Ash Zone Research Articles

Medical Waste Management and Design of a Low-Cost Incinerator for Reduction of Environmental Pollution in a Multi-System Hospital

Pollution of the environment and inappropriate management of medical wastes are major challenges facing developing countries and this must be tackled with recent technology for public health, enhanced natural ecosystems, and a better environment. This research is a two-step process that involves the assessment of the existing Hospital waste management practices in a multi-system Hospital in Ado-Ekiti, Nigeria. Excess air, kerosene (auxiliary fuel), single chamber, Batch-fed (Manual feeding), and controlled air incinerator were designed. Wastes were loaded once at the beginning of the combustion cycle followed by combustion, ash burnout, cool down, and ash removal to assist medical waste management. Findings revealed that personnel involved in handling medical waste were equipped with inadequate protective gear. Medical waste was handled together with municipal waste and both wastes were incinerated in an open dumpsite without engineered sanitary landfill at disposal locations constituting a nuisance with a high risk of pollution to the surrounding environment. The incinerator was designed for a waste load of 269 kg.day-1. It consists of four zones; the waste and combustion zone (2.7 m × 1.8 m × 1 m), the ash zone (0.23 m height), the combustion fumes and one-second retention zone (0.43 m height) as well as the excess air zone (0.46 m height). This low-cost medical waste incinerator has a lot of improvement, operational effectiveness, and efficiency to the currently available techniques. Viable recommendations made will improve the state of environmental health and reduce the harmful effects of medical waste.

ANALISIS FINANCIAL DISTRESS DENGAN MENGGUNAKAN METODE ALTMAN Z-SCORE PADA PERUSAHAAN SUB SEKTOR MAKANAN DAN MINUMAN YANG TERDAFTAR DI BURSA EFEK INDONESIA (BEI) PERIODE 2014-2018

This study aims to determine the financial distress condition of food and beverage companies listed on the Indonesia Stock Exchange for the period 2014-2018. The sampling technique used is purposive sampling. This research was conducted on 9 food and beverage companies listed on the Indonesia Stock Exchange for the period 2014-2018. The type of data used in this study is secondary data obtained from the website www.idx.co.id. The method used to analyze financial distress is the Altman Z-Score Modification method using 4 variables X1 X2 X3 and X4. Has the formula Z” = 6.56X1 + 3.26X2 + 6.72X3 + 1.05X4. Z-Score rating category > 2.6 is in the Safe Zone, 1.1 < Z-Score > 2.6 is in the Ash Zone gray so that the possibility of being saved and the possibility of going bankrupt is equally dependent on the decision of the company's management as the decision maker. Z-Score <1.1 is in the Danger Zone categorized as a company experiencing financial difficulties and at high risk of bankruptcy. The results showed that 2 companies were in the Danger Zone, including: PT Tri Banyan Tirta Tbk and PT Prasidha Aneka Niaga Tbk, 4 companies were always in the Safe Zone, including: PT Wilmar Cahaya Indonesia tbk, PT Delta Djakarta Tbk, PT Nippon Indosari Corpindo Tbk and PT Siantar Top tbk, 3 other companies are in the Gray Zone, including: PT Multi Bintang Indonesia Tbk, PT Sekar Bumi Tbk and PT Sekar Laut Tbk

The Distal and Local Volcanic Ash in the Late Pleistocene Sediments of the Termination I Interval at the Reykjanes Ridge, North Atlantic, Based on the Study of the Core AMK-340

We made the geochemical analysis of the volcanic material from the sediment core AMK-340 (the Russian research vessel “Akademik Mstislav Keldysh” station 340), the central zone of the Reykjanes Ridge. Two ash-bearing sediment units within the interval of the Termination I can be detected. They correlate with the Ash Zone I in the North Atlantic Late Quaternary sediments having an age of 12,170–12,840 years within the Younger Dryas cold chronozone and 13,600–14,540 years within the Bølling–Allerød warm chronozone. The ash of the Younger Dryas unit is presented mostly by the mafic and persilicic material originated from the Icelandic volcanoes. One sediment sample from this unit contained Vedde Ash material. The ash of the Bølling–Allerød unit is presented mostly by the mafic shards which are related to the basalts of the rift zone on the Reykjanes Ridge, having presumably local origin. Possible detection of Vedde Ash could help to specify the timing of the previously reconstructed paleoceanographic changes for the Termination I in the point of the study: significant warming in the area might have occurred as early as 300 years before the end of the conventional Younger Dryas cold chronozone.

