First discovery of Mississippian trace fossils in the Świebodzice Unit from the Witoszów region (SW Poland)

Abstract

As so ci ate Ed i tor: Micha³ Zatoñ Abun dant and mod er ately di verse trace fos sil as sem blage have been dis cov ered for the first time in mudstones of the Pogorza³a For ma tion from the Witoszów re gion, SW Po land. Fif teen ichnospecies in clud ing four teen ichnogenera are described. The ichnofauna is dom i nated by Dictyodora liebeana and con tains nu mer ous Palaeophycus tubularis, rarer Archaeonassa fossulata, Archaeonassa isp., Chondrites cf. intricatus, Curvolithus sim plex, Diplopodichnus biformis, Lockeia isp., ?Lophoctenium isp., Nereites isp., Phycosiphon isp., Protovirgularia isp., ?Psammichnites isp., Taenidium isp. and one ichnospecies of fish swim ming trails, Undichna cf. bri tan nica. Some other struc tures (wave rip ples in flu enced by micro bial mats and zig zag struc tures) also oc cur. The trace fos sil as sem blages dif fer in var i ous ex po sures, but three of them are sim i lar and dis play the Dictyodora liebeana ichnoassemblage. It is rep re sented mostly by the etho log i cal cat e go ries fodinichnia and repichnia, with fewer pascichnia, domichnia and cubichnia. This new data from the OEwiebodzice Unit sheds light on the palae on tol ogy, age and palaeoenvironment of the Pogorza³a For ma tion. The oc cur rence of D. liebeana and U. cf. bri tan nica in di cates the Mis sis sip pian age of most mudstones stud ied, for merly con sid ered Up per De vo nian. The trace fos sil as sem blage be longs to the non-stan dard Nereites ichnofacies, with out graphoglyptids. The lithological fea tures of mudstones, trace fos sil as sem blage and pov erty of macrofauna, tes tify to their de po si tion in a deeper sed i men ta tion zone be low storm wave base, most likely in dysaerobic, pro-delta con di tions. This study sug gests that rocks con tain ing D. liebeana may form a cor re la tive ho ri zon in the OEwiebodzice Unit.