Trace fossils from the Baltoscandian erratic boulders in SW Poland

Alina Chrząstek, Kamil Pluta

Abstract


Many well preserved trace fossils were found in erratic boulders and the fossils preserved in them, occurring in the Pleistocene glacial deposits of the Fore-Sudetic Block (Mokrzeszów Quarry, Świebodzice outcrop). They include burrows (Arachnostega gastrochaenae, Balanoglossites isp., ?Balanoglossites isp., ?Chondrites isp., Diplocraterion isp., Phycodes isp., Planolites isp., ?Rosselia isp., Skolithos linearis, Thalassinoides isp., root traces) and borings ?Gastrochaenolites isp., Maeandropolydora isp., Oichnus isp., Osprioneides kampto, ?Palaeosabella isp., Talpina isp., Teredolites isp., Trypanites weisei, Trypanites isp., ?Trypanites isp., and an unidentified polychaete boring in corals. The boulders, Cambrian to Neogene (Miocene) in age, mainly came from Scandinavia and the Baltic region. The majority of the trace fossils come from the Ordovician Orthoceratite Limestone, which is exposed mainly in southern and central Sweden, western Russia and Estonia, and also in Norway (Oslo Region). The most interesting discovery in these deposits is the occurrence of Arachnostega gastrochaenae in the Ordovician trilobites (?Megistaspis sp. and Asaphus sp.), cephalopods and hyolithids. This is the first report of Arachnostega on a trilobite (?Megistaspis) from Sweden. So far, this ichnotaxon was described on trilobites from Baltoscandia only from the St. Petersburg region (Russia). Arachnostega on a trilobite (Asaphus), a cephalopod and hyolithids is from Russia or Estonia. Another interesting ichnotaxon is Balanoglossites, which also was encountered in the erratic boulders from the Ordovician Orthoceratite Limestone of Sweden. So far, this ichnotaxon was known only from Russia (St. Petersburg region). Some rare borings (e.g., Osprioneides kampto, ?Palaeosabella isp.) also were found in glacial erratics of Silurian stromatoporoids, excellent outcrops of which are located in Gotland (Sweden) and Saaremaa (Estonia). In addition, stromatoporoid/coral, coral/coral and some new fossil associations are reported. The material studied probably was transported from the N, the NE, and less commonly from the NW.


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