Volcanic Source Research Articles

Comments on the paper of Peter Marchev et al. “Early Oligocene supereruption in SE Europe outlined by 33.3 Ma U-Pb ages for Lemnos tuff and correlation with regional ash deposits” – C. R. Acad. Bulg. Sci., 74, 3, 2021, 396–405.

These critical notes challenge the interpretation of the authors of the article that the volcanic source of the described tuffs on the island of Lemnos (Greece) is the source of Dazhdovnitsa tuffs (beginning of the Oligocene) and that it is located in the Bororvitsa caldera, Eastern Rhodopes. However, there are large regions between this caldera and the island of Lemnos (e.g. between the villages of Podkova and Dobromirtsi in the southern part of the Eastern Rhodopes), where no pyroclastic layers are found at the base of the Oligocene section, corresponding to the stratigraphic position of the Dazhdovnitsa tuffs. It has been suggested that the volcanic source of Lemnos tuffs may be located in the Kalotiko volcanic region, situated essentially in Northern Greece. It has a multi-phase Rupelian volcanic activity, but it is not dated in detail.

Geochemistry of Bandan River sediments in Sistan Basin (Eastern Iran): implication for provenance and environmental impact on the Hamoun Lake pollution

The catchment basin of Bandan River in Hamoun territory in E-Iran was studied to determine the origin of river sediments and its contaminant potential for the Hamoun Lake pollution. Thirty-four stream bed samples were analyzed for major oxide and trace elements. Geochemical discriminant diagram represents litharenite composition for the river sediments. On the discriminant functional diagram, the samples show oceanic arc setting with sedimentary quartzitic and intermediate volcanic sources, which almost correspond to the current geodynamic condition of the present covenant. The toxic elements Pb, As, Cr, Ni, Co, Zn, Cu, Mn, V, and Se were analyzed in all samples to evaluate the pollution potential using index of geo-accumulation (Igeo). According to Igeo value, soils were uncontaminated to moderately levels with Pb and Ni, while moderately contaminated with Cr, strongly contaminated with As and strongly to extremely contaminated with Mo. Statistical studies concluded high correlation between the examined elements and indicate that the volcanic rocks are common source of the pollutant elements in the studied catchment basin. Chromium and Ni can also be originated from ophiolitic rocks in the region. Therefore, geogenic factors control the contamination of river sediments, which may lead to Hamoun Lake pollution.

A revised AMS and tephra chronology for the Late Middle to Early Upper Paleolithic occupations of Ortvale Klde, Republic of Georgia

The nature and timing of the shift from the Late Middle Paleolithic (LMP) to the Early Upper Paleolithic (EUP) varied geographically, temporally, and substantively across the Near East and Eurasia; however, the result of this process was the archaeological disappearance of Middle Paleolithic technologies across the length and breadth of their geographic distribution. Ortvale Klde rockshelter (Republic of Georgia) contains the most detailed LMP-EUP archaeological sequence in the Caucasus, an environmentally and topographically diverse region situated between southwest Asia and Europe. Tephrochronological investigations at the site reveal volcanic ash (tephra) from various volcanic sources and provide a tephrostratigraphy for the site that will facilitate future correlations in the region. We correlate one of the cryptotephra layers to the large, caldera-forming Nemrut Formation eruption (30,000 years ago) from Nemrut volcano in Turkey. We integrate this tephrochronological constraint with new radiocarbon dates and published ages in an OxCal Bayesian age model to produce a revised chronology for the site. This model increases the ages for the end of the LMP (∼47.5–44.2 ka cal BP) and appearance of the EUP (∼46.7–43.6 ka cal BP) at Ortvale Klde, which are earlier than those currently reported for other sites in the Caucasus but similar to estimates for specific sites in southwest Asia and eastern Europe. These data, coupled with archaeological, stratigraphic, and taphonomic observations, suggest that at Ortvale Klde, (1) the appearance of EUP technologies of bone and stone has no technological roots in the preceding LMP, (2) a LMP population vacuum likely preceded the appearance of these EUP technologies, and (3) the systematic combination of tephra correlations and absolute dating chronologies promises to substantially improve our inter-regional understanding of this critical time interval of human evolution and the potential interconnectedness of hominins at different sites.

