Frequent activity on Vulcano (Italy) spanning the last 80 ky: New insights from the chemo-stratigraphy of the Brown Tuffs

The Brown Tuffs (BT) are widespread reddish-brown to grey, ash-rich pyroclastic deposits recognized in the stratigraphic sequences of the Aeolian Islands and Capo Millazzo peninsula (Sicily) that span the last 80 ky. They have very homogeneous lithological, textural and sedimentological features which make it difficult to reliably correlate units on the islands to proximal units in the source areas. Here we carefully re-interpret the stratigraphic profiles of the BT on Vulcano and Lipari where the deposits are thickest and present the most complete succession. The investigation is based on a large dataset of major and minor element geochemistry of juvenile glass components for the majority of the recognized BT depositional units, whilst also providing new radiocarbon ages. The distinctive chemical groupings observed within the glass analyses, both temporally and spatially, allow us to fingerprint the three main stratigraphically defined macro-units in which the BT succession can be sub-divided using prominent tephra marker beds, the Ischia Tephra (Monte Epomeo Green Tuff; 56 ky) and Monte Guardia pyroclastics from Lipari (herein radiocarbon dated to 27\u201326 ky). The Lower (80\u201356 ky; LBT), Intermediate (56\u201327 ky; IBT) and Upper BT (here dated at 24\u20136 ky; UBT) macro-units display K-series volcanic glasses ranging from basaltic trachy-andesites, through trachy-andesites, to more evolved trachytes, all consistent with an origin on Vulcano. The UBT are clearly distinguished from the lower macro units by their higher-SiO2 trachy-andesite to trachytic glasses, which extend to noticeably lower TiO2, CaO and MgO contents. These features make it possible to re-define the geochemical-evolutionary boundary between IBT and UBT as corresponding to the 24 ky Spiaggia Lunga scoria bed on Vulcano, which is stratigraphically higher (and younger) than the previous boundary marker (Monte Guardia). The glass compositions of the LBT, IBT and UBT are used to: (1) assess links to known proximal eruption units outcropping on Vulcano; (2) validate medial-distal BT occurrences across the Aeolian archipelago (Salina, Filicudi and Panarea) and on Capo Millazzo; (3) confirm that the BT are responsible for distal volcanic ash layers preserved in Central Mediterranean marine sedimentary archives. Interestingly, the glass compositions of the UBT are very similar to those of the Punte Nere unit, the earliest pyroclastic products erupted from the currently active La Fossa cone on Vulcano, indicating the corresponding magmatic system has likely erupted similar melts and products over the last 24 ky and thus extending its life cycle. Such information is crucial for evaluating the long-term eruption scenarios underpinning hazard assessment of the La Fossa caldera magmatic system

Unconformity-bounded units and terraced marine deposits as stratigraphic tools at Ustica (Southern Tyrrhenian Sea).

