T5

Upper Campanian Scaglia-type limestones in the transition zone between the Internal and External Dinarides (Placer 2008) contain two layers of bentonitic clays. The first 110 cm thick, and the second 10 cm thick. The geochemical composition of the bentonites indicates a rhyolitic volcanic source within an active continental margin. According to the mineralogy of the clay, the layers can be interpreted as deposition of volcanic-ash in a marine sedimentary environment with admixture of carbonates. The encompassing carbonate succession was deposited in a deeper marine environment of the Slovenian Basin. The limestones are composed of (hemi)pelagic mudstones to wackestones and thin- to medium-grained calcarenites, originating from the adjacent Adriatic Carbonate Platform. Similar Upper Cretaceous successions containing Campanian bentonitic clay horizons have been described in the Central Apennines (Graziano and Adabbo 1996; Bernoulli et al. 2004). The most likely source of these volcanoclastics is the bimodal rhyolitic/basaltic magmatic activity within the Sava suture zone, located in the present day Dinarides (Ustaszewski et al. 2009; Cvetković et al. 2014; Prelević et al. 2017; Schmid et al. 2020).

Bernoulli, D., Schaltegger, U., Stern, W. B., Frey†, M., Caron, M., & Monechi, S. (2004). Volcanic ash layers in the Upper Cretaceous of the Central Apennines and a numerical age for the early Campanian. International Journal of Earth Sciences, 93(3), 384–399. https://doi.org/10.1007/s00531-004-0389-4

Cvetković, V., Šarić, K., Grubić, A., Cvijić, R., & Milošević, A. (2014). The Upper Cretaceous ophiolite of North Kozara–remnants of an anomalous mid-ocean ridge segment of the Neotethys? Geologica Carpathica, 65(2), 117–130.

Graziano, R., & Adabbo, M. R. (1996). Segnalazione di un livello cineritico nella serie di scarpata senoniana del Gargano meridionale. Bollettino della Societa Geologica Italiana, 115(2), 459–466.

Placer, L. (2008). Principles of the tectonic subdivision of Slovenia. Geologija Revija, 51(2), 205–217.

Prelević, D., Wehrheim, S., Reutter, M., Romer, R. L., Boev, B., Božović, M., et al. (2017). The Late Cretaceous Klepa basalts in Macedonia (FYROM)—Constraints on the final stage of Tethys closure in the Balkans. Terra Nova, 29(3), 145–153.

Schmid, S. M., Fügenschuh, B., Kounov, A., Maţenco, L., Nievergelt, P., Oberhänsli, R., et al. (2020). Tectonic units of the Alpine collision zone between Eastern Alps and western Turkey. Gondwana Research, 78, 308–374. https://doi.org/10.1016/j.gr.2019.07.005

Ustaszewski, K., Schmid, S. M., Lugović, B., Schuster, R., Schaltegger, U., Bernoulli, D., et al. (2009). Late Cretaceous intra-oceanic magmatism in the internal Dinarides (northern Bosnia and Herzegovina): Implications for the collision of the Adriatic and European plates. Lithos, 108(1), 106–125. https://doi.org/10.1016/j.lithos.2008.09.010

How to cite: Gerčar, D., Zupančič, N., Waśkowska, A., Pavšič, J., and Rožič, B.: Upper Campanian volcanoclastics in the Scaglia-type limestones of the Adria continental margin, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-44, https://doi.org/10.5194/egusphere-alpshop2022-44, 2022.

Despite the structural complexity of the Alps at numerous scales, geological and geophysical investigations have respectively mapped and imaged tremendous amounts of information near the surface and at depth. However, there is an inherent gap between the two sets of approaches, leaving the middle and lower crust poorly constrained. This has been one of the main motivations to initiate the ICDP project DIVE (Drilling the Ivrea-Verbano zonE), in which three geological sites of the Ivrea-Verbano Zone will be explored through scientific drilling. In this zone, near-complete sections of the continental crust are exposed at the surface, and with careful geological preparation and geophysical site surveys we have targeted three areas with a great potential of further discoveries during DIVE. Almost all physical and chemical properties will be characterized on the recovered rock core samples, in borehole logging investigations, and additional surveys around each site. Taken together, these should cover a large range of spatial scales covering at least 6 orders of magnitude (mm to km), investigate structures and their variations in bulk properties within the lower crust, and the transition to mantle rocks in an unprecedented way. The interdisciplinary approach not only allows to correlate numerous geophysical and petrological properties, but with modelling it will also allow to investigate the causative relationships.

The detailed aims, preparatory steps, as well as the current status of project DIVE, will be presented at the conference. By that time, drilling of the first hole is expected to start near Ornavasso, followed by a second hole in Megolo (both in Val d’Ossola). For the third site near Balmuccia, which is planned for later, site survey results will be presented.

How to cite: Greenwood, A., Hetényi, G., Ziberna, L., Pistone, M., Zanetti, A., Müntener, O., and Team, P. D.: Project DIVE (Drilling the Ivrea-Verbano zonE): A joint petrological, geochemical, and geophysical exploration of the lower continental crust, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-32, https://doi.org/10.5194/egusphere-alpshop2022-32, 2022.

Due to the collision of the European and Adriatic plates, about 3 mm/yr of N-S convergence are accommodated in the Eastern and Southern Alps. This shortening is mainly taken up by c. E-W-trending reverse faults along the South Alpine Front and on NW-SE-trending dextral strike-slip faults in western Slovenia. Strong historical earthquakes and instrumental seismicity, however, show that some deformation also occurs in the interior of the Southern Alps. Little is known about which faults are active here. In this study we present results from a regional-scale remote sensing analysis focusing on the Bellunese and Friulian sectors of the Southern Alps in northeastern Italy. Our aim was to identify areas with relatively increased tectonic activity based on landscape features. We made use of high-resolution digital elevation models from aerial laser scanning campaigns. We downsampled the data to 5 m resolution and calculated the most widely used geomorphic indices that might indicate active tectonics: normalised steepness index, the Chi­ value, terrain ruggedness index, and stream knickpoints. The results were checked with geological data, mapped faults, and seismicity. We also conducted extensive field work to verify the results on the ground. Our results show that the application of large-scale tectonic geomorphology in this particular Alpine region is complicated by numerous factors. Small-scale variations in lithologies with variable erodibility strongly influence the analysis. The same holds true for variations in dip direction and dip angles of bedding planes; occasionally, vertical strata erroneously suggest linearly trending faults. In addition, we found that glacial features and alluvial deposits have locally overprinted the traces of known faults. Despite of these challenges, we found hints for active deformation in the landscape, in particular in the epicentral area of the 1976 Friuli earthquakes. We highlight potential pitfalls of the applied methods and discuss ways to overcome some of the problems we encountered.

How to cite: Grützner, C., Grenier, M., Stubenrauch, J., Hermann, M., Reicherter, K., and Ustaszewski, K.: Remote sensing of active tectonics in NE Italy, eastern Southern Alps, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-16, https://doi.org/10.5194/egusphere-alpshop2022-16, 2022.