Geochemistry of Eocene Bawang Member turbidites of the Belaga Formation, Borneo: Implications for provenance, palaeoweathering, and tectonic setting

The Belaga Formation of the Rajang Group or Rajang Fold and Thrust Belt (Late Cretaceous to Late Eocene) is mostly exposed in Sibu Zone along with some exposures in the Miri Zone of Central Sarawak. This entire turbiditic sequence was believed to have been deposited in a deep marine environment in a basin having an overall passive margin setting, that is, the Rajang Sea. However, the Eocene age‐related stratigraphic record of this group (including Bawang Member) is much more complex, due to the complicated geological and tectonic settings which prevailed during their deposition. Here, we present field observations along with the application of various geochemical proxies and their constraints for the understanding of provenance, palaeo‐weathering, and tectonic evolution of the area during the deposition of Bawang turbidites. Based on field observation, it has been found that this member consists of four main lithofacies, including massive sandstone facies (MSF), thick‐bedded facies (TBF), heterolithic facies (HF), and mud facies (MF). Using geochemical data, chemical weathering indices (CIA and CIW) values and A‐CN‐K plot show that the source area for Bawang turbidites has undergone a moderate to an intense degree of chemical weathering and was influenced by the recycling effect. The slight depletion in sandstones and shales for Cr, Ni, and V values is consistent with the felsic dominated source region; however, La/Sc versus Co/Th and La/Th versus Hf plots show a mixed source (felsic and intermediate volcanic source) with some input of recycled sediments from the older sedimentary to metasedimentary rocks. Various geochemical ratios and discriminant diagrams verify that the Schwaner Mountains and its metamorphic group of rocks were the principal provenances for these sediments, along with some input from West Borneo. The results of the geochemical analysis also show that Bawang turbidite sediments were deposited in a basin associated with an initial active continental margin setting and the basin was shifting towards a passive setting (Late Eocene–Oligocene). The volcanic input in Bawang Member during the Late Eocene also suggests the involvement of some subsequent possible arc setting around the “Bawang subbasin”.

The Patagonian intraplate basalts: A reflection of the South Atlantic convection cell

Based on an extensive literature dataset on Cenozoic intraplate basalts from Patagonia, Argentina, we provide a revised interpretation of the mantle sources of volcanism and suggest a relation to the South Atlantic hotspots and mantle flow. Furthermore, we present 16 elemental analyses of North Patagonian basalts as well as 12 Sr, Nd and Pb-isotopes. The new data reveal that the North Patagonian basanite-nephelinite rocks with HIMU OIB-type trace element patterns do not have highly radiogenic Pb-isotopes and are unrelated to the South Patagonian HIMU-type Pali Aike source. Instead, they were formed within the lifetime of the South Atlantic Ocean by metasomatism of the local lithospheric mantle (SCLM) by carbonatitic melts from the ambient South Atlantic asthenosphere. Thus, they are an example of a very young HIMU source supporting that the HIMU OIB-type signature was formed by carbonate metasomatism of lithospheric mantle and not by recycling of oceanic crust. In contrast, the EM1-type basalts dominating in Central Patagonia have significantly elevated FeOT/MnO (up to 79) and low CaO contents (mostly between 8 and 9 wt%). This indicates derivation from a pyroxenitic source, which presumably formed by melt metasomatism of the SCLM. In isotopic space, the Patagonian basalts can be modelled by mixing of depleted South Atlantic MORB mantle (representing the SCLM) with 2–7% Discovery and Bouvet hotspot melts in varying proportions (representing the metasomatizing agents). The latitudinal variation in isotopic compositions of the Patagonian basalts is a mirror image of the variation at the mid-Atlantic Ridge. This observation is consistent with the westward direction of the mantle flow and drift of South America and suggests that the hotspot locations and flow direction of the South Atlantic convection cell has been stable for a significant part of the lifetime of the South Atlantic ocean bringing plume influenced asthenosphere westwards beneath Patagonia.

