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Alpejskie fazy orogeniczne w Tatrach

Lefeld L.

Przegląd Geologiczny

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2009

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Vol. 57, nr 8

669-673

EN

The Alpine, orogenic phases which had shaped the Tatra Mts. are set forth. It is argued that the thrust of the Krina nappe over its High-Tatric substratum was a long-lasting and complicated process. The Krina (Lower Sub-Tatric) nappe has various High-Tatric fragments at its sole and in some places rests even on the crystalline core. The overthrusting process had taken place not only in the late Cretaceous times only but also during the Paleogene. In result of the thrust of the European substratum under the Carpathian orogen the Tatra massiv overlapped rock masses (presumably sedimentary in origin) that exhibit now very low resistance as it is shown by magneto-telluric soundings. The High-Tatric sheets were thrust in form of "flakes" (Oxburgh's term (1972)) and not as regular fold nappes as it was argued so far. The lowermost of these "flakes" is detached from the Tatra crystalline core,contrary to previous views stating to be "autochthonous". The higher High-Tatric units known so far as nappes are, in fact smaller or larger(?) "flakes" that have advanced one over another during the later phases of the Alpine orogeny. In many cases they contain folded parts as remnants of the initial shortening process which had taken place in pre-Coniacian times.

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Cenozoic tectonic evolution of the Poznań-Oleśnica Fault Zone, central-western Poland

Widera M., Ćwikliński W., Karman R.

Acta Geologica Polonica

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2008

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Vol. 58, no. 4

455-471

EN

The Poznań-Oleśnica Fault Zone (P-OFZ) of central-west Poland is an over 150 km long, up to 10 km wide, and up to 200 m deep graben that developed during Early Oligocene to Pliocene times on the flank of the NE-dipping Fore-Sudetic Homocline. Fault systems of this extensional structure appear to reach pre-Zechstein basement in the area ofthe Fore-Sudetic Homocline that forms an integral part of the Bohemian Massif. The P-OFZ was affected by several stages of subsidence, separated by periods of inversion and/or tectonic quiescence between the Triassic and Cenozoic. Structurally, this dislocation zone can be linked with the Variscan faults, reactivated at that time. During the second half of the last century, the northern parts of the P-OFZ graben were intensively explored by cored boreholes because of their lignite content. Conventional back-stripping methods could not be applied to the tectonic analysis of the POFZ due to the limited thickness of the graben fill, its poor dating and the presence of relatively thick lignite seams. Therefore, phases of accelerated subsidence were determined by comparing the thickness of individual lithostratigraphic units within the graben and on its flanks. The total subsidence of the different graben segments was quantified by determining the aggradation coefficient (AC) and by taking the consolidation coefficient (CC) of lignite seams into consideration. Subsidence analyses indicate that the initial Early Oligocene extensional phase of the P-OFZ was followed by an Early.Middle Miocene extensional subsidence phase and a probably latest Miocene.Pliocene final extensional phase.

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Pre-Ordovician polyphase tectonics of the Cambrian sequences in the Kielce Unit, Holy Cross Mts. (Central Poland)

Gągała Ł.

Geological Quarterly

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2005

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Vol. 49, No. 1

53--66

EN

On a basis of tectonic mesostructures, the pre-late Tremadocian tectonic event (Sandomirian “phase”), believed to account for deformation of the Cambrian system in the Kielce Unit (Holy Cross Mts., Central Poland), has been subdivided into 3 successive tectonic episodes of different kinematics. During the first stage (D1), flat, westerly vergent thrusts originated, giving rise to gravitational sliding. Subsequently, during D2, the entire sequence was imbricated by the northerly vergent thrusts. In the terminal phase (D3), map-scale folds developed, changing inclinations of previously formed structures.Mode of deformation during the D2 stage is typical for thrust and fold belts. Absolute dating of these events remains speculative, but the pre-late Tremadocian age of the D1 and D2 phases is evident. The D3 is considered as a continuation of the D2, but alternative concepts are also acceptable in the light of the presented data.

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Analiza paleotektoniczna paleogeńskiej i neogeńskiej aktywności północnych fragmentów strefy dyslokacyjnej Poznań–Oleśnica

Widera M., Banaszak J., Cepińska S., Derdowski R.

Przegląd Geologiczny

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2004

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Vol. 52, nr 8/1

665-–674

EN

Northern part of the Poznań–Oleśnica Dislocation Zone (SDP–O), including Mosina and Naramowice grabens, is located between Czempiń and northern districts of Poznań. In this article, the aim of study is to determine the Palaeogene and Neogene tectonic evolution of both grabens. Basing on combination of cross-sections and aggradation coefficient — AC analysis, three periods of tectonic subsidence were recognized. The first one took place from the Lower Mosina Formation to the Upper Mosina Formation sedimentation with maximum development during the Czempiń Formation accumulation (Lower Oligocene). During the Ścinawa Formation (Middle Miocene, the lower part) sedimentation the study area was affected by the second period of tectonic subsidence. The last period of the Naramowice and Mosina grabens tectonic evolution is not exactly known. However, this its timing may be determined. It lasted after the Middle–Polish Member, lower part of the Poznań Formation, and before the Pleistocene glacial sedimentation (after the middle part of the Middle Miocene). Finally, these periods of tectonic subsidence in the SDP–O are correlated with tectonic phases recognized by Stille (1952). The first two periods relate to Pyrenean and Styrian (Early Styrian) phases. The third one may be connected to post-Moldovian (post-Late Styrian) phase or phases (Attican, Wallachian, etc.).

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Phases of Palaeogene and Neogene tectonic evolution of selected grabens in the Wielkopolska area, central-western Poland

Widera M.

Annales Societatis Geologorum Poloniae

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2004

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Vol. 74, No 3

295-310

EN

In the Wielkopolska (Great Poland) area, there occur numerous tectonic grabens which were active in the Palaeogene and Neogene. The similarities and differences between their development are presented on the example of the Czempiń, Szamotuły, Lubstów, and Władysławów Grabens. Using various methods of palaeotec- tonic analysis, the stages of accelerated subsidence of the grabens, i.e. tectonic phases, were indicated. The extent of vertical movement in the studied grabens were compared and it was affirmed that there is a connection between the occurrence of older dislocations and salt structures in the deep basement. From among the examined grabens, the Lubstów Graben is the deepest one, and shows the most complex geological structure. The Czempiń and Szamotuły Grabens are characterized by relatively simple geological structure, where the stratigraphic complete- ness and tectonic style are very legible. These three grabens were active in different tectonic stages from the turn of the Eocene/Oligocene till the end of the Neogene, and perhaps also in the Prepleistocene. The Władysławów Graben is a very shallow tectonic structure and its evolution lasted for the shorter period of time. The time of its development extended from the Early through the Middle Miocene. These grabens provide a good example of the relationship between the fault throw and graben location. The Czempiń, Szamotuły, and Lubstów Grabens, connected with deeply-rooted dislocations, came to existence in the Pyrenean phase (latest Eocene - Early Oligocene). However, the Władysławów Graben was affected mainly by salt structure activity. Thus, its first stage of tectonic evolution took place in the Savian phase (Early Miocene).