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Stepwise clockwise rotation of the Cenozoic stress field in the Western Carpathians as revealed by kinematic analysis of minor faults in the Manín Unit (western Slovakia)

Šimonová V., Plašienka D.

Geological Quarterly

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2017

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Vol. 61, No. 1

251--264

EN

This study aims at quantitative kinematic analysis of fault-slip data and palaeostress reconstruction of polyphase brittle structures developed in the Manín Unit cropping out in the Middle Váh River Valley of western Slovakia. The Manín Unit neighbours the Pieniny Klippen Belt that follows the boundary between the Paleogene accretionary wedge of the Outer Carpathians and the Cretaceous nappe system of the Central Western Carpathians. After the nappe emplacement during mid-Cretaceous times, the Manín Unit was incorporated into the Pieniny Klippen Belt and attained its complex tectonic style. Based on kinematic analysis of meso-scale faults with slickensides, six (D1–D6) brittle deformation stages have been discerned. The relative succession of individual palaeostress states was derived from field structural relationships; their stratigraphic age was estimated primarily by comparison with other published data. Palaeostress analysis in the Manín Unit revealed the existence of six different palaeostress fields acting from the Middle Eocene to the Quaternary. The first three generations of meso-scale brittle structures were formed under a transpressional tectonic regime during the pre-Late Eocene–Early Miocene D1–D3 deformation. Generally, the maximum horizontal stress axis rotated clockwise from a W–E to an approximately N–S direction. Thereafter, a transtensional tectonic regime was characterized by a WNW–ESE to NNW–SSE oriented minimum horizontal stress axis during Middle and Late Miocene D4–D5 deformation. A general extensional tectonic regime influenced the structural evolution of the area in the Pliocene to Quaternary, when a gradual reorientation of the palaeostress field resulted in the development of variable, often reactivated, fault structures.

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Multi-stage development of the joint network in the flysch rocks of western Podhale (Inner Western Carpathians, Poland)

Ludwiniak M.

Acta Geologica Polonica

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2010

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Vol. 60, no. 2

283-316

EN

The geometry and morphology of joints have been examined in the flysch rocks in the western part of the Podhale synclinorium. They form a regular network, which has been developed in several stages connected with the structural evolution of the synclinorium. The initiation of the oldest diagonal system (D[R], D[L] sets), in the form of strength anisotropy in horizontal beds, took place during the successive increase in NNE-SSW compression. The formation of the majority of the L. set and of a small portion of the L set took place during gentle open folding connected with the setting of the general structural framework of the synclinorium. The beginning of the formation of the T set was related to WNW-ESE extension connected with the uplift of the synclinorium. The youngest joints - the majority of the L and a small portion of the L. set, were formed as the result of stress relaxation in the rock masses during progressive uplift lasting up to recent times. The formation of the joints proceeded in two stages: (I) their initiation in the form of joint-anisotropy and (II) opening of joints. These stages have often been significantly separated in time. Sometimes the process of joint opening continues up to recent times. There is a regional tendency that the double shear angle (20) values increase from the axial zone towards the marginal parts of the synclinorium, as well as downward in the flysch lithostratigraphic section. This is probably caused by the increase in confining pressure and rock ductility attributed to the increase in overburden load. The 20 values could also have been controlled by tectonic factors.

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Możliwość zastosowania analizy fałdów niecylindrycznych w rekonstrukcji paleonaprężeń

Szczęsny R.

Przegląd Geologiczny

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2004

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Vol. 52, nr 11

1060--1066

EN

Reconstruction of the axes of first order folds was performed to establish the directions of s1 stress in the Polish part of the Outer Carpathians. Results of two independent reconstructions were compared. In the first one, only cylindrical parts of folds were analyzed, whereas in the second interpretation, the database was supplemented by selected noncylindrical parts of folds. In regional pattern of s1 stress axes, determined using each method, no significant differences are visible. It seems that the orientation of fold axes reconstructed from noncylindrical parts of folds, under certain conditions, could be used as additional data in such reconstructions.

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Structural evolution of the Gnieździska Syncline : regional implications for the SW Mesozoic margin of the Holy Cross Mountains (Central Poland)

Konon A., Mastella L.

Annales Societatis Geologorum Poloniae

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2001

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Vol. 71, No 3

189-199

EN

Basing on analysis of tectonic mesostructures, the structural evolution stages of the Gnieździska Syncline have been determined. The structure represents a typical example of folds occurring in the SW margin of the Holy Cross Mountains. The well-exposed syncline displays a wide variety of structures, including: shear and extension joints, stylolites, cleavage, strike-slip and dip-slip faults as well as master joints. Tectonic structures resulting from flexural slip indicate that the Gnieździska Syncline developed as a flexural-slip fold as a result of horizontal NE-SW compression. The subsequent deformation phase included mesostructures pointing to the increasing activity of a nearby Gnieździska-Wola Morawiecka dextral strike-slip fault of regional extent. In the terminal phase of the post-kinematic uplift of the Holy Cross Mountains, T joints and master joints appeared.

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Jointing in the Dukla Nappe (Outer Carpathians, Poland) : an attempt at palaeostress reconstruction

Mastella L., Zuchiewicz W.

Geological Quarterly

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2000

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Vol. 44, Nr 4

377-390

EN

The joint network in the portion of the Dukla Nappe studied originated in two stages showing different orientations of the stress field axes. The older, compressive stage I was characterised by a N45°E-orientated (at present coordinates) horizontal s1, and formation of the diagonal, shear (SL and SR) joint system. The younger, extensional stage II was characterised by vertical s1 and horizontal, N35°E-orientated (also at present coordinates) s3, suitable for formation of the fold-parallel joints. At the turn of the first stage, under diminishing horizontal compression (s1 trending N35°E), the cross-fold T joints developed. The orientation of the maximum compression axis changed between stages I and II. The first stage probably commenced while strata which were not fully lithified underwent shortening, and lasted until the termination of nappe emplacement. The second stage, in turn, is associated with post-orogenic collapse of the Carpathians, whose onset in the study region began at least in Late Miocene times.