Four Years of Continuous Seafloor Displacement Measurements in the Campi Flegrei Caldera

We present 4 years of continuous seafloor deformation measurements carried out in the Campi Flegrei caldera (Southern Italy), one of the most hazardous and populated volcanic areas in the world. The seafloor sector of the caldera has been monitored since early 2016 by the MEDUSA marine research infrastructure, consisting of four instrumented buoys installed where sea depth is less than 100 m. Each MEDUSA buoy is equipped with a cabled, seafloor module with geophysical and oceanographic sensors and a subaerial GPS station providing seafloor deformation and other environmental measures. Since April 2016, the GPS vertical displacements at the four buoys show a continuous uplift of the seafloor with cumulative measured uplift ranging between 8 and 20 cm. Despite the data being affected by environmental noise associated with sea and meteorological conditions, the horizontal GPS displacements on the buoys show a trend coherent with a radial deformation pattern. We use jointly the GPS horizontal and vertical velocities of seafloor and on-land deformations for modeling the volcanic source, finding that a spherical source fits best the GPS data. The geodetic data produced by MEDUSA has now been integrated with the data flow of other monitoring networks deployed on land at Campi Flegrei.

Occurrence of anatase in reworking altered ash beds (K-bentonites and tonsteins) and discrimination of source magmas: a case study of terrestrial Permian–Triassic boundary successions in China

AbstractPotential secondary influences on titanium distribution should be evaluated when using ash beds as volcanic source indicators and for correlation purposes. In this study, well-correlated altered ash beds in Permian–Triassic boundary (PTB) successions of various facies in South China were investigated to better understand their use in source discrimination and stratigraphic correlation. The ash beds deposited in lacustrine and paludal facies contain significantly more Ti relative to deposits in marine facies. Neoformed anatase grains nanometres to micrometres in size are associated closely with clay minerals, whereas detrital anatase was observed in the remnants of altered ash beds of terrestrial facies. Extraction of the clay fraction of altered ash beds may exclude significantly detrital accessory minerals such as anatase and rutile added during sediment reworking, and the concentrations of immobile elements in the clay fraction may therefore be used to interpret more effectively their source igneous rocks.

Multi-Sensor Analysis of a Weak and Long-Lasting Volcanic Plume Emission

Volcanic emissions are a well-known hazard that can have serious impacts on local populations and aviation operations. Whereas several remote sensing observations detect high-intensity explosive eruptions, few studies focus on low intensity and long-lasting volcanic emissions. In this work, we have managed to fully characterize those events by analyzing the volcanic plume produced on the last day of the 2018 Christmas eruption at Mt. Etna, in Italy. We combined data from a visible calibrated camera, a multi-wavelength elastic/Raman Lidar system, from SEVIRI (EUMETSAT-MSG) and MODIS (NASA-Terra/Aqua) satellites and, for the first time, data from an automatic sun-photometer of the aerosol robotic network (AERONET). Results show that the volcanic plume height, ranging between 4.5 and 6 km at the source, decreased by about 0.5 km after 25 km. Moreover, the volcanic plume was detectable by the satellites up to a distance of about 400 km and contained very fine particles with a mean effective radius of about 7 µm. In some time intervals, volcanic ash mass concentration values were around the aviation safety thresholds of 2 × 10−3 g m−3. Of note, Lidar observations show two main stratifications of about 0.25 km, which were not observed at the volcanic source. The presence of the double stratification could have important implications on satellite retrievals, which usually consider only one plume layer. This work gives new details on the main features of volcanic plumes produced during low intensity and long-lasting volcanic plume emissions.

Major volcanic eruptions linked to the Late Ordovician mass extinction: Evidence from mercury enrichment and Hg isotopes

Abstract The Late Ordovician mass extinction (LOME) was the second most severe Phanerozoic biodiversity crisis. While environmental deterioration and oceanographic changes associated with the Hirnantian glaciation have been frequently invoked as potential extinction drivers, recent evidence for a large igneous province eruption at that time has challenged this prevailing view. As such, the triggering and killing mechanisms of the LOME remain debated. Here we report mercury (Hg) concentrations, isotopic compositions, Hg/total sulfur (Hg/TS), and Hg/total organic carbon (Hg/TOC) in Late Ordovician limestone/black shale alternations from two successions in South China and Laurentia that straddled the paleoequator. Our results, in both areas, show multiple Hg enrichments before and during the LOME, suggesting a global, or at least a widespread increase in environmental Hg loading. The initial Hg enrichments occur in the mid-upper Katian units and are followed by additional Hg anomalies in the lower Hirnantian strata that coincide temporally with the first pulse of the LOME. Extremely high levels of Hg, Hg/TS, and Hg/TOC, with maximum values of 737 ng g−1, 633 ng g−1 Hg/wt% TS, and 167 ng g−1 Hg/wt% TOC, respectively, represent ~3–13 × background values, indicating increased Hg input to the ocean. The absence of mass-independent fractionation of Hg isotopes in the Hg-enriched intervals suggests a volcanic source for the observed Hg anomalies. The temporal coincidence of Hg anomalies with the extinction horizon in both continents suggests that extensive and widespread volcanism may have had global climatic and ecological impact, and was a primary trigger for prolonged and synergetic deterioration of Late Ordovician environment such as climate changes, ocean acidification, and anoxia, causing the LOME.

