A new lowermost middle Cambrian (Series 3, Stage 5) faunule from Saxony (Germany) and its bearing on the tectonostratigraphic history of the Saxothuringian domain

The core of borehole 1209/78 west of Doberlug–Kirchhain and south of Herzberg in the Torgau–Doberlug Syncline records an atypical lower part of the Tröbitz Formation with thin limestone horizons. These limestone layers include the remains of a low to moderately diverse fauna with the trilobites Protolenus (Hupeolenus) bergstroemi n. sp., Cambrunicornia saxonica n. sp., Ornamentaspis? aff. todraensis Geyer 1990a, Calodiscus? n. sp., the remains of two undetermined olenelloid? and paradoxidid? species, at least two brachiopods (Trematobolus, undetermined acrotretoid), and one hyolith. The fauna clearly suggests a position in the lower Agdzian stage of the West Gondwana chronostratigraphic scheme and correlation with the lowermost to lower Middle Cambrian strata in regions such as the Moroccan Atlas ranges and northern Spain, so the assemblages represent the oldest Middle Cambrian fauna known from the Saxothuringian domain and reconfirm the palaeogeographic position in the Perigondwanan segment. The lithological differences of the fossiliferous cores from those of the typical Tröbitz Formation and the recorded high-energy conditions indicate high-frequency sea-level changes suggesting that this part of the succession may be a late stage of the subglobally recognizable eustatic sea-level fluctuations at the traditional Lower–Middle Cambrian boundary interval.