Skole Nappe Research Articles

Distribution of transitional flow deposits in sedimentary environments of mixed sand-mud turbidite system

Predicting facies distribution in turbidite systems is essential for resource exploration and identifying geohazards from an economic standpoint. Models that describe facies distribution depend heavily on understanding the mechanisms of particle transport and deposition. These processes are closely tied to the volume, concentration, and composition of sediment gravity flows, which display a range of behaviours between turbulent and laminar flow extremes. Recently, there has been a rise in studies on transitional flow deposits, although they remain much less understood than fully turbulent or laminar flows.For the first time, the distribution of Structured sandstone–mudstone associated with transitional flow deposits has been quantitatively presented for various sedimentary environments within the turbidite system. The distribution of Structured sandstone–mudstone was analysed for six areas of the Ropianka Fm (Skole Nappe, Polish Outer Carpathians) across twelve sedimentary environments, including channels, channel-levees, channel-mouths, and sub-environments of the depositional lobe. An increased amount of Structured sandstone–mudstone was observed in proximal settings away from the transport axis and in the distal parts of the turbidite system. It was found that flow transformation can occur in both proximal and distal zones of the turbidite system. Structured sandstone–mudstone in proximal zones is more often deposited from diluted mud-laden flows of small volume, where fine-grained cohesive material likely underwent vertical segregation. In contrast, Structured sandstone–mudstone formed basinward tend to be initially formed by larger flows. In proximal part of depositional lobe setting, the flow transformation due to longitudinal or longitudinal and vertical segregation of fine-grained cohesive material occurs slowly. At this point the velocity of sediment gravity flow is too high and the concentration of cohesive particles is too low for common development of cohesive bonds. Flow transformation accelerates in lobe fringe and lobe distal fringe/interlobe, due to flow deceleration, changes in sand-to-mud ratio, and the time required for development of cohesive bonds and the transition to a transitional flow regime, leading to increased deposition of Structured sandstone–mudstone distally.

Sediment bypass in a marl-dominated margin of a turbidite system in a narrow basin setting

Submarine sediment density flows play a pivotal role in transporting clastic material to the deep sea. The volume of sediment they transport, which bypasses a specific point or geographical location, shapes the stratigraphic record of the entire turbidite systems. Hence, recognition of bypass-dominated zones is crucial in facies prediction and understanding the architecture of turbidite systems. This understanding is linked to the economic aspects of exploring hydrocarbon deposits, the occurrence of geohazards that impact submarine infrastructure, the distribution of pollutants, and carbon sequestration.In the western part of the Ropianka Fm (Skole Nappe, Polish Outer Carpathians), three bed types showing evidence of sediment bypass were identified in the channel-mouth setting of marl-dominated slope and base-of-slope successions. The varying proportions of these bed types in studied successions and relationship with adjacent facies associations led to the identification of two channel-mouth zones. This study provides insights into deposits with characteristics differing from the previously described channel-mouth setting, evidenced by a significantly lower sand-to-mud ratio and smaller scale of erosional and depositional structures. The reported channel-mouth zones are interpreted as the marginal parts of a channel mouth, formed by subcritical flows. This study broadens the understanding of the channel-mouth setting by introducing dynamic and mud-dominated zones that experience sediment bypass and weak erosion. The identified bed types and typical characteristics of Marginal channel-mouth zones 1 and 2 can serve as a reference for interpreting marginal areas of channel-mouth settings in mud-dominated successions with scattered thin-bedded and coarse-grained deposits in other deep-water basins.

