Revising the stratigraphy of the oldest rocks of the Elbtalschiefergebirge (Elbe Zone, Saxo-Thuringia) based on the discovery of trace fossils

Ediacaran glacial deposits have been described in recent years from several peri-Gondwana units, including the Weesenstein Group of the Elbtalschiefergebirge (Elbe Zone, Saxo-Thuringia) (e.g. Linnemann et al. 2018, Int. J. Earth Sci., 107, 885-911). These sedimentary rocks with only low-grade metamorphic overprint have been considered the oldest rocks of the region. The Weesenstein Group comprises two formations, following Linnemann et al. (2018): the older (but see below) Seidewitz Formation overlain with gradual transition by the Müglitz Formation. The former comprises quartzite and quartz schist horizons and a thick quartzite unit, named the Purpurberg Quartzite, interpreted to be a glacio-eustatic controlled low-stand deposit. The Müglitz Formation comprises mainly greywacke, partly pebble bearing, of the Weesenstein diamictite; the latter has been interpreted to belong to the Ediacaran glaciomarine diamictites of Cadomia. The stratigraphic concept, however, has recently been put into question based on the findings of a low-diversity trace fossil assemblage in the Purpurberg Quartzite, indicating a Palaeozoic, most likely Early Ordovician age, and evidence for an inverted stratigraphic order of the two formations (Meinhold et al., 2025, Geol. Mag., 162, e10). Palaeoenvironmental models of glacio-eustatic controlled deposition of the Purpurberg Quartzite of the Seidewitz Formation due to sea-level fall during an Ediacaran glaciation need to be abandoned. Both the age (Ediacaran or Palaeozoic?) of the Müglitz Formation and the nature of its contact with the Seidewitz Formation, are in need of further study. The term Weesenstein Group requires a revision, adjusting for the new stratigraphic concept of the area.