Fresh Glass Research Articles

Earth's longest lava flows erupted from its largest igneous province: The submarine Ontong Java Plateau

We use high-precision analyses of fresh basalt glasses from the submarine, Cretaceous Ontong Java Plateau (OJP) recovered by the Ocean Drilling Programs (ODP) to test for long submarine lava flows. Major elements and Cl show that glasses from ODP Holes 1185B and 1186A, which are 200 km apart, are compositionally identical and must have erupted simultaneously from the same well-mixed magma chamber. Identical CO2 contents show they erupted at the same water depth, but 1185B is directly downslope from 1186A and has a corrected basement depth that is >700 m deeper. Remarkably, <2 °C cooling took place over 200 km, requiring a cooling rate <0.01 °C/km.Further evidence of long flows is the lack of vesicles in OJP's glasses, in contrast to mid-ocean ridge basalt glasses that almost always contain vesicles and are often oversaturated in dissolved CO2. We propose that OJP's lavas degassed to saturation levels of dissolved CO2 +H2O and lost all bubbles because they remained liquid for much longer periods during long distance flow. Dissolved CO2+H2O are used to estimate paleoeruption depths which are compared to current corrected basement depths. Using a fixed value of plateau subsidence (500 m) we reconstruct flow distances of 0 to 900 km for eight lava groups from six drill sites. Eruption depths in Hole 807 C are 3040 m for Kwaimbaita-type lavas but 1110 m for Singgalo-type lavas that directly overlie them suggesting that the Singgalo lavas erupted 900 km away (near Site 1183).Paleoeruption depths for Cretaceous glasses from the Jurassic East Mariana and Nauru Basins adjacent to OJP are shallower than most glasses recovered from OJP even though their reconstructed basement depths are 1500–3800 m deeper. It is very likely that the basins’ lavas were erupted on OJP and flowed up to 1600 km: longer than any lava flow known on Earth. Flow distances are shorter (≤1000 km) if a plateau subsidence of 1500 m is used in the calculations. Extremely high Cl in Nauru Basin glasses also supports eruption from OJP. Long distance flow with minimal cooling was facilitated on OJP by favorable slopes, lack of barriers, insulation of rapidly forming glass, and possibly by flow within lava tubes. Lava effusion rates were probably >100 m/sec and flow rapid: >1 m/sec.

Glass working and recycling in Pompeii: new evidence from the landfill of the Sarno Baths (VIII 2, 17–23)

Forty-six glass finds, including vessel fragments, windows, one inlay and one indicator of production (moil) excavated in the dump of the Sarno Baths in Pompeii were selected for an interdisciplinary technological, typological and chemical study. The identification of the moil demonstrates that a glassblowing workshop most likely existed in Pompeii, thus putting an end to a long-standing scientific debate. The LA-ICP-MS chemical data show that Roman-Mn base glass predominates, along with few Egyptian natron-type glasses and some plant-ash glass of probable Egyptian origin as well. A large proportion of the analysed glass, including the moil, consists of recycled compositions, suggesting the existence of an efficient system of collection and recycling of glass, which was active even at a time when the city had an abundant supply of fresh glass. The demand for raw glass in Pompeii far exceeded the average demand of other Roman towns, because glass containers were essential for the flourishing perfume industry in Pompeii and Campania. The proximity of the Sarno dump to the perfume district in the south-western part of the city and to the horrea of the Sanctuary of Venus suggests the possible location of the glass workshop in this area.

