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48
I. PHYSICAL GEOGRAPHY.
System. The four last-named only occur within the Province of Skåne.
In addition there are deposits of gravel, sand, clay, etc., dating from
the most recent period, the Quaternary Period; these deposits form as a
rule a more or less complete surface-covering.
The Archaean rocks are of many different species, e. g. gneisses and
granites, porphj’ries, leptites, limestone, mica-schist, phyllite, quartzite,
and greenstones. >
The largest £meiss-district of Sweden extends over the western half of the
southern and central parts of the country, from Skåne to Lake Vänern, and further
northwards through western Värmland. Another less extensive area occupies the
main part of Södermanland and has outliers stretching into the adjoining
provinces. Gneisses prevail too in a large area along the Norrland coast. In all
these areas the gneisses are very varied as regards structure, composition, etc.
The so-called iron-gneiss, a red, even-grained variety impregnated with small
grains of magnetite, is typical of the first-named area; besides it a grey, banded,
and distinctly schistose gneiss is important. In the Södermanland district the grey
"garnet-gneiss" is the most characteristic variety; it often contains the accessorial
minerals: sillimanite, graphite and cordierite. Of other characteristic varieties
met with in the gneiss areas there may be mentioned the green pyroxene-bearing
"Varberg granite", which has been quarried to a large extent at Varberg in
Hal-land.
Porphyry is found in several of the provinces of Sweden, though principally
in the eastern half of Småland, in Dalarne, and in Lappland. In the Dalarne
porphyry region, especially in the parish of Älvdalen, several hard, beautiful,
rich-coloured varieties are found; they are worked up at the Älvdalen Porphyry
Works. — The porphyries have the character of surface eruptives; they are
supposed to have flowed over the previous rock-surface and solidified there as
more or less extensive beds, like the lavas of a later date.
Partly allied to the porphyries, and sometimes difficult to distinguish from
them, are the fine-grained crystalline schists termed leptite (formerly
"hälleflint-gneiss" and "eurite"). Leptites prevail over fairly wide areas in northern Sweden,
as well as in the provinces of Västmanland and Dalarne; small areas are met
with also in other parts of central and eastern Sweden. In the coast district
near Västervik in Småland, as well as in Dalsland Archæan quartzite has a
considerable distribution.
In the leptite areas, and — though more rarely — in certain gneiss areas too,
there occur layers and lenticular masses of crystalline limestone or marble.
This is mainly the case in the eastern parts of central Sweden. At several
places the röck is utilized for architectural and decorative purposes, and also for
burning to produce lime.
The leptites, gneisses, etc., are as a rule found pressed and folded, and in
many respects altered and transformed in character and appearance, so
that it is a matter of difficulty to determine their original nature; in
close proximity to them there are, however, in some localities sedimentary
rocks, whose clastic nature is still preserved. Of these deposits the
Grythytte formation, in Örebro Län, deserves to be mentioned first; it
consists mainly of slates but also of a coarse conglomerate containing
pebbles of the rocks of the gneiss and leptite division, but not of the
adjacent granites. Further there may be mentioned the occurence of the
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