Geology
The Odenwald, along with many of Germany’s low mountain ranges, belongs to the Variscan, which more than 300,000,000 years ago in the Devonian ran through great parts of Europe. The cause of this orogeny was the collision of Africa’s and Europe’s forerunner continents.
In the Triassic, about 200,000,000 years ago, the land sank again, forming the so-called “Germanic Basin” in which the metre-thick layers of red sandstone could build up. These were later covered over with layers of muschelkalk from a broad inland sea, then followed by sediments from the Late Triassic (or Keuper). The South German Cuesta Land thus formed.
When the land in the Odenwald was uplifted again about 180,000,000 years ago, more than 100 m of the sedimentary layering, in parts, was eroded away down to the bedrock, as can still be seen in the western Odenwald. The bedrock here is made out of a remarkably great number of different minerals, among them gneiss, granite, diorite, gabbro in the Frankenstein pluton, and so on. In the eastern Odenwald, the red sandstone is all that is left of the sedimentary mixture. Farther east in the Bauland, the muschelkalk deposits still overlie the Early Triassic layers. Furthermore, in the south near Heidelberg, there is still zechstein under the Early Triassic deposits.
Roughly 50 to 60 million years ago, volcanoes formed along the great geological faults. Still bearing witness to this time are the Otzberg, the Daumberg and the Katzenbuckel, all extinct volcanoes in the Odenwald. Furthermore, vulcanism with acidic minerals has left a legacy of rhyolites near Dossenheim.
At roughly the same time, the Central European plate began to tear apart so that the Upper Rhine Rift developed. Even as the Upper Rhine Rift valley still sinks today by just under a millimetre each year, the Odenwald, relatively to that, was uplifted to the height it has today. Along the faults, the small rivers Gersprenz and Weschnitz have, in part, carved their courses.
The Upper Rhine Rift is part of a fracture zone reaching from the Mediterranean Sea to Norway. Right on the edge of the Odenwald, it is roughly 2 500 m deep, but has been filled in to its current height by river and sea sediment, for until about 20,000,000 years ago, the North Sea reached far inland, across the Wetterau Depression into the Rhine Valley.
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