Early age structural build-up and pore stability in raw foam at ambient conditions: Implications for the final properties of glass-ceramic foam

Alkali activation followed by foaming techniques is an effective method for glass-ceramic foam development where early-age reactions in the alkali-activated precursors and the foaming reaction happen simultaneously. Therefore, this early reaction stage must be clearly understood to control the pore characteristic in the glass-ceramic foams. However, correlations between early-age structural build-up and foaming stability and their consequences on the final properties of the sintered glass-ceramic foams have not been investigated. This research aims to examine this relationship. 80–95 wt % of waste glass and 5–20 wt % of slag were used as alkali-activated precursors in this research. Using the alkali activation and combined foaming technique, the raw glass foam was developed and hardened at ambient conditions. The early-age reactivity and structural build-up of the binder and foamed suspension were studied through the rheological parameter and chemical structure analysis over the hardening period. During the hardening process, the percolation effect and development of reaction gels contribute to network formation and stability of the foamed suspension. As the hardening time increases, the matrix strengthens, and the pores stabilise through crosslinking of the gels. After hardening, the raw glass foams were sintered and their properties were evaluated and correlated with early-age structural build-up in fresh glass foam. This study demonstrates that the early-age interaction during matrix development and the foaming process controls the pore stability, connected pore volume, and strength of the final glass-ceramic foams. By understanding these parameters, the properties and pore stability in final glass-ceramic foams can be controlled effectively.

Temperature-controlled Se-S isotope fractionation during seawater mixing and sulfide precipitation in black smoker chimneys

Submarine hydrothermal venting leads to the formation of black smoker chimneys with complex internal zoning. These emerge through mineral precipitation under changing fluid conditions caused by variable degrees of fluid-seawater mixing. This study explores the potential of selenium (Se) isotopes as a novel tool to understand the enrichment processes and identify the sources of chalcophile elements in seafloor hydrothermal systems. In-situ trace element analysis of hydrothermal sulfides combined with high-precision Se and S isotope analysis of micro-domains through the wall of black smoker chimneys from the Nifonea vent field (New Hebrides back-arc, SW Pacific) revealed variations in sulfide chemistry at small spatial resolution. The δ82/76Se values (deviation of 82Se/76Se relative to NIST SRM 3149) of the sulfide micro-domains range from +0.6 to −3.7 ‰ ± 0.2 ‰ (2 s.d.) with a general decrease from the inner chalcopyrite lining towards the outer chimney wall. The highest δ82/76Se values overlap with the mean value of fresh basaltic glass from Nifonea caldera (+0.6 ± 0.4 ‰, n = 4), indicating that Se is primarily leached from the surrounding back-arc basalts. The trace element contents of sulfides revealed systematic variations between vent sites, linked to differences in fluid vapor content induced by sub-seafloor boiling, which did not cause any Se isotope fractionation. Instead, decreasing Se/Tl ratios of pyrite together with decreasing δ82/76Se values of sulfide micro-domains and calculated δ34SH2S fluid values towards the outer chimney wall are indicative of temperature-dependent Se and S isotope fractionation at 370 to <200 °C during fluid-seawater mixing within the chimney wall. This study presents Se isotopes as a new robust instrument to unravel the sources of chalcophile elements and related fluid processes in seawater-diluted hydrothermal systems, enhancing our understanding of their geochemical complexities.

Material and mechanical properties of young basalt in drill cores from the oceanic island of Surtsey, Iceland

Characterization of 2017 drill core samples from Surtsey, an oceanic island produced by 1963−1967 eruptions in the offshore extension of Iceland’s east rift zone, reveals highly heterogeneous microstructural, physical, and mechanical properties in subaerial, submarine, and subseafloor basaltic deposits. The connected porosity varies from 42% in weakly consolidated lapilli tuff in a submarine inflow zone to 21% in strongly lithified lapilli tuff in upper subseafloor deposits near the explosively excavated conduit. Permeability, however, varies over six orders of magnitude, from 10−18 m2 to 10−13 m2. Uniaxial compressive strength, P-wave velocity, and thermal conductivity are also highly variable: 10−70 MPa, 1.48−3.74 km·s−1, and 0.472−0.862 W·m−1·K−1, respectively. Synchrotron X-ray microdiffraction analyses integrated with major-element geochemistry and quantitative X-ray powder diffraction analyses describe the initial alteration of fresh glass, incipient consolidation of a fine-ash matrix, and partial closure of pores with mineral cements. Permeability, micromechanical, and thermal property modeling highlight how porosity and pore size in eruptive fabrics—modified through diverse cementing microstructures—influence the physical properties of the pyroclastic deposits. Borehole temperatures, 25−141 °C (measured from 1980 to 2018), do not directly correlate with rock strength properties; rather, the abundance and consolidation of a binding fine-ash matrix appears to be a primary factor. Analytical results integrated with archival data from 1979 drill core samples provide reference parameters for geophysical and heat transfer studies, the physical characteristics of pyroclastic deposits that lithify on a decadal scale, and the stability and survival of oceanic islands over time.

