The Periadriatic Fault system (PAF) ranks among the largest post-collisional structures of the European Alps. Recent geodetic data suggest that a fraction of the Adria–Europe convergence is still ...being accommodated in the Eastern Alps. However, the historical seismicity records along the easternmost segment of the PAF are ambiguous, and instrumental records indicate that seismotectonic deformation is mostly concentrated in the adjacent Southern Alps and Dinarides. Both electron spin resonance (ESR) and optically stimulated luminescence (OSL) dating methods can be used to date coseismic slip (with a combined range covering a few decades to a couple of million years) in slowly deforming fault zones, such as the PAF. Since the saturation doses of the quartz ESR signals are larger than quartz and feldspar OSL, ESR enables establishing a maximum age of the last resetting event of the system, while OSL allows constraining their minimum age when the signal is in saturation. We collected fault gouge samples from three localities along the easternmost segment of the PAF. For ESR, we measured the signals from the Al center in quartz comparing the results from the single aliquot additive dose (SAAD) and single aliquot regenerative (SAR) dose protocols. For OSL, we recorded the infrared stimulated luminescence signal at 50°C (IR
50
) and post-infrared infrared-stimulated luminescence signal at 225 °C (pIRIR
225
). Our dating results indicate that the studied segment of the PAF system accommodated seismotectonic deformation during the Quaternary, with a maximum age for the last resetting event of the system ranging from 1075 ± 48 to 552 ± 26 ka (ESR SAR) and minimum ages in the range from 196 ± 12 to 281 ± 16 ka (saturation of pIRIR
225
). The obtained ages suggest that the studied segment of the PAF could be considered at least as a potentially active fault.
Graphical abstract
Increasing awareness of the importance of effective communication of scientific results and concepts, and the need for more accurate mapping and increased feature visibility led to the development of ...novel approaches to visualization of high-resolution elevation data. While new approaches have routinely been adopted for land elevation data, this does not seem to be the case for the offshore and submerged terrestrial realms. We test the suitability of algorithms provided by the freely-available and user-friendly Relief Visualization Toolbox (RVT) software package for visualizing bathymetric data. We examine the algorithms optimal for visualizing the general bathymetry of a study area, as well as for highlighting specific morphological shapes that are common on the sea-, lake- and riverbed. We show that these algorithms surpass the more conventional analytical hillshading in providing visualizations of bathymetric data richer in details, and foremost, providing a better overview of the morphological features of the studied areas. We demonstrate that the algorithms are efficient regardless of the source data type, depth range, resolution, geographic, and geological setting. The summary of our results and observations can serve as a reference for future users of RVT for displaying bathymetric data.
The Miocene deformation history of magmatic and host metamorphic rocks and surrounding sediments was reconstructed by measuring meso- and microscale structures and anisotropy of magnetic ...susceptibility (AMS) data in order to constrain the structural evolution of the Pohorje pluton during the onset of lithospheric extension at the Eastern Alps–Pannonian Basin transition. Principal AMS axes, lineation and foliation are very similar to mesoscopic lineation and foliation data from the main intrusive body and from some dykes. Although contribution from syn-magmatic texture is possible, these structures were formed during the cooling of the pluton and associated subvolcanic dykes just shortly after the 18.64 Ma pluton intrusion. Dykes emplaced during progressively younger episodes reflect decreasing amount of ductile strain, while firstly mesoscopic foliation and lineation, and then the tectonic AMS signal gradually disappears. In the structurally highest N–S trending dacite dykes, the AMS fabric only reflects the magmatic flow. The Miocene sediments underwent the same, NE–SW to E–W extension as the magmatic and host metamorphic rocks as indicated by both AMS and fault-slip data. All these events occurred prior to ~ 15 Ma, i.e., during the main syn-rift extension of the Pannonian Basin and during the fastest exhumation of the Tauern and Rechnitz windows, both demonstrating considerable extension of diverse crustal segments of the Alpine nappe pile. After a counterclockwise rotation around ~ 15 Ma, the maximum stress axis changed to a SE–NW orientation, but it was only registered by brittle faulting. During this time, the overprinting of a syn-rift extensional AMS texture was not possible in the cooled or cemented magmatic, metamorphic and sedimentary rocks.
