optically stimulated luminescence osl dating of coastal aeolian sand accumulation in sanday orkney islands scotland optically stimulated luminescence osl dating of sand has been used to identify periods of enhanced aeolian activity at two coastal archaeological sites in orkney that coincide with periods of holocene climatic deterioration recorded elsewhere in both scotland and w europe areas of tofts ness sanday were settled from the neolithic abandoned in the late neolithic early bronze age reoccupied and permanently abandoned in the iron age sand layers above the neolithic soils have been osl dated to about 4000 bp correlating well with a period of increased aeolian activity elsewhere in w europe osl dating of aeolian sands above midden deposits and a bronze age burial at lopness on sanday suggest dune development by 3000 bp although both sites also contain sand that was deposited during the little ice age several possible mechanisms may have contributed to an increase in aeolian activity during the holocene that led to the abandonment of these sites although volcanic eruptions in iceland cannot be disc

geochemistry mineralogy and technological properties of the main stephanian carboniferous coal seams from the puertollano basin spain this study is focused on the occurrence and distribution of mineral matter and major and trace elements in the high volatile bituminous coal from puertollano south central spain the relationship between ash behaviour and inorganic composition as well as the possible formation of fouling and slagging deposits in boilers during the conversion process were investigated the puertollano coals do not exhibit plastic properties despite their rank probably because of their high ash and inertinite contents the puertollano coal has medium to low total s content 0 48 to 1 63 db with a mean of 1 0 db and is characterised by relatively high contents of si pb sb and cs some elements such as as cd co cr cu ge li mn ni w and zn are also present in relatively high contents the enrichment in a number of heavy metals could be attributed to the common sulphide ores occurring near the puertollano coal deposit the following trace elements affinities are deduced a sulphide affinity as co cd cu ni sb tl and zn b aluminum silicate affinity k ti b co cr cs cu ga hf li nb rb sn ta th v zr and lree c carbonate affinity ca mg mn and b d organic affinity b the very high si levels and the anomalous enrichment in cs ge pb sb and zn shown by the puertollano coals account for the high contents of these elements in the puertollano fly ash when compared with the other spanish coal fly ashes the chemical composition of the high temperature ash hta is consistent with the trend shown by the ash fusion temperatures aft and also with the predictive indices related to slagging and fouling propensities thus the ash fusion temperatures increase with high values of al2o3 as well as with the decrease in fe2o3 cao and mgo

frost rings in trees as records of major volcanic eruptions new data about climatically effective volcanic eruptions during the past several thousand years may be contained in frost damage zones in the annual rings of trees there is good agreement in the timing of frost events and recent eruptions and the damage can be plausibly linked to climatic effects of stratospheric aerosol veils on hemispheric and global scales the cataclysmic proto historic eruption of santorini thera in the aegean is tentatively dated to 1628 26 bc from frost ring evidence

age and impacts of the caldera forming aniakchak ii eruption in western alaska the mid holocene eruption of aniakchak volcano aniakchak ii in southwest alaska was among the largest eruptions globally in the last 10 000 years vei 6 despite evidence for possible impacts on global climate the precise age of the eruption is not well constrained and little is known about regional environmental impacts a closely spaced sequence of radiocarbon dates at a peatland site over 1000 km from the volcano show that peat accumulation was greatly reduced with a hiatus of approximately 90 120 yr following tephra deposition during this inferred hiatus no paleoenvironmental data are available but once vegetation returned the flora changed from a cyperaceae dominated assemblage to a poaceae dominated vegetation cover suggesting a drier and or more nutrient rich ecosystem oribatid mites are extremely abundant in the peat at the depth of the ash and show a longer term increasingly wet peat surface across the tephra layer the radiocarbon sample immediately below the tephra gave a date of 1636 1446 cal yr bc suggesting that the eruption might be younger than previously thought our findings suggest that the eruption may have led to a widespread reduction in peatland carbon sequestration and that the impacts on ecosystem functioning were profound and long lasting