Hawaiian Volcanic Ash, an Airborne Fomite for Nontuberculous Mycobacteria.

Nontuberculous mycobacteria (NTM) are environmentally acquired opportunistic pathogens that can cause chronic lung disease. Within the U.S., Hawai'i shows the highest prevalence rates of NTM lung infections. Here, we investigated a potential role for active volcanism at the Kīlauea Volcano located on Hawai'i Island in promoting NTM growth and diversity. We recovered NTM that are known to cause lung disease from plumbing biofilms and soils collected from the Kīlauea environment. We also discovered viable Mycobacterium avium, Mycobacterium abscessus, and Mycobacterium intracellulare subsp. chimaera on volcanic ash collected during the 2018 Kīlauea eruption. Analysis of soil samples showed that NTM prevalence is positively associated with bulk content of phosphorus, sulfur, and total organic carbon. In growth assays, we showed that phosphorus utilization is essential for proliferation of Kīlauea-derived NTM, and demonstrate that NTM cultured with volcanic ash adhere to ash surfaces and remain viable. Ambient dust collected on O'ahu concurrent with the 2018 eruption contained abundant fresh volcanic glass, suggestive of inter-island ash transport. Phylogenomic analyses using whole genome sequencing revealed that Kīlauea-derived NTM are genetically similar to respiratory isolates identified on other Hawaiian Islands. Consequently, we posit that volcanic eruptions could redistribute environmental microorganisms over large scales. While additional studies are needed to confirm a direct role of ash in NTM dispersal, our results suggest that volcanic particulates harbor and can redistribute NTM and should therefore be studied as a fomite for these burgeoning, environmentally acquired respiratory infections.

Submarine landslides on the Eastern South Korea Plateau (ESKP)—Do pumice-rich tephra layers control slope stability?

Tephra layers embedded in marine sediments can be significant in controlling submarine landslide dynamics and seafloor morphology, but their preconditioning effects on slope failure remain uncertain. Here, we study the morphology and preconditioning factors of submarine landslides from a volcanically active region, the Eastern South Korea Plateau (ESKP) using a recently acquired multibeam echosounder (MBES), high-resolution sub-bottom chirp profiler, and piston core data, together with previous geophysical data. At least 50 translational landslides were identified on the southern margin of the ESKP in an area of ∼470 km2, with a relatively small volume of remobilized sediment (∼10 km3). The landslide headscarps are arcuate, up to 400 m in height, and lie at water depths of 980 to 2300 m. Landslides on the upper ESKP margin are more disintegrative (debris flow type) than those on the lower margin which consists largely of blocky type failures with small runouts. Landslide deposits identified in the cores consist of debris flows and slides/slumps while background deposits contain hemipelagic mud interbedded with ca. 10-cm-thick coarse-grained, poorly-sorted pumiceous tephra. Seismic and core integration indicate that the glide planes of the observed slides correspond to the pumice-rich tephra layers. These tephras are predominantly composed of fresh volcanic glass devoid of clay, indicating that the composition of the tephra did not control the formation of weak layers or slide planes. We infer therefore that the weakness of the glide planes resulted from high hydraulic (pore) pressure at the interface between some of the porous tephra layers and their overlying, relatively impermeable, hemipelagic mud. In addition to burial compaction and build-up of pore pressure in the tephra layers, fluid overpressure could have been facilitated by earthquakes causing granular convection within, and compaction of, the poorly sorted tephra. The landslide predominantly formed > ca. 84 ka ago, which suggests time-restricted triggering associated with a temporary increase in seismicity and/or sediments reaching their overpressure threshold during burial compaction. Our study suggests that regional occurrences of discrete layers of porous tephra deposits within finer grained hemipelagic sediments can potentially control the generation of landslides in subaqueous environments affected by explosive volcanism.

