U–Pb zircon ages from Permian volcanites of the Čierna Hora Mts. (Western Carpathians, Slovakia): Regional tectonic implications
Abstract: U–Pb dating of magmatic zircons from the Permian meta-andesites of the Čierna Hora Mts. yielded the Concordia ages of 267.0±1.5 Ma, which correspond to the Guadalupian Epoch in the time span of the Wordian Stage. The sequence was correlated with the Northern Veporic Permian rocks from the Čierťaž Mts. From the geochemical point of view, the studied volcanic rocks belong to a peraluminous calc-alkaline magmatic suite, linked to the post-collisional lithospheric extension. Lithosphere extension and attenuation will promote upwelling of hot asthenosphere. In this context, the calc-alkaline affinity may result through extensive crustal contamination of basaltic magma. Continuous extensional setting, succeeded by overheating is indicated by the newly formed zircon rims of 252.2±3.2 Ma age at the edges of the Wordian zircon grains. The Neoproterozoic (618±8 Ma) and Paleoproterozoic (2080±13 Ma) ages were found within the xenocrystic cores in the studied magmatic zircon grains. The presented xenocrystic zircon ages indicate derivation from the Variscan basement rocks with reworked fragments of Cadomian crust.
Geochronology, geochemistry and tectono-magmatic evolution of the upper Carboniferous–lower Permian Kula pluton in the Istranca (Strandja) Massif, NW Turkey
Abstract: Upper Carboniferous–lower Permian plutonic rocks (i.e. the Kula pluton) are exposed in Istranca (Strandja) Zone, NW Pontides on both sides of Turkish and Bulgarian border. The Kula pluton is composed of monzogranite, granodiorite, and quartzmonzodiorite facies with a medium to coarse-grained, mylonitic–blasto mylonitic texture. It was affected by low-grade greenschist facies metamorphism, and displays distinct foliation as a result of intense tectonism. This pluton was classified as metaluminous and peraluminous (ASI values 0.95–1.13), I-type, calc-alkaline to high-K calc-alkaline in character. Zircon U–Pb crystallization ages of the pluton are between 298.0.6 ± 0.68 Ma (early Permian – Asselian) and 311.91 ± 1.34 Ma (late Carboniferous – Moscovian). Based on new geochemical and geochronological data, the Kula pluton was generated from a subduction-related magmatic arc-setting during the late Carboniferious to early Permian. This period corresponds to the closure of the Paleo-Tethys Ocean following northward subduction of the Paleo-Tethyan oceanic lithosphere and development of a magmatic arc along the Eurasian continental margin.
Tectonic evolution of the Vršac Mts. (NE Serbia): Inferences from field kinematic and microstructural investigations
Abstract: The Vršac Mts. in NE Serbia represent the key area to investigate structural relations between the Northern Serbo-Macedonian Subunit and Supragetic Unit of the Dacia Mega-Unit. The geodynamic events during the Variscan orogeny in the Late Paleozoic colligated the two units and led to their metamorphic differentiation. The Late Cretaceous extension exhumed the medium-grade Serbo-Macedonian metamorphic rocks and structurally juxtaposed them against the low-grade metamorphosed basement of the Supragetic Unit along an E-dipping shear zone, which outcrops in the crystalline basement of the Vršac Mts. The subsequent Oligocene–Miocene extension, which led to the formation of the Pannonian Basin, overprinted the effects of earlier tectonic phases to a large extent. Hence, large segments of the Northern Serbo-Macedonian Subunit and the Supragetic Unit, including their contact, were buried beneath the Neogene deposits of the southern part of Pannonian Basin. The tectonic uplift of the Vršac Mts. occurred in middle to late Miocene times along the SW-dipping normal faults that controlled deposition in the adjacent Zagajica Depression. The Miocene extension, triggered by the retreat of Carpathian slab, exhumed the crystalline basement of the mountains, and exposed the Late Cretaceous Serbo-Macedonian/Supragetic extensional contact.
Early–Middle Miocene paleoenvironmental and paleoclimate changes in the Toplica Basin (Serbia) inferred from plant biomarkers, biochemical and elemental geochemical proxies
Abstract: The study investigates the influence of alluvial-lacustrine processes and paleoclimate variations on the distribution of terpenoids and unsubstituted Polycyclic Aromatic Hydrocarbons (PAHs). The XRF, ICP-MS, Rock-Eval, and organic geochemical analyses were employed to investigate thirty Lower and Middle Miocene sedimentary samples from the Prebreza and Čučale formations, collected from boreholes BL3 and BL5, situated in the central part of the Toplica Basin (Serbia). The development of the studied basin part was influenced by alluvial-lacustrine processes, which affected the type of organic matter (OM) and the paleoenvironment. Sandy silt and gravel layers in the profile of the BL3 borehole indicate the contribution of thicker clasts brought by rivers. In the BL5 borehole, there are fine-grained intrabasinal lacustrine sediments in the lower part, and swamp sediments in the upper part. The lowest total organic carbon (TOC) content is in alluvial sediments of BL3 and some lacustrine sediments of BL5. Based on Hydrogen Index (HI) and C/N ratio, various mixtures of terrigenous and algal organic matter are present in the sediments, while an increase in the proportion of terrestrial organic matter with higher HI (Type II kerogen) is recorded in upper parts of both boreholes, which may be related to paleoclimatic changes. Based on Tmax, the OM is immature and/or in the initial stage of maturity. The presence of plant terpenoids and unsubstituted PAHs, which reflected paleoflora and paleoclimate changes, was associated with the suggestion of predominating Type III kerogen in the studied sediments. Various factors influenced the application of gymnosperms/angiosperms parameters. For instance, the progressive aromatization of triterpenoids occurred in the BL5, whereas the process was hindered in the upper part of the BL3, probably as a result of high sedimentation rates. Based on C-value, Sr/Cu, and Rb/Sr ratios, during the deposition of the Lower and Middle Miocene formations of Čučale and Prebreza, a warm and humid climate prevailed, reflecting the Middle Miocene Climatic Optimum (MMCO). The production of unsubstituted PAHs in the studied samples probably relates to paleo-wildfires, anoxic conditions, or the presence of specific biomass precursors.
Updated Miocene mammal biochronology of Slovakia
Abstract: Revisory studies together with the new research results have made it possible to update our knowledge about the biochronology of terrestrial records from the Miocene epoch in the Slovak territory of the Western Carpathians. Data from more than 30 localities, mainly based on mammalian assemblages, provide an overview of the evolution of terrestrial vertebrate communities in response to climate and environmental changes in the Central Paratethys region (especially in its NW area) for about 12 million years, from the early Miocene (MN3) to the end of this epoch (MN13). Based on the determined faunistic assemblages, local reference localities (LRL) were determined and correlated with MN units. These are as follows: localities in the territory of Devínska Nová Ves (MN6), Borský Svätý Jur (MN9), Pezinok (MN10), Triblavina (MN11), and Šalgovce (MN12). Well-documented paleontological and geological records at sites from the territory of Devínska Nová Ves have also made possible to introduce the name “Devínska Nová Ves” for the local faunal complex, corresponding to the MN6 unit.