The basement of the south-eastern part of the Miocene Pannonian back-arc basin is represented by the Tisza Unit. The deep structure of the Tisza unit is poorly studied, despite its significant geothermal and CH potential.  This work is a first step in our structural mapping project, which investigates the structures within the basement of the Pannonian Basin. 

The Tisza unit is composed of Proterozoic to Early Paleozoic poly-metamorphic basement rocks, and Late Paleozoic to Mesozoic sedimentary cover. The Tisza Unit is built up by three main nappes, the Mecsek, the Villány-Bihar and the Codru subunits. The Tisza Unit is exposed in inselbergs (Mecsek, Villány, Apuseni Mts.), however, most of it is covered by several km thick Miocene succession. The pore space containing energy source materials is located in the Miocene Pannonian Basin cover sediments, and in the fractured basement rocks near its surface and in their deeper part, especially in the Cretaceous sedimentary formation. Our research targets the better understanding of the Alpine shortening tectonics and structure of the Tisza Unit, with special attention to the structures of these tectonically buried sedimentary basement patches.

In this study we use modern 3D seismic data sets and well data to investigate the central part of the Tisza Unit. Based on that, the Tisza Unit is a Late Cretaceous fold and thrust belt, which can be characterized by major thick-skinned nappes, and second-ordered thin-skinned structures. Such second-ordered structures are the active and passive roof-duplexes below the Villány nappe (Derecske), and out-of-the-syncline thrusts in the front of the Codru nappe (Vésztő). The basal thrust of the Villány nappe cuts across pre-existing normal faults and associated half-grabens, demonstrating the presence of the early Alpine rift-related structures. Major nappes are unconformably overlain by Santonian to Maastrichtian beds, nevertheless, the presence of growth-synclines in this succession indicates ongoing shortening after major nappe emplacement during the latest Cretaceous. The Cretaceous fold and thrust belt of the Tisza Unit is strongly overprinted by Miocene extensional and transtensional structures, which are related to the rifting of the Pannonian back-arc basin.

How to cite: Héja, G., Lőrincz, K., Bereczki, L., Markos, G., Maros, G., and Palotai, M.: A buried fold and thrust belt: the structural geometry of the central part of the Tisza Unit, East Hungary, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-63, https://doi.org/10.5194/egusphere-alpshop2022-63, 2022.

Stratiform U-Cu mineralization (0.02-1.13 % U) in the eastern part of the Kozie Chrbty Mts. is bound to the Permian volcano-sedimentary complex of the Ipoltica Group, Hronic Unit (Western Carpathians). The wide surroundings of the deposits are formed by other, Triassic sediments of Hronic Unit (limestones, dolomites, quartzites, shales) also by Paleogene sedimentary complexes of the Podtatranská Group (sandstones, conglomerates, claystones). The ore deposits (Vikartovce, Kravany, Švábovce, Spišský Štiavnik) are situated in the arcosic sandstones of the Upper Permian part of the Kravany Beds with carbonized fragments of higher plants. The deposits were exploited during the survey (60s – 70s of the 20th century).

Relatively late tectonic events affected the volume and the quality (and also minig-technical conditions) of considered ore deposits. This tectonics resulted in iregular distribution of mineral ore in this region. In the western part of the Dúbrava Mts. (Vikartovce, Kravany deposits), the distribution of the ore is relatively regular, limited to 1 – 2 ore bearing horizons. In this case the structure of the deposits is limited mainly by Vikartovce Fault with subvertical sence of movement.

Concerning the tectonic condition, Kravany and Vikartovce deposits are situated to the north (in the bedrock block) and in close proximity (200 – 300 m) of Vikartovce Fault of east-to-west direction. On the contrary, the Švábovce and Spišský Štiavnik deposits are located on a neotectonic structure that limits Dúbrava Mts. from the north (W-E direction). The Kravany and Vikartovce deposits are disrupted by disjunctive tectonics in two directions: faults east-to-west causing 5 – 10 m declines of southern blocks faults, and faults with northeast-to-southwest direction causing 10 m declines of southwestern blocks. The deposit conditions on the eastern part of the Dúbrava Mts. are limited by the combination of the neotectonic fault systems: Vikartovce, Gánovce and Muráň-Divín.

At the Kravany deposit, local tectonic caused the formation of so-called „zone ore mineralization“, when U-Cu mineralization occurs in the tectonic zone (reprocessed carbonized plant residues, uraninite, pyrite, chalcopyrite and carbonates).

Stratiform, infiltration U-Cu-Pb mineralization in the eastern part of the Kozie Chrbty Mts. is bound to the Upper Permian clastic sediments (Kravany Beds, member of Malužiná Formation, Hronic Unit). Their lithological composition is represented  by green  to dark gray fine to medium-grain arcosic sandstones, arcoses, gray-black sandstones and siltstones with a significant content of carbonized plant debris. Uranium mineralization together with Cu and Pb mineralization are concentrated mainly in the cracks and pores of corbonized organic matter. Stratiform U-Cu-Pb mineralization is represented by minerals: uraninite, coffinite, U-Ti oxides accompanied by arsenopyrite, chalcopyrite, pyrite, marcasite, tetrahedrite, tennantite, galena, sphalerite, quartz, calcite and dolomite. The age of stratiform mineralization was set at 263 – 274 Ma, based on U-Pb dating.

Secondary minerals described in the supergene zone of U ore deposits are uranophane, autunite, torbernite, metatorbernite, azurite, malachite, arsenopyrite, goethite, limonite, covellite, chrysocolla, gypsum and zálesíite.

Acknowledgements: This work was supported by the Slovak Research and Development Agency under the contract APVV-19-0065, VEGA 1/0563/22, KEGA 033UMB-4/2021.

How to cite: Hoppanová, E., Ferenc, Š., Šimonová, V., and Kopáčik, R.: New knowledge about U-Cu mineralization in the Kozie Chrbty Mts. and its relationship to the late (Neotectonic) structures (Hronic Unit, Western Carpathians, Slovakia), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-53, https://doi.org/10.5194/egusphere-alpshop2022-53, 2022.