Silicoflagellates and other siliceous micro- and nannofossils from Rupelian diatomites, southeastern Poland

The Eocene-Oligocene Transition is one of the major stages of the Cenozoic reshaping of the world oceans with associated changes in climate, of ocean coastlines and circulation patterns. This altogether created challenging environments for fossilization and preservation of native biota. Consequently, well preserved Oligocene fossils are infrequent worldwide and just as rare in the Central Paratethys. The well-preserved Rupelian (Early Oligocene) diatomites from the Skole Nappe, the external unit of the Outer Carpathians in southeastern Poland were deposited in the Central Paratethys. In some samples, in addition to diatoms, sediments also contain a great diversity of other silicified micro- and nannofossils. Here we report our findings of silicoflagellates (fifteen taxa from five genera), two rotosphaeridians, and several morphotypes of fossil scales, some of uncertain taxonomic affinity. Among silicoflagellates, the most common are species from genera Corbisema (C. triacantha, C. hastata, and C. apiculata) and Dictyocha (D. clinata and D. fibula). We also recovered scales of rotosphaeridians (Pinaciophora and possibly Rabdiophrys) and remains of organisms of uncertain affinity (Clathropyxidella and Macrora) often reported together with silicoflagellates. All of these taxa are the first reports for the Central Paratethys. Silicoflagellate species composition is consistent with the datums derived from other fossils. Silicoflagellates, marine diatoms and archaeomonads suggest a neritic depositional environment.

Evolution of a turbidite system in a narrow basin setting: the Ropianka Fm (Campanian–Paleocene) in the Skole Nappe of the Polish Carpathians

Evolution of a turbidite system in a narrow basin setting: the Ropianka Fm (Campanian–Paleocene) in the Skole Nappe of the Polish Carpathians

Maceral and calcareous nannofossil assemblages as proxies of late Rupelian (Oligocene) environmental changes in the Paratethys: An example from a section of the Menilite Formation in the northern Outer Carpathians

The Menilite Formation (Oligocene) of the Skole Nappe in the Polish Carpathians was deposited in the Paratethys. Deep-sea unbioturbated fine-grained carbonates of the Dynów Marl Member contain cold-water calcareous nannoplankton from Zone NP23 (Rupelian), including Reticulofenestra ornata and Pontosphaera fibula, which are typical of brackish waters in the Paratethys. It is likely that the water column was brackish in the upper part and fully marine and anoxic in the lower part. The Dynów Marl Member records the maximum isolation of the Paratethys from the oceanic circulation (the Upper Solenovian Event). The overlying green mudstones (probably the Krępak Member) are shallowly bioturbated. They contain fully marine, warm-water calcareous nannoplankton from Zone NP24. The environmental change (marine/brackish) is reflected in the quantity and type of organic matter. The abundance and preservation of organic matter are very high (TOC varies from 2.7 wt % to 26 wt %; HI values are >300 mg HC/g TOC) in brown, laminated shales, which were accumulated in saline anoxic conditions. The macerals in the shales are predominantly composed of the liptinite group, including lamalginite, telalginite, liptodetrinite, and bituminite. These macerals are primarily derived from planktonic and benthic algae as well as bacteria. The percentages of vitrinite and inertinite, originating from terrestrial sources, range up to 10% and 0.5%, respectively. The macerals are much less abundant in marls of the Dynów Marl Member because of dispersion in the carbonate groundmass during the calcareous nannoplankton blooms in brackish surface waters. The overall liptinite (mainly liptodetrinite and lamalginite) contribution is 77%–99.7%. Vitrinite and inertinite contents are in average 4.6% and 0.3%, respectively. Macerals are also infrequent in the overlying green mudstones, likely because of oxidation and consumption by organisms in warmer waters.

Dinoflagellate cyst biostratigraphy of Upper Cretaceous turbiditic deposits from a part of the Bąkowiec section in the Skole Nappe (Outer Carpathians, southern Poland)

Dinoflagellate cysts from turbiditic deposits of the Ropianka Formation in an interval of the Bąkowiec section (Skole Nappe, Outer Carpathians, southern Poland) have been analyzed. This interval, previously attributed to the Cretaceous–Paleogene boundary transition based on planktic and benthic foraminifera, contains organic-walled dinoflagellate cysts (dinocysts) of a latest Campanian age. The difference in age, revealed here between foraminifera and dinocyst findings, is considered as an unresolved dilemma, which is pending some explanations, probably on the basis of further multidisciplinary studies envisaged in the same outcrop. The palynological content is well preserved and rich in dinocyst cyst taxa, including 37 upper Campanian index species among 92 species in total. The dinocyst assemblages observed in this interval are similar to those previously recognized in biostratigraphically well-calibrated sections of Western Europe. The dinocyst marker events enabled a correlation of the studied interval with the Samlandia mayi dinocyst Zone of Slimani (2001a), which is an equivalent to the Belemnitella minor Zone in the northwestern Europe. These dinocyst events include the first occurrences (FOs) of Kleithriasphaeridium truncatum, Nematosphaeropsi philippotii, Samlandia carnarvonensis, Samlandia mayi and last occurrences (LOs) of Corradinisphaeridium horridum, Raetiadinium truncigerum, Odontochitina operculata and Xenascus ceratioides subsp. ceratioides. The palynological content shows significant reworking of Campanian dinocyst taxa and a richness in palynodebris of continental origin, which are likely related to deposition by turbiditic currents.

