Post-Caledonian tectonic evolution of the Precambrian and Palaeozoic Platforms boundary zone offshore Poland based on the new and vintage multi-channel reflection seismic data

Abstract. The structure of the post-Caledonian sedimentary cover in the transition from the Precambrian to the Palaeozoic Platforms in the Polish sector of the Baltic Sea is a matter of ongoing debate, due to the sparsity of quality seismic data and insufficient well data. The new high-resolution BalTec seismic data acquired in 2016 contributed greatly to deciphering the regional geology of the area. Here we develop an optimal seismic data processing workflow for the selected BalTec seismic profiles offshore Poland. Due to the acquisition in a shallow water environment, the processing strategy focused on suppressing multiple reflections and guided waves, through a cascaded application of SRME, τ-p deconvolution, water bottom F-K filtering, and parabolic Radon multiple elimination. We also perform reprocessing of the legacy PGI97 regional seismic data, achieving significant improvement in overall data quality compared to the original processing. We showcase the potential of the new and reprocessed data focusing seismic interpretation on the area of the Koszalin Fault. In the light of the data available, the Koszalin Fault was the main structure controlling Mesozoic subsidence and Late Cretaceous-Paleocene inversion of the eastern portion of the Mid-Polish Trough offshore Poland. The inversion changed its character from thin- to thick-skinned towards the north, away from the Polish coast. The Koszalin Fault reactivated older structural grain inherited from the time of Devonian continental rifting at the margin of Laurussia. The fault runs obliquely to the CDF, the feature that remained inactive since its formation at the Silurian-Devonian transition.