Investigated section is located on the eastern slope of the Ždiarska Vidla, Tatra Mts. (Slovakia), along the old tourist path.  The section belongs to the Križna nappe and to the Havran and the Bujačí unit. Pelagic and hemipelagic sedimentation of the spotted limestones and marls prevailed on the margin of the Zliechov (Križna) during the Early and Middle Jurassic. The spotted limestones of the Tatra Mts. depending on the authors, are included in the Janovky Formation or in the Sołtysia Marlstone Formation. The investigated Ždiarska Vidla section is 200-m thick. This unit is dated to the Bajocian based on lithological similarity to the Kopy Sołtysie area, where rare ammonite fauna was described. The lithology is composed of spiculite limestones and marly spiculite limestones (with marly spiculite wackestone–packstone, and marly bioclastic filament wackestone microfacies). Field magnetic susceptibility (MS) and gamma–ray spectrometric measurements (indicating content of potassium, K (%); uranium, U (ppm,); thorium, Th (ppm)) have been carried out. The Ždiarska Vidla section has also been sampled for carbon isotopes with resolution of ca. 0.5-1 m. The bulk carbonate obtained carbon isotope curve is characterized by positive shift. It is assigned to the Lower Bajocian as based on data of O’Dogherty (2006). The section is subdivided into three parts (IIA, IIB, III) on the basis of the MS, K, Th, U and δ13C curves. The oldest IIA interval is characterized by a weak positive linear correlation between MS to Th, Th/U and CGR, which suggests an association of MS with the supply of terrigenous elements to basin. The p-values associated with received Pearson R are much above the assumed significance level (0.05), indicating that received results are statistically insignificant. In the IIB and III interval, MS correlates inversely to Th, CGR, Th/U, what it might show that increase MS is related to oxygen deficiency. Within the level IIB, values of Pearson r-value for correlation between MS and Th, CGR, U and K varies between -0.2 and -0.43 with p-values in the range from 0.03 to 0.3 meaning, that only part of the results is statistically significant. The III interval is characterized by a moderate negative linear correlation between MS and Th, K and CGR, where Pearson R reaches values from -0.42 to -0.56 with p-values much below the assumed level of 0.05, meaning that received results are statistically significant. Spectral analyses done on the MS signal in Intervals II and III reveal cycles of 18 m, 4-5 m and 1.3-1.8 m, respectively related to the 405-kyr, 100-kyr and 40-kyr cycles. The duration of Intervals II and III are thus assessed at 4.4 to 4.5 Myr, with a mean sedimentation rate of 4.4 cm/kyr.

How to cite: Iwańczuk, J., Martinez, M., and Bobek, K.: Recording of cyclicity in the sediments of the Bajocian  and Lower Bathonian on the basis of magnetic susceptibility (Carpathians, Poland)., 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-59, https://doi.org/10.5194/egusphere-alpshop2022-59, 2022.

Conodont biozonation of the Norian (Upper Triassic) of the Western Tethys realm is in development from the 1970’s, however, a satisfactory scheme has not yet been established. The problem originates in the over-simplified taxonomy of Norian conodonts, since biostratigraphic investigations have never coupled with thorough and detailed systematic studies. Even the zonal schemes proposed after the millennium were based mainly on the species described in the second half of the 20^th century. Consequently, conodont zones of the existing schemes cover longer time intervals, although a finer subdivision would be possible. An ongoing research attempts to refine the Norian conodont biozonation of the Circum-Pannonian Region based on abundant conodont faunas of various localities.

The old trench at Mátyás Hill of the Buda Hills (Transdanubian Range, Hungary) exposes a ca. 20 m thick sequence of hemipelagic cherty dolostones of Lower to Middle Norian age. Dense sampling of the section yielded well-preserved conodont elements in high numbers. The lower half of the succession can be dated as Lower Norian (Lacian-3) based on the presence of Norigondolella navicula, Norigondolella hallstattensis and Ancyrogondolella ex gr. triangularis. In the upper half of the section, bedding is often disturbed, intervals of fractured blocks are common. Conodonts with morphological characters transitional to those of typical Middle Norian species first occur at the lower level of this interval, though Lacian forms remain dominant. This part represents the Lower-Middle Norian transition, which is often characterized by sedimentary breccias and/or fissure fills (e.g., Dovško section – Karádi et al., 2021; Kälberstein quarry section – Gawlick and Böhm, 2000). Species indicating inevitably Middle Norian age (Alaunian-1) were found 1.5 m below the top of the section where Lacian species are absent. This fauna is composed of Ancyrogondolella equalis, Ancyrogondolella ex gr. transformis and Mockina ex gr. matthewi.

Due to the large morphological variety and the very low number of figured specimens, the taxonomic revision of these Norian assemblages is yet to be done. Anyhow, the establishment of a high-resolution Norian conodont biozonation of the Circum-Pannonian Region seems feasible, which will allow a better correlation potential within the Western Tethys realm.

The research was supported by the National Research, Development and Innovation Office NKFIH PD-131536 grant.

References:

Gawlick, H.-J., & Böhm, F. (2000). Sequence and isotope stratigraphy of Late Triassic distal periplatform limestones from the Northern Calcareous Alps (Kälberstein Quarry, Berchtesgaden Hallstatt Zone). International Journal of Earth Sciences, 89, 108–129.

Karádi, V., Kolar-Jurkovšek, T., Gale, L., & Jurkovšek, B. (2021). New Advances in Biostratigraphy of the Lower/Middle Norian Transition: Conodonts of the Dovško Section, Slovenia. Journal of Earth Science, 32, 677–699.

How to cite: Karádi, V.: On the way to building the Norian conodont biozonation of the Circum-Pannonian Region, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-36, https://doi.org/10.5194/egusphere-alpshop2022-36, 2022.

Since the onset of continental collision in the eastern Alps, several large-scale reorganizations have affected the crustal structure, such as Adriatic indentation, eastward extrusion or the Tauern window exhumation. This work aims to improve the understanding of the tectonic history of the region, by providing a new shear-velocity model of the eastern Alpine crust. It makes use of data from the AlpArray and the dense SwathD networks from which phase velocities are measured. These are inverted in a two-step approach based on a Markov-Chain Monte Carlo sampler to obtain the model structure and its uncertainties. The shallow structure is well correlated with the major faults in the area. Additional information from the anisotropy at mid to lower crustal levels is interpreted in terms of the strain direction. Eastward orientated fast axis are observed at a large depth range in the central part of the mapped region. This may indicate that the eastward extrusion affects all crustal levels down to Moho depths. The mapped features are compared to previous works from local earthquake tomography and receiver functions to provide a joint interpretation of the crustal structure.

How to cite: Kästle, E. and the AlpArray Working Group: Crustal structure in the eastern Alps from ambient-noise tomography, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-49, https://doi.org/10.5194/egusphere-alpshop2022-49, 2022.

The systematic paleomagnetic investigations concentrating on the northern part of stable Adria and the External Dinarides provided tectonically applicable results for nearly 200 localities from Italy, Slovenia and Croatia. The ages of the studied localities were tightly controlled by a bed by bed checking of the fossil content. The age of the acquisition of the magnetization was constrained by between-locality fold/tilt test, which often proved the pre-deformation “primary” age of the magnetization. It is important to emphasize that most of the sampled sediments were shallow water carbonates with weak natural remanent magnetizations (about 30% of the sampled localities failed to yield paleomagnetic signal). However, those providing results are extremely valuable, for inclination flattening is practically absent in platform carbonates, therefore the estimation of the paleolatitudes are reliable. 
The majority of the tectonic models published for the area are in agreement about the existence of two Mesozoic carbonate platforms, an Adriatic and a Dinaric, which came into contact during the Late Eocene-Oligocene thrusting of the latter over the former. They are in the External Dinarides, but the exact boundary between them is a matter of discussion. The tectonostratigraphic complexity of the External Dinarides is the main reason for the large number of models published for the Northern Adriatic area.
The paleomagnetic results, which permit to conclude as to the absence or existence of large-scale relative movement between areas, suggest that stable Adria and the whole chain of the Adriatic islands moved in a co-ordinated manner, i.e. the islands represent the imbricated margin of stable Adria, at least from the Aptian onward. During the Late Cretaceous, the area was close (38°N) to the northernmost limit (40°N) of the intensive carbonate production, the carbonate factory. Stable Adria with its imbricated margin exhibits about 30° larger CCW rotation than the High Karst belonging to the Dinaric platform, thus giving further support to considering the chain of the Adriatic island as belonging to Adria. The practically parallel “primary” paleomagnetic declinations characterizing the Northern Adriatic area are at variance with the oroclinal origin of the arcuated shape of the chain of the Adriatic islands and of the thrust front between them and stable Adria. We attribute this shape to the dominance of the Late Cretaceous E-W compression in the northern segment, the Late Eocene-Oligocene NE-SW compression in the central segment, and the N-S oriented Neotectonic compression in the Central Adriatic area. 
This work was financially supported by the National Development and Innovation Office of Hungary project K 128625.

