Późnoneogeńska aktywność tektoniczna w centralnej części zapadliska przedkarpackiego (Witów koło Nowego Brzeska)

Abstract

Late Neogene tectonic activity of the central part of the Carpathian Foredeep (Witów near Nowe Brzesko, South Poland).S u m m a r y. Normal faults of different orientations appear to be the youngest manifestations of faulting in the Carpathian Foredeep which is filled with Lower to Middle Miocene sediments. Structural studies of the Late Miocene–Pliocene(?) fresh-water molasses of the Witów Series and the overlying Late Pleistocene loessial complex provide a possibility to reconstruct the Late Neogene to Recent (?) stress field in the central part of the Polish Carpathian Foredeep. Strata of such a young age are very rare in the foredeep, thus providing a key record of structural deformation during the latest stages of orogenic evolution of the Carpathian orogen. The molasses are cut by joints, and normal and strike-slip faults, formed in two successive events: (1) a syn-depositional one for the molasses (Late Miocene–Pliocene?), proceeding under NNW–SSE to N–S-oriented horizontal compression, possibly coeval with reactivation of a NE-striking sinistral fault of the Kurdwanów–Zawichost Fault Zone in the basement; (2) a post-depositional one for the molasses (Pliocene to Middle Pleistocene) during N–S to NE–SW-oriented extension, and (3) both syn- and post depositional ones for the loessial complex (Late Pleistocene). In the first event, reactivation of the NE-striking sinistral fault led to formation of N–S-oriented joints, as well as NW-striking dextral, and NNW-trending normal faults. In the second event, both W–E and NW–SE – oriented joints andWNW-striking normal faults were formed. The latter most probably originated due to reactivation of the Early PalaeoceneWNW- and NW-striking normal faults in the basement. In the third event, both NE–SW and NW–SE-oriented joints and NE-striking normal faults formed as a result of reactivation of the SW- and WSW-striking faults in the basement. Therefore, normal faults detected in the Carpathian Foredeep appear to be a result of different successive events. This extensional episode lasted at least to the Late Pleistocene. We also provide evidence for the recent, N- to NNE-directed, tectonic compressive stress, typical for that segment of the Carpathian arc. This stress resulted in the formation of an orthogonal system of joints striking N–S and W–E, produced during the (4) event.