T3

The Rute Plateau is a region located 25 km south of Ljubljana. Structurally, it belongs to the External Dinarides, which form an extensive fold and thrust belt. The study area is located in the eastern part of the Hrušica Nappe in a very complex tectonic area between two major NW-SE fault zones.
The peculiarity of the Rute Plateau consists in a varied succession of sedimentary and volcanoclastic rocks of Ladinian and Carnian age, while the whole area is divided into different tectonic blocks with local differences in stratigraphic evolution. The reason for these deformations and the variability of the paleotopography lies in the Middle Triassic extensional phase, which completely disintegrated the uniform Slovenian carbonate platform at the end of the Anisian age (for details see Rožič et al., this volume). Subsequently, the Ladinian strata of the External Dinarids reveals, that deep marine sediments in this area were deposited in small basins or tectonic depressions, while carbonate deposition continued on higher or relatively less subsided tectonic blocks (isolated platforms). During the Ladinian, tectonic movements were also accompanied by volcanic activity. 
Six sedimentological sections were logged in the studied area, and the Ladinian strata were divided into four different facies: F1 - deep marine (volcano)clastic rocks, F2 - hemipelagic limestone, F3 - resedimented limestones and F4 - shallow marine carbonates. Each of these Ladinian facies is characteristic of a particular sedimentary environment and is indicated from the most distal sedimentary environment (F1) to the most proximal carbonate platform environment (F4). Facies F1 consists of greenish to light ochre bentonitic clays, tuffitic sandstone, pelitic tuffs, and subordinate felsic extrusive rocks. Facies F2 consists of laminated black micritic limestone (mudstone to wackestone) with horizons of bioclastic packstone rich in filaments, limestone rich in organic residue and interbedded with dark chert laminas and marlstone. In facies F3 we find up to 30 cm thick beds of calcarenites, limestone breccias often with large olistoliths, graded and laminated calciturbidites - mostly packstone, grainstone and rudstone beds with rare chert laminas and nodules. Finally, facies F4 consists largely of massive, light grey calcimicrobial and dasycladacean limestone with horizons or lenses of white bioclasts and intraclasts derived from reefs. The last two facies are commonly dolomitized.
At the end of the early Carnian, the entire region was subjected to the regional emersion phase when deposition of clastic sediments began. It is characterized by facies F5 - red clastic sediments consisting mainly of sandstone with quartz grains and carbonate lithoclasts and conglomerate. Within all these facies, we were able to determine 28 different microfacies, which, based on their composition, further elucidate sedimentation in different paleoenvironments.

How to cite: Kocjančič, A., Rožič, B., Gale, L., Vodnik, P., Kolar-Jurkovšek, T., and Celarc, B.: Facies analysis of Ladinian and Carnian beds in the area of Rute Plateau (External Dinarides, Central Slovenia), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-37, https://doi.org/10.5194/egusphere-alpshop2022-37, 2022.

The largest Mesozoic paleogeographic perturbation of the present-day Alpine-Dinaric transition zone occurred in the Ladinian. The entire area was subjected to intense tectonic extension related to the rifting of the Neotethys Ocean. The most intense subsidence occurred in the central part of this segment of the continental margin, and the area remained deep-marine (called the Slovenian Basin) until the end of the Mesozoic. To the south, extension also resulted in differentiation, but the predominant paleoenvironments were either continental (often emerged areas) or shallow-marine. Locally, however, small-scale, short-lasting, deep-marine environment also developed. Herein we present the study of the Kobilji curek Basin in the Rute Plateau (central Slovenia, 25 km south of Ljubljana), where the the Ladinian platform to basin transition has recently been studied in detail. The study includes sedimentological analysis, biostratigraphy, mineralogical analysis, and detailed mapping. In the studied area, following Ladinian facies were outlined: F1 - deep marine (volcano)clastic rocks (bentonitic clays, tuffitic sandstone, tuffs), F2 - hemipelagic limestone (micritic and filament limestone), F3 - resedimented limestone (breccia and calcarenite), and F4 - shallow marine carbonates (bioclastic limestone and dolomite) (for details see Kocjančič et al, this volume). The base is Anisian dolomite and the top Carnian clastites. In contract, the highly variable Ladinian facies merge both laterally and vertically. Detailed geological mapping revealed that the area can be divided into four tectonic blocks with characteristic sequences, separated by roughly N-S and E-W trending paleofaults. In the NW tectonic block (B1), the most basinal succession is outcropping with two intervals of platform carbonates, while the sequence in the SE block (B4) is entirely characterized by platform carbonates. In the transition blocks (B2 and B3), platform carbonates predominate with minor basinal intervals. The entire Ladinian succession shows five major subsidence pulses followed by partial or twice also complete platform progradation. The first subsidence is documented exclusively in B2 and B3 (F1 and F2), followed by platform progradation (F4). During the second subsidence, the major paleofault between B1 and B2 is activated. This pulse is evident in B1 as a fairly thick basinal succession (F1) containing carbonate resediments (F3) in the upper part, indicating distant platform progradation. This pulse is also seen in B2 as thin deep marine limestone (F2 and F3), again followed by platform carbonates (F4). The third pulse is seen in B1 as coarse resediments (F3) followed by general platform progradation (F4), and in B2 as thin deep marine carbonates (F2 and F3) followed by platform carbonates (F4). This platform progradation seals the paleofault between B1 and B2. The fourth pulse is uniform in blocks B1 and B2 and consists of a continuous basinal interval (F1 and F2) followed by a final rapid platform progradation (F4). The fifth subsidence is uniform in B1, B2, and B3 and begins with hemipelagic limestone (F2) followed by (volcano)clastic rocks (F1) with some felsic extrusive rocks. In B4, this pulse either did not occur or the rocks were eroded during regional emersion in the early Carnian.

