Conodonts across the Permian-Triassic boundary in the Bükk Mountains (NE Hungary)
Abstract: The results of micropaleontological studies, especially of conodonts, across the Permian-Triassic (P-T) boundary interval in the Balvany-North, Balvany-East and Gerennavar sections of the Bükk Mountains (NE Hungary) are presented. Conodont zones for the boundary interval have been identified on the basis of biostratigraphic data for conodont taxa (Hindeodus parvus, H. praeparvus, Hindeodus sp., Isarcicella cf. prisca, Hindeodus/Isarcicella sp.) and the FOD of H. parvus. The praeparvus Zone possibly the Late praeparvus Zone (uppermost part of Changhsingian, Late Permian) in the Nagyvisnyó Limestone, inclusive of the ‘Boundary Shale Bed’, and the parvus Zone (earliest Induan, Early Triassic) in the Gerennavar Limestone are discriminated.
Stratiform manganese mineralization in the Paleogene and Jurassic shale formations of the Western Carpathians: mineralogy, geochemistry and ore-forming processes
Abstract: Manganese mineralization is bound to Paleogene (Oligocene; Rupelian) and Jurassic (Toarcian, Aalenian and Bathonian–Callovian) shales. Mineralization is represented by manganese carbonates (rhodochrosite, kutnohorite and Mn-calcite). Mn-oxyhydroxides (pyrolusite, manganite and rancieite) were formed later during supergene processes by oxidation of manganese carbonates. Paleogene and Jurassic black shales with abundant framboidal pyrite are enriched in organic matter. The average content of organic carbon is 1.04 wt. % in Paleogene shale and 1.11 wt. % in Jurassic shale. The Si/Al ratios of 3.09 in Paleogene shale and 4.04 in Jurassic shale are close to typical marine-sediments and hydrogeneous-detrital manganese accumulations. The distribution of the rare earth elements in the shale suggests continental source and formation in more reducing environment than the Jurassic manganese crusts. Cobalt, copper and nickel contents of mineralized shale are distinctly lower than in oxidic ores in the Jurassic manganese crusts of Western Carpathians. Isotopic composition of calcite in sediments shows positive values δ13C in most samples of Paleogene and Jurassic carbonates. Increased manganese content in Mn-carbonates is closely associated with distinctly negative values of δ13C down to –9.9 in Paleogene carbonates and down to –11.2 in Jurassic carbonates. The dominant negative δ13C composition suggests early-diagenetic origin of Mn-carbonates affected by organic carbon.
Post-Cretaceous differential block rotation in the Slovensky raj Mts (Western Carpathians, Slovakia): inferences from paleomagnetic data
Abstract: Results of paleomagnetic study of Triassic limestones, sandstones and serpentinites of the Stratena and Borka Nappes (Silicic and Meliatic Units), as well as of the Upper Cretaceous sandstones (Gosau Group) from the area of the Slovensky raj Mts and Dobsina area are presented. Characteristic components of remanence were isolated in six localities representing several nappe slices. The isolated characteristic remanences are carried by secondary minerals. They are of chemical origin and normal polarity. They were probably acquired during the latest Cretaceous at paleolatitudes of about 28°N to 22°N showing that the area was in that time of African affinity. The whole study area moved from the South to North, nappes and nappe slices formed due to intensive compressive Paleoalpine tectonics. During the transtensive and extensive Neoalpine periods of Alpine orogenesis they disintegrated into different blocks which moved mainly horizontally, some of them were backthrusted, or rotated. Finally they were amalgamated into the recent megablocks. The individual rotations calculated against the reference declination Dref = 6° for European data for the Miocene are as follows: Dolka 1: 21° CW (Clockwise), Dolka 2: 15° CW, Dedinky: 14° CCW (Counter-clockwise), Kopanec: 41° CCW, Dobsina: 55° CCW, Dobsinska ladova jaskyna: 16° CW.
Oligocene-Miocene sandstone suites from the Gibraltar and Calabria-Peloritani Arcs: provenance changes and paleogeographic implications
Abstract: Oligocene-Miocene turbiditic flows which formed thick sedimentary successions cropping out in the internal sectors of the Betic-Maghrebian Chain, Tell and Calabria-Peloritani Arc, are commonly related to the dismantling of pre-Alpine crystalline basements. These are now included in different tectonic edifices along the central-western peri-Mediterranean Alpine Chain but originally they could have belonged to the same crustal block, known as the AlKaPeCa Block (Al = Alboran, southern Spain and northern Morocco, Ka = Kabylian, Algeria, and PeCa = Calabria-Peloritani Arc). Detrital modes from Oligocene-Miocene late-orogenic sandstone suites, unconformably overlying the uppermost structural units of the Betic-Rifian Chain and the Rifian “Dorsale Calcaire” Units, show a provenance closely related to source areas mainly formed by Mesozoic carbonate sedimentary covers and, partially, by very slightly metamorphic rocks. In contrast, sandstones of equivalent late-orogenic successions from the Calabria-Peloritani Arc appear to be mainly derived by the erosion of high rank metamorphic and plutonic sources, which can be identified with the Hercynian basement rocks, now forming the highest structural units of the Arc. This bimodality of provenance (carbonate covers with, partially, epimetamorphic sources against a mainly plutonic and/or gneissic supply in the Gibraltar and Calabria-Peloritani Arcs, respectively) occurring between coeval late-orogenic sandstone suites, equivalent for age, geological significance and structural position, can be justified by admitting that the Internal Domains, which played a role as sediment sources, did not belong to the same crustal block or they were already separated as the consequence of an incipient break-out and fragmentation of the AlKaPeCa Block before the Late Oligocene (age of the base of the studied late-orogenic deposits).
New Paratethyan biozones of planktonic foraminifera described from the Middle Miocene of the Transylvanian Basin (Romania)
Abstract: Recent investigations of the Upper Badenian and Sarmatian of the Transylvanian Basin revealed particular, small sized planktonic foraminiferal assemblages. SEM investigation permitted more precise taxonomic interpretations of the planktonic species. The Late Badenian assemblage — with trochospiral, microperforate, and pustulose Tenuitellinae — occurring in relation to a transgressive event close to the end of the Badenian, makes possible an increased biostratigraphic resolution. The Sarmatian assemblage with Streptochilus (biserial Chiloguembelinidae) provide evidence for the paleogeographic connections to the Indo-Pacific area, and support new paleoenvironmental and biostratigraphic interpretations.
Serravallian sequence stratigraphy of the northern Vienna Basin: high frequency cycles in the Sarmatian sedimentary record
Abstract: Middle Miocene global and regional factors affecting the development of depositional systems and sedimentary architecture were studied in the northern Vienna Basin. In the Serravallian sedimentary record (Upper Badenian and Sarmatian, Central Paratethys regional stages) two individual 3rd-order cycles of sea-level changes were confirmed. They can be more or less compared with Haq’s Mediterranean cycles TB 2.5 and TB 2.6. The presented sequence stratigraphy approach also proved existence of four 4th-order relative sea-level changes in this time interval here. Furthermore, the late Serravallian (Sarmatian) record documents the strong influence of astronomical forcing on cyclic sedimentation. Detected high frequency cycles are most likely result of climatic (orbital) forcing on the eccentricity band with period of 400 and 100 kyr in a shallow water depositional environment. The sequence stratigraphy scheme of the northern Vienna Basin fits well with development in the whole basin, as well as with development in other basins in the Carpathian-Pannonian region (Styrian and Transylvanian Basins). This fact therefore led to the assumption of an interregional character of the high frequency cycles initiated by impulses common for different basins in the Central Paratethys realm.