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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.

The Bled Basin was a Middle Triassic–Early Cretaceous basin whose remnants are preserved in the eastern Southern Alps in western Slovenia. The early evolution of the basin is recorded in the Upper Ladinian to Lower Jurassic Zatrnik cherty limestone formation, which in the Pokljuka Nappe overlies Middle Triassic volcanics, volcaniclastics and hemipelagic limestones. The Zatrnik Limestone is poorly documented and biostratigraphically not well constrained. The base of the Zatrnik Limestone was logged in four sections in the eastern part of the Pokljuka plateau. An Upper Ladinian Muelleritortis cochleata Radiolarian Zone was recognised in the lowermost part, whereas conodont data indicate Julian to latest Tuvalian/early Norian age for the rest of the logged sections. Microfacies analysis indicates hemipelagic deposition on a basin plain and/or distal slope, which is often interrupted by distal calciturbidites.

Horseshoe crabs are an archetypal chelicerate group with a fossil record extending back to Early Ordovician time. Although extensively studied, the group generally has a low diversity across the Phanerozoic Eonothem. Here, we expand the known diversity of true horseshoe crabs (Xiphosurida) by the description of a new taxon from the Middle Triassic Strelovec Formation of the Slovenian Alps. The mostly complete fossil is preserved as an external mould and assigned to the family Limulidae Zittel, 1881 asSloveniolimulus rudkini, n. gen., n. sp. The use of landmark and semilandmark geometric morphometrics is explored to corroborate the systematic palaeontology and suggests that the new genus and species are valid. We also provide the first quantitative evidence for the extensive diversity of Triassic horseshoe crabs. We suggest that Triassic horseshoe crabs likely filled many ecological niches left vacant after the end-Permian extinction.

The earthquake with magnitude ML=6.2 that occurred on 29th December 2020 has caused significant material damage to objects and infrastructure in the towns of Petrinja, Sisak,Glina and the surrounding area. According to the satellite interferometry data, the coseismic and postseismic deformation area covers around 500 square kilometers. The existing geodetic benchmarks have been set in the affected towns, and their coordinates have been determined based on previous GPS campaigns. The GPS network was set up and adjusted at the State Geodetic Administration's request for geodetic monitoring of infrastructure and cadastral projects. These points are not primarily intended for high accuracy measurements at the level of a few millimeters, so their accuracy and the absolute shift concerning geodynamic processes in the region should be taken into account. Nevertheless, the data obtained by their observation after the earthquake can provide valuable information about the horizontal and vertical displacements with a certain level of confidence. The field survey has detected disappearance of a large number of benchmarks and some valuable information has been lost. Still, 58 points were found and observed and it has been concluded that 52 points are reliable and can be used for future research. Because the network of benchmarks is not developed in rural areas, there is a gap in the distribution of benchmarks in affected area. Therefore, the additional data was collected using the benchmarks established for the engineering and cadastral projects and studies. From a total of 67 points that have been found and observed, 42 points will be used. Along with the data collected in urban areas, there will be a total of 94 benchmarks. The accuracy of the geodetic benchmark measurements is at the centimeter level, while the values of deformation are at the level of a few decimeters. Therefore, the obtained data can be used to better assess the displacement recorded during the 29 December 2020 event. In the future, field research will focus on finding additional benchmarks to reach a better spatial distribution.

