Pages: 381 - 393
Abstract: The Horna Nitra Depression is an Upper Miocene–Quaternary intramontane sedimentary basin. This N–S elongated half-graben structure is rimmed from the west by the marginal Mala Magura fault which is the most distinctive fault in the Horna Nitra Depression, traditionally considered as an active fault during the neotectonic phase. This dislocation is attended by contrasting landforms and their parameters. The low S-index of about 1.10, at least two generations of well-preserved faceted slopes along this fault, and longitudinal river valley profiles point to the presence of a low-destructed actual mountain front line, which is typical for the Quaternary active fault systems. Comparison with known normal fault slip rates in the world makes it possible to set an approximate vertical slip rate between 0.3–1.1 m•kyr–1. The present-day fault activity is considered to be normal, steeply dipping towards the east according to structural and geophysical data. The NNW–SSE present-day tectonic maximum horizontal compressional stress SH and perpendicular minimum horizontal compressional stress Sh was estimated in the Horna Nitra region. The Quaternary activity of the Mala Magura fault is characterized by irregular movement. Two stages of important tectonic activity along the fault were distinguished. The first stage was dated to the Early Pleistocene. The second stage of tectonic activity can by dated to the Late Pleistocene and Holocene. The Mala Magura fault is permeable for gases because the soil atmosphere above the ca. 150 meters wide fault zone contains increased contents of methane and radon.
Keywords: Western Carpathians, Mala Magura fault, neotectonics, morphotectonics, intramontane depressionDownload PDF document