Origin, secondary processes and migration of oil and natural gas in the central part of the Polish Outer Carpathians

The origin, migration pathways, and the influence of secondary processes of oil and natural gas accumulated in Lower Cretaceous to Lower Miocene strata of the central part of the Polish Outer Carpathians are investigated based on organic geochemical analyses. Oil and thermogenic hydrocarbon gases were mainly generated from both types II and III kerogens in the Oligocene Menilite beds of the Silesian, Skole and Dukla nappes. Moreover, some gases originated from Type III kerogen of Lower Cretaceous Veřovice shales in the Silesian Nappe and Lower Cretaceous Spas shales in the Skole Nappe. These gases migrated and subsequently mixed with oil and gas produced from Type II kerogen in the Menilite beds. The most extensive biodegradation and water washing were observed in oils from Harklowa and Iwonicz fields, and in oil from the BF (Franek) dug-well in Bóbrka-Rogi field (one of the world's oldest with exploitation started in 1854) of the Silesian Nappe. Oils most affected by evaporative fractionation come from Krościenko and Iwonicz Zdrój fields. Natural gas originated mainly from low-mature thermogenic processes (“oil window”) with some primary microbial gas contribution (primary carbon dioxide reduction), and many gas samples show secondary alteration caused by biodegradation. Carbon dioxide originated from both thermogenic kerogen decarboxylation and microbial processes.

Maastrichtian climate changes – the calcareous nannofossil record from flysch deposits of the Outer Carpathians

The Outer Carpathians are known for a few sections, where transitions from the Upper Cretaceous to the Palaeogene, including the K-Pg boundary interval, were described. One of them, the Bąkowiec section in the Skole Nappe, was examined with reference to the record of biostratigraphy and palaeoenvironmental changes, mainly based on the analysis of calcareous nannofossil assemblages. This study shows no evidence for the K-Pg boundary; however, the presence of the nannofossil species Micula prinsii , marking the topmost Maastrichtian UC20dTP Zone, was noted. The appearance of this low-latitude taxon and relevant changes in the composition of nannofossil assemblages indicate an influx of Tethyan warm water into the northern Carpathian basins during the latest Maastrichtian, shortly before the K-Pg boundary event. Therefore, the authors infer that the upper part of the Bąkowiec section recorded the latest Maastrichtian warming of climate, probably triggered by Deccan volcanic activity.

Provenance of Upper Oligocene to Lower Miocene Krosno Formation sandstones in the Skole Nappe (southeast Poland): New insights from heavy minerals

Heavy minerals have been studied in order to address the problem of provenance and source area for the uppermost Oligocene to Early Miocene Krosno Formation in the Skole Nappe (Poland). The heavy mineral composition of the Krosno Formation in the Skole Nappe points to a metamorphic origin, mainly from pelites affected by amphibolite facies conditions. The Krosno Formation was deposited at least partly as a result of the uplift of the Sanok Island, whose petrography and geological affiliation remain enigmatic. This island was probably built of metamorphic and/or sedimentary rocks belonging to a pre‐Alpine‐uplifted ridge and its cover, exhumed in the transpression belt of the Węglówka Ridge, an interbasinal ridge located between the Skole and Silesian basins. Chemical composition of provenance sensitive minerals from the Krosno Formation suggests that their parent rocks could be genetically related to the Variscan system of ridges in the Carpathian region.

