Upper Jurassic - seashores and juniper heaths
The Bahamas south of Stuttgart: a tropical sea with water temperatures of 19 to 23°C, coral reefs in the water, palm ferns and ginkgo trees on islands. A tourist‘s paradise right on our doorstep? Not any longer, but 150 million years ago, during the Upper Jurassic period, a tropical sea existed where now the Swabian Alb is located.
Nowadays, if you look to the south from the Stuttgart television tower, you get a completely different picture. An escarpment of several hundred metres in height rises up from the foreland. This is what remains, as it were, of the tropical sea that once covered large areas of Europe. The layers of the Alb escarpment are composed of solidified sea mud and numerous remains of shells and calcareous secretions of sponges, algae and corals. Alternating with the limestones there are thin layers of marl, a succession related to rhythmic climate fluctuations. Together with the thin layers of marl, the limestone beds give the impression of stacked-up walls. This „well-bedded limestone“ is so beautifully stacked in parts that an observer could easily doubt it is the result of nature and wonder if it may in fact be the work of man. Some rocks look completely different: from indistinct layers to compact, massive limestones. The sponges were at work there, marine animals that were widely distributed throughout the Jurassic Sea and which have built reefs similar to those of corals.
As there were so many limestone outcrops, this understandably encouraged people to think of variety usages. For example, large quarries can still be seen in the area to the present. Limestone gravel was and still is exploited here for building purposes as well as limestone as a raw material for the cement industry. As the long-distance transport of limestone would have been too expensive, large cement works are usually located near quarries, for example in Allmendingen, Dotternhausen and Schelklingen. The quarries are admittedly an intrusion in the natural landscape, but after a while they are an important habitat for peregrine falcons, eagle owls and other rare animals and some of them have therefore even become protected nature reserves.
Due to the shallow soils, the limestones of the Alb are visible on the surface in almost every bank of a path or can be found collected together in large clearance cairns or in walls at the edge of fields. „There were a lot of stones and not much bread,“ this is how the Härtsfeld plateau near Neresheim was used to be described and an observer today may well still ask how crops could grow between the stones which are almost completely covering the fields.
The water-soluble and „water swallowing“ limestone of the Alb is not just a geological phenomenon but also forces humans, animals and plants to make special adjustments. The Alb is famous for its bright colourful meadows, known as limestone grasslands, with numerous orchids and carline thistles. The extensive juniper heaths, virtually typical of the „original“ Alb, would not normally occur here. They have been laid out, as it were, by man. Flocks of sheep prevented the growth of deciduous trees which otherwise would have formed a sparse beech forest here. The prickly juniper which no sheep would want to bite, although hungry, was the only plant that remained.
continue with Tertiary Period