The Unconformity-bounded units are employed for the reconstruction of the geological evolution of the Ustica Island as the result of the interaction between volcanic activity, tectonics, and sea-level fluctuations. The Ustica Island is located in the Southern Tyrrhenian sea in the eastern sector of the Sicilian-Maghrebian Chain. It mainly consists of volcanic products, basaltic to trachitic in composition and belonging to a sodic-alkaline series and, subordinately, of marine deposits (conglomerates, sands and fossiliferous sediments) belonging to a well-preserved series of terraces intercalated within the volcanic succession. Seven successive raised paleo-shorelines are recognized at elevation ranging from 115 m to 8 m a.s.l and are attributed to major sea-level highstand peaks by means of stratigraphic relationships with dated volcanic products, relative dating of fossils and relative chronostratigraphic attribution: paleoshoreline I is attributed to marine oxygen-isotope stage (MIS) 13, paleoshoreline II and III to distinct peaks during MIS 9, paleoshorelines IV, V and VI to MIS 7, paleoshoreline VII order (a, b, c) to MIS 5. Following modern stratigraphic procedures to stratigraphic analysis in volcanic areas, marine deposits are adopted as a powerful means of correlation by adopting the unconformity-bounded concept. They are interpreted as transgressive deposits formed during main sea-level highstands and are bounded by sub-horizontal unconformities: the basal unconformity is the marine erosion surface formed during the sea-level raising, whereas the top unconformity is the surface of subaerial exposure and erosion developed during the following sea-level lowering. In addition, several unconformities formed in relation to endogenous processes of modification of the volcano (quiescence periods, shifting of eruptive centres, ecc.) are introduced at Ustica and hierarchized according to their areal extendibility. First-order unconformities UI and UII bounding MIS 5 marine deposits have a potential regional stratigraphic significance and are documented at Ustica after their first definition across the Aeolian archipelago. Then, five second-order (and one third-order) unconformities with stratigraphic significance for the whole Ustica Island are introduced. The resulting unconformity-bounded stratigraphy allows reconstruction of the geological evolution of Ustica as the result of four successive constructive, relatively short-lived stages of volcanic activity (eruptive epochs), which are separated by longer inter-eruption periods of quiescence when erosion and mass-wasting processes in subaerial and marine environments become prevailing. Most ancient volcanic products dated at more than 750 ka are represented by subaerial pyroclastic deposits emplaced from dilute pyroclastic density currents coming from an eruptive centre located SWwards offshore the Ustica Island. Then, the second and third eruptive epochs document the progressive transition from submarine volcanism (hyaloclastites and pillow lavas) to subaerial eruptive activity with the emplacement of lava products, and of pyroclastic deposits from both dilute and concentrated pyroclastic density currents originated from eruptive centres located in the central sector of Ustica. The fourth and most recent volcanic activity, between 200 and 124 ka, determines the construction of the eccentric Falconiera tuff cone, located in the NE portion of the island. The Ustica Island is inactive during the last 124 ka, and is charaterized by diffuse and recurrent subaerial erosion and reworking

Unconformity-bounded units and terraced marine deposits as stratigraphic tools at Ustica (Southern Tyrrhenian Sea)

none3The Unconformity-bounded units are employed for the reconstruction of the geological evolution of the Ustica Island as the result of the interaction between volcanic activity, tectonics, and sea-level fluctuations. The Ustica Island is located in the Southern Tyrrhenian sea in the eastern sector of the Sicilian-Maghrebian Chain. It mainly consists of volcanic products, basaltic to trachitic in composition and belonging to a sodic-alkaline series and, subordinately, of marine deposits (conglomerates, sands and fossiliferous sediments) belonging to a well-preserved series of terraces intercalated within the volcanic succession. Seven successive raised paleo-shorelines are recognized at elevation ranging from 115 m to 8 m a.s.l and are attributed to major sea-level highstand peaks by means of stratigraphic relationships with dated volcanic products, relative dating of fossils and relative chronostratigraphic attribution: paleoshoreline I is attributed to marine oxygen-isotope stage (MIS) 13, paleoshoreline II and III to distinct peaks during MIS 9, paleoshorelines IV, V and VI to MIS 7, paleoshoreline VII order (a, b, c) to MIS 5. Following modern stratigraphic procedures to stratigraphic analysis in volcanic areas, marine deposits are adopted as a powerful means of correlation by adopting the unconformity-bounded concept. They are interpreted as transgressive deposits formed during main sea-level highstands and are bounded by sub-horizontal unconformities: the basal unconformity is the marine erosion surface formed during the sea-level raising, whereas the top unconformity is the surface of subaerial exposure and erosion developed during the following sea-level lowering. In addition, several unconformities formed in relation to endogenous processes of modification of the volcano (quiescence periods, shifting of eruptive centres, ecc.) are introduced at Ustica and hierarchized according to their areal extendibility. First-order unconformities UI and UII bounding MIS 5 marine deposits have a potential regional stratigraphic significance and are documented at Ustica after their first definition across the Aeolian archipelago. Then, five second-order (and one third-order) unconformities with stratigraphic significance for the whole Ustica Island are introduced. The resulting unconformity-bounded stratigraphy allows reconstruction of the geological evolution of Ustica as the result of four successive constructive, relatively short-lived stages of volcanic activity (eruptive epochs), which are separated by longer inter-eruption periods of quiescence when erosion and mass-wasting processes in subaerial and marine environments become prevailing. Most ancient volcanic products dated at more than 750 ka are represented by subaerial pyroclastic deposits emplaced from dilute pyroclastic density currents coming from an eruptive centre located SWwards offshore the Ustica Island. Then, the second and third eruptive epochs document the progressive transition from submarine volcanism (hyaloclastites and pillow lavas) to subaerial eruptive activity with the emplacement of lava products, and of pyroclastic deposits from both dilute and concentrated pyroclastic density currents originated from eruptive centres located in the central sector of Ustica. The fourth and most recent volcanic activity, between 200 and 124 ka, determines the construction of the eccentric Falconiera tuff cone, located in the NE portion of the island. The Ustica Island is inactive during the last 124 ka, and is charaterized by diffuse and recurrent subaerial erosion and reworking.noneRuggeri G.; Lucchi F.; Tranne C.A.Ruggeri G.; Lucchi F.; Tranne C.A

