Stylolity tektoniczne jako wskaźnik tektogenetyczny na obszarze południowo-zachodniego obrzeżenia Gór Świętokrzyskich

Abstract

TECTONIC STYLOLITES AS TECTOGENETIC INDEX FOR THE AREA OF SW MARGIN OF THE HOLY CROSS MTS Summary The tectonic significance of stylolites is related to their usability as direct index of stress field making possible to draw some tectogenetic conclusions. The stylolites, studied with reference to other tectonic structures of south-western margin of the Holy Cross Mts, made it possible to reconstruct conditions under which Mesozoic strata have been deformed during the Laramie synorogeny. Four generations of stylolites were differentiated taking into account: 1) direct observations of relations between stylolites differing in orientation of lineation, 2) inclination of lineation in relation to bedding planes, 3) results of constructional rotation of layers and stylolite lineation developed in them to the horizontal plane around the strike line. The finding of relations between the stages of stylolitization and development of fold deformations made it possible to differentiate stylolites older than the folding, coeval with early and late stages of the folding, and younger. Stylolites older than the folding and those originating in first phases of folding evidence marked significance of horizontal compression in the direction of 55°. The compression was of the regional character and it effected still horizontally laying strata. In its field there were found two discontinuity systems, before the development of the oldest stylolites. The third generation of stylolites is related to the late phases of folding, evidencing vertical movements of the basement blocks along longitudinal faults. Stylolites younger than the folding, with direction 90°, evidence stress field twisted due to sinistral wrench movements which were taking place along already existing, WNW-ESE oriented longitudinal faults.