Northwestern Dinarides Research Articles

Species conservation profiles of the endemic spiders Troglohyphantes (Araneae, Linyphiidae) from the Alps and the north-western Dinarides.

The genus Troglohyphantes Joseph, 1882 (Araneae, Linyphiidae) includes 131 species, mainly distributed across the main European mountain ranges. The Alps and the north-western Dinarides account for 66 species, most of them showing narrow or even point-like distributions. The majority of Troglohyphantes spiders dwell in subterranean habitats including caves, mines, soil litter, rocky debris and other moist and shaded retreats. Despite being intensively studied from taxonomic, ecological and biogeographic standpoints, knowledge on the status of conservation and on the potential risk of extinction of these spiders is lagging. To date, only three species have been included in the global IUCN Red List, but their status has not been updated ever since their last assessment in 1996. The aim of this contribution is to assess the Alpine and north-western Dinaric species of the genus Troglohyphantes and to re-assess the species previously evaluated, according to the last version of the IUCN Red List Categories and Criteria. Amongst the 66 species here considered, 62 had sufficient data to allow the quantification of their Extent Of Occurrence (EOO) and Area Of Occupancy (AOO). Most of the species have a narrow distribution range, with an estimated EOO < 20,000 km2 and AOO < 2,000 km2, meeting the thresholds for the inclusion in the threatened categories. Five species have a more widespread distribution (EOO > 20,000 km2), extending across multiple countries. The quality of the data on distribution of four species was not sufficient to provide a reliable estimation of the distribution range.A continuing decline in EOO, AOO and habitat quality was inferred for 30 species. The majority of them were subterranean specialised species, with a reduced thermal tolerance and a low dispersal ability. Accordingly, changes in subterranean microclimatic conditions due to climate change represent a major threat for these species. Land-use change and habitat alteration were identified as additional relevant threats for several species.A considerable proportion of the species here assessed was found in protected areas and in sites of the Natura 2000 network. In addition, 14 species are formally protected by national and sub-national legislation. At present, 25 species are listed in the regional Red Lists.Long-term monitoring programmes, management plans for both the species and their habitats, expansion of the extant protected areas and designation of new ones, should be considered as the most effective approaches to species conservation.

One-dimensional velocity structure modeling of the Earth's crust in the northwestern Dinarides

Abstract. The studied area of the northwestern (NW) Dinarides is located in the northeastern (NE) corner of the Adriatic microplate and is bordered by the Adriatic foreland, the Southern Alps, and the Pannonian basin. Its complex crustal structure is the result of interactions among different tectonic units, the most important of which are the Eurasian plate and the Adriatic microplate. Despite numerous seismic studies in this tectonically complex area, there is still a need for a detailed, small-scale study focusing mainly on the upper, brittle part of the crust. In this work, we investigated the velocity structure of the crust with one-dimensional (1-D) simultaneous hypocenter–velocity inversion using routinely picked P- and S-wave arrival times. Most of the models computed in the combined P and S inversion converged to a stable solution in the depth range between 0 and 26 km. We further evaluated the inversion results with hypocenter shift tests, high- and low-velocity tests, and relocations. This helped us to select the best performing velocity model for the entire study area. Based on these results and the seismicity distribution, we divided the study area into three subregions, reselected earthquakes and stations, and performed the combined P and S inversion for each subregion separately to gain better insight into the crustal structure. In the eastern subregion, the P velocities in the upper 8 km of the crust are lower compared to the regional velocities and the velocities of the other two subregions. The P velocities between 8 and 23 km depth are otherwise very similar for all three models. Conversely, the S velocities between 2 and 23 km depth are highest in the eastern subregion. The NW and southwestern (SW) subregions are very similar in terms of the crustal structure between 0 and 23 km depth, with slightly higher P velocities and lower S velocities in the SW subregion. High vP/vS values were obtained for the layers between 0 and 4 km depth. Below that, no major deviations of vP/vS in the regional model from the value of 1.73 are observed, but in each subregion we can clearly distinguish two zones separated by a decrease in vP/vS at 16 km depth. Compared to the model currently used by the Slovenian Environment Agency to locate earthquakes, the obtained velocity models show higher velocities and agree very well with some of the previous studies. In addition to the general structural implications and the potential to improve the results of seismic tomography, the new 1-D P and S velocity models can also be used for reliable routine earthquake location and for detecting systematic travel time errors in seismological bulletins.