How to cite: Márton, E., Ćosović, V., Drobne, K., Moro, A., Bućković, D., and Imre, G.: Tectonic implications of paleomagnetic results from the Northern Adriatic area: an overview, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-41, https://doi.org/10.5194/egusphere-alpshop2022-41, 2022.

The Sesia zone is a rifted portion of the Adriatic Margin that subducted to high-pressure conditions during the Alpine Orogeny. It consists of two main complexes: the Internal Complex (IC) and the External Complex (EC). The IC is made up of polymetamorphic micaschists, eclogites, and ortho-gneisses equilibrated at eclogite facies conditions; the EC consists of alpine monometamorphic orthogneiss with minor paragneiss and quartzites metamorphosed at epidote blueschist facies conditions and intensely retrogressed at greenschist facies conditions. The question is therefore to understand if we can trace the Alpine metamorphic history through methods that do not rely only on chemical equilibration.

To tackle this objective, we used elastic geobarometry to derive pressure and temperature (P-T) conditions reached by three micaschists from the IC and one garnet-orthogneiss from the EC. Entrapment P obtained for the quartz inclusions in garnet in the IC range from 1.5-2 GPa at 600-650°C, in agreement with the P-T estimates determined through thermodynamic modelling. Coupled quartz and zircon in garnet geobarometry in the garnet-orthogneiss from the EC also display P-T conditions of 1.8 GPa and 650°C. These estimates disagree with the greenschist facies mineral assemblage of the rock (Ttn + Grt + Phg + Chl) and with the results of thermodynamic modelling (0.6-0.8 GPa and 500°C). The misfit in P-T estimates between elastic geobarometry and thermodynamic modelling might be due to an elastic reset of the quartz and zircon host-inclusion pairs at HP conditions. The use of coupled elastic geobarometry and thermodynamic modelling can help to unravel complex tectonometamorphic histories.

How to cite: Mingardi, G., Gilio, M., Giuntoli, F., Musiyachenko, K. A., and Alvaro, M.: Quartz and zircon in garnet elastic geobarometry of HP rocks from the Sesia Zone, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-28, https://doi.org/10.5194/egusphere-alpshop2022-28, 2022.

In the Dinarides the reef rim to the open marine deep-water depositional realm (outer shelf) of the Late Triassic Dachstein Carbonate Platform is not known. On the road from Gradac to Šula near to the village Poros a more than 120 m thick far travelled and overturned Late Triassic succession of reefal to bedded siliceous limestones was studied (biostratigraphy, microfacies). The section is slightly tectonic overprinted, with slump deposits in the central and upper part.

The section starts with a roughly 20 m thick reefal to fore-reefal limestone succession with deep-water matrix in the upper part (Lacian 2 in age with following conodonts: E. rigoi, E. abneptis). Near the base the reefal limestone is think-bedded to massive (rudstones), higher up in the section various bedded. We attribute these fore-reefal limestones as part of the Late Triassic Dachstein Limestone, interestingly with a deepening upward sequence from the middle Lower Norian onwards. Around the Lacian 2-3 boundary the depositional characteristics changed relatively abrupt from reefal-rudstones to bedded siliceous limestones intercalated by few and turbidite layers containing shallow-water debris. The next, 30 m thick part of the succession consists of dm-bedded limestones with chert nodules and layers, grey limestones and reddish limestones (radiolarian-filament wackestones), in parts with slump intercalations or medium-grained microbreccias. Conodont dating show that the age this part of the section is Lacian 3 to Alaunian 1-2 in the upper part (dated by E. spatulata to E. slovakensis) probably reaching the Alaunian 3. The Alaunian 3 to Sevatian (with E. bidentata) is characterized by a thick series of slump deposits with carbonate turbidite intercalations. Upsection follow polymictic breccias (debris flows) and microbreccias (turbidites) with older open-marine hemipelagic components, as proven by conodonts. The overlying dm-bedded grey-reddish siliceous limestones with red chert nodules are Rhaetian in age dated by the appearance of M. hernsteini. Upsection 5-10 cm-bedded grey siliceous and slightly marly limestones (in a thickness of less than 20 m) follow, overlain by roughly 10 m thick dm-bedded red-grey siliceous limestones with red marl to claystone intercalations, in the lower part with slump deposits, again overlain by 5-10 cm-bedded grey siliceous and slightly marly limestones. An exact age of this part of the series could not be determined, only conodont multielements could be isolated from this part of the succession. The age is most likely Rhaetian 2-3, but earliest Jurassic for highest parts of the sequence cannot be excluded.

The higher Lacian to Late Norian part of the succession corresponds to the reef-near facies belt in open shelf position, known in the type-area in the Northern Calcareous Alps as Gosausee Limestone facies. However, the section Poros shows during the Norian a general deepening trend during the time span Lacian 3 to the end of the Rhaetian opposite of the well-known platform margin in the Northern or Southern Alps. In the Dinarides a backstepping of the reef belt in the late Early Norian result in a drowning unconformity of the Early Norian part of the long-living Dachstein Carbonate Platform.

How to cite: Mrdak, M., Gawlick, H.-J., Đerić, N., Đaković, M., and Sudar, M.: Partial drowning or backstepping of the Early Norian Dachstein Carbonate Platform in the Dinarides (Poros, Montenegro), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-54, https://doi.org/10.5194/egusphere-alpshop2022-54, 2022.