After the earthquake of 29/12/2020 in Petrinja (ML6.2, ImaxVIII-IX EMS), an attempt was made to characterize the active structure associated with the earthquake. As a first step towards this goal, we performed a geomorphological analysis in order to contribute to the identification and characterization of the surface expression of the active Pokupsko dextral strike-slip fault. We focused on the area between the southernmost parts of Vukomeričke Gorice and the southernmost parts of Hrastovica Mountain, where the NW-SE striking Pokupsko fault has slipped during and after the recent earthquake (Ganas et al., 2021). Using available 1 : 5 000 scale topographic maps and various 10 m resolution digital elevation model visualizations, we mapped lineaments that could represent relatively recently active fault segments. We used a quantitative approach to perform stream sinuosity analysis (e.g., Leopold et al., 1964; Zamolyi et al., 2010) on major streams crossing the structure to identify distinct changes in channel patterns that may be associated with vertical movement along the predominantly strike-slip fault. We observed changes in the shape of the valleys, especially the changes in width, height, and direction. By summarizing various geomorphological indicators of active fault segmentation at the surface with available geological data (Pikija, 1987) and so far limited field observations, we provide insights into the structure of the Pokupsko fault.Preliminary results show good agreement between lineament mapping, changes in valley shape, changes in the stream sinuosity index, and (to some extent) previously mapped faults. In addition, some of the changes in stream sinuosity correspond to locations where coseismic surface ruptures occurred during the December 29 earthquake (Budić et al., this session; Pollak et al., 2021). Results suggest that the several-kilometer-wide zone of uplifted Neogene deposits results from the dextral-transpressive structure, which at the surface consists of a series of subparallel fault strands branching off the main fault that runs along the SE slopes of the Hrastovica Mountain. The SW-most fault strands are associated with significant changes in the shape of the valleys: the wide valleys of Petrinjčica, Utinja and Šanja change to narrow and deeply incised as they cross the uplifted structure. Paleocene and Eocene rocks, which otherwise underlie the Neogene, outcrop in the NE parts of the fluvial breakthrough valleys, indicating the uplift of the Hrastovica Mountain. Topographic data show a decrease of the mountain range elevation towards the SW. This evidence suggests that the main fault runs on the NE side of the mountain, strikes NW-SE and dips steeply towards the SW. The fault strike deviates between Župić and Farkašić. The fault plane solution for the December 29 earthquake suggests a nearly pure strike-slip fault, while geomorphic evidence strongly indicates areas of active uplift along the fault, further supported by the general antiformal structure. We interpret this as an indication of either a general current transpressional character of the fault or as local kinematic variations due to segmentation and changes in the strike of the fault; further analyses are pending.

After conducting a successful GPR pilot study in a tectonically complex area of the Karst Thrust Edge, a follow-up study was carried out. In the pilot study, the geometry and spatial extent of the Socerb thrust-fault, which separates limestone above from flysch below, were investigated using a 50 MHz antenna in the Črnotiče quarry. After one part of the quarry was deepened and widened, new flysch outcrops were exposed and GPR profiling was made possible in areas where the thrust contact could not be reached before. By comparing the first GPR results with the locations of new flysch outcrops, we found it reached the surface almost exactly where we had predicted. In order to gain new information about the location of the thrust contact, nine new profiles were recorded. In this newly deepened area, the thrust contact runs close to the surface, therefore a 250 MHz antenna was used in addition to the 50 MHz antenna in order to ensure an adequate level of resolution. This combination of antennas provided the depth penetration of 34 m as well as resolution high enough to obtain accurate information from the shallowest parts. GPR profiles were used to create a 3D model of the thrust-fault plane, providing information about the spatial position and lateral undulations of the thrust contact. The results provided new data about the geometry of the Socerb thrust-fault and correlated well with existing borehole data. The results also showed the importance of using appropriate antenna frequencies as other features capable of becoming hazardous during excavation (air-filled and sediment-filled karst caves) could otherwise be misinterpreted or overlooked. The follow-up research not only provides new data important for understanding the tectonic setting of the area, but also information needed for calculating exploitable material quantities and for planning safe excavation processes.

The Julian Alps (western Slovenia) structurally belong to the eastern Southern Alps. The Upper Triassic succession mostly consists of shallow water platform carbonates of the Dolomia Principale-Dachstein Limestone system and a deep water succession of the Slovenian Basin outcropping in the southern foothills of the Julian Alps. In addition to the Slovenian Basin, a few other intraplatform basins were present, but they remain poorly researched and virtually ignored in the existing paleogeographic reconstructions of the eastern Southern Alps. Herein, we describe a deepening-upward succession from the Tamar Valley (north-western Slovenia), belonging to the Upper Triassic Tarvisio Basin. The lower, Julian-Tuvalian part of the section comprises peritidal to shallow subtidal carbonates (Conzen Dolomite and Portella Dolomite), and an intermediate carbonate-siliciclastic unit, reflecting increased terrigenous input and storm-influenced deposition (Julian-lowermost Tuvalian shallow-water marlstone and marly limestone of the Tor Formation). Above the drowning unconformity at the top of the Portella Dolomite, Tuvalian well-bedded dolomite with claystone intercalations follows (Carnitza Formation). The latter gradually passes into the uppermost Tuvalian–lowermost Rhaetian bedded dolomite with chert and slump breccias, deposited on a slope and/or at the toe-of-slope (Bača Dolomite). Finally, basinal thin-bedded bituminous limestone and marlstone of Rhaetian age follow (Frauenkogel Formation). The upper part of the Frauenkogel Formation contains meter-scale platform-derived limestone blocks, which are signs of platform progradation. The Tarvisio Basin may have extended as far as the present Santo Stefano di Cadore area, representing a notable paleogeographic unit at the western Neotethys margin.

