Element Composition Of Glass Shards Research Articles

New evidence of the Green Tuff deposits and post-caldera, recent explosive volcanic activity at Pantelleria volcano (Sicily Channel, Italy) recorded in near-vent marine areas

The record of the explosive activity of Pantelleria volcano is well documented by several distal tephra collected in various areas in and around the Mediterranean, while few tephrochronological studies exist on proximal marine areas. In this paper, we investigate three selected coring sites from the northern shoulder of the Pantelleria graben, about 15–30 km from the island, in near-vent position with respect to that volcanic source. Our multiproxy analyses revealed nine tephra layers, totally composed of juvenile materials, mostly ash and pumice fragments, as well as a coarse-grained tephra deposit at the bottom of one of the cores. The major element composition of glass shards indicates a very homogeneous geochemical composition for the tephra layers, suggesting their primary origin. Using litho-stratigraphic and paleoenvironmental proxies, we associated the tephra layers to the latest (<∼13.7 ka) explosive activity of Pantelleria. The coarse-grained deposit, instead, due to its distinctive composition is considered to represent the near-vent, marine equivalent of the distal Y-6 tephra layer, related to the ∼45 ka old co-ignimbrite fallout deposit of the Green Tuff event. The geochemical characterization of such deposit, mostly rhyolitic and partly trachytic, appears to enlarge the bimodal composition recorded in other distal tephra (Y-6) reported in the literature, highlighting the potential of near-vent record in providing additional information on the eruptive history.

Historical explosive activity of Mount Melbourne Volcanic Field (Antarctica) revealed by englacial tephra deposits

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.

Holocene tephra record of Lake Veliko jezero, Croatia: implications for the central Mediterranean tephrostratigraphy and sea level rise

Core M1‐A from Mljet Island, Croatia, was retrieved from a submerged sinkhole to investigate tephra and reconstruct past sea levels. Eleven tephra layers were found, out of which six are macroscopically visible, while five are cryptotephra. For two of the tephra layers, glass shard concentrations were below the critical amount necessary for reliable analysis, while two more originated from a stratigraphical interval likely disturbed by drilling operations. Major and trace element compositions of glass shards were determined by wavelength dispersive spectroscopy (WDS) using an electron microprobe analyser (EMPA) and by laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS). The tephra discrimination relied on a novel approach based on a multivariate analysis of element selection and the use of log‐ratio scatterplots and common bivariate plots. The results enabled correlation of five tephra to known eruptions originating from Somma‐Vesuvius and Campi Flegrei. Specifically, we identified Avellino Pumice, Mercato, Agnano Monte Spina and Neapolitan Yellow Tuff, extending known distributions for Avellino and Agnano Monte Spina. Moreover, our findings possibly support an earlier proposition that Agnano Monte Spina tephra originated from two eruptions with a pause of a few decades in between. Based on the tephra correlations and radiocarbon dating, an age‐depth model was compiled that provided chronological constraints for the sea level during the formation of the lake (10.7 cal. kaBP, 49 m b.s.l.) and sea intrusion (2.3 cal. kaBP, 2.5 m b.s.l.).

Rittmann volcano, Antarctica as the source of a widespread 1252 ± 2 CE tephra layer in Antarctica ice

