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Late Pleistocene tephras derived by large explosive volcanic eruptions are widespread in the Mediterranean and surrounding areas. They are important isochronous markers in stratigraphic sections and therefore it is important to constrain their sources. We report here tephrochronology results using multiple criteria to characterize the volcanic products of the Late Pleistocene Ciomadul volcano in eastern–central Europe. This dacitic volcano had an explosive eruption stage between 57 and 30 ka. The specific petrological character (ash texture, occurrence of plagioclase and amphibole phenocrysts and their compositions), the high‐K calc‐alkaline major element composition and particularly the distinct trace element characteristics provide a strong fingerprint of the Ciomadul volcano. This can be used for correlating tephra and cryptotephra occurrences within this timeframe. Remarkably, during this period several volcanic eruptions produced tephras with similar glass major element composition. However, they differ from Ciomadul tephras by glass trace element abundances, ratios of strongly incompatible trace elements and their mineral cargo that serve as discrimination tools. We used (U‐Th)/He zircon dates combined with U‐Th in situ rim dates along with luminescence and radiocarbon dating to constrain the age of the explosive eruptions of Ciomadul that yielded distal tephra layers but lack of identified proximal deposits. [ABSTRACT FROM AUTHOR]

Abstract The presence of the Early Bronze Age Avellino (AV) tephra in the Holocene lacustrine deposits of the Agro Pontino and Fondi basin provides a unique opportunity to reconstruct the Holocene depositional environment at the time of AV-tephra deposition. Marine terraces of the last Pleistocene transgression have been consolidated by soil formation and incised during the last glacial. This created a gully landscape in the Fondi basin and in the southeastern Agro Pontino. The inland central part of the Agro Pontino was drained by one major gully. At the final part of subsequent Holocene sea level rise, beach ridges closed the southeastern marine lagoons, creating a lacustrine and marshy environment. Shortly after, the Avellino eruption deposited its sandy tephra in these freshwater environments. By comparing altitudes of the AV-tephra in different environments two major implications emerge. First, at those locations where the AV-tephra is underlain by thick Holocene peaty and clayey deposits, significant subsidence occurred, while this has been limited at locations where the Pleistocene marine terrace occurs close to the surface. This subsidence is independently checked by comparing a modern LiDAR DEM and a detailed DEM from 1928. Second, the altitude of the AV-tephra reflects sea level in the coastal positions around −1.5 to −2 m a.s.l., while the only gully draining the lacustrine and marshy inland Agro Pontino was blocked around 0.5 m a.s.l. by the expanding sediment wedge of the Amaseno River, the major draining axis of the Agro Pontino. The AV-tephra layer will continue to play an important role in regional geological, palaeoenvironmental and geo-archaeological research. [ABSTRACT FROM AUTHOR]

Heavy mineral associations from tephra layers in the Quaternary deposits of the Sea of Okhotsk and their chemical characteristics were studied by various techniques. It was shown that such investigations may have a bearing on the problems of tephrostratigraphic correlation. We assessed the possibility of application of the mineral composition of distal tephra for identification and, in particular, estimation of the relation of tephras to the explosive volcanism of back-arc and frontal zones of island arcs. The investigation of the compositions of minerals and use of mineral geothermometers and geobarometers (two-pyroxene, magnetite-ilmenite, and amphibole) provided evidence on the physicochemical parameters of melt crystallization during the explosive volcanic eruptions that produced the distal tephra layers. It was established that the pyroclastic material of some tephra layers was supplied during explosive eruptions not only from shallow magma chambers but also from deeper and higher temperature reservoirs. Together with the geochemical signatures of volcanic glasses, the obtained results on mineral associations and the geochemistry of mineral inclusions are applicable for the comparative analysis and correlation of tephras from marine and continental sequences, as well as for the identification of explosive volcanic products in adjacent land areas. [ABSTRACT FROM AUTHOR]