In our paper Diercks et al. (2021) we presented geomorphological data and field observations from W Slovenia and NE Italy to develop a model for the formation of the Pradolino (slov. Pradol) dry ...valley. After publication we were kindly pointed to existing studies on the area that we were unaware of. To fill that gap and to properly credit previous work, in this addendum we summarise the research history on the study area and briefly compare earlier views with our model.
We applied an interdisciplinary approach to analyze the late Quaternary activity of the Sava Fault in the Slovenian Southern Alps. The Sava Fault is an active strike-slip fault, and part of the ...Periadriatic Fault System that accommodated the convergence of Adria and Europe. It is one of the longest faults in the Southern Alps. Using high-resolution digital elevation models from lidar and photogrammetric surveys, we were able to overcome the challenges of assessing fault activity in a region with intense surface processes, dense vegetation, and relatively low fault slip rates. By integrating remote sensing analysis, geomorphological mapping, structural geological investigations, and near-surface geophysics (electrical resistivity tomography and ground penetrating radar), we were able to find subtle geomorphological indicators, detect near-surface deformation, and show distributed surface deformation and a complex fault pattern. Using optically stimulated luminescence dating, we tentatively estimated a slip rate of 1.8 ± 0.4 mm/a for the last 27 ka, which exceeds previous estimates and suggests temporal variability in fault behavior. Our study highlights the importance of modern high-resolution remote sensing techniques and interdisciplinary approaches in detecting tectonic deformation in relatively low-strain rate environments with intense surface processes. We show that slip rates can vary significantly depending on the studied time window. This is a critical piece of information since slip rates are a key input parameter for seismic hazard studies.
Though recent investigations have contributed substantially to our understanding of the Alpine-Dinaric radiation of the genus Zospeum Bourguignat, 1856, its southernmost member, Zospeum ...troglobalcanicum Absolon, 1916, has remained a taxonomic ghost. The assumed absence of type material, the insufficient original description, and the lack of new samples from its Western Balkan type locality have stymied further clarification. The recent discovery of a single syntype shell housed at the Natural History Museum Vienna now enables the first morphological assessment via 3D X-ray and SEM imaging. Based on this image data, different characters for assessing the southernmost members of the genus are determined and a lectotype is designated. Eleven allied species from 15 Western Balkan populations are described from museum material and recent sampling efforts: Z. amplioscutum Jochum & Ruthensteiner sp. nov., Z. biokovoense Jochum & Ruthensteiner sp. nov., Z. constrictum Jochum & Ruthensteiner sp. nov., Z. dubokidoense Jochum & Ruthensteiner sp. nov., Z. intermedium Jochum & Ruthensteiner sp. nov., Z. kolbae Jochum, Inäbnit, Kneubühler & Ruthensteiner sp. nov., Z. neuberti Jochum & Ruthensteiner sp. nov., Z. njegusiense Jochum & Ruthensteiner sp. nov., Z. njunjicae Jochum, Schilthuizen & Ruthensteiner sp. nov., Z. tortuosum Jochum & Ruthensteiner sp. nov. and Z. tumidum Jochum, Schilthuizen & Ruthensteiner sp. nov. One species, Z. kolbae, is described using DNA sequence data and one species, Z. simplex Inäbnit, Jochum & Neubert, 2021 for which DNA sequence data is already available, is supported by morphological data presented in this study. The DNA sequence dataset (COI, 16S and H3) is included here and implemented in the most recent phylogenetic reconstruction of the genus. A translation of Karel Absolon’s notes from the Balkan scientific expeditions is provided.
