LATE SILURIAN/EARLY DEVONIAN GENTLE TECTONIC DEFORMATION IN THE CALEDONIAN FORELAND BASIN (EAST EUROPEAN CRATON, NORTHERN POLAND)

New 3D seismic data, acquired by the Polish Oil and Gas Company during exploration for unconventional hydrocarbon resources in the Ordovician and Silurian shale formations from the northern part of the Caledonian Foreland Basin (e.g. Poprawa et al. 1999) display for the first time gentle tectonic deformation. The present-day location of the study area is several tens of kilometers to the east from the Caledonian Deformation Front (Mazur et al. 2016). Contractional structures formed within the foreland basin in response to thrusting in the eastern part of the thin-skinned Caledonian fold-and-thrust belt during late Silurian and Early Devonian (Lochkovian) times. The structures are dominated by folds with amplitudes up to 40 m and reverse faults with up to 200-m throws. The geometry of the folds displays the geometry of detachment folds, in which the detachment horizons developed in Precambrian rocks. Geomechanical modeling allowed to estimate range of the direction of horizontal maximum compression stress dominating during the fold growth (S_Hmax = 15-30^o).

The research was conducted in the frame of the ShaleMech project funded by the Polish National Centre for Research and Development (NCBiR), grant no. BG2/SHALEMECH/14.

REFERENCES

Mazur, S., Aleksandrowski, P., Kryza, R. & Oberc-Dziedzic, T., 2006. The Variscan Orogen in Poland. Geological Quarterly, 50, 89-118.

Poprawa P., Šliaupa S., Stephenson R.A. & Lazauskiene J., 1999. Late Vendian-Early Palaeozoic tectonic evolution of the Baltic basin: regional implications from subsidence analysis. Tectonophysics, 314, 219-239.