Widespread tephra dispersal and ignimbrite emplacement from a subglacial volcano (Torfajökull, Iceland)

The tephra dispersal mechanisms of rhyolitic glaciovolcanic eruptions are little known, but can be investigated through the correlation of eruptive products across multiple depositional settings. Using geochemistry and geochronology, we correlate a regionally important Pleistocene tephra horizon—the rhyolitic component of North Atlantic Ash Zone II (II-RHY-1)—and the Thorsmork Ignimbrite with rhyolitic tuyas at Torfajokull volcano, Iceland. The eruption breached an ice mass >400 m thick, leading to the widespread dispersal of II-RHY-1 across the North Atlantic and the Greenland ice sheet. Locally, pyroclastic density currents traveled across the ice surface, depositing the variably welded Thorsmork Ignimbrite beyond the ice margin and ~30 km from source. The widely dispersed products of this eruption represent a valuable isochronous tie line between terrestrial, marine, and ice-core paleoenvironmental records. Using the tephra horizon, estimates of ice thickness and extent derived from the eruption deposits can be directly linked to the regional climate archive, which records the eruption at the onset of Greenland Stadial 15.2.

40Ar/39Ar dating of the Thorsmork ignimbrite and Icelandic sub-glacial rhyolites

Robust correlation of paleoclimatic archives (e.g. marine sediments, ice, speleothems) necessitates an increase of the number of independent and accurately dated stratigraphic markers using numerical methods. Icelandic rhyolitic volcanism has a strong chronological interest because these products are found as tephra in the North Atlantic marine archives as well as in Greenland ice cores. In this study, we have dated, using the 40Ar/39Ar method, subglacial rhyolites of the Tindfjallajökull, Kerlingarfjöll and Torfajökull volcanoes which are the main sources of rhyolitic tephra identified in marine and glaciological records.The Thorsmork ignimbrite (Tindfjallajökull) which correlates with the rhyolitic component (II-RHY-1) of the North Atlantic Ash Zone II (NAAZ II) layer is dated at 55.6 ± 2.4 ka, an age that agrees with the ones given by the ice core chronologies (GICC05: 55.4 ± 1.2 ka). The eruptions of Rauðfossafjöll and Fannborg are respectively dated at 77.0 ± 3.0 ka and 149.3 ± 3.4 ka.These new ages along with the published ones confirm, as already concluded by Flude et al. (2010) that there is no clear evidence, at least at the latitude of Iceland, that climate warming is the main mechanism that triggered rhyolitic eruptions.Combining major and trace element compositions with our new age determinations, it appears that the Rauðfossafjöll and the Snaefell rhyolitic eruptions have not yet been discovered in marine sediment cores. Nevertheless, given the accuracy and precision of our dating, these rhyolitic eruptions have the potential to become chronostratigraphic markers, once tephra shards corresponding to these eruptions are discovered in ice and or marine sediment records. The Fannborg eruption might be recorded in the marine core LINK 16 during MIS 6 prior to the transition to MIS5e.