Concordance of V-in-olivine and Fe-XANES oxybarometry methods in mid-ocean ridge basalts

Oxygen fugacity (fO2) is a fundamental parameter controlling the behavior of redox-sensitive elements, as well as the speciation of degassing volatiles in igneous systems. Therefore, the average fO2 of typical mid-ocean ridge basalts (MORB) is important to constrain for models of atmospheric and mantle chemical evolution. Although there are several independent oxybarometry methods, in recent years, the Fe X-ray absorption near edge spectroscopy (Fe-XANES) oxybarometry of volcanic glasses has become the gold standard for evaluating the fO2 of modern lavas. Other oxybarometry methods, such as the V-in-olivine method, are useful for samples in which fresh glass is not preserved, but it is not clear whether the two methods give comparable results when applied to the same samples due to the lack of inter-calibration studies. Presented here are V-in-olivine oxybarometry data for eleven MORB lavas, eight of which have been previously characterized by Fe-XANES oxybarometry. The new data show that the V-in-olivine method is not applicable to MORB with glass containing <8.3 wt. % MgO, and that MORB with glass having MgO >8.3 wt. % have an fO2 averaging -0.28 ± 0.28 ΔFMQ, overlapping with the global Fe-XANES MORB average of -0.18 ± 0.16 ΔFMQ. It is therefore recommended that this oxybarometry technique only be applied to MORB with primitive (>8.3 wt. % MgO) glass. The lack of any systematic offset between the data from the two oxybarometers supports our previous conclusion that ocean island basalt sources (OIB) are more oxidized than average MORB, and that the majority of Archean komatiite sources record significantly lower fO2 than modern MORB.

Did the Troodos ophiolite of Cyprus form during subduction inception?

Understanding whether ophiolites formed during subduction inception or above long-lived subduction zones poses an outstanding challenge as modern examples of incipient subduction zones are rare. It is generally agreed that the Troodos ophiolite of Cyprus was formed at a spreading center above a subduction zone within the closing Neo-Tethys Ocean during the Late Cretaceous; beyond this, however, details of its geodynamic origin have been widely debated. To explore this problem, we examine further the analogy previously made between the Troodos ophiolite and the Mariana fore-arc, by here comparing extrusive rocks from the Troodos ophiolite to Pliocene-aged basalts from the southeastern Mariana fore-arc rifts (SEMFR), which formed by near-trench spreading above a highly dehydrating, mature subducted slab. The SEMFR basaltic glasses and olivine-hosted melt inclusions possess the highest markers of water-rich, slab-fluids (Rb/Th, Cs/Th, H2O/Ce, Ba/Th) of any worldwide arc magmas, a signature that may be consistent with efficient slab dehydration within ∼90–100 km from the trench. Troodos ophiolite lavas, which have preserved fresh glasses, recorded similar, elevated slab-fluid markers to those of the SEMFR glasses. Although geodynamic comparisons cannot be direct, we nevertheless propose that the chemical similarities in these slab-fluid markers support the formation of the Troodos ophiolite above a highly dehydrating, shallow subducted plate in a near-trench setting. Unlike the southern Marianas, lack of juvenile arc volcanism and associated volcaniclastics, but presence of an extensive boninitic sheeted dyke complex with associated extrusive section, demonstrates that Troodos presumably developed by organized seafloor spreading in a near-trench setting, immediately following subduction inception of the Neo-Tethyan plate. As such, the chemical similarities between the SEMFR magmas and the Troodos ophiolite can only be used to provide constraints upon the geodynamic and the petrogenetic conditions of magma formation. Hence, deciphering precisely the original setting of ophiolites requires us to integrate thoroughly accurate geology and petrographic descriptions, along with comparison with modern analogues of infant subduction zones.