New chronostratigraphic constraints for the eruptive history of Alicudi volcano (Aeolian archipelago, Italy)

By adopting an unconformity-bounded stratigraphic approach, raised terraced marine deposits developed during marine isotope stages (MIS) 5c-5a (100-81 ka) provide new insights into the late Quaternary eruptive history of Alicudi volcano (Aeolian archipelago, southern Italy). Given the occurrence of widespread Brown Tuffs tephra-layers (<70 ka) from Vulcano Island, marine deposits allow identification of the inter-island-scale allogenic unconformities UII, UI and L3, driven by sea-level fluctuations. These unconformities make possible effective correlation of the volcanic succession of Alicudi with the stratigraphic sequences of volcanic rocks on the other islands of the Aeolian archipelago. Combined with four autogenic unconformities of volcanic and volcano-tectonic origin (A1, A2, A3, aa), the allogenic unconformities are regarded as a tool for reconstructing the geological evolution of Alicudi volcano, as the result of the interaction between local and external volcanism, volcano-tectonic processes and sea-level oscillations. Refined morphostratigraphy between marine deposits and volcanic products, combined with re-examination of available radiometric ages, indicates that a large part of volcano development occurred in the course of the last interglacial (=MIS 5), between 120-110 ka (age of the oldest exposed volcanic rocks) and 110-81 ka. Over this period of time, volcanism was characterized by constant localisation of eruptive vents in the summit area, homogeneous effusive to strombolian explosive eruptive style and progressive slight chemical differentiation of the erupted products (from CA basalts to andesites). The eruptive history of Alicudi was repeatedly interrupted by prolonged periods of dormancy and three distinct and successive episodes of volcano-tectonic collapse of the summit volcano. The most recent volcanic activity occurred in the late Pleistocene (~41-26 ka), with the emplacement of high-K CA endogenous lava domes, filling the morphologic depression related to the latest summit collapse, and of several lava flows descending the south-eastern flanks of Alicudi volcano

Educational strategy aimed at enjoying a volcanic geosite: the active Vulcano island growing between fire and water