environmental change and tephra deposition the strath of kildonan northern scotland pollen analysis tephra counts and geochemical data are presented from the upper 200 cm of a core from a basin mire in the strath of kildonan northern scotland three main tephra concentrations are located and tentatively dated to c 7650bp k1 c 4250 bp k2 and 3250 bp k3 by cross correlation with the regional pollen chronology the identity of the tephra layers is unknown but the peak at 4250 bp may be from the hekla 4 eruption the associated changes in catchment soils and vegetation are highly variable k1 is associated with a major vegetation disturbance but no significant change occurs at k3 k2 is correlated with a large regional rise in pine pollen these results conflict with previous studies on distal impacts of volcanic activity during the holocene and demonstrate the diversity of environmental changes associated with holocene volcanic activity

the impact and significance of tephra deposition on a holocene forest environment in the north cascades washington usa high resolution palaeoecological analyses stratigraphy tephra geochemistry radiocarbon dating pollen and ordination were used to reconstruct a holocene vegetation history of a watershed in the pacific northwest of america to evaluate the effects and duration of tephra deposition on a forest environment and the significance of these effects compared to long term trends three tephra deposits were detected and evaluated mlf t158 and mlc t324 from the climactic eruption of mount mazama mlc t480 from a late pleistocene eruption of mount mazama and mlc t485 from a glacier peak eruption records were examined from both the centre and fringe of the basin to elucidate regional and local effects the significance of tephra impacts independent of underlying long term trends was confirmed using partial redundancy analysis tephra deposition from the climactic eruption of mount mazama approximately 7600 cal years bp caused a significant local impact reflected in the fringe location by changes to open habitat vegetation cyperaceae and poaceae and changes in aquatic macrophytes myriophyllum spicatum potamogeton equisetum and the alga pediastrum there was no significant impact of the climactic mazama tephra or other tephras detected on the pollen record of the central core changes in this core are potentially climate driven overall significant tephra fall was demonstrated through high resolution analyses indicating a local effect on the terrestrial and aquatic environment but there was no significant impact on the regional forest dependent of underlying environmental changes

impacts and timing of the first human settlement on vegetation of the faroe islands abstract stratigraphically precise ams radiocarbon dated plant remains pollen charcoal and microtephra analyses from the faroe islands were used to establish the timing and effects of the first human settlement the first occurrence of cultivated crops from three locations dated from as early as the sixth century a d and was older than implied from previous archaeological and historical studies but consistent with earlier palaeoecological investigations the effects of settlement on the vegetation were rapid and widespread the transformation of the flora of this fragile ecosystem was best expressed by the large assemblage of ruderal postsettlement plants recorded as macrofossils the earliest known introduction of domestic animals sheep goat was ca a d 700 their arrival on these relatively small islands probably contributed to the widespread change in vegetation and the loss of restricted native woody cover settlement was the critical disturbance that transformed an ecosystem that was already stressed by climatic change as sensed by regional marine sediments the settlement dates conform to a pattern of older dates developing from throughout the north atlantic region

dates of holocene icelandic volcanic eruptions from tephra layers in irish peats tephra from historic and prehistoric eruptions of oraefajokull and hekla iceland have been found in irish peats using a series of stratigraphically related high precision radiocarbon measure ments the date of a known age eruption has been satisfactorily estimated based on the same techniques the calendrical date of the hekla 4 eruption has been estimated as 2310 20 bc

dendrochronological evidence for a lower water table on peatland around 3200 3000 bc from subfossil pine in northern scotland tree ring analysis of subfossil pinus sylvestris l from nine new peatland sites located beyond the species current northern limit in scotland established a regional chronology called wrath 9 the chronology has been provisionally dated against irish pine chronologies and provides the first annual resolution picture of scots pine expansion from c 3200 bc and subsequent demise from c 3000 bc pine germination and growth is suggested to be associated with a widespread fall in bog water tables that indicates a regional climatic control bog pines progressively declined in number rather than died out in a single event reflecting their growth in a marginal habitat close to a critical ecological threshold the use of tree ring sequences from in situ bog pine macrofossils provides a higher resolution insight into past conditions than possible with existing radiocarbon and pollen based chronologies