Patzkea paniculata grasslands in the north-western Dinarides – a crossroad between the Alps and the Balkan mountains

Patzkea paniculata grasslands in the north-western Dinarides – a crossroad between the Alps and the Balkan mountains

Crustal Thickness Beneath the Dinarides and Surrounding Areas From Receiver Functions

AbstractKnowledge about the crustal thickness is one of the key elements in the reconstruction of the regional tectonic history. The Dinaric mountain belt is one of the most enigmatic segments of the Alpine‐Mediterranean collision zone, characterized by large variations in crustal thickness and not studied sufficiently. We present a new Moho depth map for the wider Dinarides region which was created using teleseismic earthquake recordings from 87 permanent and temporary seismic stations in the region. Teleseismic data were analyzed using the receiver function method to extract converted P to S waves.The resulting Moho topography fits well within a structural framework comprising a thicker crust under the Dinarides, which gradually becomes thinner toward the Pannonian and Adriatic domains. The profiles crossing the northwestern Dinarides are marked by a relatively sharp decrease in crustal thickness north of the main thrust front. This transition is followed by significant crustal thinning toward the Pannonian basin. The Mohorovičić discontinuity lies the deepest in the central and southern Dinarides, at depths of over 55 km. Here similarly to the northwestern segment we observe a jump in the crustal thickness when transitioning toward the Internal Dinarides, which hints at possible underthrusting (or subduction) of the Adria plate in this region. Moho depths in the transition zone toward the Pannonian basin and in the Pannonian basin proper vary between 25 and 35 km. In the Adriatic domain, we find crustal thickness ranging from 30 km to more than 45 km around the Central Adriatic islands.

A Geophysical-Geochemical Approach to the Study of the Paleogene Julian—Slovenian Basin “Megabeds” (Southern Alps—Northwestern Dinarides, Italy/Slovenia)

The Paleogene “megabeds” of the Julian-Slovenian Basin are regional, basin-wide deposits, produced by catastrophic carbonate platform collapses. They record the emplacement of a bipartite slide mass behaving as a cohesive blocky/debris flow in the lower part, and as a grain to turbulent flow in the upper part. Several types of primary (sedimentary) soft sediment deformation structures testify fluid overpressure conditions during emplacement. Such structures are identified within a brecciated, fine grained matrix that encloses and intrudes slide blocks and clasts, characterized by NE-, NW- and SW-directed paleo-transport directions, indicating a depositional setting close to the basin margins. Here we present an updated review of some representative megabeds, exposed in the open-pit quarry outcrops of Anhovo (SW Slovenia). In particular, we here discuss new interpretations based on X-ray fluorescence spectrometry (XRF), thermo-gravimetry (TG) and electric resistivity tomography (ERT). Our results indicate that basal marly clasts of the megabeds are markedly different from the uppermost draping marls, suggesting two different coeval sources. The relationships with the underlying successions are strongly erosive, with deep localized scouring of the substrate and amalgamations between different megabeds, and the depositional units inside individual megabeds, supporting the geochemical differences.

Lithospheric thickness under the Dinarides

The nature of the interaction between Adriatic and Euroasian lithospheric plates in the Dinarides is important for understanding the complex tectonic history of the central Mediterranean. Using the data from permanent and temporary seismic stations in the wider Dinaric region, we imaged the lithospheric and upper mantle structure under this area. Specifically, we focused on mapping the lithosphere asthenosphere boundary (LAB) using the S receiver functions in order to establish boundaries between different tectonic domains present in this region. The lithospheric thickness in the investigated area varies between ∼50 and ∼160 km with high degree of variability between adjacent tectonic realms. Below northwestern Dinarides the LAB depth varies between 100 and 120 km thinning towards Adriatic sea and Pannonian basin, to 90 and 70 km respectively. In the central Dinaric region (Lika region) we find anomalously thin lithosphere with thickness varying between 50 and 70 km and weak velocity gradient defining the LAB. Further south the signal from the LAB is more pronounced with lithosphere getting thicker again with average depths around 90 km. The intriguing observation of thinned lithosphere under central part of the Dinarides coincides with the zone of lower seismicity and with the tomographic images showing the slab gap in this area.

