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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)

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Strzeboński P.

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tom 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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Osady wczesnokredowych spływów rumoszowych w warstwach cieszyńskich rejonu Żywca

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Słomka T.

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tom T. 27, z. 1

89-110

PL

W warstwach cieszyńskich (kimeryd - hoteryw) serii śląskiej rejonu Żywca stwierdzono kilkanaście wychodni utworów spływów rumoszowych. Wyróżniono dwa typy osadów. W typie I udział klastów waha się od 15 do 25% i są to wyłącznie otoczaki oraz fragmenty ławic skał osadowych (wapienie pelityczne, detrytyczne i organodetrytyczne, piaskowce i węgiel). W typie II klasty są rzadkie (do 5%), ale wśród nich stwierdzono także otoczaki skał magmowych i metamorficznych. Spoiwo buduje mikrytowy węglan wapnia, zapiaszczony i zażelaziony z okruchami wapieni. Towarzyszą im nieliczne ooidy, onkoidy, otwornice oraz szczątki szkarłupni, małży i mszywiołów. Osady spływów rumoszowych dokumentują neokimeryjskie ruchy wypiętrzające, które przekształciły podmorski grzbiet śląski w aktywną kordylierę. Ruchy te wydźwignęły także fragmenty dna basenu zbudowane z warstw cieszyńskich. Poddane erozji były redeponowane do basenu spływami rumoszowymi

EN

Several outcrops of debris flow deposits were encountered in the Cieszyn Beds (Kimmeridgian - Hauterivian) of the Silesian Series in Żywiec region. Two types of flows were distinquished. In type I percentage of clasts varies from 15 to 25% and their composition includes only pebbles and layer fragments of sedimentary rocks (pelitic, detrital and organo-detrital limestones, sandstones and coal). In the type II flows clasts are rare (up to 5%) but igneous and metamorphic rock pebbles were observed. Cements consist of micritic calcite with admixture of sand function, iron hydroxides and limestone fragments. Accompanying components are ooids, oncolites, foraminifers and fragments of echinoderms, bivalves and bryozoans. The debris flow deposits reflect the Neo-Cimmerian uplift movements which transformed the submarine Silesian Ridge into the active cordillera. There movements uplifted also the basin floor fragments covered by the Cieszyn Beds which, in turn, were subjected to erosion and redeposited as debris flow deposits

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Revised holostratigraphy of the Tithonian-Berriasian transition at Tré Maroua (Le Saix, Hautes-Alpes, SE France): study of a rejected Berriasian GSSP candidate

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Granier B. R. C. , Benzaggagh M. , Ferry S.

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2023

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tom Vol. 21

1--18

EN

The study of the Tithonian and lower Berriasian succession of Le Saix (Hautes-Alpes, France) has made it possible to better characterize the lithological succession at a former Berriasian GSSP candidate, its set of microfacies, the stratigraphic ranges of the main groups of marine plankton and therefore the calpionellid and saccocomid biozonations. On the lithological level, the Tithonian strata are characterized by thick-bedded breccias representing debris flows and related calciturbidites, whereas the Berriasian strata are typically white limestones. The lower part of the Berriasian is comprised of scattered intercalations of thin-bedded breccias and calciturbitides (including cryptic mud calciturbidites). In thin sections, the white limestones display mud- to wackestone textures and their allochems are mostly tiny bioclasts (e.g., radiolarians, calpionellids, saccocomids). Calciturbidites have wacke- to grainstone textures and their allochems are mostly pseudointraclasts and extraclasts, comprising various bioclasts and some ooids. Mud turbidites are made of micrograin-stones some yielding almost exclusively well-sorted calpionellids, which were previously erroneously interpreted as the signature of “explosions” or “blooms” of Calpionella alpina. Breccias are mostly lithoclastic floatstones with a matrix similar to that of the calciturbid- ites. Their lithoclasts are either extraclasts sensu stricto, i.e., material derived from updip shallow-water areas, or pseudointraclasts representing reworked subautochthonous material, i.e., mud- and wackestone lithoclasts with radiolarians, saccocomids and/or calpionellids. Radiolarians are common over the whole studied interval. Saccocomids are part of the dominating biota reported from the lower and lower upper Tithonian interval whereas calpionellids replace them in the uppermost Tithonian to lower Berriasian interval. Minor plank- tonic groups comprise calcareous dinoflagellates and Globochaete alpina; Iranopsis nov. group is also present. Intervals with saccocomid sections characteristic of zones 4-5 and zone 6 are respectively ascribed here to the lower Tithonian (4-5) and the lower upper Tithonian (6). The biozonation of the calpionellid group sensu lato allows identification of i) the Boneti Subzone of the chitinoidellids, ii) the Cras- sicollaria Zone, more specifically its Tintinnopsella-Intermedia (A1), Intermedia-Alpina (A2) and Brevis-Massutiniana (A3) subzones, and iii) the Alpina Zone, with its Alpina-Parvula (B1) and its Alpina-Remaniella (B2) subzones. On the basis of biostratigraphical and sedimentological data, most zonal boundaries prove to be hiatal, located at the erosional base of breccia or turbidite layers whereas the Tithonian/Berriasian stage boundary appears to be located at a strike-slip fault plane in the Tré Maroua section.