Ventilation history of Nordic Seas overflows during the last (de)glacial period revealed by species‐specific benthic foraminiferal 14C dates

AbstractFormation of deep water in the high‐latitude North Atlantic is important for the global meridional ocean circulation, and its variability in the past may have played an important role in regional and global climate change. Here we study ocean circulation associated with the last (de)glacial period, using water‐column radiocarbon age reconstructions in the Faroe‐Shetland Channel, southeastern Norwegian Sea, and from the Iceland Basin, central North Atlantic. The presence of tephra layer Faroe Marine Ash Zone II, dated to ~26.7 ka, enables us to determine that the middepth (1179 m water depth) and shallow subsurface reservoir ages were ~1500 and 1100 14C years, respectively, older during the late glacial period compared to modern, suggesting substantial suppression of the overturning circulation in the Nordic Seas. During the late Last Glacial Maximum and the onset of deglaciation (~20–18 ka), Nordic Seas overflow was weak but active. During the early deglaciation (~17.5–14.5 ka), our data reveal large differences between 14C ventilation ages that are derived from dating different benthic foraminiferal species: Pyrgo and other miliolid species yield ventilation ages >6000 14C years, while all other species reveal ventilation ages <2000 14C years. These data either suggest subcentennial, regional, circulation changes or that miliolid‐based 14C ages are biased due to taphonomic or vital processes. Implications of each interpretation are discussed. Regardless of this “enigma,” the onset of the Bølling‐Allerød interstadial (14.5 ka) is clearly marked by an increase in middepth Nordic Seas ventilation and the renewal of a stronger overflow.

Study of mutations in aminolevulinic acid dehydratase (ALAD) gene in cattle from fly ash zone in Maharashtra, India

The experiment was undertaken collaboratively at the Department of Animal Genetics and Breeding, Nagpur Veterinary College, Nagpur; National Environmental Engineering Research Institute (NEERI), Nagpur to study the mutagenic effect of fly ash on bovine Amino Levulinic Acid Dehydratase (ALAD) gene. DNA was extracted from blood samples of 49 fly ash exposed cattle born and reared in vicinity of two Thermal Power Plants, Koradi and Khaperkheda and 41 healthy animals reared at organised farms located more than 10 kilometres away from the plants as the control group. Polymerase Chain Reaction and DNA sequencing of the PCR products were carried out for mutation analysis. ‘MEGA- 5, Bioedit and ‘Clustal Omega’ software were used to analyse the sequenced data. Thirteen animals from fly ash exposed group revealed mutations at different loci. Most of the animals exhibiting mutations had phenotypic expression of heavy metal toxicity. The nucleotide substitution variant G → C was observed in highest frequency. Mutations in bovine ALAD gene may be due to a prolonged exposure to heavy metals and other toxic elements present in fly ash released from the thermal power plants. Further, it serves as ALAD gene may be used as a good candidate for further toxico-genomic studies.

Isolation of Phosphate Solubilizing Microorganism (PSM) from Reclaimed Fly Ash Zone of Mejia Thermal Power Station (MTPS) and its Implications

3 Abstract: The present world is greatly inclined towards alternating energy, but yet the use of coal as a primary energy source cannot be avoided. Disposal of huge amount of fly ash from the thermal power plants cannot be bypassed, since we cannot circumvent the second law of thermodynamics. The management of fly ash is a matter of great concern, in the present century. It has great potentiality in agriculture due to its efficacy in modification of soil health and crop performance. The present paper aims to highlight the optimum use of the metal phosphorus, present in the fly ash generated from Mejia Thermal Power Station (M.T.P.S), in boosting the agricultural production. The paper also identified strains of Phosphorus Solubilizing Bacteria (PSBs) that are capable of converting the insoluble form of phosphorus present in rock soil into a more accessible soluble form.

Last glacial period cryptotephra deposits in an eastern North Atlantic marine sequence: Exploring linkages to the Greenland ice-cores

The establishment of a tephra framework for the Greenland ice-cores spanning the last glacial period, particularly between 25 and 45 ka b2k, provides strong potential for precisely correlating other palaeoclimatic records to these key archives. Tephra-based synchronisation allows the relative timing of past climatic changes recorded within different depositional environments and potential causal mechanisms to be assessed. Recent studies of North Atlantic marine records have demonstrated the potential of tracing cryptotephra horizons in these sequences and the development of protocols now allows a careful assessment of the isochronous nature of such horizons. Here we report on tephrochronological investigations of a marine sequence retrieved from the Goban Spur, Eastern North Atlantic, covering ∼25–60 ka b2k. Density and magnetic separation techniques and an assessment of potential transport and depositional mechanisms have identified three previously unknown isochronous tephra horizons along with deposits of the widespread North Atlantic Ash Zone II and Faroe Marine Ash Zone III. Correlations between the new horizons and the Greenland ice-core tephra framework are explored and despite no tie-lines being identified the key roles that high-resolution climatostratigraphy and shard-specific trace element analysis can play within the assessment of correlations is demonstrated. The previously unknown horizons are new additions to the overall North Atlantic tephra framework for the last glacial period and could be key horizons for future correlations.