Origin and secondary processes in petroleum in the eastern part of the Polish Outer Carpathians

A geochemical study of crude oil and natural gas from producing wells and seeps within the Lower Cretaceous–Oligocene sandstone reservoirs of the most eastern part of the Polish Outer Carpathians was conducted for the evaluation of their origin, migration pathways and the effects of secondary processes (biodegradation, water washing and evaporative fractionation). The petroleum was generated from mixed marine/terrigenous organic matter (type-II/III kerogen) occurring mostly in Oligocene Menilite beds in the Silesian and Skole nappes. Shales within Upper Cretaceous–Palaeocene Istebna and Lower Cretaceous Veřovice, Lgota and Spas beds are considered as an additional source of hydrocarbons (mainly gaseous). Biodegradation processes were recorded in numerous oils, especially occurring in seeps, but the extent of these processes is not severe, because steranes and terpanes were not affected. All oils are more-or-less water washed, while the evaporative fractionation processes are developed only on a minimal scale. The natural gases are primarily of thermogenic origin, usually co-genetic with oil and often contain components of secondary microbial degradation of both oil and natural gas (13C-enriched CO2 and 13C-depleted CH4). Gases with the highest microbial methane contribution have been recorded in petroleum accumulated in Dwernik and Łodyna fields.

New interpretation of the provenance of crystalline material from Oligocene flysch deposits of the Skole Nappe, Poland: evidence from heavy minerals and clasts in the Nowy Borek section

Abstract The Futoma Member (Oligocene, Rupelian) of the Menilite Formation is present only in the northern part of the Skole Nappe. Some diatomitic layers of this member in the Nowy Borek section contain coarse-grained detrital material composed of a variety of metamorphic, volcanic and sedimentary rock fragments. The material derives from primary and secondary sources. Most abundant are debris of metamorphic rocks, mostly gneisses and mica schists. The metamorphic origin of these rocks is confirmed by the composition of heavy mineral assemblages and garnet chemistry. These rocks could have been transported from a local source located close to the margin of the Skole Basin or within that basin. The volcanic rocks reflect Paleogene volcanic activity that was widespread in the Carpathian region. Cherts, which could have been subjected to synsedimentary erosion, may have been derived from the older portions of the same formation.

The Late Cretaceous Fucoid Marl of the Ropianka Formation in the Kąkolówka Structure (Skole Nappe, Outer Carpathians, Poland) – lithology and foraminiferal biostratigraphy

A 250-m-thick sedimentary succession dominated by siliciclastic deposits occurs in the Kąkolowka Structure of the Skole Nappe. The succession was deposited in the inner part of the Skole Basin during the Late Cretaceous. In position and age, it corresponds to the Kropivnik Fucoid Marl of the Wiar Member (a subdivision of the Ropianka Formation), which was comprehensively described in the external part of the Skole Nappe. In this study, the authors provide the first complete data set on the lithological development and biostratigraphy of the Kropivnik Fucoid Marl from the inner part of the Skole Nappe. The results are compared to previous data from the outer part of the Skole Nappe. In the Kropivnik Fucoid Marl of the Kąkolowka Structure, three main heterolithic facies associations are distinguished: shale-sandstone, marl-sandstone and sandstone-shale. The occurrences of hard, platy and soft marls within siliciclastic rocks are typical of the sections studied. The features observed indicate a turbiditic origin of the deposits studied, including the hard, platy marls. The allogenic material of the strata described includes the small, fragile tests of planktonic foraminifera, which were redeposited from the outer parts of the Skole Basin. Particularly large concentrations of planktonic foraminifera were observed in the hard, platy marls. They are less common in the soft marls and shales. In the Zimny Dzial section, a diverse assemblage of benthic and planktonic foraminifera was found. The Kropivnik Fucoid Marl was dated as uppermost Campanian to lowermost Maastrichtian on the basis of planktonic foraminifera, which represent the Gansserina gansseri Zone. The agglutinated foraminiferal assemblages are representative for the lower part of the Rzehakina inclusa Zone and the co-occurrence of the Caudammina gigantean (Geroch) acme with Rzehakina inclusa (Grzybowski) was observed.

