Two Permian sphinctozoan sponges from the Shotori Mountains (eastern Iran)
Abstract: Two sphinctozoan sponge taxa, Shotorithalamia tubulara nov. gen., nov. sp. and Amblysiphonella cf. A. vesiculosa vesiculosa (de Koninck), are described from the Permian deposits of the Jamal Formation, exposed in Bagh-e Vang Mountain, and from a locality near the town of Deh-e Mohammad, both in the Shotori Mountains, north of Tabas, eastern Iran. The new genus Shotorithalamia is characterized by having ring-chambers — like Amblysiphonella — and also by possession of multibranched tubes that extended from the imperforate exo- and endowalls into the chamber interiors. The validity of families Amphorithalamiidae Senowbari-Daryan & Rigby and Girtyocoeliidae Finks & Rigby is discussed.
Magmatic fluid segregation and overprinting hydrothermal processes in gabbro pegmatites of the Neotethyan ophiolitic Szarvaskő Complex (Bükk Mountains, NE Hungary)
Abstract: Pegmatites of the Szarvaskő Ophiolite Complex, Bükk Mts, NE Hungary were classified according to their shape (pockets, dykes) and texture (zoned, homogeneous), representing different stages of fluid enrichment during crystallization of the host gabbro. Local assimilation of adjacent sedimentary rocks increased the volatile-, and incompatible-element content of the melt. Most pegmatites crystallized from a locally segregated hydrous silicate melt, but some were intruded later. Pegmatites have mineral contents similar to their host gabbro, but are enriched in amphibole, biotite, Fe-Ti-oxides, quartz, and apatite. During formation of the pegmatites a fluid phase separated and caused deuteric alteration under magmatic-submagmatic conditions. Post-magmatic sea-floor hydrothermal activity is recognized by intense alteration and formation of a greenschist facies mineral assemblage at temperatures of 250–400 °C. Fluid inclusion studies revealed two aqueous fluid types related to this polyphase hydrothermal process. Alpine regional metamorphism caused intense deformation of the rocks, accompanied by veining of a low-grade metamorphic mineral assemblage. Primary fluid inclusions in vein-filling minerals and chlorite thermometry were used to obtain proposed conditions of 270–285 °C and 150–200 MPa for this process.
Chemical composition of spinels from Mesozoic alkali basalts of the Western Carpathians: implications for sources of detrital spinels in flysch sediments
Abstract: Cr-spinel is a relatively widespread accessory heavy mineral in Mesozoic alkali volcanic rocks in the Central Western Carpathians. According to their chemical composition, spinels from these rocks (basalts, submarine hyaloclastites) can be divided into several groups (volcanic — Cr-spinel and Fe-Ti spinel, and peridotitic spinel, altered). Volcanic spinels crystallized in the plumbing system, and peridotitic spinels ultimately originated from peridotitic xenoliths, entrapped and brought to the surface by magmas. Melt/silicate inclusions (clinopyroxenes, plagioclases, melt) were found only in Cr-spinels of volcanic origin. Alteration processes are similar in all studied samples (enrichment in Ti4+, Fe2+, Fe3+ and depletion in Mg2+ and Al3+). The chemical composition of Cr-spinels from Cretaceous alkali basalts from the Western Carpathians is different to those of detrital Cr-spinels of volcanic origin from the Albian Poruba flysch Fm. Mesozoic alkali volcanites were not important sources for widespread detrital spinels of volcanic origin in Cretaceous sediments (mainly in the Tatric and Fatric tectonic units).