none3In the meanframe of the “EDU-GEO” Project sponsored by FIST, we propose a prototype of a geological field excursion across the active Vulcano island (Aeolian archipelago) which provides a 130 ka old outstanding record of building and destruction processes in volcanic terranes and of ongoing volcanic phenomena. Studied since at least the 18th century, the Vulcano Island is the paradigm of the Vulcanian type of eruptions and has featured significantly in the vulcanological literature for more than 200 years, still continuing to provide a fundamental field for volcanological studies of on-going development of landforms. The excursion is focused on mature high-school students (17-19 years old) and on their teachers by means of an appropriate educational strategy based on high scientific content. We believe that Vulcano is an excellent field example for introducing Volcanology to students because it addresses all main criteria in the geosites definition suggested by European ProGeo that is: 1) representativeness; 2) scientific interest; 3) rarity; 4) landscape importance; 5) educational value; 6) accessibility; 7) conservation standing; 8) vulnerability. The whole excursion is performed on the field because landforms and deposits are perfectly exposed at Vulcano, whereas introductory concepts are provided through the Internet by guidelines for teachers and lecture notes for students. We aim at improving students knowledge of rocks and landforms as tools for studying a volcanic area through a typical scientific approach based on the objective observation of field data and their consequent interpretation. So, independent observation and interpretation by the students are always stimulated by means of cause-effect examples and of comparison with other reknown examples. The following main geological aspects of a volcanic area are addressed at Vulcano: 1) building and destruction of a volcano; 2) origin and emplacement mechanisms of volcanic deposits; 3) criteria for the evaluation of volcanic hazard and risk. The first part of the excursion is focused on the fundamental stages of birth and evolution of the Vulcano island by means of an easily accessible (even for disable people) route from the harbour of Vulcano to the base of the La Fossa cone. The route consists of a few stops which are especially meaningful for the high degree of exposure of landforms aimed at showing a logically set out sequence of geological events from the progressive emergence of the volcanic island (e.g. the 2000 years old Vulcanello peninsula) to its subaerial stabilization (e.g. the 6000 years old and still active La Fossa cone). Traces of main caldera collapses displacing the volcanic apparatus are shown so to highlight the role of destructive events in the evolution of a volcano. The second part of the excursion is developed across the footpath that goes to the summit crater of La Fossa. There, detailed observation of lavic and pyroclastic deposits is possible and the connection to the corresponding source of provenance and emplacement mechanisms (effusive activity, fallout processes, pyroclastic density currents) is explained. Finally, the last part of the excursion is performed across the summit crater of the La Fossa cone with the purpose of showing main procedures of geochemical monitoring (e.g. the crateric high-T gas fumaroles) and evaluation of volcanic hazard from pyroclastic currents.mixedForni F.; Lucchi F.; Tranne C.A.Forni F.; Lucchi F.; Tranne C.A

Educational strategy aimed at enjoying a volcanic geosite: the active Vulcano island growing between fire and water

In the meanframe of the \u201cEDU-GEO\u201d Project sponsored by FIST, we propose a prototype of a geological field excursion across the active Vulcano island (Aeolian archipelago) which provides a 130 ka old outstanding record of building and destruction processes in volcanic terranes and of ongoing volcanic phenomena. Studied since at least the 18th century, the Vulcano Island is the paradigm of the Vulcanian type of eruptions and has featured significantly in the vulcanological literature for more than 200 years, still continuing to provide a fundamental field for volcanological studies of on-going development of landforms. The excursion is focused on mature high-school students (17-19 years old) and on their teachers by means of an appropriate educational strategy based on high scientific content. We believe that Vulcano is an excellent field example for introducing Volcanology to students because it addresses all main criteria in the geosites definition suggested by European ProGeo that is: 1) representativeness; 2) scientific interest; 3) rarity; 4) landscape importance; 5) educational value; 6) accessibility; 7) conservation standing; 8) vulnerability. The whole excursion is performed on the field because landforms and deposits are perfectly exposed at Vulcano, whereas introductory concepts are provided through the Internet by guidelines for teachers and lecture notes for students. We aim at improving students knowledge of rocks and landforms as tools for studying a volcanic area through a typical scientific approach based on the objective observation of field data and their consequent interpretation. So, independent observation and interpretation by the students are always stimulated by means of cause-effect examples and of comparison with other reknown examples. The following main geological aspects of a volcanic area are addressed at Vulcano: 1) building and destruction of a volcano; 2) origin and emplacement mechanisms of volcanic deposits; 3) criteria for the evaluation of volcanic hazard and risk. The first part of the excursion is focused on the fundamental stages of birth and evolution of the Vulcano island by means of an easily accessible (even for disable people) route from the harbour of Vulcano to the base of the La Fossa cone. The route consists of a few stops which are especially meaningful for the high degree of exposure of landforms aimed at showing a logically set out sequence of geological events from the progressive emergence of the volcanic island (e.g. the 2000 years old Vulcanello peninsula) to its subaerial stabilization (e.g. the 6000 years old and still active La Fossa cone). Traces of main caldera collapses displacing the volcanic apparatus are shown so to highlight the role of destructive events in the evolution of a volcano. The second part of the excursion is developed across the footpath that goes to the summit crater of La Fossa. There, detailed observation of lavic and pyroclastic deposits is possible and the connection to the corresponding source of provenance and emplacement mechanisms (effusive activity, fallout processes, pyroclastic density currents) is explained. Finally, the last part of the excursion is performed across the summit crater of the La Fossa cone with the purpose of showing main procedures of geochemical monitoring (e.g. the crateric high-T gas fumaroles) and evaluation of volcanic hazard from pyroclastic currents