The Klagenfurt Basin in the southern Austrian region of Carinthia was glaciated during the Last Glacial Maximum (LGM). Next to numerous lakes, the present-day landscape predominantly exhibits landforms such as moraines and large river terraces systems. These landforms can be seen as markers for post-LGM tectonics: If they are deformed, the basin has taken up a share of the ~N-S shortening prevailing due to the ongoing collision of Adria and Europe. If the landforms are undeformed, this deformation is accommodated elsewhere, most likely further south along the Periadriatic and Sava Fault system or by a NW-SE-trending strike-slip fault system at the junction between Southern Alps and Dinarides in Slovenia. Our study is motivated by the recent discovery of earthquake-triggered mass movements in Carinthian lakes and new data on Late Pleistocene-Holocene speleothem damage in the Karawanken mountains, illustrating that the area is seismically active. We used newly available high-resolution digital elevation models to scan the area for post-glacial deformation but found no conclusive evidence for tectonic activity since the Würm glaciation. We then analysed several outcrops of Late Pleistocene sediments throughout the Klagenfurt Basin to check for soft-sediment deformation features that could be linked to strong seismic shaking. These outcrops were documented as 3D virtual models. Deformed silty-sandy layers were encountered in several places, and one outcrop showed spectacularly folded fluvial gravels. However, we do not need to invoke tectonics as the causative mechanism. Instead, we interpret these structures as evidence for a late glacial advance. Luminescence dating is underway to put constraints on the timing of this event. Our study implies that although there are records for recent strong earthquakes around the Klagenfurt Basin, the rates of deformation are so low that they can not be detected in the post-LGM landscape. 

How to cite: Mücklisch, M., Grützner, C., Prince, E., Tsukamoto, S., and Ustaszewski, K.: New data on the Late Pleistocene evolution of the Klagenfurt Basin, Austria, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-17, https://doi.org/10.5194/egusphere-alpshop2022-17, 2022.

Orogenic deformation patterns show intricate overprinting and structural relations, variations of style and orientation of folds and sense of shear, which are traditionally interpreted as due to polyphase deformation, i.e. distinct deformation phases separated by periods of tectonic quiescence. The Adula nappe in the Central Alps displays exceptional exposures of complex internal structures involving heterogeneous rocks (meta-pelitic and meta-granitic gneisses, micaschists, amphibolites, eclogites, minor quartzites and limestones). The Adula structures are distinguished through the style and the orientation of folds, schistosity and the observation of refolded folds. Structural features show a great variability within the unit, making the structures along the nappe difficult to correlate. However, the Adula deformation patterns are classically interpreted as generated by multiple, distinct deformation phases (five deformation phases; D1-5), despite only one schistosity and lineation may be clearly recognized in the field. Kinematic indicators indicate dominant top-to-N sense of shear, although local top-to-S shear is interpreted as developed during the D3 backfolding phase (e.g. Löw 1987; Nagel 2008). In this contribution, we show a recognition of sheath folds from the central part of the Adula nappe, the largest high-pressure nappe of the Central Alps. We performed detailed geological mapping (scale 1:10000) and structural characterization of the spectacular outcrops of the Piz de Cressim glacial cirque. Here a large antiform is described as the main structure classically associated with the D3 backfolding phase. We show that the meso/leucocratic heterogeneous rocks (orthogneisses, micaschists, migmatitic gneisses, amphibolitic lenses) form highly non-cylindrical folds. Sheath folds are highlighted by several cm to km scale omega and elliptical eye-structures in cross sections perpendicular to the shear direction (y-z plane). Local variations of style and orientation of folds and sense of shear are easily explained by the three-dimensional structure of the sheath folds. All lithological units show one penetrative foliation and a related stretching lineation with variations in orientation. We suggest that the Cressim antiform formed during a progressive, highly non-cylindrical folding under top-to-N deformation accomplished within rheological heterogeneous rocks.

How to cite: Perozzo, M., Maino, M., Schenker, F., and Seno, S.: Discovery of sheath folds in the Adula nappe and implications forthe tectonic evolution (Central Alps), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-15, https://doi.org/10.5194/egusphere-alpshop2022-15, 2022.

The Lower to early Middle Jurassic terrigenous clastic deposits witness the early breakup processes of Pangaea. Rifting and subsequent ocean-floor spreading of the Central Atlantic branch that propagated eastward into the Alpine–Carpathian realm split several continental blocks (Adria, Tisia, Dacia, Moesia), and smaller intervening fragments (such as Cervinia and Oravic), off the southern European plate margin. Alongside the ocean-faced margins of Europe and drifting blocks, the initial rifting phases are recorded by terrigenous terrestrial fluvial-limnic, deltaic to open marine clastic formations. Although showing some regional variations in composition and age, they share many common developmental characteristics.

In the Carpathian Pieniny Klippen Belt (PKB), the Lower – early Middle Jurassic clastics are partly preserved in the Šariš (Grajcarek) Unit that was derived from the outer (northern) margin of the continental ribbon surrounded by the Pennine oceanic branches. Palaeogeographically, this continental splinter is known as the Czorsztyn Ridge and its detached Jurassic–Eocene sedimentary nappes are designated as the Oravic tectonic units (Šariš, Subpieniny and Pieniny).

The Šariš sedimentary succession related to the incipient rifting stage begins with massive quartzitic sandstones of probably Hettangian age deposited in continental to shallow-marine environs. The mature rifting stage is represented by quartz-calcareous, partly turbiditic sandstones rich in imprints of Sinemurian ammonites intercalated by thin layers of grey shales. Overlying spotted marlstones of the Fleckenmergel facies of the Pliensbachian–Toarcian Allgäu Fm. are locally passing into black shales representing the Toarcian oceanic anoxic event. Deposition of dysoxic black shales continued to the Aalenian and early Bajocian by the Szlachtowa Fm., which is characteristic of the Šariš Unit. In addition to micaceous black shales with common imprints of pelagic bivalves of Bositra buchi, it comprises also beds of black turbiditic siliciclastic sandstones rich in white mica flakes and few allochthonous coal seams. Black shales with pelocarbonate nodules out of the reach of turbiditic currents are identical with the concomitant Skrzypny Fm. recognized also in the successions of the Subpieniny Nappe. Beds of calciturbiditic crinoidal limestones occurring in the upper part of the formation indicate input of shallow-marine bioclastic material derived from the adjacent Czorsztyn Ridge uplifted during the middle–late Bajocian. Subsequent latest Bajocian hiatus and drowning of the Czorsztyn Ridge, along with a sudden decline of clastic input in the Šariš Basin, are interpreted as the breakup phase of a nearby oceanic zone.

The post-breakup pelagic succession represents the drifting stage and consists of the late Middle–Upper Jurassic dark, calcite-poor siliceous shales, red ribbon radiolarites, red marlstones and cherty limestones,  followed by the Lower Cretaceous spotted micritic limestones with cherts, mid-Cretaceous Fleckenmergel and dark silicitic shales and Upper Cretaceous red calcite-free claystones. Finally, the synorogenic phase is recorded by the Maastrichtian–Paleocene calcareous flysch with olistostrome bodies and limestone megaolistoliths derived from the overriding Subpieniny Nappe.

How to cite: Plašienka, D., Molčan Matejová, M., and Potočný, T.: Lower–Middle Jurassic clastic formations of the Western Carpathian Klippen Belt: testimony to the rifting-breakup-drifting processes, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-40, https://doi.org/10.5194/egusphere-alpshop2022-40, 2022.