Silicification of quartz arenites overlain by volcaniclastic deposits: an alternative to silcrete formation
Abstract: The origin of the flat-lying body of quartzite at Skalice near Litomerice, Ohre Rift graben, Bohemian Massif, is explained by the effect of emplacement of dense tuff of tephritic mineral composition on Eocene quartz sands. In the upper part of the ca. 10 m thick quartzite body, broad quartz overgrowths on detrital grains are visible in CL images, with individual zones/bands having variable Al contents. The lower part of the quartzite body features isopachous growth bands with less variation in Al contents, passing to euhedral quartz precipitation. Porosity of the quartzite decreases upwards, reaching 3.8 % below the tuff base. Two main silicification stages are inferred: 1. dealkalization of the tuff and volcanic glass recrystallization, reflected in isopachous precipitation of poorly crystalline silica in deeper parts of the quartzite profile from fluids with high silica concentration and high amount of impurities; 2. hydrothermal argillization of the basal tuff portions connected with the origin of euhedral quartz cement deeper in the quartzite profile and opal coatings in shallower parts of the profile. Simple mass balance calculation shows that the tuff itself could not produce much silica for the underlying quartzite, and that most silica was produced by the corrosion and dissolution of sand grains by alkaline fluids in a zone immediately underlying the tuff. The Skalice quartzite should be viewed as a product of hydrothermal silicification rather than silcretization.
Nannofossil biostratigraphy of the Oligocene deposits in the Grybów tectonic window (Grybów Unit, Western Carpathians, Poland)
Abstract: The Grybów tectonic window belongs to the Grybów Unit of the Fore-Magura Group of units. This tectonic window is located in the marginal part of the Magura Nappe, and is composed of Oligocene — Grybów Marl Formation and Cergowa Beds. On the basis of calcareous nannoplankton investigation the Grybów Marl Formation has been assigned to Zone NP24, while the Cergowa Beds belong to Zones NP24–NP25. The Oligocene sequence of the Grybów tectonic window (Grybów Unit) display strong similarities to sediments of similar age in the inner part of the Dukla Unit in the Polish, East Slovak and Ukrainian sectors of the Outer Carpathians. On the basis of these similarities it is supposed that the Grybów Unit continues towards the south-east as an innermost part of the Dukla Unit (Ślaczka 1971), and further on into the Ukrainian Carpathians as the Dusino (Berezna) Subunit within the inner part of the Dukla Unit.
40Ar/39Ar dating of Miocene tuffs from the Styrian part of the Pannonian Basin: an attempt to refine the basin stratigraphy
Abstract: In this study we present new 40Ar/39Ar age data obtained from volcaniclastic material intercalated within shallow-marine to neritic sediments of the Styrian part of the Miocene Paratethyan Sea, which allow a better control of the sedimentation. At Retznei quarry, a volcaniclastic layer has been deposited in erosional patches above a consolidated rhodolite limestone (“Leitha Limestone”) of the siliciclastic/marine Badenian Weissenegg Formation. Ar-release plots of a biotite bulk-grain concentrate (30 grains) and a concentrate of three sanidine crystals (0.5–1 mm) display fairly flat release-patterns with minor fluctuation in the low-energy gas-release steps. From the statistical point of view the biotite concentrate yielded a high-precision plateau age of 14.21±0.07 Ma, the three sanidine crystals yielded a plateau age of 14.39±0.12 Ma. The radiometric ages obtained match the biostratigraphic record (Upper Lagenide Zone). A drill-core recovered from the well Hörmsdorf, exposes several sand-dominated horizons and two layers of crystal tuff, of the Karpatian Eibiswald Formation. Ar-analyses of one single biotite grain (> 1 mm) from the hanging-wall, another biotite single-grain from the lower tuff both display slightly disturbed Ar-release spectra. However Ar-plateau ages of 15.08±0.09 Ma and 15.22±0.17 Ma, respectively, have been obtained. Volcaniclastic rocks from Pöls are intercalated within the Florian Formation., for which previous authors suggested a Lower Badenian age (16.4–ca. 15 Ma according to Rögl 1996). A concentrate of two clear sanidine crystals (0.5–1.0 mm), yielded a perfect Ar-plateau recording an age of 15.75±0.17 Ma, which is more precise than previously published K-Ar results.
