Once upon a time…
…225 million years ago. At the time when the present continents were still connected and were not yet separated by the continental drift, the present wine-growing area of Franconia was situated in the midst of a huge flat basin (Germanic basin), within the continental landmass, which then included North America as well as Central and Northern Europe. Between the northern land mass and Godwanaland, the southern land mass, which would later form South America, Africa, Australia and Asia, there was a large ocean, the so-called Thetys Sea. This ocean included numerous islands and was characterized by considerably varying depths. This ocean’s coastline could be found in the region of the contemporary Lower Franconia, which consequently was repeatedly flooded by the Thetys Sea. At that time, plants and animals existed on the whole world. Conifers and ferns were the most common plants on the land, and reptiles (dinosaurs) were the most common land mammals. Fish and amphibians lived in the inland waters and in the oceans there were mussels and mussel-like animals. The first mammals came into existence. Humans did not emerge until 224 million years later!
During this geological period, in today’s wine-growing Franconia those stone layers were deposited which nowadays represent the largest surface part and thus characterize geology, the landscape, the soil and after all, the wine. This period of time is called TRIAS, because in this period three particular and different epochs are distinguished: The NEW RED SANDSTONE, MUSCHELKALK, and the KEUPER. These epochs, which are geologically expressed in three rock layers, fall slightly eastwards and thus create the Franconian stratum landscape.
The New Red Sandstone
225 million years ago, the flat basin of Lower Franconia was surrounded by high mountain regions – in Franconia’s east the Bohemian mass, in the south Vindelician land, which was later on swallowed by the first formation of the Alps. Erosion caused the flowing of weathering products from there into the rivers which lead them into the basin where they were spread. The erosion products of the huge rivers were alternating coarse, fine sandy or clayey. These sedimentation order lead to the current manifold layers of the New Red Sandstone. In certain layers of the upper New Red Sandstone the fossilized trail prints of the “hand animal” (chirotherium) can be discovered, which was a predator-like dinosaur whose skeleton could not yet be found. At that time, the climate was mainly dry and extremely warm, similar to the contemporary desert regions in inner Asia.
The sandstones of the New Red Sandstone, which is of a red colour, is mainly formed by quartz grains, which are covered by an iron layer – this leads to the red colour and the name – or by a manganese layer (black).
The Muschelkalk - shell limestone
10 to 15 million years later, the Thetys Sea flows on the sedimentary sandstone layers into the flat basin of today’s Franconia. Back then, Franconia might have been located at the deepest spot of the basin. The flooding by the sea was alternating shallow or deep. At the same time, the climate changed – it became dry and worm, comparable with the current conditions of the southern Mediterranean. Thus an abundant flora and fauna could evolve. The sea was rich in lime algae, sea lilies, mussel-like animals (terebrates), mussels, oysters and cephalopods (ceratites). There was a high number of sharks, as the numerous fossilized shark teeth findings show. Even many dinosaurs existed in the sea!
The change between flooding and dry seasons formed the numerous sedimentary layers of the Muschelkalk. Three main categories can be distinguished: the wave lime, the central Muschelkalk and the main Muschelkalk. The Muschelkalk rocks are clayey limestone.
The Keuper
After further 10 – 15 million years, together with a new climatic change towards humid (subtropical) and arid (desert-like) conditions, the epoch of the Keuper starts. The basin, in which Lower Franconia can be found, is not as deep as before due to the sedimentation of the New Red Sandstone and the Muschelkalk. A steady change of the sea, brackish water, mud flats, lagoon, swamp, delta and rivers characterizes the formation of the Keuper. The flora is rich and varied. Horsetails, ferns, palm ferns and conifers cover the large vegetation belts of the basin. Among the animals, insects and mussels are the most common. Sharks, lungfish and ray-finned fish (caridosuctor) are the animals represented most often in the oceans. The most common land animals are lizard dinosaurs, amphibian dinosaurs and dinosaurs. Dependent on these varied conditions many sedimentation layers and rocks deposited due to the alluvial land, dying plants or evaporation. Here, just as it is the case for the Muschelkalk, as well as distinction between three categories is made: the lower Keuper, which is the so-called “Lettenkeuper”, (clay Keuper), the central Keuper and the upper Keuper. The dominant Keuper rocks are clay rocks, clay types and clay marl, these are called “Letten” when wet. Furthermore, there are large amounts of gypsum rock and sandstone. The name of “Keuper” allegedly originated from the old terms “Köper” for colourful cloth, “Küpper” for potter’s clay or “Kipper” for earth and stone chippings.
How our landscape evolved…
During the TRIAS, rock formations were mainly horizontally deposited. The present landform was not created until 170 million years later, i. e. 30 million years ago. At that time, large tectonic movements of the earth’s crust began. Due to the lowering or the fall respectively of the present upper Rhine fault by 2.000 metres in Western Franconia, the layer plates of the Trias were put up in slopes, partly tilted and warped. These elevation was 1.000 metres in the Spessart region, 500 metres around Würzburg and 200 metres in the Steigerwald area. This leads to the sloping position from the west to the east in the stratum landscape of wine-growing Franconia. In the east this process was limited by the formation of the Thuringian forest, the Franconian forest and the Fichtelgebirge. The formation of the Alps in the south of this huge clod of earth was the driving force for these enormous movements of the earth’s crust.
The physical and chemical erosion processes then could influence these sloping stratum plates of the TRIAS. Between a period of 65 million to 2,4 million years ago, in the Tertiary Period, the climate was humid (chemical erosion). This resulted in fine erosion particles which was washed away by the surface water. This lead to a large-scale erosion of rock layers. Afterwards, from 2,4 million years ago up to now, in the Quaternary Period, i. e. the period of glacial epochs and warm epochs, the physical erosion (e. g. frost bursting) resulted in the formation of coarse rock debris, which were washed away by the rivers, thus leading to the creation of valleys.
In this way large amounts of the former sedimentation layers Muschelkalk and Keuper were removed. This explains, too, why in the Spessart the New Red Sandstone can be found in the lowest stratum and Muschelkalk and Keuper are missing altogether – they were broken up by erosion and were transported southwards by the water. Rock layers of different hardness more or less resisted the erosion, resulting in the characteristic plains (Gäu areas) or steep slopes (Steigerwald), which dominate the typical landscape of wine-growing Franconia today.