High tensile strength glass fiber with different ratios of Na2O and SiO2 prepared by chemical strengthening method

In this paper, chemical strengthening method was used to prepare high strength glass fiber with different Na2O/SiO2 molar ratios (N/S). The structure, viscosity and tensile strength of glass samples were investigated by Molecular dynamics (MD) simulation, Raman, rotational viscometer and tensile strength tests. Results showed that the variation trends of Qn units obtained by MD simulation and Raman spectra were consistent, both indicating the decrease of the degree of network polymerization (DNP) with N/S ratio increasing. Additionally, the DNP had excellent linear relationships with the glass forming temperature and tensile strength of fresh glass fiber, respectively. However, the tensile strength was significant improved after chemical strengthening. When N/S ratio increased or chemical strengthening time prolonged, the enhancement rate of tensile strength of treated glass fiber was increased. The optimal tensile strength of glass fiber was 3089.38 ± 7 MPa after chemical strengthening at 390 °C for 30 min with N/S ratio 0.17.

Experimental determination of the reactivity of basalts as a function of their degree of alteration

The element release rates from naturally altered basalts were measured in batch experiments at 27 °C, and in mixed-flow experiments at 25 °C in reactive fluids initially consisting of pH 3 or 4 aqueous solutions. The basalts reacted in this study consist of 1) surface weathered basalts ranging in age up to 13 million years, and 2) hydrothermally altered basalts from zeolite to actinolite alteration zones (temperatures of ∼50 to 300 °C). The in situ pH in the batch experiments increased over time with the final pH of the fluids ranging from to 4 to 8. Most experiments exhibited a preferential release of Ca and Mg compared to Si from the dissolving basalts, both initially and over the long-term. This behavior is attributed to the combination of an initial rapid cation-proton exchange reaction and the relatively fast dissolution rates of Ca-bearing minerals. The BET surface area normalized Si release rates for all of the altered basalts are within one order of magnitude of each other, and from one to two orders of magnitude lower than corresponding rates from fresh basaltic glass and fresh crystalline basalts. This is interpreted to stem from 1) the fast removal of reactive basaltic glass and olivine from fresh basalts during the natural alteration of the rocks, 2) the similarity of the dissolution rates of the remaining albitic plagioclase, pyroxenes, epidote, and zeolites, and 3) the high surface areas of some less reactive secondary minerals such as clays. Overall, the results suggest that altered basalts will be effective in consuming CO2 during both natural and engineered processes, though at a somewhat slower rate than unaltered basalts.

A pilot study on glass finds discovered in the Geto-Dacian settlements from Cârlomăneşti and Pietroasa Mică, Buzău County, Romania

Thirty six glass items excavated at Cârlomăneşti and Pietroasa Mică, Buzău County, Romania (3rd c. BC – 1st c. AD) were analysed for their chemical composition using external PIXE-PIGE at AGLAE accelerator, Paris and external PIXE at the 3 MV Tandetron™ accelerator, Măgurele, to reveal the raw materials and manufacturing procedures, trying to reconstruct the links between the Geto-Dacian populations and the Hellenistic, Celtic and Roman ones during that historical time.The archaeological hypothesis was that these vitreous artefacts were luxury goods imported as such, made of fresh glass. The analyses showed that the objects were shaped from natron glass, with recipes typical for the Hellenistic period. Occasionally, glass recycling indicators were evidenced. Hints about the decolorizers (antimony, manganese) or chromophores (manganese, iron, cobalt, copper) were obtained.This archaeometric study is a pioneering one, considering the absence from the literature of compositional data on glass finds discovered in Geto-Dacian settlements.

