Paola Del Carlo

Reconstructing the eruptive history of Antarctic volcanoes is often challenging due to limited outcrops exposure, extensive ice cover, and extreme environmental conditions. Here, we present detailed volcanological, textural, and geochemical analyses of three tephra layers (DPT 1, DPT 2, and DPT 3) from an englacial ice sequence at 2581 m asl on the southwest flank of Mount Melbourne, northern Victoria Land (Antarctica). Using robust statistical methods, including cluster analysis and data visualization approaches based on dimensionality reduction [i.e., principal component analysis (PCA) and t-distributed stochastic neighbor embedding (t-SNE)], we identified a previously unrecognized sequence of explosive eruptions. Our findings underscore the crucial role of ice in preserving volcanic records and highlight the potential of tephra investigations to enhance our understanding of magma evolution and volcanic hazard in remote environments. The geochemical characterization, including major and trace element analyses, confirmed that the tephra layers originated from Mount Melbourne but represent three distinct eruptive events not previously documented. The DPT 1 layer is interpreted as a fallout deposit from a more intense eruption (possibly Subplinian), while DPT 2 and DPT 3 layers were produced by less energetic events occurring in close succession. Although precise dating was not possible, the stratigraphic context suggests a recent, potentially historical age for these eruptions. This study refines the eruptive history of Mount Melbourne and emphasizes the importance of englacial tephra records for understanding Antarctic volcanism.

Fe-rich filamentary textures are almost ubiquitous in products from explosive eruptions at basaltic volcanoes and, in particular, they characterize the groundmass of ash and lapilli emitted during high-energy events. Here, we present a multidisciplinary study integrating petrological analyses with computational fluid dynamics simulations to propose a new mechanism responsible for their formation. Detailed textural and compositional features of Fe-rich filaments were examined in the products of explosive eruptions with different intensities from Stromboli and Etna (Italy) volcanoes. Results reveal that they represent compositional boundary layers developed at the plagioclase-melt interface in response to the interaction between magmas with different compositions and volatile contents. Numerical simulations indicate that boundary layers can detach from crystals and disperse into resident melts due to their higher density and can survive as metastable melts for some days under magmatic conditions. We suggest that Fe-rich filaments testify to the recharging of deep magma a few days before high-energy explosive events at basaltic open-vent volcanoes, even when primitive magmas are not erupted.

Five tephra layers named BRH1 to 5 were sampled in an ice cliff located on the north-eastern flank of Mount Melbourne (northern Victoria Land, Antarctica). The texture, componentry, mineralogy, and major and trace element compositions of glass shards have been used to characterize these layers. These properties suggest that they are primary fall deposits produced from discrete eruptions that experienced varying degrees of magma/water interaction. The major and trace element glass shard analyses on single glass shards indicate that Mount Melbourne Volcanic Field is the source of these tephra layers and the geochemical diversity highlights that the eruptions were fed by compositionally diverse melts that are interpreted to be from a complex magma system with a mafic melt remobilizing more evolved trachy-andesitic to trachytic magma pockets. Geochemical compositions, along with textural and mineralogical data, have allowed correlations between two of the englacial tephra and distal cryptotephra from Mount Melbourne, recovered within a marine sediment core in the Edisto Inlet (~ 280 km northeast of Mount Melbourne), and constrain the age of these englacial tephra layers to between the third and the fourth century CE. This work provides new evidence of the intense historical explosive activity of the Mount Melbourne Volcanic Field and better constrains the rates of volcanism in northern Victoria Land. These data grant new clues on the eruptive dynamics and tephra dispersal, and considerably expand the geochemical (major and trace elements) dataset available for the Mount Melbourne Volcanic Field. In the future, this will facilitate the precise identification of tephra layers from this volcanic source and will help define the temporal and spatial correlation between Antarctic records using tephra layers. Finally, this work also yields new valuable time-stratigraphic marker horizons for future dating, synchronization, and correlations of different palaeoenvironmental and palaeoclimatic records across large regions of Antarctica.

The impacts on ostracods and foraminifers caused by three Late Quaternary ashfalls of different intensities and recovered in the ANTA02-NW2 core sediments (Drygalski Basin, western Ross Sea) were analysed for the first time. Albeit with different timing, both associations demonstrated similar response patterns associated with the deposition of material from volcanic eruptions. In particular, based on the palaeontological evidence, it was possible to divide the cores into four intervals/phases recording the evolution of the ecosystem before and after the deposition events: (1) Pre-extinction phase (high abundance and high diversity values). (2) Extinction phase, characterised by the complete disappearance of ostracod fauna; the foraminiferal assemblage, although not entirely absent, records extremely low values of abundance and diversity (survivor assemblage). (3) Recovery phase (increasing abundance and diversity values), characterised by the recolonisation of some opportunistic taxa; species such as Australicythere devexa and Australicythere polylyca dominate the ostracod assemblage. (4) Post-extinction phase (high abundance and high diversity values), with the return to an environmental equilibrium characterised by the colonisation of specialised taxa such as Argilloecia sp., Cytheropteron sp., Echinocythereis sp., and Hemicytherura spp. Our results may aid in the understanding of how communities (i.e., ostracods and foraminifers) recovered after the impact of direct deposits of volcanic ash into ocean waters. The mechanisms by which disappearance and/or mortality was induced are still not clear. The release of toxic metals during the reaction of the volcanic ash with seawater, the resulting chemical alteration in the seawater, and the change in pH, together with the possible suppression of planktonic organisms, may have caused the two main extinction phases recorded by the ANTA02-NW2 core sediments.