Refining the Icelandic tephrachronology of the last glacial period – The deep-sea core PS2644 record from the southern Greenland Sea

The PS2644 deep-sea core sequence, retrieved from the northwestern margin of Iceland and covering the last 86ka, exhibits high sedimentation rates during the last glacial cycle that allow the clear distinction of Greenland stadial (GS)/interstadial (GI) cycles in the various proxy records. Abundance records of rhyolitic, basaltic and tachylytic tephra grains reveal several maxima. Tephra grains of all types were geochemically analyzed in 44 levels. A total of 92 tephras with a distinctive character have been defined within the glacial sequence of gravity core PS2644-5, whereas the Holocene record is dominated by reworked Vedde Ash grains and not suitable for tephra stratigraphic work. Of the 92 tephras only 19 geochemical populations have been linked with confidence to previously defined tephras such as from the Vedde Ash, Faeroe Marine Ash Zones (FMAZ) II and III and North Atlantic Ash Zone (NAAZ) II. For the glacial period informal names were given to 78 new tephras, most of which are basaltic tephras. Several of these layers have a unique geochemical character and might become new chronostratigraphic markers in the North Atlantic region. Linking the tephra populations to the volcanic system producing them, respectively, revealed that Icelandic eruptions dominate with 83 tephra geochemical populations and Jan Mayen with 9. Around 48% of the informal tephra layers linked to the Icelandic volcanic province are produced from either the Grimsvötn or the Veidivötn-Bardarbunga volcanic systems. The intervals spanning from Greenland Stadial (GS) 3 to Greenland Interstadial (GI) 4 (24.5–29ka BP), from GI 8 to GS 10 (36.9–40.5ka BP) and from GI 14 to GI 15.2 (50–56ka BP) are the periods with the highest number of eruptions, all of which are associated with known tephra zones.

Differently Defined Flying Zone and State Approach in Case of Airborne Volcanic Ash: Impact on Flight Operations

Current European regulation that allows flying in forecasted, differently contaminated, volcanic ash zones as long as specific Safety Risk Assessment (SRA) is approved has the goal to reduce adverse impact that volcanic ash ejected in the atmosphere can have on air traffic management (ATM). However, the European States do not have unique understanding of this approach meaning that, in a few cases, States still decide to close their airspace in case of ash presence. Therefore, in this contribution, we analyze how definition of flying area within SRA and different State’s approach affect operations. We use volcanic ash data from the International Civil Aviation Organization’s (ICAO’s) volcanic ash exercise (VOLCEX13/01) and daily European traffic for simulation.

Optimising the use of marine tephrochronology in the North Atlantic: a detailed investigation of the Faroe Marine Ash Zones II, III and IV

Tephrochronology is central to the INTIMATE1 goals for testing the degree of climatic synchroneity during abrupt climatic events that punctuated the last glacial period. Since their identification in North Atlantic marine sequences, the Faroe Marine Ash Zone II (FMAZ II), FMAZ III and FMAZ IV have received considerable attention due to their potential for high-precision synchronisation with the Greenland ice-cores. In order to optimise the use of these horizons as isochronous markers, a detailed re-investigation of their geochemical composition, sedimentology and the processes that deposited each ash zone is presented. Shard concentration profiles, geochemical homogeneity and micro-sedimentological structures are investigated for each ash zone preserved within core JM11-19PC, retrieved from the southeastern Norwegian Sea on the central North Faroe Slope. This approach allows a thorough assessment of primary ash-fall preservation and secondary depositional features and demonstrates its value for assessing depositional integrity in the marine environment. Results indicate that the FMAZ II and IV are well-resolved primary deposits that can be used as isochrons for high-precision correlation studies. We outline key recommendations for future marine tephra studies and provide a protocol for optimising the application of tephrochronology to meet the INTIMATE synchronisation goals.