Uranium Retention in Silica-Rich Natural Glasses: Nuclear Waste Disposal Aspect

Uranium-containing glass samples with an age of 140–145 million years were collected within the volcanic rocks of the largest volcanic-related uranium ore deposit in the world. Main features of their composition are high concentrations of silica and uranium, the largest for the rocks of this type. In contrast to this, the ages of fresh (unaltered) low-silica natural glasses of a basic composition (basalts) usually do not exceed a few million years. The volcanic low-silica glass is unstable at longer times and in older ancient rocks is transformed into a crystalline mass. The geochemistry of uranium including the behavior in solids and solutions is similar to that of long-lived transuranic actinides such as radioactive Np and Pu from high-level radioactive waste. This allows uranium to be used as a simulant of these long-lived hazardous radionuclides both at the synthesis and for the study of various nuclear wasteforms: glasses, glass crystalline materials and crystalline ceramics. The data obtained on long-term behavior of natural glasses are of importance for prognosis and validation of stability of nuclear wasteforms disposed of in geological disposal facilities (GDF).

Compositional changes by SIMS and XPS analyses on fresh and aged Roman-like glass

This study reports important analytical evidence of an unusual non-uniform element distribution in the superficial layers of glass matrices (from few nm up to 1 µm). The unforeseen observation was made on silica-soda-lime glass mock-ups before and after their artificial ageing, using secondary ion mass spectrometry (SIMS) and X-ray photoelectron spectroscopy (XPS) surface analysis techniques. The analyses showed a marked non-homogeneous element distribution at the glass surface. The results indicated a very low concentration of Na at the surface up to a depth of around 500 nm below the surface, where its concentration increases reaching a plateau. In addition, the profile distribution of H in the first 200 nm of the pristine glass surface indicated a diffusion of hydrogen from the surrounding environment to the glass network. Additional modifications during the glass ageing process related to external factors (such as temperature and humidity) were also identified in relation to sodium atoms, with atoms on the glass surface showing a different chemical state from those in the bulk. This study confirms that glass composition as well as glass alteration are non-homogeneous locally supporting the importance of studying glass surface as region of interaction with surrounding environment.

The effects of submarine alteration and phosphatization on igneous rocks: Implications for Sr-, Nd-, Pb-isotope studies

A suite of fresh and variably phosphatized submarine volcanic rock samples from NW Pacific seamounts from the Mid Cretaceous were subject of a detailed trace element and isotopic leaching study to examine the effect of phosphate alteration on the use of Sr-, Nd-, and Pb- radiogenic isotope systems. The study particularly focuses on the behavior of the respective parent/daughter element pairs during phosphatization and leaching in order to evaluate the impact on radiogenic ingrowth correction (“age correction”) for old seafloor samples and their use in geochemical studies. For this purpose, variably intense leaching procedures (no leaching; 2 M HCl at 70 °C for 1 h; 6 M HCl at 130 °C for 3 h) were applied to diverse sample materials (rock powder, rock chips and fresh volcanic glass chips).Phosphatization causes significant modification of isotope ratios and elemental proportions of most trace elements including the rare earth elements. As opposed to common seafloor weathering, Rb/Sr decreases in the lavas with increasing phosphatization, while U/Pb enrichment appears slightly amplified. Mild acid leaching of rock chips, however, generally yields Sr, Nd and Pb isotope ratios largely in accordance with values from fresh glass fractions of the same samples and comparable with the results for similarly leached rock powders. Applying original (non-leached) elemental concentration ratios for the radiogenic age correction of mildly leached sample chips produces mixed results for 87Sr/86Srin but generally agrees with expected 143Nd/144Ndin, 206Pb/204Pbin, 207Pb/204Pbin, and 208Pb/204Pbin values.All residua of strongly leached powders yield significantly more radiogenic 206Pb/204Pbm, 143Nd/144Ndm and higher U/Pb than mildly leached rock chips or powders or even non-leached powder of the respective samples, opposite to what is expected when removing seawater-derived secondary phases by stronger acid leaching. We suggest that this enrichment, after removal of most of the magmatic Pb and Nd, reflects minor refractory components that formed in association with the phosphatization and developed high 206Pb/204Pb ratios by radiogenic ingrowth since the eruption of these lavas in the Mid Cretaceous due to high U/Pb.Utilizing modeled parent/daughter ratios based on magma evolution systematics of associated fresh glass yields no satisfying initial isotopic compositions for the strongly leached samples despite supposed removal of secondary isotopic signals upon leaching. Applying the modeled parent/daughter ratios to age correct mildly leached sample chips and powder otherwise slightly improves the accordance with their respective fresh glass fractions for 208Pb/204Pbin but yields similar results as if using the actual parent/daughter ratios for 143Nd/144Ndin, 86Sr/87Srin, 206Pb/204Pbin, and 207Pb/204Pbin.

