Search Results

You are looking at 1 - 4 of 4 items for

  • Author: Ondrej Pelech x
Clear All Modify Search
Open access

Ondrej Pelech, Anna Vozárová, Pavel Uher, Igor Petrík, Dušan Plašienka, Katarína Šarinová and Nikolay Rodionov

Abstract

This paper presents geochronological data for the volcanic dykes located in the northern Považský Inovec Mts. The dykes are up to 5 m thick and tens to hundreds of metres long. They comprise variously inclined and oriented lenses, composed of strongly altered grey-green alkali basalts. Their age was variously interpreted and discussed in the past. Dykes were emplaced into the Tatricum metamorphic rocks, mostly consisting of mica schists and gneisses of the Variscan (early Carboniferous) age. Two different methods, zircon SHRIMP and monazite chemical dating, were applied to determine the age of these dykes. U-Pb SHRIMP dating of magmatic zircons yielded the concordia age of 260.2 ± 1.4 Ma. The Th-U-Pb monazite dating of the same dyke gave the CHIME age of 259 ± 3Ma. Both ages confirm the magmatic crystallization at the boundary of the latest Middle Permian to the Late Permian. Dyke emplacement was coeval with development of the Late Paleozoic sedimentary basin known in the northern Považský Inovec Mts. and could be correlated with other pre-Mesozoic Tethyan regions especially in the Southern Alps.

Open access

Lenka Šamajová, Jozef Hók, Miroslav Bielik and Ondrej Pelech

Abstract

Density modelling was carried out along five profiles oriented across the expected deep contact between the Bohemian Massif and the Internal Western Carpathians in western Slovakia. The density models reveal the continuation of the Bohemian Massif beneath the External and Internal Western Carpathians tectonic units. The eastern margin of the Bohemian Massif is situated at depth south-east of the surface outcrops of the Pieniny Klippen Belt and changes its position in the surveyed area. The contact of the Internal Western Carpathians with the Bohemian Massif and External Western Carpathians is subvertical. This sharp contact is manifested as the transtension to extension zone towards the surface.

Open access

Ondrej Pelech, David Kušnirák, Marián Bošanský, Ivan Dostál, René Putiška and Jozef Hók

Abstract

The Tatricum crystalline basement in the northern Považský Inovec Mts. contains several narrow tectonic slices with different rock composition. Some of them composed of the Upper Cretaceous mass flow deposits (the Horné Belice Group) are considered unique within the framework of the Internal Western Carpathians and particularly within the Tatricum. Tectonic interpretation of their structural position is longer a matter of debate. Contrasting resistivity properties of the Hercynian mica schists and the Upper Cretaceous sandstones and shales were confirmed by the parametric geophysical measurements. The Hranty section, the structurally highest and most internal Upper Cretaceous tectonic slice was investigated by the electric resistivity tomography. Two longitudinal and two transverse resistivity profiles were measured and combined into a 3D image which suggests that the low resistivity Upper Cretaceous rocks form relatively shallow and flat lying structures folded and deformed between the crystalline basement slices.

Open access

Jozef Hók, Michal Kováč, Ondrej Pelech, Ivana Pešková, Rastislav Vojtko and Silvia Králiková

Abstract

The tectonic evolution of the pre-Cenozoic basement, as well as the Cenozoic structures within the Danube Basin (DB) and its northern periphery are presented. The lowermost portion of the pre-Cenozoic basement is formed by the Tatricum Unit which was tectonically affected by the subduction of the Vahicum / Penninicum distal continental crust during the Turonian. Tectonically disintegrated Tatricum overlaid the post-Turonian to Lower Eocene sediments that are considered a part of the Vahicum wedge-top basin. These sediments are overthrust with the Fatricum and Hronicum cover nappes. The Danube Basin Transversal Fault (DBTF) oriented along a NW–SE course divided the pre-Neogene basement of the DB into two parts. The southwestern part of the DB pre-Neogene basement is eroded to the crystalline complexes while the Palaeogene and Mesozoic sediments are overlaid by the Neogene deposits on the northeastern side of the DBTF. The DBTF was activated as a dextral fault during the Late Oligocene – Earliest Miocene. During the Early Miocene (Karpatian – Early Badenian) it was active as a normal fault. In the Middle – Late Miocene the dominant tectonic regime with NW – SE oriented extension led to the disintegration of the elevated pre-Neogene basement under the simple and pure shear mechanisms into several NE – SW oriented horst and graben structures with successive subsidence generally from west to east. The extensional tectonics with the perpendicular NE – SW orientation of the Shmin persists in the Danube Basin from the ?Middle Pleistocene to the present.