Tephra occur in many ice cores from Antarctica and are important time markers that assist in correlations between cores and in dating their valuable climate records. Major element compositions of glass shards in a trachytic tephra found in ice cores drilled at WAIS Divide, Roosevelt Island and Styx Glacier, and blue ice patches at Brimstone Peak and the Rennick Glacier in Victoria Land, are similar and suggest they are the same tephra. The composition of the tephra is also similar to tephra layers reported in 3 others ice cores from the East and West Antarctica Ice Sheets. In the WAIS Divide WDC06A ice core the tephra is dated as 1252±2 CE. The distribution of the tephra implies a source in northern Victoria Land, Antarctica. The Pleiades, Mt. Melbourne and Rittmann volcano in northern Victoria Land all have evidence of recent eruptive activity which has resulted in the occurrence of trachytic tephra in ice cores, blue ice/snow areas and as surficial tephra layers. Although there is a significant area of geothermal activity at Mt. Rittmann, until now there has been no evidence of any recent eruptive activity. A pyroclastic breccia, with glassy fiamme-like clasts was formed by an explosive eruption from Rittmann volcano. Analyses of the glass clasts and whole rock analyses of some lava samples have trachytic compositions very similar to the 1252 CE tephra. Rittmann volcano is now considered the source of this tephra, which is here named the Rittmann tephra. Rittmann tephra is spread over 2000 km and the 8 known occurrences makes it the most widely correlated tephra layer in Antarctic ice and a valuable marker layer. The wide distribution implies a large possibly Plinian eruption which makes it the largest known eruptions from any Holocene volcano in the western Ross Sea area. This discovery of young explosive eruptions from Rittmann volcano and other northern Victoria Land volcanoes show that there is a significant volcanic hazard from these volcanoes especially to aircraft operations.

One Million Years tephra record at IODP Sites U1436 and U1437: Insights into explosive volcanism from the Japan and Izu arcs

AbstractThe 1 Myr tephra records of IODP (International Ocean Discovery Program) Holes U1436A and U1437B in the Izu‐Bonin fore‐ and reararc were investigated in order to assess provenance and eruptive volumes, respectively. In total, 304 tephra samples were examined and 260 primary tephra layers were identified. Tephra provenance was determined by means of major and trace element compositions of glass shards and distinguished between Japan and Izu‐Bonin arc origin of the tephra layers. A total of 33 marine tephra compositions were correlated to the Japan arc and 227 to the Izu arc. Twenty marine tephra layers were correlated between the two drilling sites. Additionally, we defined eleven correlations of marine tephra deposits to major widespread Japanese eruptions; from the 1.05 Ma Shishimuta‐Pink Tephra to the 30 ka Aira‐Tn Tephra, both from Kyushu Island. These eruptions provide independent time markers within the sediment record and six correlations were used to date tephra layers from Japan in Hole U1436A to establish an alternative age model for this hole. Furthermore, the minimum distal tephra volumes of all detected events were calculated, which enabled the comparison of the tephra volumes that derived from the Japan and the Izu‐Bonin arcs. For some of the major Japanese eruptions these are the first volume estimations that also include distal deposits. All of the Japanese tephras derived from events with eruption magnitude Mv ≥ 5.6 and three of the investigated eruptions reach magnitudes Mv ≥ 7. Volcanic events of the Izu‐Bonin arc have mostly eruption magnitudes Mv ≤ 5.

Tephrostratigraphy of Changbaishan volcano, northeast China, since the mid-Holocene

A detailed tephrostratigraphy of an active volcano is essential for evaluating its eruptive history, forecasting future eruptions and correlation with distal tephra records. Changbaishan volcano is known for its Millennium eruption (ME, AD 940s; VEI 7) and the ME tephra has been detected in Greenland ice cores ∼9000 km from the vent. However, the pre-Millennium (pre-ME) and post-Millennium (post-ME) eruptions are still poorly characterized. In this study, we present a detailed late Holocene eruptive sequence of Changbaishan volcano based on single glass shard compositions from tephra samples collected from around the caldera rim and flanks. Tephra ages are constrained by optically stimulated luminescence (OSL) and AMS 14C dates. Tephra from the mid-Holocene pre-ME eruption can be divided into two pyroclastic fall subunits, and it cannot be correlated with any known Changbaishan-sourced tephra recorded in the Japan Sea based on major element composition of glass shards, such as the B-J (Baegdusan-Japan Basin) and B-V (Baegdusan-Vladivostok-oki) tephras. ME pyroclastic fall deposits from the caldera rims and volcanic flanks can be correlated to the juvenile pumice lapilli or blocks within the pyroclastic density current (PDC) deposits deposited in the valleys around the volcano based on glass shard compositions. Our results indicate that the glass shard compositions of proximal ME tephra are more varied than previously thought and can be correlated with distal ME tephra. In addition, widely-dispersed mafic scoria was ejected by the ME Plinian column and deposited on the western and southern summits and the eastern flank of the volcano. Data for glass from post-ME eruptions, such as the historically-documented AD 1403, AD 1668 and AD 1702 eruptions, are reported here for the first time. Except for the ME, other Holocene eruptions, including pre-ME and post-ME eruptions, had the potential to form widely-distributed tephra layers around northeast Asia, and our dataset provides a proximal reference for tephra and cryptotephra studies in surrounding areas.