geochemistry of holocene cryptotephras from the north iceland shelf md99 2269 intercalibration with radiocarbon and palaeomagnetic chronostratigraphies tephra grain counting morphology and geochemistry in the 150 1000 m size fraction were used to identify 22 individual tephra horizons and one visible tephra layer saksunarvatn from postglacial sediment of the north iceland shelf core md99 2269 66 37 53 n 20 51 16 w water depth 365 m length 2533 cm from the reykjafjardarall basin is constrained at the base by the vedde tephra c 12 000 cal yr bp geochemical analyses and stratigraphical position of the 22 tephra horizons were used to identify the following cryptotephras kol 1372 ad 1372 hekla 1104 ad 1104 snaefellsnes 1 c 1790 cal yr bp hekla 3 c 2970 cal yr bp hekla 4 c 4230 cal yr bp tv 5 c 6860 cal yr bp and suduroy c 8070 cal yr bp a tephra of the same geochemistry as kol 1372 was found near the base of the core and is here named kol3 2269 11 000 cal yr bp eleven additional cryptotephras were geochemically typed to their respective icelandic volcanic centres of origin and their ages constrained four teph

assessing the impact of volcanic activity on mid holocene climate in ireland the need for replicate data analyses of pollen tephra mineral input and degree of peat humification from three neighbouring raised peat profiles at corlea central ireland covering the period of the deposition of a tephra

assessing the potential for cryptotephra studies in northeastern china quaternary tephrochronology and tephrostratigraphy are employed globally for chronological control and site correlation but the potential for these approaches in northeastern china has not been fully explored in spite of this being a volcanically active region microscopic and precise electron microprobe geochemical analyses were performed on crypto or macrotephra layers in maar lake sediments from sihailongwan and peat from gushantun from the longgang volcanic field in ne china tentative links have been made to volcanism in the longgang and changbaishan volcanic fields from published radiocarbon dating data for sihailongwan and new ams dating for the gushantun tephra layer crypto tephrostratigraphy and tephrochronology for the longgang region have been constructed and their limitations are assessed

seven tephra isochrones in scotland this paper reports the presence and geochemical characteristics of seven separate tephras in scotland that fell in ad 1510 and about 450 bp 2100 bp 3600 bp 3830 bp 5600 bp and around 6000 bp the results come from 14 peat bogs spread throughout the highlands and islands where 26 tephra deposits have been characterized using over 400 grain discrete electron probe micro analysis firstly tephras are identified and defined by major element characteristics at a reference site secondly tephras are linked between sites on the basis of geochemistry and dated informal names based on british sites are suggested for tephras not yet linked to precise sources in iceland despite some apparent variation in colour all analysed grains in these seven deposits are silicic or intermediate in composition sio2 57 this phenomenon does not appear to be an artifact of preservation for two reasons first small 40 m basic glass shards in peat bogs in northern iceland are found to have undergone minimal alte

the impact of high tephra loading on late holocene carbon accumulation and vegetation succession in peatland communities abstract peatlands are major terrestrial stores of carbon c of importance to the global climate system recent studies have made progress in understanding the climatic controls on the c cycle however important interactions between volcanic deposition and peatland c stores remain to be addressed this study uses a 3000 year peatland record from northern japan to examine the interactions between carbon accumulation vegetation community succession and volcanic ash deposition plant macrofossil and testate amoebae records are presented alongside records of total organic carbon nitrogen and phosphorous age depth models are developed using a bayesian approach with seven ams radiocarbon dates and two identified historical tephras from baitoushan ad 969 981 cal bp and hokkaido komagatake ad 1640 310 cal bp volcanoes results show that moderate to high tephra loading can shift peatland plant communities from sphagnum to monocotyledon domination this vegetation change is associated with increased peat humification and reduced carbon accumulation where tephra deposition and reworking has occurred the apparent rate of carbon accumulation can be halved while high tephra loading of the mire surface is sustained sphagnum species vary in their tolerance to tephra deposition after each ash fall sphagnum magellanicum disappeared from the plant macrofossil record whereas sphagnum papillosum showed apparent continuity of development through the 1856 94 cal bp ko c1 tephra high rates of carbon accumulation peaking at 100 g m 2 yr 1 2 3 times faster than the average for northern peatlands were recorded in the sphagnum communities that established after the cessation of tephra deposition and reworking from the ad 969 baitoushan ash fall b tm tephra this peak in c accumulation was coincident with a radical shift in mire nutrient cycling most probably caused by the interaction of s magellanicum with leachates from the underlying tephras the phase of high c accumulation continued for over 300 years offsetting the initial negative impact of the b tm tephra on peatland c accumulation these results suggest that management for ash tolerant sphagnum species could be a highly effective strategy for minimising volcanic disruption to peatland carbon accumulation the study also shows that consideration of volcanic impacts on peatlands is essential for development of more realistic terrestrial carbon balance models in volcanically active regions