Faroe Marine Ash Zone IV: a new MIS 3 ash zone on the Faroe Islands margin

Abstract A basaltic tephra layer from MIS 3 has been discovered by analysis of cores from the Faroe Islands margin. The tephra layer appears up to 20 cm thick in some records. After the first main fall-out event the tephra is believed to be mainly deposited and redistributed by bottom currents. Geochemical analyses suggest that the tephra is relatively undisturbed by allochtonous tephra grains and unmixed. The peak occurrences are in the lower part of GIS (Greenland Interstadial) 12 and we suggest naming this new tephra Faroe Marine Ash Zone IV (FMAZ IV), following the nomenclature adopted for previous ash zones found on the Faroe Islands margin. Geochemical analyses of the tephra show affinities with the Grímsvötn volcanic system in the Eastern Volcanic Zone in south Iceland. The average age of FMAZ IV from four independent age models is 46 800±1000 years BP. We suggest that the V5 ash zone, found on the Reykjanes Ridge is a correlative to the FMAZ IV. Supplementary material: Single-grain analyses of tephra from FMAZ IV in cores from the northern Faroe margin and the central Faroe-Shetland Channel are available at http://www.geolsoc.org.uk/SUP18714

Revisiting the Faroe Marine Ash Zone III in two Greenland ice cores: implications for marine‐ice correlations

ABSTRACTNineteen new Icelandic tephra layers are identified in NGRIP and NEEM ice spanning Greenland Interstadial‐9 (GI‐9) and the early phase of GI‐8 (∼38 000–40 500 b2k). Fourteen tephras are identified in the NGRIP record and five direct correlatives are identified in NEEM, thus indicating the occurrence of 14 separate volcanic events. With two exceptions, the tephras are tholeiitic basalt in composition and despite having very similar geochemical signatures can, in most cases, be discriminated from one another using their TiO2 values. All of these tephra layers fall within the compositional range of the Faroe Marine Ash Zone III (FMAZ III) deposit previously identified in ocean cores from the Faroes region and previously correlated to NGRIP 2066.95 m by Davies et al. (). Thus, the FMAZ III in the marine realm is most likely a complex ash zone that represents a series of closely timed Grimsvötn eruptions that, as yet, can only be stratigraphically separated in the high‐resolution ice‐core records. The geochemical signatures and stratigraphic positions of the new ice‐core layers means that the FMAZ III tephra deposit, as currently defined in the marine realm, cannot be correlated to NGRIP 2066.95 m or any other ice‐core tephra horizons preserved during this interval.

Geology of the Early Arikareean Sharps Formation on the Pine Ridge Indian Reservation and Surrounding Areas of South Dakota and Nebraska

Based on geologic mapping, measured sections, and lithologic correlations, the local features of the upper and lower type areas of the Early Arikareean (30.8–20.6 million years ago) Sharps Formation are revised and correlated. The Sharps Formation above the basal Rockyford Member is divided into two members of distinct lithotypes. The upper 233 feet of massive siltstones and sandy siltstones is named the Gooseneck Road Member. The middle member, 161 feet of eolian volcaniclastic siltstones with fluvially reworked volcaniclastic lenses and sandy siltstone sheets, is named the Wolff Camp Member. An ashey zone at the base of the Sharps Formation is described and defined as the Rockyford Ash Zone (RAZ) in the same stratigraphic position as the Nonpareil Ash Zone (NPAZ) in Nebraska. Widespread marker beds of fresh water limestones at 130 feet above the base of the Sharps Formation and a widespread reddish-brown clayey siltstone at 165 feet above the base of the Sharps Formation are described. The Brown Siltstone Beds of Nebraska are shown to be a southern correlative of the Wolff Camp Member and the Rockyford Member of the Sharps Formation. Early attempts to correlate strata in the Great Plains were slow in developing. Recognition of the implications of the paleomagnetic and lithologic correlations of this paper will provide an added datum assisting researchers in future biostratigraphic studies. Based on similar lithologies, the Sharps Formation, currently assigned to the Arikaree Group, should be reassigned to the White River Group.