Provenance of the Upper Miocene clastic material in the southwestern part of the Pannonian Basin
Abstract: Upper Miocene clastic material in the SW part of the Pannonian Basin originates from two clearly different source areas. The mineralogy and texture of the detritus of the older part of the deposits (Croatica, Ozalj and Medvedski Breg Units) are immature. These sediments originated from intense mechanical weathering of the hinterland. Detrital composition varies greatly and clearly reflects the composition of the source rocks. The mineralogy and texture of the detritus of younger deposits (Andrasevec, Hum Zabocki, Cernik and Pluska Units) are relatively mature, showing a uniform composition in the entire study area. The sediments were generated by weathering of various sources, mainly siliciclastic sediments and metamorphic rocks, and to a lesser degree, basic and ultrabasic magmatic rocks. The composition of the main detrital modes of the arenites and paleotransport measurements suggest that the source rocks were part of an orogenic belt located to the NW, W and NE of the studied area, namely the Eastern Alps and Carpathians. On the SW edge of the Pannonian Basin, in the Hrvatsko Zagorje and Mt Zumberak area, at the contact between the Upper Miocene and Pliocene deposits, a gradual change of the heavy mineral assemblage was determined. This change could be linked with structural changes in the Alpine-Carpathian orogen when rocks from deeper parts were brought to the surface, or with a rearrangement of source areas within the orogen area. Towards the east, in the area of the Slavonian Mts, sands in the Upper Miocene and lowest part of Pliocene deposits do not show similar changes, and probably belong to a separate clastic system, which, contemporaneously prograded towards the south.
Geochronology of Neogene magmatism in the Carpathian arc and intra-Carpathian area
Abstract: Neogene to Quaternary volcanism in the Carpathian-Pannonian Region was related to the youngest evolutionary stage of the Carpathian arc and the intra-Carpathian area, with subduction, extension and asthenospheric upwelling as the main driving mechanisms. Volcanism occurred between 21 and 0.1 Ma, and showed a distinct migration in time from West to East. Several groups of calc-alkaline magmatic rock-types (felsic, intermediate and mafic varieties) have been distinguished, and several minor alkalic types also occur, including shoshonitic, K-trachytic, ultrapotassic and alkali basaltic. On the basis of spatial distribution, relationship to tectonic processes and their chemical composition, the volcanic formations can be divided into: (1) areally distributed felsic calc-alkaline formations related to the initial stages of back-arc extension, (2) areally distributed intermediate calc-alkaline formations related to advanced stages of back-arc extension, (3) “arc-type” andesite volcanic formations with a complex relationship to subduction processes, and (4) alkali basaltic magmatism related to post-convergence extension. Petrological data and geotectonic reconstructions, which involve these magmatic groups, place significant constraints on geodynamic models of the Carpathian-Pannonian area. Subduction and back-arc extension were not contemporaneous across the whole Carpathian arc and intra-Carpathian area. Instead, three major geographical segments can be defined (Western, Central, Eastern segments) with a progressively younger timing of subduction roll-back and back-arc extension: 21–11 Ma, 16–9 Ma, 14–0 Ma, respectively. Short-lived subduction-related volcanic activity can be interpreted as either an indication of a limited width of subducted crust (not greater than 200 km) or an indication of detachment of the sinking slab. Interpretation of the areally distributed felsic and intermediate calc-alkaline volcanic formations are considered as being initiated by back-arc extension induced by diapiric uprise of “fertile” asthenospheric material.
Caddis-fly (Insecta: Trichoptera) from the Badenian volcano-sedimentary succession (Western Carpathians, Slovakia)
Abstract: Vodnik prapovodnik Sukatcheva et Vrsansky, gen. et sp. nov. is described from the Badenian volcano-sedimentary succession of the Plastovce Member, Sebechleby Formation in southern Slovakia. It represents a taxon closely related to the common European caddis-flies Chaetopterix Stephens, 1829 and Chaetopterna Martynov, 1913 of the family Limnephilidae Kolenati, 1848. In a seasonal climate, these partially psychrophilic insects emerge in masses during the autumn. Larvae are fixed to water and thus the seasonality in otherwise warm Badenian climate, with characteristic mangroves, might have been caused by temperature changes in streams and/or rivers coming from adjacent steep elevations.