The Bromacker Project (https://bromacker.de/) investigates the “Ursaurier” vertebrate Lagerstätte of the same name in Early Permian redbeds of the Tambach Formation. Its geologic-paleontologic subproject contributes key parameters such as paleoecology, paleoclimate, paleogeography, and depositional environments to the reconstruction of the Tambach Basin.
Two research boreholes were drilled in 2022 and 2023 to complement information from outcrops and several legacy boreholes near the Bromacker site. Forschungsbohrung (Fb) Altenbergen 01/2022, located in the northwest of the basin, cored 250 m of the Tambach Formation and terminated in the basal Bielstein Conglomerate Member. Fb Tambach-Dietharz 01/2023 in the southeast of the basin terminated at 199 m depth in the pre-Tambach Rotterode Fm. The Bielstein Conglomerate Member is correlated between both boreholes; it consists of well-rounded volcanic clasts of a braided river setting. In the Altenbergen borehole, fluvial deposits of the Tambach Sandstone Member consist of massive mudstones interbedded with laminated shale in fluvial floodplain settings interspersed with temporary ponds and paleosols; whereas this member is present as gravelly fluvial-channel sandstone facies in the Tambach-Dietharz borehole. Fluvial channel deposition is terminated by prograding alluvial fan sedimentation represented by the Finsterbergen Conglomerate Member present in both cores. The influx of fluvial sandstones bearing plutonic and metamorphic clasts, observed in both boreholes, marks the exposure of the Ruhla Crystalline Complex to the west.
Especially the Tambach Sandstone Member shows different sedimentary facies throughout the core on a distance within the basin of around 4 km, showing also a clear distinction between habitats within the Tambach Basin.