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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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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.).