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Eustatic and tectonic control on late Eocene fan delta development (Orava Basin, Central Western Carpathians)

Starek D., Sliva L’., Vojtko R.

Geological Quarterly

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2012

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Vol. 56, No 1

67-84

EN

The evolution of the Central Carpathian Paleogene Basin (CCPB) reflects an important role of relative sea level changes on a tectonically active basin margin. After the initial upper Lutetian/Bartonian transgression, the next regressive-transgressive cycle played a key role in a formation of the late Eocene fan delta facies associations in the southern Orava region of Northern Slovakia. Detailed sedimentary analysis allowed the separation of the following three facies associations which represent distinct depositional environments: alluvial fan (subaerial fan delta; Unit 1); subaqueous fan delta (Unit 2); and prodelta/slope and basin (Unit 3). The first stage of delta development is connected with eustatic sea level fall at the Bartonian/Priabonian boundary, accompanied by subaerial exposure, fluvial incision and deposition of alluvial fan sediments. Subaerial deposition was characterized by a variety of mass flow conglomerates with a red muddy matrix, interfingering with stream or sheetflood deposits. The next stage of the delta corresponds to high-amplitude transgression related to rapid tectonic subsidence along the CCPB margins during the Priabonian. The vertical arrangement of facies suggests retrograde delta development that shows rapid submergence of the subaerial parts and onlap of subaqueous mass flow conglomerates, often reworked by waves or wave-induced shallow-marine currents. Continuous deepening of the depositional environment during the late Priabonian/early Rupelian led to the relatively rapid superposition of prodelta/slope and basin facies associations by slowly accumulated hemipelagic deposis.

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Late Eocene to Quaternary deformation and stress field evolution of the Orava region (Western Carpathians)

Peskova I., Vojtko R., Starek D., Sliva L.

Acta Geologica Polonica

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2009

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Vol. 59, no. 1

73-91

EN

The northern part of theWestern Carpathians suffered polyphase deformation at the boundary between their Central and Outer parts. Palaeostress analysis in the Orava region revealed the existence of five different stress fields in the period from the Late Eocene to the Quaternary. The evolution of the stress fields was determined by detailed structural analysis of the fault slip and fold orientation data. The orientation of the stress fields shows an apparent clockwise rotation from the Late Eocene to the Quaternary. During the Late Eocene to Oligocene, E-W compression and perpendicular tension affected this area. This was the time when the Central Carpathian Palaeogene Basin formed. After this compression, the palaeostress field rotated approximatly 40-50[degrees], and NW-SE compression and NE-SW tension took place in the Early Miocene. The Middle Miocene to Pliocene was characterised by progressive rotation of the palaeostress field from NW-SE to the NE-SW direction of the maximum principal compressional stress axis ([sigma][1]). This clockwise rotation of the Oligocene to Quaternary palaeostress fields here is explained by the effect of the counterclockwise rotation of the ALCAPA microplate, and by the regional stress field changes in this region. The Quaternary stress field was reconstructed on the basis of structural measurements in the Pliocene sedimentary formations of the Orava-Nowy Targ Basin. The results of the palaeostress analysis show that the Quaternary stress field is characterised by E-W-oriented S[h] (minimum horizontal compression) and N-S-oriented S[H] (maximum horizontal compression).

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Pliocene to Quaternary stress field change in the western part of the Cen tral West ern Carpathians (Slovakia)

Vojtko R., Hók J., Kováč M., Sliva L’., Joniak P., Šujan M.

Geological Quarterly

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2008

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Vol. 52, No 1

19-19

EN

Knowledge of the current tectonic regime plays an essential role in natural hazard assessment, especially in the risk assessment of fault activity. Structural analysis of brittle deformations (using in version techniques) was used to determine the stress field state occurring within Pliocene and Quaternary deposits in the western part of the Central Western Carpathians. The deformation pattern of the reduced stress tensor showed that all structural measurements could be separated into two groups. An older, Late Pliocene fault population was activated un der NNW-SSE oriented extension. A younger, Quaternary fault population reflected origin in a NE–SW extensional tectonic regime and it distinctly showed a change the orientation of the S3 of about 70. The change in tectonic activity, as well as in the stress field orientation, is dated to the Pliocene-Pleis to cene boundary. The Quaternary stress field developed dur ing the post-collisional stage of the orogen. Our study shows that the West ern Carpathian internal units document NE-SW to NNE-SSW extension in the broader region around of the north ern Danube Basin.