ALMA Observations of Io Going into and Coming out of Eclipse

Abstract We present 1 mm observations constructed from Atacama Large (sub)Millimeter Array (ALMA) data of SO2, SO, and KCl when Io went from sunlight into eclipse (2018 March 20) and vice versa (2018 September 2 and 11). There is clear evidence of volcanic plumes on March 20 and September 2. The plumes distort the line profiles, causing high-velocity (≳500 m s−1) wings and red-/blueshifted shoulders in the line profiles. During eclipse ingress, the SO2 flux density dropped exponentially, and the atmosphere re-formed in a linear fashion when reemerging in sunlight, with a “post-eclipse brightening” after ∼10 minutes. While both the in-eclipse decrease and in-sunlight increase in SO was more gradual than for SO2, the fact that SO decreased at all is evidence that self-reactions at the surface are important and fast, and that in-sunlight photolysis of SO2 is the dominant source of SO. Disk-integrated SO2 in-sunlight flux densities are ∼2–3 times higher than in eclipse, indicative of a roughly 30%–50% contribution from volcanic sources to the atmosphere. Typical column densities and temperatures are N ≈ (1.5 ± 0.3) × 1016 cm−2 and T ≈ 220–320 K both in sunlight and in eclipse, while the fractional coverage of the gas is two to three times lower in eclipse than in sunlight. The low-level SO2 emissions present during eclipse may be sourced by stealth volcanism or be evidence of a layer of noncondensible gases preventing complete collapse of the SO2 atmosphere. The melt in magma chambers at different volcanoes must differ in composition to explain the absence of SO and SO2, but simultaneous presence of KCl over Ulgen Patera.

Array and spectral ratio techniques applied to seismic noise to investigate the Campi Flegrei (Italy) subsoil structure at different scales

Abstract. The purpose of this work is to study the subsoil structure of the Campi Flegrei area using both spectral ratios and array techniques applied to seismic noise. We have estimated the dispersion curves of Rayleigh waves by applying the Frequency–Wavenumber (f–k hereinafter) and Modified Spatial Autocorrelation (MSPAC) techniques to the seismic noise recorded by the underground short period seismic Array “ARF”, by the broadband stations of the UNREST experiment and by the broadband stations of the seismic monitoring network of INGV – Osservatorio Vesuviano. We have performed the inversion of a dispersion curve (obtained averaging the f–k and MSPAC dispersion curves of seismic noise and single phase velocity values of coherent transient signals) jointly with the H∕V spectral ratio of the broadband station CELG, to obtain a shear wave velocity model up to 2000 m depth. The best-fit model obtained is in a good agreement with the stratigraphic information available in the area coming from shallow boreholes and deep wells drilled for geothermal exploration. In active volcanic areas, such as Campi Flegrei, the definition of the velocity model is a crucial issue to characterize the physical parameters of the medium. Generally, a high quality characterization of the medium properties helps to separate the contributions of the volcanic source, path and site in the geophysical observables. Therefore, monitoring possible variations in time of such properties in general can help to recognize anomalies due to the volcano dynamics, i.e. fluid migration connected to the volcanic activity.

Volcanic emissions and atmospheric pollution: A study of nanoparticles

The influence of emissions of an active volcano on the composition of nanoparticles and ultrafine road dust was identified in an urban area of the Andes. Although many cities are close to active volcanoes, few studies have evaluated their influence in road dust composition. Air quality in urban areas is significantly affected by non-exhaust emissions (e.g. road dust, brake wear, tire wear), however, natural sources such as volcanoes also impact the chemical composition of the particles. In this study, elements from volcanic emissions such as Si > Al > Fe > Ca > K > Mg, and SiAl with K were identified as complex hydrates. Similarly, As, Hg, Cd, Pb, As, H, Cd, Pb, V, and salammoniac were observed in nanoparticles and ultrafine material. Mineral composition was detected in the order of quartz> mullite> calcite> kaolinite> illite> goethite> magnetite> zircon> monazite, in addition to salammoniac, a tracer of volcanic sources. The foregoing analysis reflects the importance of carrying out more studies relating the influence of volcanic emissions in road dust in order to protect human health. The road dust load (RD10) ranged between 0.8 and 26.8 mg m−2 in the city.