Stratigraphy, provenance, and timing of Neogene sedimentation in the western Valdés Basin, Patagonia. Accurate paleogeographic reconstructions as a key piece for andean-passive margin integration

With the aim to better understand the timing and geological evolution of the late Cenozoic stratigraphic record of the onshore, western Valdés Basin in northeast Chubut province (Patagonia, Argentina), we perform sedimentological, stratigraphic, and zircon U–Pb geochronologic analyses. The study includes the terrestrial Early Miocene Trelew Member of the Sarmiento Formation, the shallow marine Early Miocene Gaiman Formation, the shallow marine to estuarine Late Miocene Puerto Madryn Formation, and the Plesitocene fluvial conglomerates of the Rodados Patagónicos. Based on our data set, together with the recognition of relevant stratigraphic surfaces, we divide the succession into stratigraphically bounded units and define three cycles of sedimentation. The Lower Cycle rests on top of Surface 1, which comprise a long hiatus including the entire Oligocene Epoch. This cycle is in turn divided into two subunits separated by the transgressive, ravinement Surface 2. The Lower Cycle is separated from the overlying Middle Cycle (=Puerto Madryn Formation) by the flat and regionally extensive Surface 3. Finally, the latter is separated from the Upper Cycle (=Rodados Patagónicos) by Surface 4, a complex surface at the base of gravel deposits forming several terrace levels. Maximum depositional ages calculated from 10 zircon U–Pb samples indicate the succession between surface 1 and 4 extends from 21.5 to 2.7 Ma (Aquitanian-Piacenzian). The Lower Cycle is restricted to the 21.5–16 Ma interval (Aquitanian-Burdigalian); the Middle Cycle between 12 and 2.7 Ma (latest Serravalian-Piacenzian), with most of the new and previous ages clustering in the Tortonian; whereas the Upper Cycle is restricted to the Pleistocene. Although most of the analyzed sediments show fresh volcanic glass particles, older zircon ages are dominant, representing detrital components with a dominant peak of Permian-aged grains, with subordinated Devonian, Jurassic, Cretaceous, and Paleogene peaks. We interpret the analyzed succession as a condensed section compared to the offshore Valdés Basin depocenter area. Sedimentation in the study area was controlled by periods of slow subsidence, probably related to thermal subsidence and sediment compaction in the depocenter. Two main sources of sediments for the analyzed succession are envisaged: one represented by explosive volcanism located either in the Andes or in the North Patagonian Massif, the other through erosion of older rocks surrounding the North Patagonian Massif where late Paleozoic plutonic rocks are abundant. Particularly for the Middle and Upper cycles, an increase in Mesozoic contribution suggests erosion from sediments of the Cañadón Asfalto Basin. The new ages and stratigraphic analyses here reported are of major relevance for the integration of the onshore and offshore stratigraphies of the Valdés Basin which is key to connect the geologic evolution of the Andean and passive margin areas of southern South America. They are also of major relevance for the calibration of fossil communities, particularly for the abundant and diverse marine vertebrates preserved in the Burdigalian Gaiman Formation.