Kamchatka is one of the world's most active volcanic regions and has hosted many explosive eruptions during the Holocene. These eruptions had the potential to disperse tephra over wide areas, forming time-synchronous markers wherever those tephras are found. Recent research in Kamchatka has begun to focus on the geochemical analysis of individual glass shards in order to characterise tephra layers. We have applied this approach to the study of visible tephras from three lakes – one in central and two in northern Kamchatka – with the aim of identifying key tephras and potential issues in the application of distal (> 100 km from an active volcano) tephra in volcanically complex regions. In total, 23 tephras from 22 tephra beds have been geochemically analysed, representing products from at least four volcanic systems in Kamchatka. We demonstrate that distal lake sediments in the region can yield reliable tephrostratigraphies, capturing tephra from eruptions that have the greatest potential to disperse volcanic ash beyond the region. We draw attention to issues relating to correlating and distinguishing key marker horizons from the highly active Shiveluch Volcano, namely the need to ensure inter-lab comparability of geochemical data and good chronological control of the proximal and distal tephras. Importantly, we have also extended the known distribution of two key tephra isochrons from the Ksudach volcano. Our work contributes valuable glass geochemical on data several key marker beds that will facilitate future tephra and palaeoenvironmental research within and beyond Kamchatka. [ABSTRACT FROM AUTHOR]

The main phase of the moderately sized November 2004 eruption of the Grímsvötn volcano, located in the center of the 8100 km2 Vatnajökull glacier, was monitored by the Icelandic Meteorological Office C-band weather radar in Keflavík, 260 km west of the volcano. The eruption plume reached a height of 6-10 km relative to the vent. The distribution of the most distal tephra was measured in the autumn of 2004, while the deposition on the glacier was mapped in the summers of 2005 and 2006. The tephra formed a well-defined layer on the glacier in the region north and northeast of the craters. The total mass of the tephra layer is quantitatively compared with the retrieved values, obtained from an improved version of the volcanic ash radar retrieval (VARR) algorithm. VARR was statistically calibrated with ground-based ash size distribution samples, taken at Vatnajökull, and by taking into account both antenna beam occlusion and wind-driven plume advection. The latter was implemented by using a space-time image phase-based cross-correlation technique. Accuracy of the weather radar records was also reviewed, noting that a large variability in the plume height estimation may be obtained using different approaches. The comparisons suggest that, at least for this subglacial eruption, the surface tephra mass, estimated by using the VARR inversion approach, is in a fairly good agreement with in situ measurements in terms of spatial extension, distribution, and amount. [ABSTRACT FROM AUTHOR]

Abstract: Clearly defined distal tephras are rare in rockshelter sediment records. Crvena Stijena, a Palaeolithic site in Montenegro, contains one of the longest (>20m) rockshelter sediment records in Europe with deposits ranging in age from Middle Pleistocene to mid-Holocene. A distinctive tephra is clearly exposed within the well stratified record approximately 6.5m below the present land surface. We present geochemical data to confirm that this tephra is a distal equivalent of the Campanian Ignimbrite deposits and a product of the largest Late Pleistocene eruption in Europe. Originating in the Campanian volcanic province of southwest Italy, this tephra has been independently dated to 39.3ka. It is a highly significant chronostratigraphic marker for southern Europe. Macrostratigraphic and microstratigraphic observations, allied with detailed particle size data, show that the tephra layer is in a primary depositional context and was transported into the rockshelter by aeolian processes. This site is unique because the tephra forms an abrupt boundary between the Middle and Upper Palaeolithic records. Before they can be used as chronostratigraphic markers in rockshelter and cave-mouth environments, it is essential to establish the stratigraphic integrity of distal tephras and the mechanisms and pathways involved in their transport and deposition. [Copyright &y& Elsevier]

