At the site of the Willershausen clay pit, before the Ice Age, about 3 million years ago, there was a small, deep lake. A stream flowed into the lake. The bottom of the lake sank steadily deeper, because in the underground salt of the Zechstein formation was dissolved by groundwater (subrosion).
In the lake basin sediments were deposited: in front of the steep shore boulder, in the shallow water sand, on the deeper basin floor fine silt with clear annual stratification. The slopes under water were so steep that the deposits could slip off. In this lake lived besides algae and higher aquatic plants a rich wildlife: several species of fish, water turtles, giant salamanders, frogs, crabs, snails and aquatic insects. From the surrounding area, leaves and fruits of many tree species and herbs were blown in and infused, but also mice, mosquitoes, locusts, crickets, bees, dragonflies and bird feathers. Even large mammals were embedded: a forest elephant, a tapir and a deer.
The water of the lake was layered throughout the year. The silt of the seabed was thus closed by the oxygen of the air. The deep seabed was hostile to life. Here, black sludge was formed, in which all corpses and organic remains were preserved undecomposed. For about 300 years, salt-rich groundwater entered the lake. During this time, the sediment was cemented into a hard rock by calcium- magnesium carbonate (calcite and dolomite). This is how the famous fossil layer of Willershausen was created, from which more than 50,000 fossils of 500 species were recovered.
The fossils are famous for their unique conservation. Leaves are preserved with all cells, mice with skin and hair, a frog even with spawning cords. In the clay, the organic compounds from the formerly living tissue are still preserved. The uniquely complete connection of the pelvic floor, the excellently preserved fossils and more than 50 years of research work, especially by Professor Dr. Hermann Schmidt and Dr. Adolf Straus, make Willershausen a site of world renown. The environment and the climate before the Ice Age can be reconstructed in detail.
Directions see: Tongrube Willershausen