U-Pb SHRIMP zircon dating of andesite from the Dolomite area (NE Italy): geochronological evidence for the early onset of Permian Volcanism in the eastern part of the southern Alps

The Athesian Volcanic District (AVD), a thick sequence of andesitic to rhyolitic lava and ignimbrite, overlies both the Variscan basement of the Dolomites and, where present, the continental basal conglomerate of Upper Carboniferous(?) to Early Permian age. This volcanic activity is known to mark the margin of the intra-Pangea megashear system between Gondwana and Laurasia, the onset age of which is determined in this study. SHRIMP U-Pb dating on zircon from Ponte Gardena/Waidbruck (Isarco/Eisack valley) basaltic andesite yields an age of 290.7 ± 3 Ma, providing the oldest record of andesite volcanic activity yet documented in the AVD. Two younger dates (279.9 ± 3.3 and 278.6 ± 3.1 Ma) obtained for the andesitic necks of M. dei Ginepri (Eores/Aferer valley) and Col Quaterna (western Comelico), respectively, probably represent a second pulse of andesite magmatic activity. Near Chiusa/Klausen, the volcanoclastic deposits at the bottom of the Funes/Villnoss valley volcano-sedimentary complex only contain detrital zircons, dated at 469 ± 6 Ma; these probably derive from erosion of Paleozoic porphyroids. Other zircons from the same sediments and inherited cores of magmatic andesite crystals give Paleoproterozoic (1953.6 ± 22.1, 1834.6 ± 69.3, 1773.6 ± 25.1 Ma), Early Neoproterozoic (1015 ± 14 Ma) and Late Neoproterozoic (728.4 ± 9.6, 687.6 ± 7.6 Ma) ages. These ancient detrital and inherited zircon ages fit the model that envisages the Dolomite region as being tectonically coherent with Africa, at least until the Lower Permian

Structural Complexity and Seismogenesis: The Role of the Transpressive Structures in the 1976 Friuli Earthquakes (Eastern Southern Alps, NE Italy)

We reconstructed the seismotectonic setting of the area comprising the northeastern Friuli Plain and the Julian pre-Alpine border (NE Italy) by integrating geological and seismological data. The study area represents the junction between the SSE-verging polyphase thrust-front of the southAlpine Chain and the NW–SE-trending strike-slip faults of the eastern Friuli–western Slovenia domain. Following a multidisciplinary approach, the 3D geometry of the Susans–Tricesimo thrust system was reconstructed through the elaboration of four geological cross sections derived from the interpretation of ENI industrial seismic lines. In a second step, the seismogenic volume of the central-eastern Friuli area was investigated through hypocentral distribution analysis: the seismic events of the latest 50 years (1976–1977 and 1978–2019 time intervals) were plotted on four NE-SWoriented seriated sections together with the fault plane’s geometry. Through this procedure, we were able to investigate the relationship between the NW-SE-striking high-angle faults, which characterize the northern Julian pre-Alps, and the WSW-verging medium-angle reverse fronts located at the piedmont of the Friuli plain, which experienced NW-SE-to NNW-SSE-oriented compression starting at least from the Pliocene. In detail, we examined the involvement of these structures during the seismic sequences of May and September 1976, in terms of activation and/or interaction. The resulting seismotectonic model highlights the interplay between transpressive/strike-slip and reverse planes. In particular, this study suggests that Predjama and Maniaglia transpressive faults strongly control the stress release and likely played a fundamental role both during the 6 May (Mw 6.5) and 15 September (Mw 6.0) Friuli earthquakes

Assessing the long-term effectiveness of channel control works and supporting watershed management through sediment dynamics studies

In risk management of mountain basins, quite often, there is a lack of information on the efficiency of existing structures, the evolution of the ongoing process, and a priori in-depth study to analyse the sediment morphology dynamics and the interaction with existing channel control works. The growing capability of producing High-Resolution Topography data (HRT) greatly simplifies the analysis of geomorphological changes at multiple spatial and temporal scales and enables the development of innovative approaches to monitor sediment morphology dynamics and understand the interaction with channel control works. Indeed, thanks to multi-temporal HRT surveys (e.g., Airborne Laser Scanning - ALS), it is possible to derive accurate multi-temporal Digital Terrain Models (DTMs), and reliable DTMs of Difference (DoDs) useful to quantify the morphological changes also in catchment areas covered by vegetation. However, without a methodological and detailed workflow that considers the differences in terms of accuracy between old “legacy” data sets and recent surveys and the errors associated with the processes of co-registration, it would not have been possible to obtain accurate and valid multi-temporal DoD. The information provided by sediment morphology dynamics (i.e., exploiting multi-temporal DoDs at catchment and reach scale) coupled with a very simple, quick, and user-friendly efficiency index of channel control works, could help to support the development of watershed management strategies, assess afterward the effectiveness of existing structures, and foster a more complete decision-making chain. Therefore, this research aims to introduce a methodological approach based on integrating the sediment morphology dynamics data over large time spans in some mountain catchments with an updated state of efficiency of existing interventions. Various examples of the proposed methodology emphasized the usefulness of providing more complete information, than in the past, by exploiting field surveys and remote sensing data, in a context such as the risk management process where uncertainty and incomplete information on the ongoing phenomena prevails. The realized database could be a starting point for further analysis or provide numerical data for prediction models of the life-cycle of channel control works in risk management processes. Finally, the methodological workflow proposed could provide increasingly up-to-date information to constantly identify the areas most prone to hazards, support effective risk management decisions, improve intervention planning, find more appropriate solutions, or direct the maintenance works

