Saxothuringian Zone - Geology

Geology

The Saxothuringian Zone consists of early Paleozoic marine sediments that were deposited in the so-called Saxothuringian Basin. They were slightly metamorphosed during the Hercynian orogeny. The sedimentary sequence is assumed to be continuous from the Ediacaran to the Visean (330 million years ago). These metasediments form a wide zone north of the city of Dresden in Saxony.

Tectonostratigraphically, gneisses (high grade metamorphic rocks) and granites are found under these metasediments. They crop out as the competent massifs of the Erzgebirge and Saxonian Granulite Massif. They were deformed and recrystallized during the Cadomian orogeny (in the Ediacaran, 650-550 million years ago) and intruded by felsic plutons during the Cambrian and Ordovician (540-420 million years ago).

In some places klippes of allochthonous crystalline rocks are found on top of these two units. These klippes are the Münchberg complex, Wildenfels complex and Frankenberg complex. They consisted originally of a sequence of deep-marine (flysch) sediments of Ordovician to Devonian age (480-360 million years old) and early Paleozoic mid-oceanic ridge basalts. The latter have been metamorphosed at a high grade (up to eclogite facies). These allochthonous nappes can probably be correlated with the Teplá terrane in the Moldanubian Zone further south.

The Saxothuringian Zone is often also supposed to include the Mid-German Crystalline High, which then forms the northern part of the zone and lies directly next to the Rhenohercynian Northern Phyllite Zone. The Mid-German Crystalline High crops out in the Odenwald, the Spessart and the northern Vosges. It consists of Proterozoic orthogneisses and early Paleozoic volcanic (amphibolites with MORB-protoliths and tuffs) and sedimentary (pelites, calcareous schists and marbles) rocks that were metamorphosed at high grade during the Hercynian orogeny (up to amphibolite facies). These rocks were intruded by two generations of plutons: Silurian to Early Devonian (440-400 million years old) granitoids and middle Carboniferous (Hercynian, 340-325 million years old) granites.