Wide carbonate platform environments developed on the western passive margin of the Tethys during the Late Triassic, after a major climate change (Carnian Pluvial Episode) that produced a crisis of high-relief microbial carbonate platforms. The peritidal succession of this epicontinental platform (Dolomia Principale/Hauptdolomit, Dachstein Limestone) is widespread in the Mediterranean region. However, the start-up stage is not fully understood. The original platform to basin depositional geometries of the system have been studied in the north-eastern Southern Alps, close to the Italian/Slovenian boundary where they are exceptionally preserved. Sedimentological features have been investigated in detail by measuring several stratigraphic sections cropping out along an ideal depositional profile. The analysis of the facies architecture allowed reconstruction of the paleoenvironments of the Dolomia Principale platform during its start-up and early growth stages in the late Carnian. The carbonate platform was characterized by an outer platform area, connected northward to steep slopes facing a relatively deep basin. Southward, the outer platform was connected to inner sheltered environments by a narrow, often emerged shelf crest. Behind this zone, carbonate sedimentation occurred in shallow lagoons and tidal flats, passing inward to a siliciclastic mudflat. The Dolomia Principale platform was initially aggrading and able to keep pace with a concomitant sea-level rise, and then prograding during the late Carnian. This stratigraphic interval was correlated to the Tuvalian succession of the Dolomites, allowing depiction of the depositional system on a wide scale of hundreds of kilometrew. This large-scale depositional system presents features in common with some Palaeozoic and Mesozoic carbonate buildups (fo example, the Permian Capitan Reef complex, Anisian Latemar platform), both in terms of architecture and prevailing carbonate producers. A microbial-dominated carbonate factory is testified in the outer platform and upper slope. The recovery of high relief microbial carbonate platforms marks the end of the Carnian Pluvial Episode in the Tuvalian of Tethys. This article is protected by copyright. All rights reserved.

The Karstic thrust edge, a pronounced geomorphologic step, which is a result of the tectonostratigraphic evolution of the active Adria–Dinarides thrust zone, represents a major obstacle for the planned new railway route Divaca–Koper. Thus, the geotechnical and structural properties as well as the geometry of the thrust-fault planes in this area are of great importance. Since geological mapping cannot give insight into the subsurface to reveal a complex 3D structure, and the numerous boreholes needed to investigate the area would be too expensive and time consuming, the application of a geophysical method such as ground penetrating radar (GPR) is needed. To test the method for determining near surface features and detecting low-angle inclined thrusts, a low frequency GPR system with 50 MHz rough terrain antenna was used to record 13 GPR profiles along all three floors of the Crnotice quarry, where the spatial position of the Socerb thrust fault that separates limestones above and flysch layers below is relatively well documented. The profiles were positioned across selected existing boreholes. The GPR results were correlated with borehole data as well as geological mapping results. The GPR provided not only precise information on the geometry of the Socerb thrust fault, but was also very useful for establishing the position of some known as well as several potential cavities, both air- and sediment-filled. In areas further from the thrust-fault zone, where the limestone is less tectonically damaged, it was also possible to determine apparent dip angles of the strata, which after reconstruction matched the true dips gathered from geological mapping.

