The Nysa-Morava Zone: an active tectonic domain with Late Cenozoic sedimentary grabens in the Western Carpathians’ foreland (NE Bohemian Massif)

Abstract

We give an interpretive review of the geological evolution of the Nysa-Morava Zone (NMZ)—a Late Cenozoic tectonically active region of the NE Bohemian Massif located at its contact with the Western Carpathians’ orogenic front. This crustal domain, delimited by generally NW–SE-striking fault system, is characterised by Oligo-Miocene and Plio-Pleistocene volcanic activity, regionally anomalous, weak historical and present-day seismicity and increased CO2 flux. The NMZ hosts several elongated, mostly NW–SE-trending, graben-like sedimentary basins (Upper Morava Basin System), which are filled by more than 300-m-thick succession of clastic fluvial/lacustrine sediments of Pliocene–Quaternary age. Based on geometric relations, basin architecture, coincidence of seismicity with CO2 escape and sparse focal mechanism data, a model is proposed, which explains this active domain as a transfer zone developed between major WNW–ESE and NW–SE faults in a right-lateral transpressional setting. It is suggested that slow horizontal slip at these faults resulted in local permutations of the largest and medium stress directions and formation of transtensional crustal domains in the NMZ. Moreover, relation of the NMZ to the Alpine–Carpathian system and sedimentary grabens in its foreland is discussed. The absence of Paleogene and Lower Miocene deposits suggests that subsidence in the NMZ was commenced later than in the European Cenozoic Rift System (ECRIS), which is in agreement with later thrusting in Western Carpathians at ~17 Ma. The quantitative contrasts to the ECRIS in terms of faulting and subsidence rates are explained by the absence of lithospheric/crustal thinning in the NMZ.