How to cite: Rožič, B., Kocjančič, A., Gale, L., Popit, T., Žvab Rožič, P., Vodnik, P., Zupančič, N., and Kolar-Jurkovšek, T.: Architecture and sedimentary evolution of the Ladinian Kobilji curek Basin of the External Dinarids (Rute Plateau, central Slovenia), 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-27, https://doi.org/10.5194/egusphere-alpshop2022-27, 2022.

Ivanščica Mt. is an inselberg in the transitional area where S-verging Southern Alpine structures overprint NNW-verging Dinaric structures (van Gelder et al. 2015, and references therein). It is composed of Triassic to Cretaceous shallow to deep-marine sedimentary succession of the Adriatic continental passive margin (Šimunić et al. 1976), overthrust by ophiolitic mélange (Babić et al. 2002). Early Cretaceous siliciclastic flysch-type deposits continuously overlaying pelagic limestones clearly indicates distal position of these successions on the continental margin. However, so far complete Jurassic succession on Mt. Ivanščica was never found, causing different interpretations of its Mesozoic history. Babić (1974) assumed the existence of Jurassic pelagic succession on top of the Late Triassic shallow-water carbonates, describing up to few meters of Early to Middle Jurassic condensed pelagic limestone overlain by Late Jurassic radiolarian cherts and pelagic limestones. Contrary, Šimunić et al. (1976) assumed shallow-marine conditions throughout the Early Jurassic followed by emersion until latest Jurassic. Our study revealed for the first time complete shallow-water to pelagic Jurassic succession on Mt. Ivanščica.

Southern slopes of Ivanščica Mt. are mostly built of ophiolitic mélange, except for prominent hills built of the Late Triassic Dachstein limestone, which were so far interpreted as klippes (Šimunić et al. 1976), or olistoliths (Babić & Zupanič 1978). Our new data indicate continuous succession on top of Dachstein limestones composed of shallow-marine carbonates, represented by intraclastic-peloidal packstones to grainstones, gradually transitioning to wackestones with pelagic influence. The onset of pelagic sedimentation took place around the end of the Early Jurassic when thin bedded marls, shales, marly limestones with intercalated fine-grained calciturbidites were deposited. Higher in the succession Callovian to possibly early Tithonian radiolarian cherts are overlaid by calcarenites, late Tithonian to Early Cretaceous pelagic limestones and Early Cretaceous flysch-type deposits.

Discovery of the Jurassic pelagic sediments allows for a new interpretation of structural relations on the Ivanščica Mt. In our opinion occurrence of Dachstein limestone, previously interpreted as klippes or olistoliths represent an imbricate fan. Because the Southern Alps thrust front in this area was interpreted according to these mapped klippes and nappe contact, our findings may also have an impact on the redefining of the easternmost Southern Alps thrust front.

Babić, Lj. (1974). Jurassic−Cretaceous sequence of Mt. Ivanščica (North Croatia). Bull. Sci. Cons. Acad. Yugoslav. (A), 19/7−8, 180−181. Zagreb.

Babić, Lj. & Zupanič, J. (1978). Mlađi mezozoik Ivanščice. In Babić, Lj. & Jelaska, V. (ured.): Fieldtrip Guidebook 3. Skupa sedimentologa Jugoslavije, 11–23. Hrvatsko Geološko Društvo, Zagreb.