Progenitor-derivative speciation in Pozoa (Apiaceae, Azorelloideae) of the southern Andes.

Studies examining patterns and processes of speciation in South America are fewer than in North America and Europe. One of the least well documented processes has been progenitor-derivative speciation. A particularly instructive example occurs in the southern Andes in the genus Pozoa (Apiaceae, Azorelloideae), which consists of only two diploid outcrossing species, the widespread P. coriacea and the geographically and ecologically restricted P. volcanica. This paper tests the hypothesis that the latter species originated from the former through local geographical and ecological isolation by progenitor-derivative speciation. DNA sequences were analysed from Pozoa and the related South American genera Asteriscium, Eremocharis and Gymnophyton from non-coding regions of the plastid genome, ndhF-rpl32 and rpl32-trnL, plus incorporation of previously reported rpl16 intron and trnD-trnT intergenic spacer sequences. Amplified fragment length polymorphism (AFLP) data from 105 individuals in 21 populations throughout the entire range of distribution of the genus were used for estimation of genetic diversity, divergence and SplitsTree network analysis. Ecological factors, including habitat and associated species, were also examined. Pozoa coriacea is more similar genetically to the outgroup genera, Asteriscium and Eremocharis, than is P. volcanica. At the population level, only P. volcanica is monophyletic, whereas P. coriacea is paraphyletic. Analyses of genetic differentiation among populations and genetic divergence and diversity of the species show highest values in P. coriacea and clear reductions in P. volcanica. Pozoa coriacea occurs in several types of high elevation habitats, whereas P. volcanica is found only in newly formed open volcanic ash zones. All facts support that Pozoa represents a good example of progenitor-derivative speciation in the Andes of southern South America.

Non‐synchronous deposition of North Atlantic Ash Zone II in Greenland ice cores, and North Atlantic and Norwegian Sea sediments: an example of complex glacial‐stage tephra transport

AbstractTephra provides regional chronostratigraphical marker horizons that can link different climate archives with highly needed accuracy and precision. The results presented in this work exemplify, however, that the intermittent storage of tephra in ice sheets and during its subsequent iceberg transport, especially during glacial stages, constitutes a potential source of serious error for the application of tephrochronology to Nordic Seas and North Atlantic sediment archives. The peak shard concentration of the rhyolitic component of the North Atlantic Ash Zone II (NAAZ‐II) tephra complex, often used to correlate marine and ice core records in Marine Isotope Stage (MIS) 3, is shown to lag the eruption event by ca. 100–400 years in some North Atlantic and Norwegian Sea cores. While still allowing for a correlation of archives on millennial timescales, this time delay in deposition is a major obstacle when addressing the lead–lag relationship on short timescales (years to centuries). A precise and accurate determination of lead–lag relationships between archives recording different parts of the climate system is crucial in order to test hypotheses about the processes leading to abrupt climate change and to evaluate results from climate models. Copyright © 2011 John Wiley & Sons, Ltd.

Sulphur capturing by an inertinite rich high ash bituminous coal during conversion in a pilot packed bed reactor

