Turbidite sedimentology, biostratigraphy and paleoecology: A case study from the Oligocene Zuberec Fm. (Liptov Basin, Central Western Carpathians)
Abstract: Outcrops of a thick turbiditic succession are exposed on the northern bank of the Liptovská Mara reservoir near Liptovská Ondrašová and Ráztoky. The section consists of rhythmic, predominantly thin- to medium-bedded turbidites of the Rupelian age. Their biostratigraphy is based on the calcareous nannofossils. Facies associations of these deposits represent different components of depositional lobe deposits in the turbidity fan system, including mainly the lobe fringe and lobe distal fringe/inter-lobe facies associations and locally the medium bedded deposits of the lobe off-axis facies association. This interpretation is supported by statistical analysis. The deep-sea turbiditic deposits contain trace fossil associations, which include deep-tier fodinichnia and domichnia up to shallow-tier graphoglyptids. Paleocurrent measurements indicate that the majority of sedimentary material was transported from SW and W.
Recycling of Paleoproterozoic and Neoproterozoic crust recorded in Lower Paleozoic metasandstones of the Northern Gemericum (Western Carpathians, Slovakia): Evidence from detrital zircons
Abstract: U–Pb (SHRIMP) detrital zircon ages from the Early Paleozoic meta-sedimentary rocks of the Northern Gemericum Unit (the Smrečinka Formation) were used to characterize their provenance. The aim was to compare and reconcile new analyses with previously published data. The detrital zircon age spectrum demonstrates two prominent populations, the first, Late Neoproterozoic (545–640 Ma) and the second, Paleoproterozoic (1.8–2.1 Ga), with a minor Archean population (2.5–3.4 Ga). The documented zircon ages reflect derivation of the studied metasedimentary rocks from the Cadomian arc, which was located along the West African Craton. The acquired data supports close relations of the Northern Gemericum basement with the Armorican terranes during Neoproterozoic and Ordovician times and also a close palinspastic relation with the other crystalline basements of the Central Western Carpathians. In comparison, the detrital zircons from the Southern Gemericum basement and its Permian envelope indicate derivation from the Pan-African Belt–Saharan Metacraton provenance.
Oligocene turbidite fans of the Dukla Basin: New age data from the calcareous nannofossils and paleoenvironmental conditions (Cergowa beds, Polish–Slovakian borderland)
Abstract: Calcareous nannofossils found in the Cergowa beds of the Dukla and Fore-Dukla tectonic units in the Outer Carpathians indicate a time of deposition in the range of the NP23–NP24 nannoplankton zones of the Lower Oligocene. Nannoplankton assemblages reflect the paleoecological changes at the Eocene–Oligocene transition from: (i) a greenhouse to an icehouse climate; (ii) brackish to normal salinity suggesting open sea conditions, which were controlled by the Paratethys Basin closure followed by opening and connection with the Tethyan Ocean. The absence of nannofossils of NP25 zone, but their presence in the tectonic windows between 40 and 80 km to the west, shows that deposition of the Cergowa beds in the western part of the basin lasted longer than in the east. Occurrences of nannofossils indicating zones NP16 and NP21, found in the uppermost mudstone-rich parts of studied sections, may prove the remobilization and redeposition of sediments of this stratigraphic age. Potentially, eroded material could be derived from some of the following lithostratigraphic units: NP16 — the Hieroglyphic beds, Przybyszów sandstones and Upper variegated shales; NP21 — the Globigerina marls, Mszanka sandstones and sub-Chert marls and shales and/or fine-grained equivalent of these units. Reworked specimens derived from the older Mesozoic strata occur occasionally in various samples.
Integrated bio- and cyclostratigraphy of Middle Triassic (Anisian) ramp deposits, NW Bulgaria
Abstract: A cyclostratigraphic interpretation of peritidal to shallow-marine ramp deposits of the early Middle Triassic (Anisian) Opletnya Member exposed in outcrops along the Iskar River gorge, NW Bulgaria, is presented. Based on facies trends and bounding surfaces, depositional sequences of several orders can be identified. New biostratigraphic data provide a time frame of the studied succession with placement of the boundaries of the Anisian substages and show that the Aegean (early Anisian) substage lasted about 1.6 Myr. In the corresponding interval in the two studied sections, 80 elementary sequences are counted. Five elementary sequences compose a small-scale sequence. The prominent cyclic pattern of the Opletnya Member can thus be interpreted in terms of Milankovitch cyclicity: elementary sequences represent the precession (20-kyr) cycle and small-scale sequences the short eccentricity (100-kyr) cycle in the Milankovitch frequency band. Medium-scale sequences are defined based on lithology but only in two cases can be attributed to the long eccentricity cycle of 405 kyr. The transgressive-regressive facies trends within the sequences of all scales imply that they were controlled by sea-level changes, and that these were in tune with the climate changes induced by the orbital cycles. However, the complexity of facies and sedimentary structures seen in the Opletnya Member also implies that additional factors such as lateral migration of sediment bodies across the ramp were active. In addition, three major sequence boundaries have been identified in the studied sections, which can be correlated with the boundaries Ol4, An1, and An2 of the Tethyan realm.
The calcareous nannofossils and magnetostratigraphic results from the Upper Tithonian–Berriasian of Feodosiya region (Eastern Crimea)
Abstract: This article is concerned with nannofossil study of Tithonian–Berriasian sediments of Eastern Crimea. The NJT 16, NJT 17a, NJT 17b, NKT, and NK 1 nannofossil zones were determined. The occurrence of Nannoconus kamptneri minor, one of the potential marker-types of the Tithonian–Berriasian boundary (the base of the NKT Zone) of the Tethyan sequence in the Feodosiyan section is assigned here to the Pseudosubplanites grandis ammonite Subzone and the magnetic Chron M18n. The base of the NKT Zone is closer to the Grandis Subzone base than to the base of the Jacobi Subzone. Contradictions in the interpretation of magnetic chrons obtained by the present authors (Arkadiev et al. 2018) and by Bakhmutov et al. (2018) might be caused by mistakes admitted in the latter work on the compiled section.