Abstract: Distal deposits of rhyolitic volcanic ash from the ∼74 ka “supervolcanic” eruption of Toba, in northern Sumatra, are preserved in numerous river valleys across peninsular India. The Toba eruption is hypothesized to have resulted in climate change and the devastation of ecosystems and hominin populations. This study reports the results of the analysis of sediments and stratigraphical sequences from sites in the Jurreru and Middle Son valleys in southern and north-central India. The aim of the study is to determine the extent of palaeoenvironmental change in both valleys as a result of the ash-fall. Inferences based on evidence from the Jurreru valley are more detailed, where pre- and post-Toba palaeoenvironmental changes are divided into seven phases. The results indicate that ash-fall deposits in both valleys underwent several phases of reworking that possibly lasted for several years, indicating that ash was mobile in the landscape for a considerable period of time prior to burial. This could have enhanced and lengthened the detrimental effects of the ash on vegetation and water sources, as well as animal and hominin populations. [Copyright &y& Elsevier]

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Detrital zircons of five sandstones were analysed based on their laser ablation multi-collector inductively coupled plasma mass spectrometry uranium–lead (U–Pb) ages and their morphological features to reveal the provenance of the Lower Cretaceous Duwon Formation in Goheung, Korea. A total of 495 valid analytical points were obtained from zircon U–Pb dating, and in terms of age distribution, there were 361 Precambrian zircons (ca. 73%), nine Palaeozoic zircons (ca. 2%) and 125 Mesozoic zircons (ca. 25%). Except for 16 Cretaceous zircons, most were interpreted to be derived from the Yeongnam Massif and the southwestern Okcheon Basin located in the area to the northwest or west of the Duwon Formation. However, the Cretaceous zircons (ca. 127–118 Ma), which accounted for ~3% of all zircons, were formed during the magmatic quiescence in the Korean Peninsula, making it difficult to interpret their provenance at this time. This period coincided with active igneous activities in eastern China due to the low-angle subduction of the Palaeo-Pacific plate. In addition, westerlies were dominant due to the atmospheric general circulation. From morphological analysis of the zircons, Cretaceous zircons were smaller in size than those from other ages and generally had good sphericity and a euhedral shape. The overall evidence suggests the possibility that predominant westerly winds supplied Cretaceous zircons to the Korean Peninsula during explosive volcanic eruptions in eastern China during the Early Cretaceous. However, further studies are needed to clarify this hypothesis. [ABSTRACT FROM AUTHOR]

Following on the discovery (in 2011) of a layer of distal tephra from the Pomici di Avellino eruption (Somma-Vesuvius, EU5) in the Agro Pontino (southern Lazio, Italy), further detailed study of the Holocene sediment archives in this graben and in the nearby Fondi coastal basin showed that distal tephra from this EU5 eruption occurs as a rather continuous, conspicuous layer. Two other, less conspicuous tephra layers were found, identified as the earlier Astroni 6 eruption from the Campi Flegrei (Fondi basin) and the later AP2 eruption of the Somma-Vesuvius (Agro Pontino). The identification of the distal tephra layers rests upon a combination of criteria, including stratigraphy, macro characteristics, mineralogy, geochemical data on glass composition, Sr-isotopic ratios, and the known tephrochronology for the period concerned, i.e. between c. 2500 and 1000 BCE. 14C datings serve to constrain their age. No significant spatial variation in the characteristics of the main tephra layer (EU5) was observed, other than distinct fining with increasing distance from the vent. Based on a detailed palaeogeographical reconstruction, the occurrence and preservation of these tephra are explained by the local environmental conditions governing their preservation during this time span (the Central Italian Bronze Age), and by the later evolution of the area. The observations underpin that multiple corings are needed to fully assess whether sedimentary hiatuses exist in palaeorecords, based on cores from sediment archives. Lastly, our study shows that hazard evaluations for future eruptions by Campanian volcanoes should pay more attention to their potential impacts on distal areas. • Sediment archives coastal southern Lazio hold three Bronze Age Campanian distal tephra. • Distal EU5 tephra conspicuous Early Bronze Age marker bed in Tyrrhenian Central Italy • Preservation tephra depends on contemporary environment and vegetation. • Absence distal tephra in Late Holocene cores from Lazial coastal area indicates hiatus • Reliable record coastal archive requires multiple cores and landscape reconstruction. [ABSTRACT FROM AUTHOR]