B–Tm Ash of a Catastrophic Eruption of Baitoushan Volcano in Terrestrial Deposits of Primorye as an Age Marker of the Medieval Warm Period in the Holocene

The first finds of B–Tm volcanic ash of the catastrophic eruption of Baitoushan Volcano in the 10th century (946/947 AD) in the terrestrial deposits of Primorye are reported. The ash layer is found in 17 cross sections of lacustrine–boggy sediments at nine observation sites, both on the coast and in the internal areas of Sikhote-Alin. Identification of the volcanic source is carried out based on the study of macroelement composition of volcanic glass. Radiocarbon dating is used for age determination. The tephra distribution and the changes in the grain size depending on the distance from the source are analyzed. A comparative analysis of the volcanic glass composition and the data on pyroclastics of the proximal zone and the results of distal tephra study has been performed. It proved that the ash layer in Primorye was formed in the final phase of the eruption, but an exception was the coast of Kit Bay and the Shkotovskoe Plateau, where glass of rhyolitic composition corresponding to the maximum phase at the beginning of the eruption is found. For the reconstruction of the environmental development, the ash is used as an age marker of the Medieval Warm Period in the Holocene, which makes it possible to compare reliably the data on the cross sections located on the coast and in the mountains, to refine the chronology of paleogeographical events of historical time, and to perform interregional correlations.

Field Survey of Tsunami Heights and Runups Following the 22 December 2018 Anak Krakatau Volcano Tsunami, Indonesia

The 22 December 2018 Anak Karakatau tsunami in Indonesia was a rare event in that few instrumental records existed of tsunamis generated by volcanic sources before this event. The tsunami, which left a death toll of 437, is of global importance as it provides opportunities to develop knowledge on generation, propagation and coastal effects of volcanic tsunamis. Here, we report results of field surveys along the coast of the Sunda Strait, Indonesia to study tsunami wave heights and coastal damage. We surveyed 29 locations and measured ranges of tsunami runup from 0.9 to 5.2 m, tsunami heights from 1.4 to 6.3 m, flow depths from 0.2 m to 3.0 m and inundation distances from 18 to 212 m. The largest tsunami heights and concentration of damage and fatalities occurred on the western shore of Java from Tanjung Lesung to Sumur. The largest cluster of fatalities occurred at Tanjung Lesung, where more than 50 people died while attending an outdoor music being held at the shoreline. The tsunami runup and tsunami height in Tanjung Lesung were 4.0 and 2.9–3.8 m, respectively. We believe this tragedy could have been avoided if the event organizers were more aware of the hazard posed by the Anak Krakatau volcano, as it had been actively erupting for several months prior to the tsunami, and simply moved the concert stage 100 m inland. Many of the locations surveyed demonstrated a similar pattern where the majority of casualties and destruction occurred within 100 m of the coast; in several locations, lives were saved where buildings were located at least this distance inland. The significant damage and numerous deaths which occurred in Sumur, despite the moderate tsunami height of 2.3–2.5 m, can be attributed to the extremely low-lying coastal land there. Flow depth in Sumur was 0.9–2.0 m. During our field surveys, nearly one year after the event, we noted that some of the damaged buildings were being rebuilt in the same locations just 10–30 m from the shoreline. We question this practice since the new buildings could be at the same tsunami risk as those damaged in the 2018 event.

