Life on the brink: Silicifications from central Germany elucidate ecosystems of Permian supervolcanoes

The Permian saw a strong diversification and spread of dryland ecosystems and is therefore a heyday of terrestrialisation. However, as life spread in environments with low preservation potential, fossil evidence of this evolutionary progress is extremely rare. Most knowledge in recent times resulted from studying fossiliferous strata of volcanic settings in the Euramerican tropics, such as the Chemnitz Fossil Forest (Germany) and the Athesian Volcanic Group (Italy). This talk elucidates the stratigraphy, taphonomy and paleoecological significance of silicifications found on fields and in river beds near Gnandstein/central Germany for two centuries. High-resolution sedimentological logging of the strata reveals that the fossils derive from epiclastic and pyroclastic deposits of the basal Kohren Formation (Asselian, lower Permian), representing the initial deposits of the voluminous NW Saxony Volcanic Complex. Anatomical studies and UV spectroscopy of polished samples from three collections identify various taphotypes in the silicifications and yielded anatomically preserved stems of tree ferns, calamitaleans and pycnoxylic gymnosperms. While the varicolored cherts formed in limnic settings, sizeable fossil trunks 1.5 m in diameter from Gnandstein could indicate the presence of an in-situ forest near the base of the Rüdigsdorf Tuff. Based on our results, the basal Kohren Fm. has a strong potential to disclose Permian tropical ecosystems that coped with extensive volcanism and advocate for future excavations in these occurrences. In addition, the Gnandstein fossils underpin the importance of late-to-post-Variscan volcanism in Euramerica to form fossil archives of deep-time life.