Compositions of glass in proximal tephras from eruptions in the Azores archipelago and their links with distal sites in Ireland

Abstract The Azores archipelago is one of the most active volcanic areas in the North Atlantic region, with approximately 30 eruptions during the last 600 years. The geochemical composition of associated tephra-derived glass is, however, not well characterized. This study presents major element compositions of glass shards from five major eruptives on the Azores: a trachybasaltic eruptive on the island of Faial (Capelinhos AD, 1957) and four explosive trachytic eruptives on the island of Sao Miguel (Fogo A c. 5600 cal yrs. BP, Sete Cidades c. AD 1440, Fogo AD 1563 and Furnas AD 1630). The major element compositions suggest that tephras from three active stratovolcanoes on Sao Miguel, Sete Cidades, Fogo and Furnas, can be distinguished from one another using bi-plots of FeOtot vs. TiO2 and FeOtot vs. CaO. Late Holocene tephras found on Ireland have previously been attributed to eruptions occurring on Jan Mayen but possess a strong geochemical similarity to proximal tephras from the Azores, especially those from the Furnas volcano. The similarity of the proximal tephras on Sao Miguel, especially Furnas AD 1563 and Furnas AD 1630 and distal tephras in Ireland is demonstrated by strong similarity coefficients (>0.95) and the closeness of major element composition. The dominant wind direction over the Azores is favourable for tephra dispersal to western Europe and we suggest that at least three tephras found in Ireland were erupted from the Furnas volcano, and that trachytic tephras erupted from explosive eruptions on Sao Miguel have a potential to contribute to the construction of a European-wide tephrostratigraphic framework.

Tephrostratigraphic studies on a sediment core from Lake Prespa in the Balkans

Abstract. A detailed tephrostratigraphic record, which dates back to Marine Isotope Stage (MIS) 5b (ca. 91 kyr), has been established from a 17.76 m long core (Co1215) from Lake Prespa (Macedonia, Albania and Greece). A total of eleven tephra and cryptotephra layers (PT0915-1 to PT0915-11) were identified, using XRF scanning, magnetic susceptibility measurements, and macro- and microscopic inspection of the sediments. The major element composition of glass shards and/or micro-pumice fragments indicates that the tephras and cryptotephras originate from the explosive volcanism of Italy. Eight tephra and cryptotephra layers were correlated with specific volcanic eruptions: the AD 512 eruption of Somma-Vesuvius (1438 cal yr BP), the Mercato eruption of Somma-Vesuvius (8890 ± 90 cal yr BP), the Tufi Biancastri/LN1-LN2 eruption of the Campi Flegrei (14 749 ± 523 cal yr BP and 15 551 ± 621 cal yr BP), the SMP1-e/Y-3 eruption of the Campi Flegrei (30 000–31 000 cal yr BP), the Campanian Ignimbrite/Y-5 eruption of the Campi Flegrei (39 280 ± 110 cal yr BP), the SMP1-a event of Ischia Island (around 44 000 cal yr BP) and the Green Tuff/Y-6 eruption of Pantelleria Island (around 45 000 cal yr BP). One tephra could be attributed to the volcanic activity of Mount Etna, but probably represents an unknown eruption at ca. 60 000 cal yr BP. Cryptotephras PT0915-6 and PT0915-10 remain unclassified so far, but according to the presented age-depth model these would have been deposited around 35 000 and 48 500 cal yr BP, respectively. Some of the tephras and cryptotephras are recognised for the first time in the Balkan region. The tephrostratigraphic work provides important information about ash dispersal and explosion patterns of source volcanoes and can be used to correlate and date geographically distant paleoenvironmental and archaeological archives in the central Mediterranean region. Moreover, the tephrostratigraphic work in combination with radiocarbon and electron spin resonance (ESR) dating is a precondition for paleoclimatic reconstructions inferred from the sediment succession Co1215.