Rapid carbon accumulation in a peatland following Late Holocene tephra deposition, New Zealand

Contemporary measurements of carbon (C) accumulation rates in peatlands around the world often show the C sink to be stronger on average than at times in the past. Alteration of global nutrient cycles could be contributing to elevated carbon accumulation in the present day. Here we examine the effect of volcanic inputs of nutrients on peatland C accumulation in Moanatuatua Bog, New Zealand, by examining a high-resolution Late Holocene C accumulation record during which powerful volcanic eruptions occurred, depositing two visible rhyolitic tephra layers (Taupo, 232 ± 10 CE; Kaharoa, 1314 ± 12 CE). Carbon accumulation rates since c. 50 CE, well before any human presence, increased from a background rate of 23 g C m−2 yr−1 up to 110 g C m−2 yr−1 following the deposition of the Taupo Tephra, and 84 g C m−2 yr−1 following the deposition of the Kaharoa Tephra. Smaller but nevertheless marked increases in C accumulation additionally occurred in association with the deposition of three andesitic-dacitic cryptotephras (each ≤ ∼1 mm thick) of the Tufa Trig Formation between the Taupo and Kaharoa events. These five periods of elevated C uptake, especially those associated with the relatively thick Taupo and Kaharoa tephras, were accompanied by shifts in nutrient stoichiometry, indicating that there was greater availability of phosphorus (P) relative to nitrogen (N) and C during the period of high C uptake. Such P was almost certainly derived from volcanic sources, with P being present in the volcanic glass at Moanatuatua, and many of the eruptions described being associated with the local deposition of the P rich mineral apatite. We found peatland C accumulation to be tightly coupled to N and P accumulation, suggesting nutrient inputs exert a strong control on rates of peat accumulation. Nutrient stoichiometry indicated a strong ability to recover P within the ecosystem, with C:P ratios being higher than most other peatlands in the literature. We conclude that nutrient inputs, deriving from volcanic eruptions, have been very important for C accumulation rates in the past. Therefore, the elevated nutrient inputs occurring in the present day could offer a more plausible explanation, as opposed to a climatic component, for observed high contemporary C accumulation in New Zealand peatlands.

An initial survey of the composition of Ethiopian obsidian

Ethiopia is rich in obsidian and prehistoric peoples were utilizing it to make artifacts since at least the Early Stone Age. The unique chemical compositions of obsidian are of considerable interest to archaeologists when obsidian artifacts are recovered at prehistoric sites, both in terms of determining provenance and cultural exchange. Here we present electron microprobe analyses to characterize the major and minor element compositions of a suite of obsidian samples from 45 volcanic source locations along a 700 km extent of the Main Ethiopian Rift and the Afar Triangle. Of the 62 analyzed obsidian, 50 are classified as rhyolite, with subordinate numbers of trachyte and dacite. The Main Ethiopian Rift and its extension into the Afar region to the north have produced obsidian with different chemical affinities which may prove useful in narrowing down possible source regions for artifacts for which sources have not yet been discovered and/or analyzed.

Revisiting the “Gercus Basalt within the Eocene Gercus Formation”: Implications for sedimentary origin of a basaltic body, Kurdistan Region, Northern Iraq

• A previously described intrusive basaltic body is re-studied. • The re-study proved that it consists of sedimentary rocks (greywacke sandstone). • The greywacke transported from remote volcanic source to its present area. • More than ten evidences are found to prove its sedimentary origin. • These evidence are such as content of bitumen, conglomerate imbricated pebbles. • Other evidences are presence of graded beds, parallel and planer bedding and ooids. • More evidences are absence of basaltic flows and chilled borders and others. Recently, a basaltic body is described geochemically and mineralogically by previous authors within the Gercus Formation, in the Bekhair Anticline (Duhok Governorate, Northern Iraq). They indicated feldspar, anorthoclase, diopside, forsterite and olivine as main minerals of the body with many accessary ones. They added that the body is anorogenic (non-tectonic), extruded on continental crust of Arabian Plate and affected by pervasive alteration with a thickness of 16 m and a width of 4 km. The present study discussed in detail the sedimentary origin of the claimed basaltic body, contesting its intrusive or extrusive igneous origin. We proved that the body consists of a volcaniclastic succession (greywacke), which was derived from remote volcanic source areas and deposited by running water in the basin of the Gercus Formation. These sediments had been transported from a northeastern source area toward southwestern by streams to the deltaic basin of the Eocene basin. For proving its sedimentary origin, we presented many field and petrographic evidences such as content of bitumen, ooid bed, thick or thin planar layers (with parallel and sharp contacts), graded bedding, conglomerate, imbricated pebbles and hosting limestone beds in addition to absence of contact metamorphism, lack of structures such as pillow lava, basaltic flow, crystals zoning, xenoliths, peperites, digitation into host rocks and dilatations features. The previous authors depended on the geochemical and thin section studies for proving its igneous origin but these methods cannot prove if the constituents (whole or broken minerals) of the body are transported or indigenous. While accurate field survey and boundary conditions studies can indicate its origin. The proof of the sedimentary origin is achieved via conjugating evidences of the body boundary, those from its internal architecture and composition. Therefore, we are sure 100% that the body is sedimentary succession not basaltic one.