The geological structure of the Western Carpathians is very complicated and is result of several deformation phases. The Meliata Unit (Meliaticum) as a significant part of the Western Carpathians proves existence of substantial tectonic movements. The Meliata Unit incorporates the Permian to Jurassic blueschists-facies Bôrka Nappe and the Jurassic low-grade mélange complexes with huge Triassic olistostrome bodies – the Meliata Unit s.s. Based on microstructural characteristics, the calcite is one of the most suitable minerals for study of deformation history. Calcitic metacarbonates are common elements of subduction-accretionary complexes and thus also a considerable element in rock composition of the Meliata Unit. Samples were taken from various Meliatic complexes either within the Bôrka Nappe, or as olistoliths embedded in the Jurassic mélange. Variations in deformation microstructures are clearly visible in sampled metacarbonates, what was main aspect to separate them into groups reflecting different P/T conditions. The distinguished groups more-or-less correspond to their regional occurrences and grade of metamorphosis of surrounding rocks. The first group (GI) contains relatively large calcite grains and microstructure pointing to the Grain Boundary Migration deformation mechanism, which suggests the higher temperature during dynamic recrystallization. The higher temperature is also proven by character of twin lamellas. The GI microstructures are related to the subduction processes after closure of the Meliata Ocean and exhumation of the high-pressure complexes. The second group (GII) is characterised by a significant grain size reduction and strong shape preferred orientation and thus with development of calcitic mylonite zones. They are related to forming of the Meliatic accretionary wedge. The third group (GIII) shows completely recrystallized microstructure of relatively uniform calcite grain size with sharp edges of grains. They were recrystallized in an annealing regime due to higher temperature gradient generated by a shallow granitic intrusion associated with the exhumation of the underlying Veporic metamorphic dome. The last deformation phase is marked by the bulging deformation mechanism, thus to a partial replacement of primary grains by newly formed fine-grained calcites and represent final stages of nappe emplacement.

Acknowledgements

Financial support from the Grant Agency for Science, Slovakia (project APVV-17-0170 & VEGA 1/0435/21) is gratefully appreciated.

How to cite: Potočný, T. and Plašienka, D.: Calcite microstructures recording polyphase deformation history of the Meliata Unit, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-38, https://doi.org/10.5194/egusphere-alpshop2022-38, 2022.

The Periadriatic Fault System (PAF) is among the most important post-collisional structures of the Alps; it accommodated between 150-300 km of right-lateral strike-slip motion between the European and Adriatic plates from about 35 until 15 Ma. The scarcity of instrumental and historical seismicity on the easternmost segment of the fault is intriguing, especially when compared to nearby structures in the adjacent Southern Alps. Through this project, we aim to show which segments accommodated seismotectonic deformation during the Quaternary by applying Electron spin resonance (ESR) dating to fault gouges produced by the fault system. The method is especially useful for dating shear heating during earthquake activity at near-surface conditions due to its dating range (~10⁴  ~10⁶ years) ) and low closing temperature (< 100°C). During our field campaigns, we acquired structural data and collected 19 fault gouge samples from 15 localities along the PAF, the Labot/Lavanttal Fault, and the Šoštanj Fault. We measured the ESR signals from the Ti and Al centers following the additive and regenerative protocols on 60 mg aliquots of quartz, and compared the measurements between different grain size fractions. Here, we present our preliminary results from select localities, suggesting Quaternary earthquake activity along the fault system.

How to cite: Prince, E., Tsukamoto, S., Grützner, C., Vrabec, M., and Ustaszewski, K.: Finding Quaternary Seismogenic Activity Along the Eastern Periadriatic Fault System: Dating of Fault Gouges via Electron Spin Resonance, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-31, https://doi.org/10.5194/egusphere-alpshop2022-31, 2022.

The Ötztal-Nappe in the central Eastern Alps represents a classical area of polyphase deformation and metamorphism. The pre-Mesozoic basement (Ötztal-Stubai Complex; OSC) comprises metasediments (paragneiss and mica schist), metaigneous rocks and metabasites that experienced a polymetamorphic overprint during Ordovician, Variscan (Devonian to Carboniferous) and Eo-Alpine (Early/Late Cretaceous) events. In the Stubai Alps, basement rocks are unconformably overlain by a monometamorphic Permo-Triassic cover sequence (i.e. “Brenner-Mesozoic”), which truncates pre-Mesozoic structures and allows discriminating pre-Alpine and (Eo-)Alpine structures.
Ordovician metagranites (analysed using LA-ICP-MS U-Pb dating of zircon), deformed together with their metasedimentary host rock, highlight the large-scale structure of the OSC. During the Variscan event, metabasitic rocks of the central OSC underwent eclogite-facies metamorphism followed by an amphibolite-facies overprint. Two pre-Alpine fold generations can be distinguished: i) NE-dipping fold axes of isoclinal folds overprinted by ii) subhorizontal NW-SE trending fold axes that are associated with a pervasive axial plane foliation. Shearbands dissecting the foliation indicate a top-NE directed shear sense, which probably correlates with post-Variscan exhumation. Locally, the shearbands show a SE-directed overprint, which is attributed to Late Cretaceous extension in the course of the Eo-Alpine event.
(Eo-)Alpine metamorphism of the Ötztal-Nappe, represented by a southward increasing gradient from greenschist-facies conditions in the northwest to epidote-amphibolite-facies conditions in the southeast, led to a differential structural overprint. Ar-Ar white mica ages from the Stubai Alps yielding Middle to Upper Pennsylvanian ages (post-Variscan cooling) and “mixed” Variscan-to-Alpine ages reflect the metamorphic gradient. Late Cretaceous ages from Rb-Sr analyses on biotite and (U-Th)/He) zircon thermochronology provide time constraints on large detachment faults that created several tectonic klippen of Mesozoic rocks in the study area. These detachments formed in a general SE-directed extensional regime, which is widely reported from Upper Austroalpine units.

How to cite: Reiser, M., Iglseder, C., Schuster, R., Schneider, D., and Gallhofer, D.: Age and structure of the Stubai Alps (Ötztal-Nappe, Tyrol/Austria), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-52, https://doi.org/10.5194/egusphere-alpshop2022-52, 2022.

The Krvavica Mountain and Čemšeniška Planina are situated on the northern limb of the Trojane Anticline as part of the Sava Folds region in middle Slovenia. This Cenozoic fold belt is situated in the transition zone of the Alps and Dinarides. This area was part of the Adriatic rifted margin of the Neotethys during the Middle-Late Triassic. Repeated rifting phases created the Slovenian Basin, which subsided until the Late Cretaceous. The extensional phase was followed by contraction in the Paleogene and Neogene during the Dinaric and Alpine phases (Placer 1998a; Schmid et al., 2020). The interplay of two-phase thrusting led to specific young-on-older tectonic contact between the Dinaridic Carboniferous-Permian clastics (“softbed” of Placer 1998b) and Mesozoic formations of uncertain origin (Placer 1998b).

The study area SW from Celje, near the Krvavica Mt. has good outcrops. According to previous studies (Buser, 1978, Premru, 1983, Dozet & Buser 2009) the Krvavica Mt. is composed of the platform Schlern Formation while the Čemšeniška Planina is partly composed of Bača dolomite, a characteristic Slovenian Basin formation. Our new observations show that through the Krvavica Mt. three formations can be traced from S to N: latest Ladinian to Carnian siliciclastic basin sediments (shale, sandstone, siltstone, micritic cherty limestone, breccia, and pyroclastics), all composing the Pseudozylian Formation, Triassic platform carbonates (Schlern Fm.) and latest Jurassic to Early Cretaceous carbonates and mixed carbonate-siliciclastic rocks. The formations are repeated at least two times by a major thrust. On the other hand, a platform progradation into the clastics basin can also be suggested; this feature is typical in central Slovenia (Gale el al., 2020).

