Tambach Formation

Tambach Formation
Stratigraphic range: Early Permian, Sakmarian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Traco quarry at Bromacker
Type	Geological formation
Underlies	Eisenach Formation
Overlies	Rotterode Formation
Lithology
Primary	Conglomerate, sandstone, mudstone
Location
Coordinates	50.8097° N, 10.6189° E
Region	Thuringia
Country	Germany
Type section
Named for	Tambach-Dietharz village

The Tambach Formation is an Early Permian-age geologic formation in central Germany. It consists of red to brown-colored sedimentary rocks (red beds) such as conglomerate, sandstone, and mudstone, and is the oldest portion of the Upper Rotliegend within the Thuringian Forest Basin.^[1][2]

The overall geology records a history with three distinct stages of sedimentation within a mountainous environment. First, tectonic activity forms a basin (the Tambach Basin) dominated by high-energy debris flows, sheetfloods, and braided rivers. These incise underlying rhyolitic rock, depositing a coarse conglomerate known as the Bielstein Conglomerate. Second, calmer conditions allow the basin to widen, and the conglomerate is marginalized by finer sediments which were previously only common at the center of the basin, such as the characteristic Tambach Sandstone. These finer sediments were deposited through repeated sequences of flooding, followed by calm water, followed by exposure to air. The overall climate would have been similar to modern tropical savannas, with hot and dry periods broken up by heavy rainfall, likely multiple times in a year. The third stage involves a return of tectonic conditions, this time inducing wide deposits of polymictic (heterogenous) conglomerate known as the Finsterbergen conglomerate.^[1][3][2]

The Tambach Formation also includes one of the most important Permian fossil localities in Europe: the Bromacker locality. This former sandstone quarry and surrounding sites preserves several different facies types, with different fossil components. Thick sandstone channel fills in the lower section at Bromacker are overlain with mudstone from ephemeral lakes. A diverse assemblage of trace fossils such as footprints are imprinted onto the mudstone drapings. The upper section of Bromacker contains siltstone deposited through sheetfloods, in which well-preserved articulated skeletons of terrestrial tetrapods have been discovered. These include early amphibians like Rotaryus and Tambaroter, and early reptiles like Eudibamus and Thuringothyris. Unlike most fossil-preserving Permian red beds, aquatic vertebrates are absent at Bromacker while carnivorous synapsids (like Dimetrodon) are rare and herbivorous diadectids are abundant. Plant and arthropod fossils have also been found in shales at Bromacker.^[1][4]