We report on the ash cloud related to the gravitational collapse of a portion of the Stromboli volcano crater rim that occurred on 19 May 2021. The collapse produced a pyroclastic density current (PDC) that spread along the northwest flank of the volcano and propagated in the sea for about 1 km. The PDC was associated with a convective ash cloud that rapidly dispersed eastward and deposited a thin layer (< 1 mm) of very fine pinkish ash over the village of Stromboli. The deposit was sampled shortly after the emplacement (within a few hours) and prior to any significant reworking or re-sedimentation. We present a comprehensive description of the deposit including dispersal, sedimentological characteristics and textural and geochemical features. We also compare the 19 May 2021 deposit with fine-ash deposits connected to other PDCs and landslides previously occurring at Stromboli and with the distal ash of a paroxysmal explosive eruption of Mt. Etna volcano. Results indicate that the distributions of the mass on the ground and of the grain size are not correlated with the distance from the source. Also, the componentry reflects a preponderance of remobilized material ingested by the PDC. Therefore, the great amount of fine ash can be ascribed to clasts comminution processes, although the prevalence of dense crystalline components records an overall equiaxial shape, revealing a paucity of elongated clast with complex morphology. Furthermore, the outcomes of this work aim to create a collection of data of a co-PDC ash cloud that may prove useful for comparison with other deposits worldwide.

We present a full characterization of a 20 cm‐thick tephra layer found intercalated in the marine sediments recovered at Site U1524 during International Ocean Discovery Program (IODP) Expedition 374, in the Ross Sea, Antarctica. Tephra bedforms, mineral paragenesis, and major‐ and trace‐element composition on individual glass shards were investigated and the tephra age was constrained by ⁴⁰Ar‐³⁹Ar on sanidine crystals. The ⁴⁰Ar‐³⁹Ar data indicate that sanidine grains are variably contaminated by excess Ar, with the best age estimate of 1.282 ± 0.012 Ma, based on both single‐grain total fusion analyses and step‐heating experiments on multi‐grain aliquots. The tephra is characterized by a very homogeneous rhyolitic composition and a peculiar mineral assemblage, dominated by sanidine, quartz, and minor aenigmatite and arfvedsonite‐riebeckite amphiboles. The tephra from Site U1524 compositionally matches with a ca. 1.3 Ma, rhyolitic pumice fall deposit on the rim of the Chang Peak volcano summit caldera, in the Marie Byrd Land, located ca. 1,300 km from Site U1524. This contribution offers important volcanological data on the eruptive history of Chang Peak volcano and adds a new tephrochronologic marker for the dating, correlation, and synchronization of marine and continental early Pleistocene records of West Antarctica.

The continental margin is a key area for studying the sedimentary processes related to the advance and retreat of the Ross Ice Shelf (Antarctica); nevertheless, much remains to be investigated. The aim of this study is to increase the knowledge of the last glacial/deglacial dynamics in the Central Basin slope–basin system using a multidisciplinary approach, including integrated sedimentological, micropaleontological and tephrochronological information. The analyses carried out on three box cores highlighted sedimentary sequences characterised by tree stratigraphic units. Collected sediments represent a time interval from 24 ka Before Present (BP) to the present time. Grain size clustering and data on the sortable silt component, together with diatom, silicoflagellate and foraminifera assemblages indicate the influence of the ice shelf calving zone (Unit 1, 24–17 ka BP), progressive receding due to Circumpolar Deep Water inflow (Unit 2, 17–10.2 ka BP) and (Unit 3, 10.2 ka BP–present) the establishment of seasonal sea ice with a strengthening of bottom currents. The dominant and persistent process is a sedimentation controlled by contour currents, which tend to modulate intensity in time and space. A primary volcanic ash layer dated back at around 22 ka BP is correlated with the explosive activity of Mount Rittmann.

We review here data and information on Antarctic volcanism resulting from recent tephrostratigraphic investigations on marine cores. Records include deep drill cores recovered during oceanographic expeditions: DSDP, ODP and IODP drill cores recovered during ice-based and land-based international cooperative drilling programmes DVDP 15, MSSTS-1, CIROS-1 and CIROS-2, DVDP 15, CRP-1, CRP-2/2A and CRP-3, ANDRILL-MIS and ANDRILL-SMS, and shallow gravity and piston cores recovered in the Antarctic and sub-Antarctic oceans. We report on the identification of visible volcaniclastic horizons and, in particular, of primary tephra within the marine sequences. Where available, the results of analyses carried out on these products are presented. The volcanic material identified differs in its nature, composition and emplacement mechanisms. It was derived from different sources on the Antarctic continent and was emplaced over a wide time span. Marine sediments contain a more complete record of the explosive activity from Antarctic volcanoes and are complementary to those obtained by land-based studies. This record provides important information for volcanological reconstructions including approximate intensities and magnitudes of eruptions, and their duration, age and recurrence, as well as their eruptive dynamics. In addition, characterized tephra layers represent an invaluable chronological tool essential in establishing correlations between different archives and in synchronizing climate records.