However, 500 m west of the Krvavica in the eastern side of Čemšeniška Planina and on the Flinskovo ridge, recent mapping showed a typical but condensed Slovenian Basin-type sequence. The succession starts with the pelagic Bača dolomite, followed by the Hettangian–Pliensbachian calciturbiditic Krikov Formation. This was followed, after a potential gap in the Toarcian by the recently described Bajocian-Bathonian Ponikve Breccia as part of the Tolmin Formation (Rožič et al., 2018, and 2022 submitted). After a possible gap in the early late Jurassic, the Late Jurassic-Early Cretaceous Biancone Formation represents the youngest exposed member.

The proximity of fundamentally different lithological sequences can shed light on the platform to basin transition and describe the border of Slovenian Basin with the Dinarides. However, the structural geometry is complex, and could also involve normal faulting to achieve young-on-older contacts. Alternatively, post-folding, gently dipping thrusts could dismember the pre-existing northern limb of the Trojane Anticline. The displacement of the tilted (folded) Mesozoic Slovenian basin succession can also be a post-folding thrust which led to the contact of the pelagic formations to the underlying folded Carboniferous-Permian rocks of the Dinarides.

The research was supported by the National Research, Development and Innovation Office of Hungary (134873).

How to cite: Scherman, B., Rožič, B., Görög, Á., Kövér, S., and Fodor, L.: Platform to basin transitions: mapping observations at the Krvavica Mountain, and Čemšeniška Planina, in the Sava Folds region., 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-58, https://doi.org/10.5194/egusphere-alpshop2022-58, 2022.

This contribution reports LA-ICP-MS zircon ages and Rb-Sr biotite ages from the Troiseck-Floning Nappe, forming the northeasternmost extension of the Silvretta-Seckau Nappe System in the Eastern Alps. The Troiseck-Floning Nappe comprises a basement formed by the Troiseck Complex and a Permo-Triassic cover sequence. The basement consists of paragneiss with intercalations of micaschist, amphibolite and different types of orthogneiss, which was affected by a Variscan (Late Devonian) amphibolite facies metamorphic overprint. The cover sequence includes Permian clastic metasediments and metavolcanics, as well as Triassic quartzite, rauhwacke, calcitic marble and dolomite. During the Eoalpine (Cretaceous) tectonothermal event the nappe experienced deformation at lower greenschist facies conditions.

Detrital zircon grains from paragneiss are in the range of 530-590 Ma, indicating an Ediacarian to earliest Cambrian source and a Cambrian to Ordovizian deposition age of the protolith. Late Cambrian to Ordovician crystallization ages from leucogranitic intrusions represent the earliest magmatic event of the Troiseck Complex. The amphibolite bodies derived from basalt with a calc-alkaline to island arc tholeiitic signature.

Leucocratic orthogneiss with K-feldspar porphyroclasts and a calc-alkaline granitic composition plots in the field of volcanic arc granite. The youngest zircon grains indicate a Late Devonian crystallization. Two pegmatite gneisses with a calc-alkaline composition are early Mississippian in age.

Mylonitic orthogneiss with a pronounced stretching lineation appears as irregularly shaped layers. It is leucocratic, very fine grained and contains scattered feldspar porphyroclasts with a round shape and a diameter of about 1 mm. Its chemical composition is granitic/rhyolitic with an alkali-calcic signature. In classification diagrams it plots in the field of syn-collision granite. Zircon ages of about 270 Ma indicate a Permian crystallization. Similar rocks interpreted as Permian rhyolitic metavolcanics appear in the cover sequence. They share a similar chemical composition and crystallization age of 270 Ma. Associated intermediate metavolcanics developed from calc-alkaline basaltic andesite.

According to Rb-Sr biotite ages cooling of the Troiseck-Floning Nappe below c. 300°C occurred at about 85 Ma in the west and 75 Ma in the east.

In summary, the Troiseck Complex developed from Cambrian to Ordovizian clastic metasediments and granitic and basaltic magmatic rocks emplaced in the same time range. During the Late Devonian, it was affected by the Variscan collisional event, causing deformation at amphibolite facies conditions and intrusion of calc-alkaline granites. In early Mississippian time pegmatite dikes intruded, maybe induced by decompression and exhumation. The deposition of clastic sediments and (sub)volcanic rocks (rhyolite and basaltic andesite) constrains a surface position of the Troiseck Complex during the Permian. Based on regional considerations an extensional environment is assumed. In Triassic times carbonate platform sediments were deposited. During the Eo-Alpine collision in the Cretaceous the unit was part of the tectonic lower plate and subducted to shallow crustal levels, indicated by a lower greenschist facies metamorphic overprint. The Troiseck-Floning Nappe was formed and exhumed since about 85 Ma. Rb-Sr as well as apatite fission track data from the literature indicate tilting with more pronounced exhumation and erosion in the eastern part during Miocene lateral extrusion of the Eastern Alps.

How to cite: Schuster, R., Iglseder, C., Reiser, M., and Gallhofer, D.: Geological history of the Troiseck-Floning Nappe (Austroalpine unit, Styria/Austria), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-12, https://doi.org/10.5194/egusphere-alpshop2022-12, 2022.