Sedimentary processes and architecture of Upper Cretaceous deep-sea channel deposits: a case from the Skole Nappe, Polish Outer Carpathians

AbstractDeep-sea channels are one of the architectonic elements, forming the main conduits for sand and gravel material in the turbidite depositional systems. Deep-sea channel facies are mostly represented by stacking of thick-bedded massive sandstones with abundant coarse-grained material, ripped-up clasts, amalgamation and large scale erosional structures. The Manasterz Quarry of the Ropianka Formation (Upper Cretaceous, Skole Nappe, Carpathians) contains a succession of at least 31 m of thick-bedded high-density turbidites alternated with clast-rich sandy debrites, which are interpreted as axial deposits of a deep-sea channel. The section studied includes 5 or 6 storeys with debrite basal lag deposits covered by amalgamated turbidite fills. The thickness of particular storeys varies from 2.5 to 13 m. Vertical stacking of similar facies through the whole thickness of the section suggest a hierarchically higher channel-fill or a channel complex set, with an aggradation rate higher than its lateral migration. Such channel axis facies cannot aggrade without simultaneous aggradation of levee confinement, which was distinguished in an associated section located to the NW from the Manasterz Quarry. Lateral offset of channel axis facies into channel margin or channel levee facies is estimated at less than 800 m. The Manasterz Quarry section represents mostly the filling and amalgamation stage of channel formation. The described channel architectural elements of the Ropianka Formation are located within the so-called Łańcut Channel Zone, which was previously thought to be Oligocene but may have been present already in the Late Cretaceous.

Late Cretaceous foraminiferids from sections in the Zabratówka area (Skole Nappe, Outer Carpathians, Poland)

Well preserved Late Cretaceous–Palaeogene planktonic and benthic foraminiferal assemblages were studied in the Zabratowka section of the Ropianka Formation in the Skole Nappe. The Racemiguembelina fructicosa and Abathomphalus mayaroensis standard foraminiferal biozones were distinguished. The K-T boundary was recognized within the interval between samples ZB10B–ZB9A, mainly composed of marly mudstones, interlayered with thin-bedded sandstones, and is characterized by the disappearance of planktonic taxa and an abundance of agglutinated species. Foraminiferal assemblages, collected from the turbiditic flysch-type sediments, indicate a primary depositional environment on the outer shelf to the upper part of the continental slope, with shallowing during the Maastrichtian in the part of the Skole Basin studied. The foraminiferids correspond to the assemblages of a palaeobiogeographical “transition” zone, located between the Boreal and Tethyan domains.

Facies heterogeneity of a deep-sea depositional lobe complex: case study from the Słonne section of Skole Nappe, Polish Outer Carpathians

This article reports on the first detailed study of the Skole Nappe’s Ropianka Formation in the Slonne outcrop section along river San. Lithological and micropalaeontological similarities indicate that the sedimentary succession correlates with the formation’s Wiar Member of Campanian–late Maastrichtian age. The sedimentary succession, more than 140 m thick, is interpreted as a deep-marine complex of turbiditic depositional lobes and the study reveals its sedimentary anatomy. Six component facies of sediment gravity-flow deposits and their stratigraphic grouping into four facies associations are recognized, with these latter considered to represent deposits of the lobe axial zone, lateral flank zone and featheredge fringe zone, as well as an interlobe outer-fringe zone. Semi-quantitative characterization and comparison of facies associations gives insight into the succession’s sedimentary heterogeneity. Six depositional lobes superimposed upon one another are recognized in the stratigraphic succession, and their pattern of vertical stacking is interpreted in terms of dynamic stratigraphy on the basis of the upward succession of facies associations. The stratigraphic arrangement of facies associations is attributed to autogenic morphodynamic changes within the evolving depositional system, although it cannot be precluded that also eustatic and local tectonic forcing came into play. The case study sheds more light on the sedimentary environment, sediment sourcing system and spatial depositional pattern in the Late Cretaceous Skole Basin, where the aggrading seafloor apparently oscillated around the lysocline depth that could be mid-bathyal at that time.

