The Owino structure (NW Mid-Polish Trough) -- salt diapir or inversion-related compressional structure?

Abstract

Interpretation of seismic data from the Pomeranian segment of the Mid-Polish Trough (MPT) shows that this part of the MPT evolved in Mesozoic times as a decoupled sedimentary basin. Regional-scale decoupling was caused by the thick Zechstein salt layer. Detailed tectonic and seismostratigraphic analysis of seismic data from the vicinity of the Owino IG 1 well allowed for significant reinterpretation of the Owino structure, which was previously interpreted as partly pierced salt diapir. This structure developed in Triassic to Jurassic times as a listric normal fault zone detached above the salt layer, resulting from activity of a master fault present within the pre-Zechstein basement. Two pulses of increased extension could be inferred for Owino fault zone: Late Triassic and Mid-Late Jurassic. The Owino fault zone was reactivated in the Late Cretaceous due to the compression responsible for inversion of the MPT. Inversion-related uplift of the axial part of the MPT created a morphological gradient and the increased pressure of uplifted overburden rocks directed towards its flanks that also contributed to reactivation of the Owino fault zone. This fault zone, together with the Drawno-Czlopa salt diapiric structure and graben system of the Fore-Sudetic Monocline, have developed due to decoupled evolution of the Mid-Polish Trough.