Babić, Lj., Hochuli P. A.. & Zupanič, J. (2002). The Jurassic ophiolitic mélange in the NE Dinarides: dating, internal structure and geotectonic implications. Eclogae Geologicae Helvetiae 95, 263–75.

Šimunić, A., Pikija, M., Šimunič, Al., Šikić, K. & Milanović, M. (1976): Stratigrafsko - tektonski odnosi centralnog i istočnog dijela Ivanščice. 8. Jugosl.geol.kongres, Bled, 1974., 2, 3003-313, Ljubljana.

van Gelder, I., Matenco, L., Willingshofer, E., Tomljenović, B., & Andriessen, P.,  Ducea, M., Beniest, A. & Gruić, A. (2015). The tectonic evolution of a critical segment of the Dinarides-Alps connection: Kinematic and geochronological inferences from the Medvednica Mountains, NE Croatia. Tectonics. 34. n/a-n/a. 10.1002/2015TC003937.

How to cite: Vukovski, M., Kukoč, D., Grgasovic, T., Fuček, L., and Slovenec, D.: Jurassic pelagic succession of NW Croatia – a key to better understanding tectonic setting of the Southern Alps – Dinarides transition zone, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-23, https://doi.org/10.5194/egusphere-alpshop2022-23, 2022.

The pelagic succession from the Slovenian Basin (Petrovo Brdo section) covers the lower Tithonian to upper Berriasian interval (ca. 40 m). At 5 m of the section a sharp transition is observed between clay rich radiolarian cherts of Tolmin Fm and calpionellid limestones of Maiolica Fm.  Calpionellid associations are not numerous and poorly preserved, therefore only rough biostratigraphic dating is possible.  Crassicollaria (upper Tithonian) was documented between 8 and 13 m of the section, while the  beginning of the Calpionella alpina Subzone (present day J/K boundary) is situated at ca. 20 m.  Transition between Tolmin and Maiolica Fm  falls in the UAZ 12 radiolarian Zone (Gorican et al. 2012) which is close to the lower/upper  Tithonian boundary. Despite poor dating, the section supplied high-resolution magnetic susceptibility, as well as chemostratigraphic data (δ¹³C, main and trace elements), acquired with portable XRF device, gamma ray spectrometer and verified with ICP-MS laboratory measurements. Lithogenic elements (Al, K, Rb, Ti, Zr etc.) and MS show prominent decrease between Tolmin and Maiolica Fm, reaching minimum values in the upper Tithonian and lower Berriasian. Lithogenic input increases again  from ca 30 m of the section. As in numerous Tethyan sections (e.g. Western Carpathians, Northern Calcareous Alps, Western Balkan) the increase of marly sedimentation starts in the lower part of the Calpionellopsis Zone (magnetozone M16n), this level is tentatively interpreted as being close to the lower/upper Berriasian boundary. Relative variations of K and Ti content  (K/Ti, Ti/Al ratios) indicate enrichment of K  and depletion in Ti in the upper Tithonian/lower Berriasian interval  which accounts for decreased chemical weathering in the provenance areas. Additionally, the interval is enriched in redox sensitive trace metals (Cu, Zn, Cd) and decreased δ¹³C values, which accounts for bottom water stratification. The overall palaeoenvironmental trends might be interpreted in favor of aridification trend throughout the upper Tithonian and lower Berriasian and more humid episodes in the lower Tithonian and upper Berriasian. The trends seems to correlate throughout the Western Tethys domain and might be related with large-scale palaeoenvironmental perturbations.

How to cite: Grabowski, J., Iwańczuk, J., Rehakova, D., Rozic, B., Zvab-Rozic, P., Slapnik, L., and Gercar, D.: Climate changes on the Jurassic/Cretaceous bonduary on the geochemical indicators - new data from the Slovenian Basin, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-60, https://doi.org/10.5194/egusphere-alpshop2022-60, 2022.