Glass from Islamic Sicily: typology and composition from an urban and a rural site

As part of the Sicily in Transition and GlassRoutes projects glass, artefacts from various medieval Sicilian sites have been analysed by LA-ICP-MS. This made it possible to collect data on the circulation of glass on the island in the Middle Ages. The comparison of the data from the coastal town of Mazara with those from the rural area of Castronovo di Sicilia allowed us to establish a continuity in the supply of fresh Levantine glass to the island as late as the end of the 7th century. The results also point to a possible role of urban centres in the redistribution of goods to the hinterland in the 8th century. During this period, the Castronovo area was supplied by imports of fresh glass from the Levant and Egypt, from regions that were part of the Umayyad caliphate. The 10th- to 11th-century glass assemblages from both sites shows a considerable Islamisation of Sicilian material culture, with typologies reminiscent of what is known from Egypt, Ifrīqiya and the Iberian Peninsula. The discovery of a compositional group at both Mazara and Castronovo, which differs from published data from other areas of the Mediterranean basin, also suggests a Sicilian origin of these objects. Islamisation is thus also evident in the adoption of production technologies typical of the Islamic world, such as the use of soda-rich plant ash as a fluxing agent.

Natural glass alteration under a hyperalkaline condition for about 4000years.

Silicate glasses are durable materials in our daily life, but corrosion rate accelerates under alkaline aqueous environment. Such situation has raised concerns, for example, in nuclear waste disposal where vitrified wastes encounter to alkaline leachate from surrounding concrete materials. Here we report volcanic glass example surviving with a hyperalkaline groundwater (pH > 11) and high flow rate for about 4000 years. The tiny glass fragments were extracted from the volcanic ash layer sandwiched between ultramafic sediments using microanalytical techniques. Sharp elemental distributions at the glass surface, where amorphous-like smectite precursors and crystalline smectites coexist, suggest the corrosion by an interface-coupled dissolution–precipitation mechanism rather than inter-diffusion. The corrosion rate was maintained at, the minimum, 2.5 orders of magnitude less than the rate observed for fresh glass, even in the presence of Fe and Mg that might have consumed Si through the silicate precipitation.

Reexamination of Eruptive Activity of Akanfuji in the Me-Akan Volcano, Eastern Hokkaido, Japan

Eruption history of Akanfuji in the Me-akan volcano, eastern Hokkaido, has been examined by comparing multiple natural outcrops. In a previous study, at least 17 layers of scoria fall deposits were recognized. To obtain more detailed geological information and reexamine the eruptive activity of Akanfuji, we conducted trench surveys. At each survey site, the scoria fall deposits from Akanfuji are layered with a total thickness of several tens of centimeters to 1 m. A light brown volcanic ash layer is deposited just under the lowest layer of Akanfuji, and the fresh glass in the light brown volcanic ash shows the glass composition of the volcanic ash that erupted at Tarumai volcano 2500 BP. In addition, volcanic ash ejected from Ponmachineshiri of the Me-akan volcano is deposited on top of the newest deposits in the Akanfuji series with a thin soil layer in between. The volcanic ash ejected from Ponmachineshiri contains patches of volcanic ash from the Mashu volcano that erupted 1000 years ago. Therefore, Akanfuji was active from about 2500 to 1000 years ago. Akanfuji ejected scoria fall deposits at least 17 times (Akf-1 to Akf-17), and assuming that it erupted an average number of times during the activity period, it would be once every 90 years. The eruption rate was estimated to be 0.12 km3 DRE/ka.

Late antique glass from Salapia: Tracking production and trading networks

AbstractThe investigation of 38 late antique vessels from the archaeological excavation of Salapia has been performed using EMPA and LA‐ICP‐MS. The collection was made using impure sands and mineral soda. Among coloured glass, most vessels were made of ‘fresh’ glass. The use of colouring agents is rare, and most decoloured glass is obtained by Mn addition. Sb‐decolouration is limited to one cup, and two colourless vessels show both manganese and antimony. As for provenance, the prevalence of Egyptian‐HIMT glass over the Levantine is evident. Among Levantine glass, Jalame glass is represented, whereas Apollonia glass is absent. Among Egyptian (and deemed Egyptian) glass, the prevalence of HIMT glass over the other types has been observed. The high attestation of fresh glass, most notable in the earlier centuries, suggests the importation of glass in the form of finished objects, especially luxury vessels.