In tectonically active mountain ranges, the landscape is shaped by the interplay of erosion/sedimentation and tectonically driven crustal deformation. Characteristic landforms such as moraines, wind ...gaps, fault scarps, and river terraces can be used to decipher the landscape evolution. However, the available data often allow for different interpretations. Here we study the Pradol (Pradolino) Valley in Western Slovenia, a deeply incised canyon whose floor rests several hundreds of metres above the surrounding valleys. We use high-resolution digital elevation models, geomorphic indices and field observations to unravel the evolution of this peculiar landform. We present a six-stage evolution model of the canyon that includes the blockage of valleys by advancing glaciers, river diversion, and rapid incision due to a high discharge of post-glacial meltwater. The formation of the Pradol Valley was most likely facilitated by an underlying fault that serves as an easily erodible weakness zone in the Mesozoic limestones. Our model indicates that the formation of the canyon could have occurred during the last glaciation, which results in incision rates of several cm/yr. With the proposed model we can explain all remote and field observations available. Our study shows that a complex interplay of different landscape-shaping processes is needed to explain the occurrence of the Pradol dry valley and that rapid changes in the morphology occurred after the last glacial maximum.
The late Eocene to Recent dynamics of the NW External Dinarides in Slovenia are described. The study is focused on the orogen-parallel NW-SE striking family of faults, which represent the main source ...of seismic hazard in the NW External Dinarides today. Approximately 1700 fault-slip datasets were collected at 70 locations and used for palaeostress analysis. Structural relationships observed in the field, allowed the construction of a relative chronology between the documented fault and shear joint sets, facilitating the reconstruction of their kinematic evolution and the chronology of palaeostress phases. Four post-Palaeocene stress tensor groups are documented corresponding to four distinct tectonic phases. The first phase is marked by NE-SW directed compression attributed to Late Eocene top-to-SW thrusting of External Dinarides. The second phase is characterized by NE-SW oriented tension, documented by normal slips recorded on NW-SE striking faults. This tension is interpreted as an expression of the Early to Middle Miocene back-arc extension in the Pannonian basin system that also affected the studied part of the External Dinarides. The third phase is manifested by approximately E-W oriented compression with approximately N-S oriented tension in a strike-slip stress regime, causing sinistral reactivation of NW-SE trending faults. Geodynamically, this phase can be correlated with the Late Miocene short pulse of E-W directed compression, documented in parts of the Pannonian basin system. The youngest phase is characterized by approximately N-S oriented compression and approximately E-W oriented tension in a strike-slip stress regime, which caused dextral reactivation of NW-SE striking faults. This phase correlates with the recent inversive/transpressive phase, well-established from seismological data.
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.
Marbles in Pohorje occur in lenses and smaller bodies in the southern and southeastern part of the massif. Marbles are very pure, predominantly calcitic and rarely calcitic-dolomitic, containing a ...maximum of 5 % of non-carbonate mineral phases. The latter comprise pyroxenes (diopside), amphiboles (tremolite), olivines (forsterite) in places replaced by serpentine, quartz, feldspars (potassium feldspars and plagioclases), epidote, zoisite, vesuvianite, scapolite, muscovite, biotite partly replaced by chlorite, phlogopite, rare grains of titanite, rutile, zircone, apatite, and small grains of ferric oxides and sulfies. Calcite exhibits intensive deformational e-twinning whereas dolomite is undeformed and untwined. All four known types of mechanical twins in calcite were recognized: thin Type I twins, straight thick Type II twins, curved, lensoid and tapered thick Type III twins, and thick patchy Type IV twins. Type III twins are the dominant mechanical twins in the Pohorje marbles indicating the temperature of deformation somewhat above 200 °C. Since they lack signs of grain boundary recrystallization, we assume that the twinning was followed by a decrease temperature during exhumation. With increasing temperature the process of recrystallization along calcite grain becomes pronounced. Small individual untwined calcite crystals are progressively replacing bigger calcite grains. In few examples second generation of Type I deformational twins develop in recrystallized calcite grains, which also implies lowering of temperature due to exhumation.
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