Geology of the Nahe valley
400 million years ago, in the
Devonian period,
Europe was near the equator and the climate was warm. A shallow ocean with
islands covered central Europe, in which Hunsrück formed a deeper basin of
this ocean with a stable layering of water. The upper water layers were rich
in oxygen and supported life, whereas the lower levels were poor in oxygen
and poisoned by hydrogen sulphide. The remains of living organisms sank into
the black mud and were quickly preserved by ferrous sulphide, which is why
they have kept so well. In the Herrenberg slate quarry near
Bundenbach
a large number of world-renowned fossils were found that, when x-rayed, showed
even the finest details. The rivers that flowed into the Devonian sea deposited
large amounts of muddy sediment, sand, gravel and clay, which, due to pressure
and heat over millions of years, became layers of stone and rock. In this
way, depending upon the material and coarseness, slate, sandstone,
and (with a high percentage of quartz grains) Taunus quartzite were
created.
300 million years ago, at the end of the
Carboniferous period,
the Devonian layers of the Hunsrück were pushed together by massive pressure
from southeast to northwest creating the Variszicum mountains (the northern
chain). Together with the Hochwald, Idarwald, and Soonwald chains, a high
mountain range was formed. The debris resulting from the erosion and weathering
of this range was deposited in the basin on the south flank, building up the
"Lower Rotliegende". After another rising of the mountains and sinking of
the basin the process was repeated creating the "Upper Rotliegende". During the
Permian period
the formation of mountains was accompanied by strong volcanic activity on
the southern fault of Hunsrück. Lava welling up from inside the earth cooled
and formed layers harder than the Rotliegende. Depending on the composition
of the lava and the rate of cooling, very different types of rock were created:
from thin lava with little silicic acid (SiO2) came basalt, melaphyre,
and dolerite
(Hellberg).
Lava with a medium level of SiO2 created andesite and porphyre
(Lemberg),
and from thick lava with a high level of SiO2 came red-coloured rhyolite
(Rotenfels).
Occasionally gas bubbles were preserved in the lava and later filled with
minerals to form
agate geodes.
Short glossary of geological terminology.
The landscape of the lower Nahe between Bad Sobernheim, Bad Kreuznach, and
Bingen still essentially resembles how it was in the
Oligocene period,
35 million years ago. At that time the valley was covered by an ocean, whose
coastline ran along the bay of Kreuznach and the bay of Staudernheim (Bad
Sobernheim) with an island archipelago in the south. It is quite exceptional
in the history of the earth for the coastlines from earlier epochs to still
exist.
In the sand pits near Bad Sobernheim you can find petrified pinecones,
which have been preserved in the sandy beach ("stony peas"), or admire the
sea cliff south of Bad Kreuznach from
Steigerberg,
an island in the Oligocene sea.