Early Paleozoic Cenerian (Sardic) geodynamic relationships of peripheral eastern north Gondwana affinities: revisiting the Ordovician of the Getic/Kučaj nappe (eastern Serbia)

Abstract

Regional tectonic synthesis suggests that a segment of the bipartite eastern Gondwana-type Carpathian-Balkan nappe-stacked Getic/Kučaj/Supragetic basement (eastern Serbia) experienced Cambro-Ordovician Cenerian (Sardic) accretionary-type deformation. The Ordovician basement of the Alpine Getic/Kučaj nappe exposes an earlier-mapped shallow-marine transgressive-type Fe-silicate-rich ironstone sequence. The Ordovician ironstone is used as second-order evidence of a hitherto untraceable tectonically-driven unconformity. Early Paleozoic compression is consistent with the controversial latest Cambrian to intra-Ordovician Cenerian (Sardic) interval, documented by (i) a 488 Ma metamorphic event and available detrital zircon data  (Serbo-Macedonian gneissic unit), (ii) a deformed Lower Ordovician Getic/Kučaj brachiopod assembly, and (iii) an intra-Ordovician unconformity dividing the Supragetic basement/”Vlasina complex”. The data further imply that mafic gabbro-dominating sills, cropping out in the northern Getic/Kučaj unit, are consistent with Ordovician back-arc activity. The Getic/Kučaj gabbro is Ordovician in age, piercing a Neoproterozoic–Cambrian (Lower Ordovician) Supragetic/”Vlasina complex”, overlain by a transgressive Silurian–Devonian sedimentary sequence. The emergence of Ordovician mafic intrusions reflects submarine volcanism, while deep-water redox conditions were capable of a sustained supply of Fe (similar to Sardinia). In terms of tectono-palaeogeographic reconstructions, the origin of Ordovician shortening and mafic volcanism is often challenged. The latter is broadly analogous with the embryonic eastern Rheic Ocean, corresponding additionally to the Armorican spur and related intra-continental magmatism.