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GEOLOGY.
43
with the grey or red limestones deposited on them, and again other
clayslates, belong to the Lower Silurian. Conformably overlaid the
Lower Silurian rocks are the Upper Silurian deposits of limestone,
marl-slates, and sandstones, which extend over the whole of Gotland, the
western part of the Silurian area of Jemtland, the greater part of
the Silurian area of Skåne and minor parts of that of Dalarne,
Östergötland, and Vestergötland. In the sandstones and alum-slates of the
Cambrian system we meet with fossil remains of the earliest animal
life known in Sweden, viz. medusæ, worm-tracks, trilobites, and others —
all water animals. The Silurian rocks contain numerous petrifications
of trilobites, orthoceras, graptolites, bivalves, crinoids, corals, and
others. In the Upper Silurian strata of Gotland have been found the
earliest air-breathing animals known, a scorpion and an insect.
Mount Kinnekulle in Vestergötland gives easy access to well
developed Cambrian and Silurian strata. A section of the mountain is
given here below.
Section of Mt. Kinnekulle.
From West to Bast. Scale of height five times as great as that of length.
a. Archæan gneiss. — 6. Sandstone, grey or yellowish, 34 meters. — c. Alum-slate with
bitaminous limestone, 22 m. — d. Lower Graptolite-slate underlaid by a layer of
Cerato-pvge-limestone, together 11 m. — e. Red and grey limestones (Orthoceras-limestone), 52
m. — /. Chasmops-limestone, 10 m. — g. Trinucleus-slate, 34 m. — h. Upper
graptolite-slate with a 3 m. thick layer of Brachiopode-slate, 56 m. — i. Diabase.
A meter = 3 281 feet = 1 094 yard.
In like manner as on Kinnekulle, there is also on Billingen, on
Halle- and Hunneberg, and some other mountains in Vestergötland a
bed of diabase, which, overlying the Silurian strata, has kept them from
destruction in consequence of its greater hardness and power of resistance.
The Silurian districts of Dalarne, Nerike, Östergötland, and Skåne, on
the other hand, have been preserved to our days, because, after the
Silurian age, they were displaced by great dislocations and sunk below
the surrounding parts of the ground, thus being protected from the
forces ordinarily active in gradually abrading and destroying röck
surfaces.
The Cambro-Silurian beds have well-nigh everywhere an almost
horizontal position, except in western Jemtland and in the alpine regions
farther north, where they have been much folded and compressed when
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