
of life until the present time. In Norway we possess the oldest
fossiliferous strata, but only up to the Devonian. Then a great
gap follows, with only a single small patch of Jurassic strata, until
the quite recent deposits of the Ice Age.
During Cambrian and Silurian time the open sea extended
over the greater part of Norway. On the bottom of that sea,
lime, mud, sand and gravel were laid down forming a series of
strata attaining a great thickness. The organic remains therein
are of invertebrate animals, graptolites, trilobites, corals and upon
the whole showing the general characters which the fossils of
these old deposits show everywhere.
The oldest deposits are called in Norway the Sparagmite
formation, after the prevailing rock. The Sparagmite is a felspar-
bearing sandstone, consequently the name corresponds somewhat
to the word Areose often used in' the geological literature of other
countries.
Strata of Sparagmite of enormous thickness and but little
disturbed, form a great portion of the rather monotonous region
in the interior of Southern Norway to the north of Kristiania
(Sp on the map).
The tract between Lake Mjosen and the little Langesunds-
fjord is called the Kristiania region. The interior consists
of Post-Silurian eruptive rocks 'which are covered with forests.
These eruptives exhibit a long and remarkable series of granular,
crystalline, granitic and syenitic rocks and of porphyries. The
eruptives are fringed by Cambro-Silurian strata. Sandstone is
present here only to a very small, extent, while clay-slate and
limestone are ' the prevalent rocks often abounding with fossils.
The rocks weather easily and we find here some of the best soils
in Norway. The beautiful hilly country and the smiling islands
in the immediate neighbourhood of the capital have this formation
as their sub-soil.