Widespread tephras in sediments from lake Ichi-no-Megata in northern Japan: Their description, correlation and significance

Lake Ichi-no-Megata is a maar in the Oga Peninsula, which is connected with the western side of Honshu Island, NE Japan. A 37-m long sediment core (IMG06) obtained from the center of the lake contains five fine ash layers. Stratigraphic positions in the core provide ages of five ashes to be 30, 21, 17, 7.3, and 1.0 cal ka BP, respectively. These layers are correlated with Aira-Tn (AT), Daisen-Kusatanihara (D-KsP), Asama-Kusatsu (As-K), Kikai-Akahoya (K-Ah) and Baitoushan-Tomakomai (B-Tm) tephras in ascending order, based on stratigraphy and petrographic characteristics such as grain assemblages, refractive indices, and major element compositions of glass shards. Although the AT, K-Ah and B-Tm tephras have been well known as widespread tephras, this study finds that the D-KsP, As-K and K-Ah tephras have more extensive distributions than the previous studies estimated. The D-KsP and As-K tephras have the potential to become useful time-markers in and around the Sea of Japan between the AT and K-Ah tephras.

Electron microprobe characterization of ash layers in sediments from the central Bransfield basin (Antarctic Peninsula): evidence for at least two volcanic sources

Bransfield Strait, a narrow active rift with three submarine basins, separates the South Shetland Islands from northern Antarctic Peninsula. Volcanism in Bransfield Strait commenced prior to 0.75 Ma and continues, with recent subaerial eruptions at Deception, Bridgeman and Penguin islands, submarine hydrothermal activity and numerous young basaltic seamounts located along the rift axis. Gravity cores were collected from five locations within the central Bransfield basin. Diatomaceous mud interbedded with terrigenous detritus and discrete ash layers up to 10 cm thick are the commonest sediment types in all the cores. The major element compositions of glass shards within the ash layers are, apart from the uppermost layer, compositionally similar to pyroclastic units preserved on Deception Island, a young (&lt;0.75 Ma) active stratovolcano. The uppermost ash layer cannot be closely matched compositionally to any known source in the Antarctic–Scotia Sea–southern South America region. Its presence indicates that a volcanic centre other than Deception Island contributed ash to the Bransfield basin. Based on the shallow stratigraphical position of the compositionally distinctive ash layer, only a few decimetres beneath the seafloor, its source volcano was probably active in historical times (&lt;few hundred years).

Dating the culmination of river aggradation at the end of the last glaciation using distal tephra compositions, eastern North Island, New Zealand

An extensive terrace (Waipaoa-1) that can be traced for about 29 km in the Waipaoa valley, eastern North Island, New Zealand, is underlain by at least 10 m of coarse, aggradational, river gravels. Terrace cover beds contain tephras erupted from central North Island volcanoes and these provide minimum ages for the underlying gravels. Tephra or tephric layers occurring in the lower cover beds were investigated at five sites using a combination of stratigraphy, mineralogy, and the major element composition of glass shards together with discriminant function analysis (DFA). The basal tephra is identified as the ca. 14,700 14C years old (ca. 17,700 cal. years B.P.) Rerewhakaaitu Tephra, erupted from Okataina Volcanic Centre. Using the stratigraphic relationship of Rerewhakaaitu Tephra, the end of aggradation is dated at ca. 15,000 14C years (ca. 18,000 cal. years). Correlation with aggradational terraces elsewhere in North Island and northern South Island indicates that aggradation ended at the same time over a wide area and confirms a climatic origin for the terraces. Subsequent downcutting was apparently rapid because Rerewhakaaitu Tephra also occurs at the base of cover beds on a ca. 15 m lower terrace. The downcutting represents a major change in river dynamics and is most likely the response to climatic change and the resultant upper catchment landscape stability.