Geochemistry of Asara Shale member of Karaj Formation, Central Alborz, Iran: Provenance, source weathering and tectonic setting

The Asara Shale Member of the Karaj Formation, Middle to Upper Eocene in age, includes mixed volcaniclastic, siliciclastic and carbonate strata, in the Alborz Mountains, northern Iran. These strata have been geochemically analyzed to constrain their source area provenance. Most of the major and trace element contents of Asara Shale samples are generally similar to the upper continental crust (UCC) values and their chemical index of alteration (CIA) values (31.7–50.9), suggesting a semi-arid climate in a weathering-limited source area. Moreover, correlation of major element oxides suggests the controlling effect of plagioclase and clay minerals on these data when XRD analysis and SEM images indicate clastic sourced illite and chlorite in the samples, probably due to the weathering of volcanic ash and glass in an aqueous transport and depositional environment. However, the chondrite-normalized REE plot of mudrocks of the Asara Shale show a similarity with the UCC composition. Mineral composition and geochemistry of the Asara Shale mudrocks reveal the rapid reworking of penecontemporaneous volcaniclastic deposits, which had covered the surrounding areas, instead of their epiclastic genesis related to erosion and transport. Major, trace, and rare earth element (REE) data, imply a felsic composition of the volcanic source, related to an active continental margin/continental island arc and most probably back-arc tectonic setting for the depositional basin, inferring a mid-upper Eocene extensional volcanism in a subduction complex.

Evidence for an unknown explosive eruption of Mt. Etna volcano (Italy) during the Late Glacial

We report on the geochemical and chronological characterization of a tephra layer, here called RdV-T1, recovered within a continental sequence at Riparo di Venere site in the Fucino Basin (central Italy). Textural, mineralogical, and detailed geochemical (major and trace elements on single glass shard) analyses indicate that Mt. Etna is the volcanic source. Radiocarbon dating of charred materials above and below this tephra layer result in 13,380 ± 40 (16,260–15,920 cal yrs BP) and 13,620 ± 40 (16,625–16,230 cal yrs BP) 14C years BP, respectively. This age points out that RdV-T1 tephra derives from the Late Pleistocene activity of the Ellittico caldera-forming phase of Mt. Etna that is significantly (up to 1750 yrs) younger than the Biancavilla Ignimbrites and upper Acireale fall, which are the last known events of this eruptive cycle. In addition, the RdV-T1 tephra geochemical signature is distinct with respect to the Biancavilla Ignimbrites and upper Acireale fall. Therefore, the radiocarbon and geochemical data consistently indicate that the RdV-T1 tephra may represent an explosive event following the Biancavilla Ignimbrites and the upper Acireale fall not yet identified.

Late-Holocene ultra-distal cryptotephra discoveries in varved sediments of Lake Żabińskie, NE Poland

Varved (annually laminated) lake sediments provide valuable archives for ultra-distal tephra preservation and at the same time allow the precise dating of volcanic eruptive events. We used a high-precision varve chronology from Lake Żabińskie in NE Poland and EPMA glass chemical data to identify cryptotephra from three large-scale, late Holocene eruptions from European and Northern American volcanoes: the White River Ash eastern lobe (WRAe) eruption from Mount Churchill, Alaska (833–850 CE); a tentative finding of the Glen Garry eruption of the Askja volcano, Iceland (1966–2210 cal a BP); and an yet undefined eruption from Furnas volcano, Azores. The varve age of 863–903 CE of the Alaskan WRAe cryptotephra in Lake Żabińskie is slightly younger than the proximal radiocarbon date and the annual layer estimate of the distal AD860B correlative in the Greenland NGRIP ice core but is within 14C dating uncertainties of distal tephra findings in the Irish peat record. The varve ages of the Glen Garry and Furnas tephras in Lake Żabińskie provide a minimum age at 1991 cal a BP (41 BCE). All three cryptotephra findings represent their easternmost occurrences from the volcanic source and hence considerably extend existing tephra dispersal maps.