Description: The youngest (last 1500 years) volcanic eruptions of Lipari, within the Aeolian Archipelago, produced the prominent pumice cone of Monte Pilato and the obsidian lava flows of Rocche Rosse and Forgia Vecchia, concentrated in the north-eastern sector of the island as well as highly dispersed white-coloured, fine-grained tephra layers of rhyolitic composition in terrestrial and marine settings on the regional scale. Here we describe in detail the stratigraphy of pyroclastic successions and lava flows erupted by different vents - Monte Pilato, Forgia Vecchia, Lami, and Rocche Rosse - combining field observations, sedimentological characteristics of the tephra deposits, and major and trace element compositions of the volcanic glass. All the pyroclastic materials consist of aphyric pumice lapilli and ash with a largely homogeneous rhyolitic composition. The Monte Pilato and Forgia Vecchia deposits primarily consist of highly vesicular pumice fragments and subordinate obsidian clasts, whilst Rocche Rosse and Lami are characterized by moderately vesicular juvenile fragments with a more significant fraction of obsidian. The Lami tephra also contains peculiar pumice clasts with a fibrous texture and breadcrust bombs. Stratigraphic relationships, and paleomagnetic and 14C ages of the lava and pyroclastic deposits are combined with the archaeological information and historical reports, enabling us to provide an accurate chrono-stratigraphic framework for the youngest eruptions of Lipari. Following the 8th century CE eruption of Monte Pilato, which produced a pumice cone and a obsidian lava flow, activity resumed in the second half of 13th century CE with the explosive eruption of Forgia Vecchia that culminated in the emission of a bilobate obsidian lava flow. This eruption was shortly followed by the explosive eruptions of Lami and Rocche Rosse, the latter concluded with the emission of the widely renowned obsidian lava flow. By integrating stratigraphy and geochemistry of tephra deposits with a new chronological scheme, our work facilitates the refinement of proximal-to-distal correlation of Lipari's rhyolitic tephra in continental marine environments of the central Mediterranean area in the last 1500 years. A fine-grained, rhyolitic ash found on Stromboli (~40 km NE from Lipari) has an origin from the Monte Pilato and thus, constrains tephra dispersion towards the NE. Very similar ash beds dispersed southwards and interlayered within the near-source deposits of La Fossa, Vulcano island (~10 km from Lipari) exhibit features that are consistent with the younger activities of the Rocche Rosse eruption. A possible link between previously identified rhyolitic ash layers identified in marine cores of the Ionian Sea and the Forgia Vecchia eruption are postulated, although the age and textural characteristics of these distal tephra are not univocal in indicating a correlation to either Monte Pilato or Forgia Vecchia.

Description: Published

Description: 107397

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: JCR Journal

Description: In Antarctica, the near-source exposures of volcanic eruption deposits are often limited as they are not well preserved in the dynamic glacial environment, thus making volcanological reconstructions of explosive eruptions extremely challenging. Fortunately, pyroclastic deposits from explosive eruptions are preserved in Southern Ocean sediments surrounding Antarctica, and the tephrostratigraphy of these sequences offers crucial volcanological information including the timing and tempo of past eruptions, their magnitude, and eruption dynamics. Here we report the results of a tephrostratigraphy and tephrochronology study focused on four sediment cores recovered from the Wood Bay area in the western Ross Sea, Antarctica. In all these sedimentary sequences, we found a well-stratified primary tephra of considerable thickness, up to 80 cm, hereafter named the Aviator Tephra (AVT). According to the characteristics of the tephra deposit and its distribution, the AVT was associated with an eruption of considerable intensity, potentially representing one of the largest Holocene eruptions recorded in Antarctica. Based on the major and trace element geochemistry and the mineral assemblage of the tephra, Mount Rittmann was identified as the source of the AVT. A Holocene age of ∼11 ka was determined by radiocarbon dating organic material within the sediments and 40Ar-39Ar dating of alkali-feldspar crystals included in the tephra. Eruption dynamics were initially dominated by hydromagmatic magma fragmentation conditions producing a sustained, relatively wet and ash-rich eruptive cloud. The eruption then evolved into a highly energetic, relatively dry magmatic Plinian eruption. The last phase was characterized by renewed efficient magma-water interaction and/or collapse of the eruptive column producing pyroclastic density currents and associated co-ignimbritic plumes. The distal tephra deposits might be linked to the widespread lag breccia layer previously identified on the rim of the Mount Rittmann caldera which share the same geochemical composition. Diatoms found in the sediments surrounding the AVT and the primary characteristics of the tephra indicate that the Wood Bay area was open sea at the time of the eruption, which is much earlier than previously thought. AVT is also an excellent tephrostratigraphic marker for the Wood Bay area, in the Ross Sea, and a useful marker for future synchronization of continental ice and marine archives in the region.

Description: Published

Description: 106629

Description: 1V. Storia eruttiva

Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici

Description: 1A. Geomagnetismo e Paleomagnetismo

Description: 5A. Ricerche polari e paleoclima

Description: JCR Journal

Description: We report on the characterization of a thick sequence of pyroclastic deposits exposed on the summit area and flanks of Mount Melbourne volcano, in northern Victoria Land, Antarctica related to eruptions during the Late Glacial period. We provide a complete characterization of tephra deposits including mineralogy, single shard major- and trace-element glass compositions, and an 40Ar-39Ar age of feldspar crystals extracted from the deposit. The pyroclastic deposits are trachybasaltic to trachytic in composition and are interpreted to have resulted from four Strombolian/Vulcanian to sub-Plinian/Plinian eruptions. The younger and more intense sub-Plinian/Plinian eruption (our eruption 2) yielded an 40Ar-39Ar age of 13.5 ± 4.3 ka (±2σ). The study of Mount Melbourne proximal deposits provides significant new data for the reconstruction of the volcano eruptive history and a better assessment of the volcanic risk connected to a possible future eruption. We also explore geochemical correlations between Mount Melbourne proximal deposits and distal tephra layers recognized in ice cores and blue ice fields of East Antarctica. A good geochemical match exists between the composition of products from the trachytic sub-Plinian/Plinian eruption 2 and some tephra layers from Talos Dome and shards in Siple Dome which is also compatible in age (c. 9.3 ka) with our 40Ar-39Ar age determination. Our new insights into the volcanic history of Mount Melbourne and the new high-quality electron microprobe and trace element composition data on its proximal products will help improve future correlations and synchronization of tephra archives in the region.

Description: Published

Description: 107457

Description: 1V. Storia eruttiva

Description: JCR Journal