Basement structure of the Paleozoic Platform in Poland

Abstract

The Paleozoic Platform comprises the southwestern half of the Polish territory, separated from the Precambrian East European Platform (EEP) by a NW–SE trending subvertical lithospheric-scale discontinuity – the Teisseyre-Tornquist Zone. In the present study, the Paleozoic Platform basement is subdivided based on geological and geophysical evidence acquired during the last decades, including deep seismic refraction and reflection results, as well as gravity, magnetic and magnetotelluric data. The units adjacent to the EEP, the Mid-Polish Domain (comprising the Łysogóry Block) and the Pomeranian Block, are characterized by a thinned three-layer EEP-type crystalline crust (age 1.7–3.7 Gy). Their oldest platform cover is probably composed of thick Ediacaran syn-rift sedimentary and volcanic rocks. Their western extension in the contiguous German and Baltic area can be traced as far as the East Elbian Massif and Thor Suture based mainly on magnetic anomaly patterns. The Upper Silesian and Małopolska blocks located in SE Poland are characterized by Cadomian (660–600 My) basement overlain by the thick deformed Ediacaran foredeep deposits. Whereas the units with the EEP-type basement are interpreted as proximal terranes displaced along the EEP margin during the late Early Paleozoic, the blocks with a Cadomian basement are conceived as exotic terranes of a possible Gondwanan provenance. All these terranes were accreted ultimately during the final, latest Silurian stages of the Caledonian deformation although the exact scenario of the amalgamation remains hypothetical. The Sudetic Domain in SW Poland is a collage of different crustal units juxtaposed ultimately in the Pennsylvanian (ca. 310 Ma) during the final episodes of the Variscan Orogeny. Their northern boundary corresponds to the Rheic Suture traceable in magnetic and gravity anomalies pattern along the northern margin of the Wolsztyn–Leszno High, and continuing westwards along the Mid-German Crystalline High. The arcuate trace of the suture in the NE is dextrally displaced along the Odra Fault, and continues southwards where it is mapped as the Moravian–Silesian Suture.