Phytocoenological analysis of grey alder (Alnus incana L.) forests in the Dinarides of Croatia and their relationship with affiliated communities

This paper provides a comprehensive survey of the results of phytocoenological research into Alnus incana forests from the alliance Alnion incanae in the Dinarides. Stands from the south-eastern Dinar-ides (Alnetum incanae = Oxali-Alnetum incanae) were analyzed and compared with those from the north-western Dinarides (Lamio orvalae-Alnetum incanae). The comparison reveals significant differ-ences in the floristic composition and in the degree of differentiation – and particularly in the presence of the species of the Illyrian floristic geoelement. Focus was placed on the area of western Croatia where a geographic variant of Helleborus dumetorum had previously been de-fined within the association Lamio orvalae-Alnetum incanae. Two of its subtypes, Salix alba and Alnus glutinosa, were determined in our research. The former subtype thrives on occasionally flooded, moist sites, where the floristic composition is dominated by hygrophytes. The latter subtype grows on elevat-ed and drier terraces and is richer in mesophilous species from the surrounding zonal forests. A floris-tic-sociological comparison of the Lamio orvalae-Alnetum incanae with the related syntaxa indicates the presence of about fourty diagnostic species which accentuate its independence and the need to assess it at the level of an independent, regional association within the alliance Alnion incanae.

Identification of tectonically active areas using DEM: a quantitative morphometric analysis of Mt. Medvednica, NW Croatia

Mt. Medvednica is an inselberg in NW Croatia which tectonically lies at the intersection between Southeastern Alps, Northwestern Dinarides and Tisza Mega-Unit of the Pannonian basin. Due to the Pliocene-Quaternary N-S directed transpression it experienced a differential uplift between 1500-2000 m and exposes pre-Neogene and Neogene tectonic and stratigraphic units surrounded by Pliocene-Quaternary sediments. This paper evaluates a set of methods in quantitative morphometry, used here for identification of tectonically active areas within a region characterized by low-rate active folding and faulting during the Pliocene-Quaternary times. Analysis employed extraction of hypsometric curves, calculation of hypsometric integral, asymmetry factor, and statistical parameters of normalized longitudinal main stream profiles of 36 drainage basins delineated from a 25-m resolution DEM of Mt. Medvednica area. Despite lithological heterogeneity, obtained morphometric parameters are considered as fairly good indicators for discriminating tectonically active from inactive areas. Based on calculated parameters, in combination with geological data, the most tectonically active areas during the Quaternary are found at the SW corner of the Mt. Medvednica related to an active segment of the North Medvednica Boundary Fault, and in the central part of the mountain related to the Kasina fault zone subdividing mountain into the NE and SW units.

Tectonothermal history of the basement rocks within the NW Dinarides: new40 Ar/39 Ar ages and synthesis

Abstract Very low-grade and low-grade metamorphosed basement rocks from distinct inliers of the Africa-derived northwestern Dinarides (Medvednica Mts and Paleozoic Sana-Una Unit, respectively) have been studied with the multigrain step-heating 40Ar/39Ar technique in order to compare and reveal their tectonothermal history. 40Ar/39Ar ages from detrital white mica of the very low-grade basement rocks of the Paleozoic Sana-Una Unit gave a Variscan age of ~335 Ma. The new age is in agreement with 40Ar/39Ar ages from the very low-grade basement exposed at Petrova and Trgovska Gora of the NW Dinarides. Within low-grade metamorphic basement rocks from the Medvednica Mts, we found no Variscan ages. White mica from phyllitic basement rocks of the Medvednica Mts gives predominantly early Alpine ages ranging between 135 and 122 Ma and younger Alpine ages of ~80 Ma. The early Alpine ages of 135 and 122 Ma are interpreted as the date to the onset of ductile nappe stacking predating the formation of Gosau-type collapse basins. The late early Alpine event of ~80 Ma can be traced in the entire Cretaceous-aged orogen of the Circum- Pannonian Region and is synchronous with subsidence of the Gosau-type basins and opening and closure of the neighbouring Sava-Vardar Zone.

