PROTEROZOIC AND CAMBRIAN SUCCESSIONS IN UPPER SILESIA - AN AVALONIAN TERRANE IN SOUTHERN POLAND

All Cambrian series and several Cambrian biozones have been recognized using acritarch biochronology within the siliciclastic successions un derlying Upper Silesia in southern Poland. The entire Cambrian success ion is around 580 m thick and contains rare Lower Cambrian trilobites of the Acado-Baltic faunal province. Acritarch associations are taxono mically comparable to those recorded in Baltica, Laurentia and Gondwan a, but their closest taxonomic affinity is with Iberia. The Cambrian s uccession accumulated in a shallow shelf environment and is almost hat -lying, unmetamorphosed, uncleaved and in nor mal stratigraphic order. It underlies paraconformably Lower Devonian deposits and overlies unc onformably steeply dipping metasediments of undetermined Precambrian a ge. Tectonic deformation and metamorphism to greenschist grade in thes e Precambrian strata must have occurred in the Proterozoic, and are at tributed to the Cadomian orogeny because similar Cadomian basement com plexes occur in the adjoining Brno Massif and in the East Avalonian an d Armorican terranes. Upper Silesia appears to be a stable crustal blo ck bordered by deep faults whose sedimentary cover has not been affect ed by tectonic deformation other than faulting. Based on the recogniti on of Cadomian age basement, the distribution of trilobites and acrita rchs and the tectonostratigraphic relationships to adjacent areas, the Upper Silesia terrane is interpreted to be a distal segment of East A valonia that in Cambrian times faced Iberia. An extension of the Tornq uist Suture from the Intra-Sudetic Fault is seen in the Krakow-Myszkow Fault Zone at the margin of Upper Silesia. The Intra-Sudetic Fault zo ne and the Krakow-Myszkow Fault Zone contain Early Palaeozoic rocks de formed during the Caledonian orogeny, and mark the boundary between th e Caledonian accretionary belt and areas unaffected by this orogeny.