Deep-sea mass-flow sediments and their exotic blocks from the Ropianka Formation (Campanian-Paleocene) in the Skole Nappe : a case from the Wola Rafałowska section (SE Poland)

Flysch deposits of the Ropianka Formation (Wiar and Leszczyny members; Skole Nappe) at Wola Rafalowska include two different sediments that contain exotic pebbles, cobbles and boulders. The first one is a graded conglomerate that contains mostly cobbles of sandstones, gneisses, Stramberk-type limestones, volcanic rocks, pegmatites and ferruginous siltstones. The second one is a pebbly mudstone that contains clasts of sandstones, stone coal, grey mudstones, volcanic rocks, schists, limestones, marls, black mudstones, conglomerates, volcaniclastic rocks and quartz gravels that are floating within a muddy matrix. Genesis of the conglomerate is unclear because it shows features typical of debris flows (poorly sorted, matrix- to clast-supported, large amount of cobble to boulder fraction) as well as high density turbiditic currents (indistinct normal gradation, small amount of cohesive material, crushed clasts that suggest interaction between grains during transportation and at least partly turbulence during flow). The pebbly mudstone represents typical debris flow deposits (large amount of cohesive material, matrix-supported, poorly sorted, lack of grain gradation and traction structures that suggest laminar flow). Limestones occurring in both exotic-bearing sediments show different Upper Jurassic–lowest Cretaceous facies of a carbonate platform, which was involved in the source area of the Skole Basin, along with its basement. They can be interpreted as deposits of: 1) platform-margin reefs and a platform slope: a) partly silicified coral boundstone, b) microbial-coral boundstone, c) silicified sponge-microbial boundstone grading into peloidal-ooidal grainstone with bioclasts, and d) strongly silicified limestone with intraclasts and bioclasts; 2) deeper, platform slope to toe-of-slope area – bioclastic wackstone; 3) inner platform, including: a) partly silicified wackstone with peloids, small intraclasts and bioclasts, and b) microbial bindstone. Moreover, some exotic clasts are built of Albian–Cenomanian wackstone with abundant sponge spicules and planktonic foraminifers, which are interpreted as deeper shelf sediments. Taking into account the geometry of thrust sheets from the site of the exotic-bearing sediments to the edge of the Skole Nappe, along the most probable transportation path, including tectonic/erosional reduction and different variants of slope inclination, the distance of the mass flows attained at least 25–97 km from the shelf edge.

Last occurrence of Abathomphalus mayaroensis (Bolli) foraminiferid index of the Cretaceous–Paleogene boundary: the calcareous nannofossil proof

AbstractIn the Gaj section (Polish Carpathians, Skole Nappe, Ropianka Formation), the Late Maastrichtian calcareous nannofossil biostratigraphy is compared with foraminiferal zonation based on the occurrence of the planktonic foraminiferid index speciesAbathomphalus mayaroensis. It appears that the LO ofA. mayaroensis, which has been used previously in the studied section as the possible K/Pg boundary indicator is located below the boundary. The disappearance ofA. mayaroensisalong with other planktonic foraminiferids before the Cretaceous–Paleogene (K/Pg) boundary mass extinction event may be a consequence of the Late Maastrichtian rapid warming pulses. Moreover, the Paleogene age cannot be supported by the FO of the benthic foraminiferidRzehakina fissistomata,because it first appears together with the nannofossilCeratolithoides kamptneri(zonal marker for the latest Maastrichtian UC20cTPZone). According to the present study, the whole studied section represents the lower Upper to the upper Upper Maastrichtian UC20bTPand UC20cTPnannofossil zones, so that it corresponds to the lower-middle part of the planktonic foraminiferalA. mayaroensisZone, which, according to the scheme by Caron (1985), should extend up to the K/Pg boundary.