Multiple glacial refugia and postglacial colonization routes inferred for a woodland geophyte, Cyclamen purpurascens: patterns concordant with the Pleistocene history of broadleaved and coniferous tree species

The phylogeographical history of mid-altitude woodland herbs that depend on moist and shaded forest habitats is poorly understood. Here, we analysed the genetic structure of Cyclamen purpurascens, a mountainous calcicolous perennial, to test hypotheses regarding its glacial survival in single or multiple refugia and postglacial colonization routes, and to explore how they are congruent with the histories inferred for temperate trees and other mountainous herbs. We gathered AFLP data and chloroplast DNA sequences (trnD-trnT region) from 68 populations spanning the entire distribution range (the Jura Mountains, Alps, western Carpathians, Dinarides). Both genetic markers revealed two main phylogeographical groups (phylogroups) in C. purpurascens. Additionally, AFLP data detected a more detailed structure of five phylogroups: two widespread, showing east−west geographical separation, and three local ones, restricted to somewhat disjunct, marginal regions of the species range. We suggest that C. purpurascens survived the last glaciation in two main regions, the foothills of the Southern Limestone Alps and the Karst area of the north-western Dinarides, and possibly also in microrefugia in the Western Carpathians. The glacial persistence and colonization routes of this woodland herb are highly concordant with those inferred for several temperate trees, especially the European beech. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 741–760.

Chemical indicators of anthropogenic impacts in sediments of the pristine karst lakes

The anthropogenic impact on the pristine karst lakes was investigated using combination of specific parameters, including multielemental analysis of major inorganic constituents (Al, K, Fe) and trace metals (Li, Ag, Cd, Sn, Pb, Bi, Cr, Co, Ni, Cu, Zn and Sb), polycyclic aromatic hydrocarbons (PAHs) and anionic surfactants of linear alkylbenzene sulfonate (LAS) type. The study was performed in the Plitvice Lakes National Park, situated in a sparsely populated area of the northwestern Dinarides, central Croatia. Dated cores of recent sediments from the two biggest lakes, Lake Prosce and Lake Kozjak, were analysed for the selected contaminants using highly specific methods, involving inductively coupled plasma mass spectrometry (ICP/MS), gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS). The concentration of inorganic constituents reflected primarily the geological background of the area as well as geomorphological and geochemical characteristics of the Plitvice Lakes. Due to the higher terrigenous input, the concentration of all elements was significantly higher in the Lake Prosce. The concentration of toxic metals was relatively low in both lakes, except for Cd (>1 mg kg −1) and Pb (up to 40 mg kg −1). The vertical profiles of these metals suggested that elevated concentrations of Cd were of natural origin, derived from the erosion of the Jurassic dolomite bedrock, while Pb was predominately of recent anthropogenic origin. A similar distribution pattern, suggesting the same prevailing mechanism of input, was observed for pyrolytic PAHs. The characteristic diagnostic PAH ratios revealed that higher PAHs prevailingly originated from the combustion of biomass and fossil fuels. LAS, which represent highly specific indicators of untreated wastewaters, were found in rather high concentrations in the recent sediment layers (up to 4.7 mg kg −1), suggesting that contaminated household and hotel wastewaters reach the Lakes, very probably by leaking through the porous karst rocks.

