Trace fossils from the Lower Muschelkalk of Raciborowice Górne (North Sudetic Synclinorium, SW Poland) and their palaeoenvironmental interpretation

Alina Chrząstek

Abstract


The following trace fossils have been recognised in the Lower Muschelkalk of Raciborowice Górne (North Sudetic Synclinorium, SW Poland): Archaeonassa fossulata, Balanoglossites triadicus, ?Gastrochaenolites isp., Lockeia isp., Palaeophycus tubularis, Palaeophycus isp., ?Planolites beverleyensis, P. montanus, Planolites isp., ?Protovirgularia isp., Rhizocorallium commune var. auriforme, R. commune var. irregulare, R. jenense, Skolithos linearis, Thalassinoides suevicus and Trypanites weisei. Coprolites and an unidentified trace fossil A are also described. The trace fossils allow the discrimination of five ichnoassociations in the Raciborowice Górne section: (IA 1) Rhizocorallium-Pholeus, (IA 2) Rhizocorallium-Palaeophycus, (IA 3) Thalassinoides, (IA 4) Trypanites-Balanoglossites and (IA 5) Planolites-Palaeophycus. The Lower Muschelkalk succession was deposited on a shallow carbonate ramp affected by frequent storms. Deposition commenced with sedimentation in a restricted lagoon on the inner ramp with a short episode of sabkha formation. It continued on the middle and outer ramp and then on a skeletal shoal of the outer ramp and in an open basin. Ichnoassociation IA 5 is related to a maximum transgression that commenced with the deposition of the Spiriferina Bed and which probably marked the opening of the Silesian-Moravian Gate. The basin underwent two shallowing episodes, as evidenced by ichnoassociations IA 3–IA 4, resulting in the formation of hardgrounds. Bathymetric changes in the Raciborowice Górne section correspond well with a general transgressive trend in the Germanic Basin.


Keywords


Sudetes; North Sudetic Synclinorium; Lower Muschelkalk; Trace fossils; Ichnoassociations; Carbonate ramp; Palaeoenvironment

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