A 6500-year-old history of tephra deposition recorded in the sediments of Lake Tutira, eastern North Island, New Zealand

Abstract Lake Tutira is a small lake formed as a result of a landslide about 6500 radiocarbon years BP. It is situated 100 km east, and downwind, of the central North Island volcanoes and has provided a trap for tephras which have erupted since the mid-Holocene. Detailed studies of cores from the lake and adjacent swamps have revealed 23 tephra layers, which represent tephra deposition into Lake Tutira every 300 years on average. Sixteen of these layers are macroscopic and seven are microscopic, occurring as concentrations of volcanic glass. The tephra layers mark rhyolitic and andesitic tephra eruptions from Taupo, Okataina, Egmont, and Tongariro volcanic centres. They were identified using their ferromagnesian mineralogy, major element compositions of glass shards, and their stratigraphic position, particularly with respect to radiocarbon dates. The Lake Tutira tephra record is the most detailed record yet found in eastern North Island, and the detection of microscopic tephra layers indicates the value of lake sediments and swamps as traps for distal tephras.

中国・四国地方の第四紀テフラ研究 広域テフラを中心として

A tephrochronological study has been carried out in the Chugoku and Shikoku Districts, paying special attentions to the widespread marker tephras from Mts. Sanbe and Daisen, as well as tephras from volcanoes in Kyushu. Chemical analysis of the major element composition of glass shards and/or magnetite grains collected from each tephra layer, using the electron microprobe technique, has been quite useful in identifying the individual tephra. The stratigraphy, chronology, and distribution of tephras, and their implications for Late Quaternary events are summarized as follows: (1) Aira Tn (AT; erupted about 25, 000BP), and Kikai Akahoya (K-Ah; erupted about 6, 300BP) ashes, of Kyushu origin, occur as the most distinctive markers. Both are easily identified by the major element composition of their glass shards. The Aso-4 ash is another maker tephra of Kyushu origin, distinguishable by the major element composition of its magnetite. (2) Of the many tephras erupted from Sanbe volcano, the Sanbe Kisuki (SKP), Unnan (SUn), and Ikeda (SIP) pumice layers are the most extensive and representative. The SUn and SIP pumice layers are identified in a marine core taken in the Japan Sea to the north of Tottori, 200km away from Mt. Sanbe. (3) Of the Daisen tephras, the Matsue (DMP), Kurayoshi (DKP) and Kusadanihara (KsP) pumice layers occur most extensively. KsP, of ca 18ka, was recognized in a marine core from the Japan Sea to the west of Sakata City, 600km away from Mt. Daisen. This correlates with the San'in 2 ash. (4) The followings are evident from the relationship of tephrochronology and geomorphic development in the Chugoku and Shikoku Districts: maximum sea level regression in the Late Pleistocene had occurred before the deposition of AT ash in the Izumo Plain; there were three stages of dune sand formation in the San'in District: the first was prior to the deposition of DMP, the second was between the eruptions of DMP and Aso-4, and the third was after the deposition of K-Ah; (5) Some of the unidentified tephras were examined and showed that an ash layer sampled from Pleistocene gravels near Ozu City, Ehime Pref., and one from the lowermost part of the Oetakayama pyroclastic formation in the Tsunozu Group are similar to the Guminoki ash and Yellow III of the Osaka Group respectively, from the viewpoint of the major element composition of glass shards or glassy matrix.