Sulphur is liberated from the coal structure and released in various forms during coal thermal processing. The possibility of sulphur capture, through injection of SO 2 into a packed coal bed in a pilot packed bed reactor operated under controlled conditions, was investigated. Results showed that SO 2 injection into a packed coal bed leads to sulphur capturing mainly in the coal mineral matter. Mineralogical analysis (XRD) of the ash samples obtained from the experiments indicates that the sulphur-capture products that are formed include FeS, CaS and small amounts of organically associated sulphur. Troilite (FeS) was observed in the SO 2 treated samples, while no troilite was observed in the reference samples. Calcite and dolomite are transformed into CaO and other calcium-containing compounds in the pyrolyses zone, with some CaS being formed in the gasification zone via the reaction between SO 2 and CaO in the presence of CO from the gasification reactions. CaO formed at the high temperatures in the combustion and ash zone is transformed into CaSO 4 upon reaction with SO 2 as an oxidizing atmosphere prevails in this zone. The existence of these compounds is dependent on the extent of oxidising or reducing conditions during the process, with CaS favoured under reducing conditions and CaSO 4 favoured under oxidising conditions.

Tephra in deglacial ocean sediments south of Iceland: Stratigraphy, geochemistry and oceanic reservoir ages

AbstractIcelandic tephra layers within deglacial ocean sediment cores from south of Iceland have been detected and their timing with respect to the climate shifts of the last deglaciation constrained. Geochemical analysis of the tephra allowed the likely source volcanic systems to be identified. The previously known Saksunarvatn ash and Vedde ash are recognised and described. Several other major tephra layers are examined: basaltic eruption(s) of Katla at ∼8.4 ka; a basaltic eruption of Katla at ∼12.6 ka; a rhyolitic eruption of Katla at ∼13.6 ka producing tephra similar in appearance and composition to the Vedde ash; a basaltic eruption of Katla at ∼14.0 ka; and two basaltic eruptions of Grímsvötn at ∼14.6 ka and ∼15.0 ka. Abundant rhyolitic ash with a similar appearance and chemistry to the Vedde ash is found throughout the deglacial interval, predating the Vedde ash by up to 3000 years, supporting previous suggestions that there were pre‐Vedde ash eruptions of rhyolite that may have contributed to North Atlantic Ash Zone 1.This study expands the tephro‐stratigraphic framework of the North Atlantic and provides a marine archive in which the timing of tephra layers (useful as isochrons) can be directly compared to major ocean and climate events of the last deglaciation. Furthermore, by correlating tephra layers and abundance changes in the polar foraminifera, Neogloboquadrina pachyderma (sinistral), to equivalent tephra events and inferred abrupt cooling/warming in Greenland ice‐cores, contemporaneous 14C‐dated planktonic foraminifera have been used to estimate changes in the surface radiocarbon reservoir age south of Iceland. Consistent with previous studies, larger surface reservoir ages are calculated during late Heinrich Stadial 1 and the Younger Dryas (∼2000 years and ∼800–1900 years respectively). Copyright © 2011 John Wiley & Sons, Ltd.

Microanalysis of tephra by LA-ICP-MS — Strategies, advantages and limitations assessed using the Thorsmörk ignimbrite (Southern Iceland)

Micron-scale analysis of vesicular volcanic glass can be problematic because thin vesicle walls and junctions limit the area available for analysis, subsurface vesicles limit the vertical thickness available, microcrysts at or below the surface may contaminate glass analyses and some glasses show compositional banding. In addition, distal tephra are very small (10–100 μm) and material may be sparse. We have analysed the MPI-DING reference glasses and natural tephra samples (pumice, scoria and fiamme) from the Thorsmörk ignimbrite (Southern Iceland) using laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICP-MS). Three different reduction strategies are used: averaging, uncertainty weighting and log-linear regression. We then assess the data quality achieved using the various strategies. Using our technique we show that the main limiting factor on data quality is precision, particularly for natural tephra analyses. At > 20,000 cps, relative standard deviations (%RSDs) in the Thorsmörk tephra are 5–10% — approximately twice those achieved in the MPI-DING glasses (3–5%) at the same conditions. Rhyolitic pumice and fiamme from the Thorsmörk ignimbrite are compositionally homogenous. The proximal deposit also contains subordinate basalt scoria, therefore the deposit is bimodal. The Thorsmörk rhyolite correlates with the North Atlantic Ash Zone 2 (NAAZ2) tephra described in a marine sediment core (Lacasse and Garbe-Schönberg, 2001, JVGR 170, 113–147).