Origin of siderite mineralisation in Petrova and Trgovska Gora Mts., NW Dinarides

The Petrova and Trgovska Gora Mts. (Gora=Mountain) are Variscan basement units incorporated into the northwestern Dinarides during the Alpine orogeny. They host numerous siderite-quartz-polysulphide, siderite-chalcopyrite, siderite-galena and barite veins, as well as stratabound hydrothermal-replacement ankerite bodies within carbonates in non-metamorphosed, flysch-like Permo-Carboniferous sequences. The deposits have been mined for Cu, Pb, Ag and Fe ores since Medieval times. Fluid inclusion studies of quartz from siderite-polysulphide-quartz and barite veins of both regions have shown the presence of primary aqueous NaCl−CaCl2±MgCl2−H2O±CO2 inclusions. The quartz-sulphide stage of both regions show variable salinities; 2.7–26.2 wt% NaCl eq. for the Trgovska Gora region and 3.4–23.4 wt% NaCl eq. for the Petrova gora region, and similar homogenisation temperatures (100–230°C). Finally, barite is precipitated from low salinity-low temperature solutions (3.7–15.8 wt % NaCl equ. and 115–145°C). P-t conditions estimated via isochore construction yield formation temperatures between 180–250°C for the quartz-sulphide stage and 160–180°C for the barite stage, using a maximum lithostatic pressure of 1 kbar (cc. 3 km of overburden). The sulphur isotope composition of barite from both deposits indicates the involvement of Permian seawater in ore fluids. This is supported by the elevated bromium content of the fluid inclusion leachates (120–660 ppm in quartz, 420–960 ppm in barite) with respect to the seawater, indicating evaporated seawater as the major portion of the ore-forming fluids. Variable sulphur isotope compositions of galena, pyrite and chalcopyrite, between −3.2 and +2.7‰, are interpreted as a product of incomplete thermal reduction of the Permian marine sulphate mixed with organically- and pyrite-bound sulphur from the host sedimentary rocks. Ore-forming fluids are interpreted as deep-circulating fluids derived primarily from evaporated Permian seawater and later modified by interaction with the Variscan basement rocks. 40Ar/39Ar data of the detrital mica from the host rocks yielded the Variscan age overprinted by an Early Permian tectonothermal event dated at 266–274 Ma. These ages are interpreted as those reflecting hydrothermal activity correlated with an incipient intracontinental rifting in the Tethyan domain. Nevertheless, 75 Ma recorded at a fine-grained sericite sample from the alteration zone is interpreted as a result of later resetting of white mica during Campanian opening/closure of the Sava back arc in the neighbouring Sava suture zone (Ustaszewski et al. 2008).

Volcanic facies analysis of a subaqueous basalt lava-flow complex at Hruškovec, NW Croatia — Evidence of advanced rifting in the Tethyan domain

The Hruškovec quarry of basaltoid rocks is situated on the northwestern slopes of Mt. Kalnik, within the Zagorje–Mid-Transdanubian zone, a part of the North-western Dinarides. The basaltoids are inter-bedded with radiolarites of the Middle and Upper Triassic age (Langobardian, Carnian–Norian). Spilites, altered diabases and meta-basalts form part of Triassic volcanic-sedimentary sequence, made of sandstones, shales, micritic limestone, altered vitric tuffs and radiolarian cherts, incorporated tectonically into the Jurassic–Cretaceous mélange. The architecture of the 2 km long and 100 m high pile of the extrusive basaltoid rocks is interpreted as a subaqueous basaltic lava flow. The presented research deals with a variety of volcanic facies of the subaqueous basaltic lava flow, which consists of several facial units: 1. Coherent pillow lavas, with massive core; the bending rims around the massive core, 30–50 cm thick, are dissected by polygonal columnar joints radiating from the pillow centres; 2. Closely packed pillows; densely packed and contorted pillows due to emplacement accommodation, clearly younging upward; 3. Pillow fragment breccia; clast supported, matrix poor, monomict breccia, formed proximal to the axis of the extrusion; 4. Isolated pillow breccia; matrix supported, clast poor breccia, made of lava pipes and tubes, within a matrix of fine-grained sideromelan granules and shards; 5. Pyjama-style pillows; spherical, decimetre to meter size pillow lava balls, grown and chilled in isostatic state (i.e. in a state of diminished density contrast) within water-soaked sediments, named after peculiar alternating basaltic shelves inside the sphere, which are encrusted with white secondary minerals; 6. Peperite and peperitic hyaloclastites; blocky and globular peperites developed at the contact of soft, wet sediment and hot intruding magma. Discovery of peperite and peperitic hyaloclastites within the Triassic radiolarian cherts, shales, and micritic limestone, with registration of conodonts (index microfossils), links their origin to magmatism during advanced rifting in a progressively subsiding basin during the Triassic. It precludes an affiliation of the subaqueous basaltic lava flow with the dismembered ophiolite formation, a product of oceanization created in Jurassic–Cretaceous times, which is a commonly stated alternative explanation. The basaltic rocks and their sedimentary hosts may be correlated with advanced Triassic rifting, and related volcanic-sedimentary successions in the Dinarides, Albanides, Helenides and further along the Tethyan orogenic belt.

