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Geological field trip "Hofgeismar-Warburg" (Germany) - July 2011
Early Mesozoic
Lower Triassic
240 Million years ago
All landmasses are united in one giant continent.
Pangea.
Large parts of Central Europe are flat alluvial plains at the margin of the Tethys Ocean.
Sediments from the surrounding highlands are deposited.
The so-called Buntsandstein
Sedimentary Geology up close.
A few million years later...
Middle Triassic
The Muschelkalk era.
Seawater from the Tethys Ocean floods the Central European basin.
A warm, shallow sea covers the continental Buntsandstein sediments.
Limestones get deposited above the sandstones.
Some layers are extremely fossil-rich.
Crinoids,
Brachiopods,
Squid.
From time to time, supply of fresh seawater from the Tethys is cut off.
The Central European sea evaporates.
Gypsum precipitates from the water, and gets deposited on the seafloor.
Gypsum from that time is mined here as a valuable resource.
Preparations for a trip deeply underground.
Deep in the mountain.
Fibrous gypsum crystals 100 meters below the surface.
Almost yesterday...
...geologically speaking...
Miocene
15 to 20 million years ago.
The position of the continents already looked very much like the one we know today.
Along deep fault zones, magma rises to the surface.
15 million years ago: Magma pipes reach the surface and volcanoes erupt.
Today: 15 million years of weathering have long since eroded the volcanoes.
The hard basalt in the pipes, however, holds the surrounding sediments together.
Like for example within the Desenberg - landmark of the Warburg countryside.
A final effort at the end of the field trip: Ascent to the top of the Desenberg.
The reward: a wonderful view of the landscape around Warburg - and its geological features.
Thanks go to Knauf Gips KG for giving us a tour of their underground gypsum mine. It was great fun.