The new railway route Divaca - Koper is planned to cut through the Karstic thrust edge, a prominent geomorphologic step within the active Adria - Dinarides thrust zone. This represents a major obstacle for the railway construction, therefore it is crucial to understand the structural properties and the geometry of the thrust-fault planes within the area. This knowledge is also important for the calculation of exploitable material in a limestone quarry. For determining thrusts with a low-angle inclination we evaluated the use of the low frequency ground penetrating radar (GPR). We carried out a survey in the active Crnotice quarry with a 50 MHz rough terrain antenna (RTA), correlated the GPR results with borehole data and constructed a precise 3D model of the Socerb thrust-fault plane. In addition to acquiring accurate structural information about the thrust-fault plane and dip of the strata, we were also able to detect different karst features. When the excavations in the quarry reached the thrust-fault in one part, we found it outcrops exactly where we had previously defined its position. We conducted an additional GPR survey using the 50 MHz RTA as well as a 250 MHz antenna, and obtained new information about the extent and the geometry of the Socerb thrust-fault plane.

Estimating sound velocity in seabed sediment of shallow near-shore areas submerged after the Last Glacial Maximum is often difficult due to the heterogeneous sedimentary composition resulting from sea-level changes affecting the sedimentary environments. The complex sedimentary architecture and heterogeneity greatly impact lateral and horizontal velocity variations. Existing sound velocity studies are mainly focused on the surficial parts of the seabed sediments, whereas the deeper and often more heterogeneous sections are usually neglected. We present an example of a submerged alluvial plain in the northern Adriatic where we were able to investigate the entire Quaternary sedimentary succession from the seafloor down to the sediment base on the bedrock. We used an extensive dataset of vintage borehole litho-sedimentological descriptions covering the entire thickness of the Quaternary sedimentary succession. We correlated the dataset with sub-bottom sonar profiles in order to determine the average sound velocities through various sediment types. The sound velocities of clay-dominated successions average around 1530 m/s, while the values of silt-dominated successions extend between 1550 and 1590 m/s. The maximum sound velocity of approximately 1730 m/s was determined at a location containing sandy sediment, while the minimum sound velocity of approximately 1250 m/s was calculated for gas-charged sediments. We show that, in shallow areas with thin Quaternary successions, the main factor influencing average sound velocity is the predominant sediment type (i.e. grain size), whereas the overburden influence is negligible. Where present in the sedimentary column, gas substantially reduces sound velocity. Our work provides a reference for sound velocities in submerged, thin (less than 20 m thick), terrestrial-marine Quaternary successions located in shallow (a few tens of meters deep) near-shore settings, which represent a large part of the present-day coastal environments.

In the Julian Alps (Mt. Prisojnik, NW Slovenia) and in the Kamnik–Savinja Alps (Mt. Križevnik, N Slovenia), both of which form part of the eastern Southern Alps, several meters of Upper Anisian pelagic red nodular, radiolarian-rich limestone (Loibl Formation) were deposited on the drowned platform carbonates of the Contrin Formation. The time of the platform drowning is dated with radiolarians and conodonts to the Illyrian, more precisely to the upper part of the Paraceratites trinodosus Ammonoid Zone. The red limestone is overlain by pyroclastics and volcanics (rhyolites) or carbonate (mega)breccia (Uggowitz Formation). The following unit consists of thin-bedded limestone, grainstone and subordinate marl (Buchenstein Formation) deposited during the final filling of the basin from the adjacent prograding carbonate platform (Schlern Formation) in the Ladinian. Map-scale geometry, neptunian dykes, the onset of volcanism, the presence of (mega)breccia and related paleo-escarpments, the lateral variations in thickness and the wedge-shaped geometry of the lithological units provide evidence of syn-sedimentary block faulting and the formation of small-scale, relatively shallow half-grabens within the previously uniform Slovenian Carbonate Platform. This analysis indicates a clear tectonic control over the development of the Middle Triassic stratigraphy. The described extensional event is well correlated and genetically connected with the syn-rift formation of the neighboring Slovenian Basin and other Southern Alpine basins that formed in connection with the opening of the Meliata-Maliac branch of the Neotethys Ocean.

Volcanic rocks occurring in Ladinian (?) marls, interstratified with limestone (Solčava beds), at Grohat Alpine Meadow and Lipni plaz, Mt. Raduha, are shallow intrusives bodies with porphyric structure, and basaltic andesitic, acid andesitic and dacitic composition.Abundance of major oxides and trace elements in the studied rocks is similar to those observed in the Tertiary Smrekovec volcanic rocks suggesting contemporaneous formation and close genetic relationship.