Late Miocene to present day structural development of the Polish segment of the Outer Carpathians

Abstract

This paper presents a few pieces of evidence on neotectonic structural evolution of the Polish segment of the Outer Carpathians. During the Late Neogene, structural development was largely controlled by normal faulting and block uplift. However, there are also indications of compres-sional stress setting, at least during the Pliocene and particularly within the medial and eastern parts of the belt. In the Quaternary, in turn, structural development has been mainly controlled by compressional stress arrangement, with σ 1 orientated roughly perpendicular to the belt. The Pliocene-Quaternary tectonic mobility of the Polish Outer Carpathians has been relatively weak and mostly of thinskinned character. Normal faults were formed on the margins of intramon-tane basins and in the western part of the belt. Rates of uplift of individual structures were variable and the amount of uplift was the greatest in the Late Pliocene and Early Qua-ternary times. Geomorphologically-detected zones of uplift are relatively narrow and arranged subparallel or under small angle in respect to the strike of principal thrusts and frontal parts of large slices. Such an arrangement is interpreted as resulting from the steepening of frontal thrusts due to horizontal compression within the overthrust flysch nappes. This hypothesis is confirmed by the results of recent break-out and GPS studies, as well as by focal solutions of some Outer Carpathian earthquakes.