Sedimentology of the Bromacker (Thuringian Forest Basin, Germany; early Permian): Classification of sedimentary structures

The Thuringian Forest Basin (southern Thuringia, central Germany) is composed of volcanic and sedimentary rocks belonging to the Gehren Subgroup and the Rotliegend Group of late Carboniferous–early Permian age. The ~8x10 km wide main part of the Tambach-Dietharz (sub-)basin contains the Tambach Formation, which is characterized by red-bed deposits of early Permian (Artinskian) age. Lithostratigraphically, the Tambach Formation can be subdivided into three members, in ascending stratigraphic order: Bielstein Conglomerate, Tambach Sandstone, Finsterbergen Conglomerate. So far, the best investigated outcrop of the Tambach Formation is the Bromacker section. The Bromacker is a grassland and forest area, located ~2 km north to the centre of Tambach-Dietharz, where the Tambach Sandstone Member is exposed in an active quarry, abandoned quarries, a palaeontological excavation site, and several scientific drill cores. Pronounced terrestrial palaeoenvironment conditions during the deposition of the Tambach Sandstone Member are indicated by occurrences of reptile-like tetrapods. Due to spectacular tetrapod finds of Diadectes, Orobates, Dimetrodon, Eudibamus, and others, the Bromacker site can be designated as fossil Lagerstätte. Additionally, some tetrapod footprint ichnospecies were directly assigned to certain tetrapod taxa, allowing for a track–trackmaker correlation. Besides the tetrapod footprints, other frequent continental ichnia at the Bromacker are Tambia spiralis and Striatichnium bromackerense. Imprints of plant remains, invertebrates (arthropods, hydromedusae), and invertebrate trace fossils occur as well. Lithologic characteristics (e.g., grain size, bedding, grading) of the Tambach Sandstone Member were described previously (e.g., Martens, 2007; Martens et al., 2009). During recent fieldworks, occurrences of sedimentary structures at the Bromacker were documented and classified herein into syn- and post-sedimentary structures. Syn-sedimentary structures at the Bromacker include ripples and intraformational clayey rip-up clasts. Post-sedimentary structures at the Bromacker include load casts, water level marks, tool marks, rain drop marks, and desiccation cracks as well as various kinds of bioturbation. It is hoped that the present report will motivate successive sedimentological studies in order to further reconstruct both the sedimentary environment and fossil habitat conditions of this important early Permian red-bed setting. Martens, T. (2007): Die Bedeutung der Sedimentmarken für die Analyse der Klimaelemente im kontinentalen Unterperm. – Zeitschrift für Geologische Wissenschaften, 35 (3), 177–211. Martens, T., Hahne, K. & Naumann, R. (2009): Lithostratigraphie, Taphofazies und Geochemie des Tambach-Sandsteins im Typusgebiet der Tambach-Formation (Thüringer Wald, Oberrotliegend, Unteres Perm). – Zeitschrift für Geologische Wissenschaften, 37 (1/2), 81–119.