Recent tectonic stress and crustal deformation in and around the Pannonian Basin: data and models

Abstract Recent (active) tectonics of the Pannonian Basin and its surroundings has been investigated using data from over 900 earthquake focal mechanism solutions, 200 borehole breakout analyses, some in-situ stress measurements and by applying finite element modelling technique. We have established a database for indicators of recent stress, and analysed the stress state of the region by the methods of the World Stress Map project. The alignments of the largest horizontal stresses have been mapped and the tectonic regimes were also determined. We present a map of seismoactive faults and seismic energy release combining historical and modern seismicity data and results of local seismotectonic studies. The pattern of earthquake slip vectors and the style of faulting are summarised in order to characterise the active deformations. Our results show that the alignment of the largest horizontal stress exhibits a radial pattern around the Adriatic sea. In the Southern Alps and northwestern Dinarides the largest horizontal stress (SH) is aligned N-S and thrust faulting is dominant. Along the southern Dinarides and the Dalmatian coast thrusting with strike-slip component can be observed. Here the trajectories of SH are aligned NE-SW. E-W aligned SH trajectories and normal faulting are characteristic of the Rhodope Massif. Thrust faulting of the Vrancea region seems to be distinct from the compressive regime around the Adriatic sea. In the Pannonian Basin borehole breakout analyses show that the direction of largest horizontal stress is changing from N-S in the western part to NE-SW in the east. Most of focal mechanisms and available hydraulic fracturing measurements indicate strike-slip and thrust faulting inside the basin. The lack of normal faulting mechanisms indicates that the extension of the basin has been terminated and a new compressive stress regime prevails. The crustal deformation of the area is controlled by the counterclockwise rotation of Adria with respect to Europe around a pole at the 45°N latitude and 6–10°E longitudes, which is inferred from satellite geodesy and supported by earthquake slip vectors. This movement can explain the shortening of the Southern Alps, and squeezing eastward the region between the Adriatic sea and the Mur-Murz line. Rotation of Adria generates thrusts along the Dalmatian coast, and this compressive deformation extends into the land far from the coastline, and leads to squeezing of the Pannonian Basin from the southwest. The seismicity pattern in the Pannonian Basin shows that earthquakes are restricted to the crust and the control by pre-existing (mostly Miocene) fault zones is strongly masked by random activity due to general weakness of the lithosphere. Although earthquakes are of small to medium magnitude (M ≤ 6), the cummulative energy release is remarkably higher than in the surrounding Carpathian arc. The Vrancea zone is the only exception, where high energy release in the crust and down to 200 km depth is associated with a relict subducted slab. Finite element stress modelling has been performed in order to simulate the observed stress pattern and, hence, to understand the importance of different possible stress sources in and around the Pannonian Basin. The observed radial stress pattern of the region can be well explained by the counterclockwise rotation of the Adriatic microplate as a first-order stress source. Additional boundary conditions, such as the active deformation at the Vrancea zone and the role of rigid crustal blocks at the Bohemian Massif and the Moesian Platform, can significantly effect the style of deformation and the alignment of the largest horizontal stress. Furthermore, our calculations show that differences in the crustal thickness and the presence of large scale fault zones in the Pannonian region have only local influence on the model results.