Il massiccio carbonatico della Bernadia nelle Prealpi Giulie (Friuli, Italia NE): la registrazione di eventi tettonici tra il Cretacico superiore e il Quaternario

On the basis of geological mapping and mesostructural analysis, structural framework of the Bernadia carbonate massif (southern Julian Prealps) was pointed out. It deals with a tectonic building linked to the superposition between two tectonic systems: the Paleogene External Dinaric Chain and the Neogene-Quaternary Southalpine one. During Mesozoic Bernadia massif was part of the passive margin of Adria microplate. Starting from Late Cretaceous to Lower Eocene the study area was part of the WSW \u2013 verging Dinaric foredeep-foreland system. The Paleogene imbricate thrust-system shows staircase trajectory and duplex-geometries; thrusts are mainly NW-SE trending and present WSW tectonic transport; inherited Mesozoic normal faults (NNE-SSW and NW-SE-trending) are often inverted in lateral and frontal ramps respectively. Starting from Middle Miocene the S-SSE verging Neogene- Quaternary Southalpine Chain started, giving rise to a low-angle, approximately WSW-ENE to WNW-ESE trending thrust-system. Neoalpine compression originated deformation of the Paleogene structural belt: i.e. strong ondulations of the hinges of the Dinaric folds and production of culminations and depressions of the first folds (dome-basin pattern). Moreover the Neogene \u2013 Quaternary thrusts often re-utilised the low-angle Dinaric ramp as frontal or lateral ones

La carta geologica del Massiccio della Bernadia (Prealpi Giulie meridionali, Friuli, Italia NE.

The Southern Julian Prealps (SJP) belong to the sector of the External Dinarides included in the WSW-ENE trending, SSE-verging thrust belt of the eastern Southalpine Chain in evolution from the Middle Miocene to the present. On the basis of new geological mapping and mesostructural analysis, the geological framework of the Bernadia carbonate massif was pointed out. In the Bernadia area only cover sequences outcrop ranging from Early Creataceous to Early Eocene. Scanty outcrops of glauconitic arenites (Lower Miocene) are present in the footwall of the major Neogene thrusts. During the Mesozoic the Bernadia massif was part of the Friulian Carbonate Platform (FCP). Starting from Late Cretaceous to Early Eocene the study area was part of the WSW\u2013verging Dinaric chain-foredeep system. The Paleogene imbricate thrust-system shows staircase trajectory and duplex-geometries; thrusts are mainly NNW-SSE trending and show WSW tectonic transport. Inherited Upper Cretaceous normal faults (NNE-SSW- and NW-SE-trending) are often inverted in lateral and frontal ramps respectively. Starting from Middle Miocene the S-SSE verging thrust system of the Southalpine Chain started, giving rise to a low-angle, approximately WSW-ENE to WNW-ESE trending thrusts. Neoalpine compression deformed the Paleogene structural belt, producing dome-basin structural pattern. Moreover the Neogene\u2013Quaternary thrusts often re-utilised the Dinaric ramps as frontal or lateral ones

The Seismogenic Sources of the 1976 Friuli Earthquakes: a new seismotectonic model for the Friuli area

By matching interpretation of seismic profiles of the Friuli pre-Alpine area with the surficial data collected during the detailed geological survey (CARG - FVG project), we have reconstructed the deep arrangement of the Susans-Tricesimo thrust (which is considered the seismogenic source of the 6 May 1976 earthquake, MW 6.45). The structural framework of the upper crust in Friuli is here updated, suggesting a new seismotectonic model based on the slip partitioning between the Idrija-Ampezzo right lateral strike-slip system and the SSW-verging thrust system of central-eastern Friuli. This new seismotectonic model may have crucial consequences for the assessment of seismic hazard in Friul

Tectonic and climatic inferences from the terrace staircase in the Meduna valley, eastern Southern Alps, NE Italy

Results of stratigraphic andmorphotectonic analyses on fluvial terraces at the outlet of theMeduna valley in the eastern Southern Alps are used to investigate on the tectonics and paleoclimate. TheMeduna valley, prone to destructive earthquakes, belongs to the front of the eastern Southern Alps, a south-verging fold and thrust belt in evolution from the Middle Miocene to the present, constructed by ENE\u2013WSWstriking, SSE-verging medium to low-angle thrusts, gradually propagating in the Venetian\u2013Friulian plain. In the study area, located south of the Periadriatic thrust, the main structural element is the ENE\u2013WSW striking Maniago\u2013M. Jouf thrust system. Seven depositional units, ranging in age from Pliocene to Holocene, and a hierarchy of four numbered terrace complexes were identified. Stratigraphic and geometric relationships between sedimentary units, basal surfaces and terraces allowthe reconstruction of the chronology of the depositional events. The study shows that the valley configuration has been shaped during the Pliocene\u2013Quaternary with long-lasting steady intervals, interspaced with periodic tectonic pulses of the thrust front of the eastern Southern Alps. The most recent pulse related to the Maniago thrust shows an upper Pleistocene\u2013Holocene slip rate of about 0.6 mm/yr