Geological map of the island of Filicudi, scale 1:10 000 (Aeolian archipelago)

Carta geologica dell'isola di Filicudi a scala 1:10000 basata su un approccio stratigrafico che prevede l'utilizzo di diverse unit\ue0 stratigrafiche (litostratigrafiche, litosomi, unit\ue0 a limiti inconformi). La ricostruzione stratigrafica \ue8 baqsata su rilevamento geologico e strutturale ed analisi remote sensing, in combinazione con et\ue0 radiometriche e tefrocronologiche, dati petrochimici dei corpi rocciosi ed assetto morfostrutturale di terrazzi marini di et\ue0 tardo-Quaternaria. La storia eruttiva \ue8 descritta in termini di unit\ue0 di attivit\ue0 vulcanica ed unit\ue0 eruttiv

Stratigraphic approach to geological mapping of the late-Quaternary volcanic island of Lipari (Aeolian archipelago, Southern Italy).

Geological mapping of the island of Lipari at a 1:10,000 scale is performed by adopting a stratigraphic approach based on the integrated use of lithostratigraphic units, lithosomes, and unconformity-bounded units (UBU). This approach allows the geological peculiarity of this volcanic area to be reproduced through documenting and interpreting the different rock types (using lithostratigraphic units), and defining the geometry of rock bodies (using lithosomes), or highlighting unconformities in the volcano-sedimentary architecture (using UBUs). In particular, by concentrating on accurate tephrostratigraphy and deposits formed during periods of prolonged volcanic quiescence (e.g. marine deposits and epiclastic products), UBUs provide the main stratigraphic constraints at regional level. Two first-order unconformities (UI and UII), represented by surfaces of erosion bounding marine deposits emplaced during marine oxygen-isotope stage (MIS) 5, can be correlated across most of the Aeolian archipelago. Furthermore, four second-order and seven third-order unconformities represented by erosion and non-deposition surfaces formed during main periods of dormancy 2 or minor sea-level fluctuations of MIS 5 are introduced. The reconstructed unconformitybounded stratigraphy, together with other rock-stratigraphic units, provides an effective reconstruction of the geological evolution of Lipari, ranging between ca. 220 ka and the present time, as the result of the interplay between volcanic activity of local and external provenance, sea-level fluctuations, and regional fault systems. In this framework, Lipari\u2019s eruptive history encompasses five successive eruptive epochs characterized by distinctive centres of eruption (eastwards shifting), eruption type (from mainly strombolian to hydromagmatic), and chemical composition (from calcalkaline basalt-andesite to high-K calcalkaline rhyolite)

Realizzazione ed informatizzazione dei Fogli Geologici alla scala 1:50.000 n\ub0577 bis \u201cIsole di Stromboli e Panarea\u201d, n\ub0580 bis \u201cIsole di Alicudi e Filicudi\u201d, n\ub0581/586 \u201cIsole di Salina, Lipari e Vulcano\u201d

Realizzazione, informatizzazione e stampa, in unico Foglio geologico denominato \u201cIsole Eolie\u201d, comprensivo dei fogli alla scala 1: 50.000 n. 577 bis \u201cIsole di Stromboli e Panarea\u201d, n. 580 bis \u201cIsole di Alicudi e Filicudi\u201d e n. 581/586 \u201cIsole di Salina, Lipari e Vulcano\u201