The Ozren ophiolite complex (OOC) is the second largest ophiolite complex in Bosnia and Herzegovina, and it is a part of the huge Dinaride ophiolite belt [1 and reference therein]. This contribution comprises mineralogical-petrographical descriptions of representative rocks of the OOC which were determined from polished sections by polarized light microscopy and introductory EPMA. The investigated harzburgites are composed of Ol (55%), Opx porphyroclasts with Cpx exsolution lamellae (35%), Cpx with Opx exsolution lamellae (5%) the latter following Ol-Opx boundaries or ingrowing Opx and Ol matrix. Spinel occurs in the form of anhedral grains. Lherzolites contain Ol (55%), Opx (25%) and Cpx (15%). Anhedral Opx porphyroclasts have Cpx exsolution lamellae. Similarly, porphyroclastic Cpx contains Opx exsolution lamellae. Late magmatic Cpx and Opx aggregates are ingrowing the Ol matrix and these are also surrounding deformed Opx porphyroclasts. Spinel is immersed in the Ol matrix. Dunites are rare. A remnant of the gabbroic layer is inferred only from a borehole core. This gabbro has ophitic texture and contains primary magmatic porphyric Pl, Cpx and green Amp1. Pyroxene and Amp1 are partially replaced by Amp2 and Chl. Plagioclase is weakly altered. Moreover, we found cross-cutting dykes of gabbros (micro-gabbros, called dolerites, to gabbro-pegmatites, and dunite-associated troctolite) in peridotite. These dykes have randomly oriented minerals, only locally showing mylonitization signatures. Most dykes have a discordant relationship to the peridotite structures. Dolerites and basalts also occur in the form of relatively thicker lens-like bodies in serpentinites. A basaltic dyke cross-cuts layered gabbro (in borehole). Most dolerites are composed of Cpx, Amp and Pl but we also found an exceptional Ol-dolerite dyke cross-cutting peridotite. It has well preserved magmatic ophitic texture composed of Ol, Opx, Cpx, Amp, Pl, Ilm and Ap. Pyroxenes and amphiboles are weakly chloritized and Ol is serpentinized. Dolerites and basalts have an ophitic texture, defined by fine-grained prismatic Pl, Px and Amp. Secondary Amp2 and Chl follow the grain boundaries of magmatic minerals. Ophiolitic breccias cover some peridotite parts. These breccias contain 1cm – 10m fragments of all lithological sequences of the OOC including reddish radiolarite sediments. Gabbros from ophiolitic breccia have coarse grained Pl and Px. Exsolution lamellae in Px and kink-banding are characteristic features from subsolidus magmatic conditions. A rare plagiogranite intrusion in peridotite is composed of Qz, Pl and needle-like Amp aggregates after Bt. Such an association of ultrabasic and basic rocks may indicate percolating gabbroic magmas through the peridotites. Amphibolites were found only at one locality so far and these are composed of oriented Amp and Pl aggregates in the metamorphic texture, most likely indicating metamorphic sole of an ophiolitic thrust sheet. These preliminary results shed light on the lithology and petrography of the OOC and have arisen problems for further research.

References:

[1] Babajić E. (2019) Krivaja-Konjuh ophiolite complex – petrology, geochemistry and geotectonics of mafic sequences. (Monograph), MIT-ALEX, Tuzla (Bosnia and Herzegovina)

Acknowledgement: APVV Agency Project No. APVV-19-0065 (M.P.) is acknowledged.

How to cite: Ustalić, S., Putiš, M., Nemec, O., Ružička, P., Babajić, E., and Katanić, P.: Petrography of ultrabasic and basic rocks from the Ozren ophiolite complex in Bosnia and Herzegovina, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-5, https://doi.org/10.5194/egusphere-alpshop2022-5, 2022.

Occurrences of the Albian/Cenomanian Boundary Event (OAE1d, namely Breistroffer Level), reflected in a series of four distinct positive d¹³C excursions (peak in the latest Albian) are until now not described in Serbia even various associations of late Early Cretaceous ammonite faunas are known from several locations in central Serbia. These ammonite-bearing sedimentary rocks are exposed in the narrow belt of the Belgrade-Kosmaj-Topola-Gledić Mts. above shallow-water orbitolinid foraminifera-bearing limestones (carbonate ramp deposits).

Near village Kotraža (22 km SE of Topola) a roughly 20 m thick sedimentary succession of sand- and siltstones, marls and claystones with intercalated volcanic rocks and two distinct ammonite bearing horizons is preserved (ʺStragari faciesʺ in the Serbian literature). In the lower – roughly 11 m thick - more coarse-grained part of the succession occur beside belemnites, gastropods, and plant remains, a rich, but poor to moderately preserved ammonite fauna in slump deposits together with coarse eruptive volcanic material: Kossmatella agassiziana, Puzosia (Puzosia) mayoriana, Mortoniceras (Subschloenbachia) perinflatum, Anisoceras perarmatum, Anisoceras sp., Idiohamites elegantulus, Mariella sp.,  Ostlingoceras cf. puzosianum, and Scaphites (Scaphites) sp. The occurrence of Praeschloenbachia perinflatum indicates the Upper Albian Mortoniceras perinflatum Zone. Upsection a fining-upward trend indicates ongoing deeping of the depositional realm due to the stepwise sea-level rise from the late Albian onwards and the decease of the orbitolinid-bearing carbonate ramp. In the more fine-grained and slightly organic-rich silt to fine-sand layers approx. eight meters above the first ammonite-bearing level following ammonite fauna indicate the uppermost Albian to lowermost Cenomanian (Arrhaphoceras briacensis Zone or Stoliczkaia dispar Zone): Phylloceras (Hypophylloceras) velledae, Kossmatella agassiziana, Puzosia (Puzosia) mayoriana, Beudanticeras sp., Mortoniceras sp., Stoliczkaia (Stoliczkaia) dispar, Mariella sp., and Scaphites (Scaphites) sp.

Whereas in the Western Tethys Realm the latest Albian OEA1d is mainly characterized by the deposition of organic-rich fine-grained sediments, in central Serbia west of the Drina-Ivanjica continental realm more coarse-grained sediments were deposited. However, the occurrence of the younger ammonite-rich interval in slightly organic-rich sedimentary rocks mirror the global late Albian OAE1d, whereas the older ammonite-rich intervall is a precursor event associated with intense volcanic activity near to the study area. This intense volcanic activity led to the regional drowning of the shallow-water orbitolinid foraminifera-bearing carbonate ramp and creates relief as indicated by the slump deposits. It is proposed that in central Serbia regional and global events work in concert to form in the late Albian deeper-water environment ammonite-rich horizons, which have the potential for a correlation of late Albian events in the Dinarides and adjacent areas.

In the frame of the IGCP 710 „Western Tethys meets Eastern Tethys“.

How to cite: Vuletić, M., Gawlick, H.-J., Đerić, N., Bujtor, L., Bogićević, K., and Nenadić, D.: The Albian/Cenomanian Boundary Event (OAE1d) reflected in ammonite-rich layers in central Serbia (Topola area), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-57, https://doi.org/10.5194/egusphere-alpshop2022-57, 2022.

The Koralpe-Saualpe-Pohorje Complex in the Eastern Alps represents a lithologically heterogenous (U)HP nappe with eclogite lenses embedded in gneissic and metasedimentary rocks. The aim of this project is to determine whether or not tectonic pressure occurred due to differences in viscosity of different lithologies. In this study we investigate in detail the P and T conditions during the formation of the Koralpe–Saualpe-Pohorje Complex along a NW-SE transect. In order to determine the P conditions, quartz inclusions in garnet are investigated with Raman spectroscopy (RSQI barometry). With Zr-in-rutile thermometry, the temperature conditions will be determined.
Preliminary results show an overall residual P increase of the quartz inclusions from the northern Saualpe towards Pohorje in the South. The quartz inclusions inside garnet in eclogite show higher residual P with ≤0.72 GPa with respect to the ones in the metasedimentary or gneissic lithologies with ≤0.43 GPa. Elemental maps of garnets in eclogite from three locations show rather variable results with a significant variation of Ca and Mg content in the core, whereas the Mn content is general very low. The metasedimentary and gneissic garnets are predominantly much richer in Fe and show higher Mn with respect to the eclogites.

How to cite: Wannhoff, I., Pleuger, J., John, T., Zhong, X., and Liesegang, M.: Peak pressure estimates of Koralpe-Saualpe-Pohorje Complex based on Raman Spectroscopy, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-42, https://doi.org/10.5194/egusphere-alpshop2022-42, 2022.