We present the compilation of a new database of active faults in Slovenia, aiming at introducing geological data for the first time as input for a new national seismic hazard model. The area at the ...junction of the Alps, the Dinarides, and the Pannonian Basin is moderately seismically active. About a dozen
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> 5.5 earthquakes have occurred across the national territory in the last millennium, four of which in the instrumental era. The relative paucity of major earthquakes and low to moderate fault slip rates necessitate the use of geologic input for a more representative assessment of seismic hazard. Active fault identification is complicated by complex regional structural setting due to overprinting of different tectonic phases. Additionally, overall high rates of erosion, denudation and slope mass movement processes with rates up to several orders of magnitude larger than fault slip rates obscure the surface definition of faults and traces of activity, making fault parametrization difficult. The presented database includes active, probably active and potentially active faults with trace lengths >5 km, systematically compiled and cataloged from a vast and highly heterogeneous dataset. Input data was mined from published papers, reports, studies, maps, unpublished reports and data from the Geological Survey of Slovenia archives and dedicated studies. All faults in the database are fully parametrized with spatial, geometric, kinematic and activity data with parameter descriptors including data origin and data quality for full traceability of input data. The input dataset was compiled through an extended questionnaire and a set of criteria into a homogenous database. The final database includes 96 faults with 240 segments and is optimized for maximum compatibility with other current maps of active faults at national and EU levels. It is by far the most detailed and advanced map of active faults in Slovenia.
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.
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.
A sediment infill of a small, late Anisian-earliest Ladinian half-graben, sealed by massive limestone of the Schlern Formation is exposed on the northeastern slopes of Mt. Vernar in the eastern ...Julian Alps, Slovenia. The pre-rift base of the succession is formed by a chaotic mixture of massive limestone and limestone breccia of the Anisian platform. Sedimentation in the half-graben started with a 20 m thick thinly bedded pink nodular limestone which is informally named here as the Vernar member. It consists of microbial carbonate and was probably deposited within the photic zone. The Vernar member is overlain by poorly sorted polymict breccias of the Uggowitz Breccia Formation which reaches a thickness of at least 150 m, but pinches out rapidly towards the SE graben margin, reflecting the highly asymmetric basin geometry. Individual beds of breccia represent successive debris flow deposits. The Uggowitz Breccia Formation is followed by a few metres of sandstone and sandy limestone of the Buchenstein Formation. The limestone contains abundant grains of shallow marine origin and terrestrial plant fragments. The overlying post-rift Schlern Formation consists of crudely bedded and massive limestone, covering the graben. The consistent NE-SW strike of the graben-bounding faults and of the smallscale conjugate normal faults observed in the Uggowitz Breccia Formation suggests that the half-graben originated from NW-SE directed extension.
Early beginnings of the Middle Triassic extension in the areas surrounding the western embayment of the Neotethys are evidenced in formation of small half-graben basins, local emergences of the ...underlying platform, and/or deposition of coarse-grained breccia. The succession related to the creation and infilling of one of these half-grabens is exposed on the slopes of the base of Mt. Vernar in eastern Julian Alps, Slovenia. The lowermost exposed unit within the half-graben is the Uggowitz Breccia, which attains thickness of up to 150 m. It is followed by a few tens of meters of red nodular limestone (the informal 'Vernar member'), followed by the second, thinner Uggowitz Breccia unit, succeeded by sandstone and sandy limestone (the informal “Krma member”), rich in shallow marine foraminifers and plant material. The basin-filling succession is followed by indistinctly bedded and then massive limestone of the Schlern Formation. Late Anisian (Ilyrian) age is assumed for the sediments of the half-graben based on the clast composition and comparison with regional sequence stratigraphic schemes. Breccias likely deposited in shallow marine or marginal marine setting. Individual beds are interpreted as subaqueous debris-flow deposits.
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