The Western Alpine Foreland Basin ("French Molasse Basin") is located along the western Alps and is composed of Oligo-Miocene formations resulting from the erosion of the alpine range. Although the Miocene molasse basin have been widely described since the last decades, Oligocene basins lack documentation in terms of palaeoenvironmental evolution and source to sink approach. Most of these basins formed under both the Alpine influence and the European Cenozoic Rift System influence and developed in lacustrine environment with local sedimentation next to active normal faults. Several fluvial formations with exotic materials have been briefly described and could correspond to a transport from the internal parts of the Alps, where collision started at the Eocene/Oligocene boundary. Here, we propose a new tectono-sedimentary study of these fluvial deposits based on extensive fieldwork (facies analysis, sequence stratigraphy, palynological analysis) and reinterpretation of available subsurface data (seismic profile, well data). The goal is to provide a new palaeoenvironmental reconstitution of the Oligocene molasse basin(s) with regional correlations and to determine the evolution of early alpine drainage network. We focus on the entire Western Alpine Foreland Basin from the Rhone Valley (Bas-Dauphiné, Valréas, Mormoiron) to the Digne Thrust where Oligocene molasse is called « Red Molasse » (Dévoluy, Faucon-du-Caire, St-Geniez, Esclangon, Barrême). First results show that Red Molasse is composed of massive meandering deposits, which evolve to braided river and alluvial fan in a regressive continental sequence following the flysch formation. Transition from marine distal turbidites is often missing except in Dévoluy syncline where tidal and shoreface deposits precede fluvial molasse. Exotic material from the internal alps is very common and indicates high landforms nearby. In the Rhone Valley, a massive fluvial system has been identified on seismic and well log data in the Bas-Dauphiné and we documented a 900 m field section with two meandering formations with exotic minerals in the Mormoiron basin. Paleocurrents and channels direction indicate a major divide located east of Diois-Baronnies range with Dévoluy fluvial systems flowing to the north and other Red Molasse sites located south of the divide converging to St-Geniez system. On a regional scale, it may be possible that early salt tectonic which has been widely described caused this particular drainage network. South of the divide, converging fluvial formations may have flowed in an Est-West valley between Diois-Baronnies range and Ventoux-Lure Montain where tectonic and Eocene landforms link to the Pyreneo-Provençal orogen have been documented. These deposits where probably connected with Mormoiron and Bas-Dauphiné fluvial formations and formed a major drainage system located in the Rhone Valley.

How to cite: Huet, B., Bellahsen, N., Loget, N., Lasseur, E., and Briais, J.: Palaeoenvironmental and drainage network reconstitution of the Oligocene Western Alpine Foreland Basin, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-48, https://doi.org/10.5194/egusphere-alpshop2022-48, 2022.

Lake Turiec existed from Late Middle Miocene to Pliocene in the heart of the Western Carpathians in the intermontane Turiec Basin. Despite the long-lasting lacustrine deposition, which formed a muddy succession up to 900 m thick, specific history of this basin in Western Carpathians has been a puzzle due to the missing geochronological proxies. Authigenic ¹⁰Be/⁹Be dating method was applied to determine the existence duration and regression of the long-lived Lake Turiec. Altogether 35 samples were collected from 11 different localities of the basin representing different sedimentary environments such as lacustrine, fan delta, alluvial fan and braided river. Four different localities, Late Pleistocene alluvial fans Veľký Čepčín and Malý Čepčín, Holocene river floodplains Košťany and Kalamová were considered for determining the initial ratio. The initial ratio from the Veľký Čepčín alluvial fan was used for all other localities representing lacustrine, fan delta, alluvial fan and braided river to determine ages, because it is the only N₀ in agreement with the independent age proxies indicating that the lacustrine deposits cannot be older than 11.6 Ma. Another explanation of the suitability of the Veľký Čepčín initial ratio is its rapid deposition settings, preventing it from alteration by post-depositional processes and interaction with ground water, in contrary to the remaining intial ratio sites. Weighted mean depositional ages calculated using N₀ from Veľký Čepčín imply that the Lake Turiec existed from ~9.96 Ma for more than ~3.25 Myr and regression of the lake begun nearly ~6.71 Ma.

Determining the precise timing of the lake existence will have important implications for geodynamic phases of the Western Carpathians, since it mirrors rapid increase of accommodation followed by intense increase of sediment supply during regression. The presented application of authigenic ¹⁰Be/⁹Be yielded a first radiometric age of long-lived Lake Turiec as compared to roughly estimated age described in previous studies of the Turiec Basin. This novel method also appeared as a promising dating tool to determine the beginning of regression of the lake in an intermontane settings with complicated tectonic and sedimentary history.

The study was supported by the Slovak Research and Development Agency under contract APVV-20-0120.

How to cite: Aherwar, K., Šujan, M., Vojtko, R., Braucher, R., Chyba, A., Hók, J., Rózsová, B., and Team, A.: Dating a long-lived lake in an intermontane basin: Late Miocene Lake Turiec in the Western Carpathians, 15th Emile Argand Conference on Alpine Geological Studies, Ljubljana, Slovenia, 12–14 Sep 2022, alpshop2022-46, https://doi.org/10.5194/egusphere-alpshop2022-46, 2022.