Environmental Conditions in a Carpathian Deep Sea Basin During the Period Preceding Oceanic Anoxic Event 2 - A Case Study from the Skole Nappe

Abstract Hemipelagic green clayey shales and thin muddy turbidites accumulated in a deep sea environment below the CCD in the Skole Basin, a part of the Outer Carpathian realm, during the Middle Cenomanian. The hemipelagites contain numerous radiolarians, associated with deep-water agglutinated foraminifera. These sediments accumulated under mesotrophic conditions with limited oxygen concentration. Short-term periodic anoxia also occurred during that time. Muddy turbidity currents caused deposition of siliciclastic and biogenic material, including calcareous foramini-fers and numerous sponge spicules. The preservation and diversity of the spicules suggests that they originate from disarticulation of moderately diversified sponge assemblages, which lived predominantly in the neritic-bathyal zone. Analyses of radiolarian ecological groups and pellets reflect the water column properties during the sedimentation of green shales. At that time, surface and also intermediate waters were oxygenated enough and sufficiently rich in nutri-ents to enable plankton production. Numerous, uncompacted pellets with nearly pristine radiolarian skeletons inside show that pelletization was the main factor of radiolarian flux into the deep basin floor. Partly dissolved skeletons indicate that waters in the Skole Basin were undersaturated in relation to silica content. Oxygen content might have been depleted in the deeper part of the water column causing periodic anoxic conditions which prevent rapid bacterial degra-dation of the pellets during their fall to the sea floor.

Late Maastrichtian foraminiferids and diatoms from the Polish Carpathians (Ropianka Formation, Skole Nappe): a case study from the Chmielnik-Grabówka composite section

ABSTRACT Gasiński, M.A., Olshtynska, A. and Uchman, A. 2013. Late Maastrichtian foraminiferids and diatoms from the Polish Carpathians (Ropianka Formation, Skole Nappe): a case study from the Chmielnik-Grabowka composite section. Acta Geologica Polonica, 63(4), 515-525. Warszawa. Well-preserved foraminiferids have been found in the Chmielnik-Grabowka section (Skole Nappe, Polish Carpathians). The Abathomphalus mayaroensis (late Maastrichtian) and Racemiguembelina fructicosa (earlylate Maastrichtian) standard planktonic foraminiferal biozones have been recognized, based on the occurrence of their respective index species. Sediments of the R. fructicosa Zone contain diatoms, which are a rare component of Cretaceous flysch microfossil assemblages in the Carpathians. The diatom frustules and some foraminiferid tests are pyritized, probably after burial in the sediment, below the redox boundary or in the oxygen- deficient microenvironment inside the frustules or tests of microfossils; the presence of trace fossils and bioturbational structures in the same bed indicate an oxygenated sea floor.

Detrital tourmaline as an indicator of source rock lithology: an example from the Ropianka and Menilite formations (Skole Nappe, Polish Flysch Carpathians)

Tourmaline populations studied from the Campanian–Maastrichtian part of the Ropianka (Upper Cretaceous–Paleocene) and Menilite (Oligocene) formations of the Polish Carpathians, represent a mixture of first-cycle and polycyclic grains. The tourmalines of the deposits studied display very strong resemblance in terms of optical features and chemical composition. They belong mostly to the schorl-dravite series with a minor contribution of tourmalines of foititic or Mg-foititic composition. Euhedral tourmalines originated from metasedimentary rocks, while the rounded grains crystallised in Li-poor granitic rocks or in pegmatites, Al-poor and Al-rich metasedimentary rocks. Most of the tourmalines studied crystallised during a single igneous or metamorphic event. However, tourmalines forming in evolving chemical conditions as well as polymetamorphic grains (having a metamorphic detrital core and metamorphic overgrowths) are also present. The chemical composition of the metamorphic tourmalines studied indicates their formation in medium-grade metamorphic conditions. This is supported by the crystallisation temperature of the garnet-biotite inclusion present in one of rounded metamorphic tourmalines from the Ropianka Formation. The euhedral grains derive from metasediments, directly from a massif located close to the Skole Basin. The scarcity of euhedral grains in the tourmaline populations studied suggests that their source rocks were poor in these minerals. The direct sources of rounded tourmalines (most probably polycyclic grains), may have been Paleozoic and Mesozoic sedimentary rocks of the Skole Basin foreland or crystalline rocks of remote source areas. The initial igneous and metamorphic host rocks of the tourmalines may have been crystalline domains of the Bohemian Massif and/or the crystalline basement of Brunovistulicum.