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Contrasting styles of siliciclastic flysch sedimentation in the Upper Cretaceous of the Silesian Unit, Outer Western Carpathians : sedimentology and genetic implications

Strzeboński Piotr

Annales Societatis Geologorum Poloniae

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2022

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Vol. 92, No. 2

159--180

EN

This study reports on a new set of sedimentological data and related interpretations of the Santonian–Campanian siliciclastic deposits in the Western Flysch Carpathians based on natural outcrops in the uppermost Godula Formation and lowermost Istebna Formation. The rationale was to confront the characteristics of this flysch succession with current controversies and state of knowledge on deep-water clastic sedimentation. The sedimentological analysis of the field data allowed for multi-scale synthetic classifications of the depositional components in the investigated flysch. The hierarchical and practical nature of the suggested classification schemes allows for their application to similar deposits in other regions. The siliciclastic deposits are products of gravity-driven terrigenous sediment redeposition via submarine slumps, debris flows, and turbidity currents. Sediment reworking by tractional bottom currents is considered as an accompanying factor. Point-sourced turbiditic fan lobe fringes from the submarine piedmont ramp and linearly supplied debritic covers along the slope apron are proposed as dominant. The innovative linking between the textural-structural descriptive features of the deposits and the critical determinants of specific sediment gravity-flow processes and architectural elements of the deepwater clastic depositional systems is a significant contribution to this research field.

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Late Cretaceous - Early Palaeogene sandy-to-gravelly debris flows and their sediments in the Silesian Basin of the Alpine Tethys (Western Outer Carpathians, Istebna Formation)

Strzeboński P.

Geological Quarterly

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2015

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Vol. 59, No. 1

195--214

EN

The study focuses on Upper Cretaceous - Palaeocene deposits from the Beskid Śląski mountain range in southern Poland constituting the Istebna Beds. The Istebna Beds, also referred to as the Istebna Formation, are part of the Silesian tectonic unit, which forms the Outer Carpathian fold-and-thrust belt (part of the Alpine-Carpathian system). The results of qualitative and quantitative lithological-sedimentological studies were the basis for the interpretation of lithofacies types, sedimentary processes and palaeoenvironment as well as for the reconstruction of the architecture of the depositional system. The analysis conducted on the basis of field description of the deposits shows the prevalence (nearly 70%) of siliciclastic strata representing a sandstone-conglomerate association (S-C), which is the main subject of this work. The S-C lithofacies: sandstones, gravelly sandstones, sandy conglomerates and conglomerates constitute the deposits formed mostly by mass gravity-flows such as sandy-to-gravelly debris flows. The distribution of the coarse-clastic material indicates a sediment supply from southerly directions and implies the presence of an active source area in the rear part of the Silesian Basin. A succession of the sandstone-to-conglomerate deposits with the secondary participation of other lithofacies, with a thickness of approximately two thousand metres, indicates temporary increased diastrophic activity in the Silesian Ridge (source area) and the intense denudation of this area. The uplift of the alimentation area and its destruction coinciding with enforced relative regression and the uncovering of the proximal depositional zone of the basin led to resedimentation of the older intrabasinal material and repeated mass deposition together with delivery of extraclasts of pre-existing rocks and minerals. The lithofacies development of the sandstone-to-conglomerate debrites and the related sedimentary palaeotransport directions suggest an accumulation domain in the form of a linear apron depositional system developed in a deep-water setting. Experimental modelling of subaqueous sandy flows has contributed to a better understanding of the complex genesis of deep-water sediment gravity flows developing in depositional systems rich in sand material.

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Geotectonic significance of Carboniferous deposits NW of the Holy Cross Mts. (central Poland)

Jaworowski K.

Geological Quarterly

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2002

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Vol. 46, No 3

267-280

EN

Carboniferous sandstones and shales encountered in deep boreholes drilled in central Poland, NW of the Holy Cross Mts., represent a pseudoflysch i.e. they show facies features of flysch and, simultaneously, are of cratonic provenance. Clastic sediments were derived from a peripheral bulge formed within the East European Craton as a result of stresses exerted by the accretion/thrust wedge advancing up the marginal part of the craton. In central Poland, NW of the Holy Cross Mts., a Variscan foredeep existed. The foredeep was the depositional site of interfingering exo- and pseudoflysch which, from a geodynamic point of view, are equivalent to an outer molasse. Huge masses of Carboniferous deposits (generally corresponding to flysch) from southwestern and central Poland successively represent, moving from SW to NE, Variscan ortho-, exo- and pseudoflysch.