tephra linked peat humification records from irish ombrotrophic bogs question nature of solar forcing at 850 cal yr bc this paper investigates evidence for palaeoclimatic changes during the period ca 1500 500 cal yr bc through peat humification studies on seven irish ombrotrophic bogs the sites are well correlated by the identification of three mid first millennium bc tephras which enable the humification records at specific points in time to be directly compared phases of temporarily increased wetness are suggested at ca 1300 1250 cal yr bc ca 1150 1050 cal yr bc ca 940 cal yr bc and ca 740 cal yr bc the last of these is confirmed to be synchronous at five sites suggesting external forcing on a regional scale the timing of this wet shift is constrained by two closely dated tephras and is demonstrated to be distinct from the widely reported changes to cooler wetter conditions associated with a solar minimum at 850 760 cal yr bc at which time the irish sites appear instead to experience drier conditions the results suggest the possibility of either non uniform responses to solar forcing in northwest europe at this time or the existence of unrelated climate events in the early first millennium bc the findings caution against the correlation of loosely dated palaeoclimate data if the effects of forcing mechanisms are to be understood copyright 2006 john wiley sons ltd

distal volcanic impacts on peatlands palaeoecological evidence from alaska abstract despite the fact that volcanic ash tephra layers are found preserved in peat deposits around the world comparatively little research has investigated the impacts of distal volcanic emissions on peatlands this study investigates the impacts of several late holocene volcanic eruptions on five peatlands in southern alaska using a palaeoecological approach testate amoebae analysis peat humification analysis and a basic analysis of plant macrofossil components were applied across 11 tephra layers changes in macrofossil and testate amoebae assemblages occur across several of the tephra layers the humification results were considered unreliable because of a methodological problem a finding which may have implications for other studies using this technique redundancy analyses on testate amoebae data show statistically significant changes associated with two tephras the most likely causes of the impacts are volcanic gases acidic precipitation or tephra derived leachates the finding that some tephras are associated with impacts whereas others are not may relate to the season of the eruption or meteorological conditions at the time of ash fall these results suggest the sensitivity of peatlands and peatland microbial communities to distal volcanic products and imply that changes in key palaeoclimatic proxies may be caused by a mechanism independent of climate change implications of the results for peat based palaeoclimatic studies are discussed as are possible directions for future research

calendar year ages of three mid holocene tephra layers identified in varved lake sediments in west central sweden three intermediate to rhyolitic icelandic holocene tephra horizons hekla 3 kebister and hekla 4 have been identified in annually laminated varved lake sediments in the province of varmland west central sweden calendar year ages were obtained from varve counts and are supported by additional c 14 dating based on terrestrial plant macrofossils the varve ages of the three tephras are 3295 95 cal bp hekla 3 4030 103 cal bp kebister and 4390 107 cal bp hekla 4 the varve age of hekla 3 refines the former calibrated 14 c age based on studies in the british isles and germany considering the age error estimates associated with the varve chronology and calibrated c 14 ages the ages of kebister and hekla 4 are in agreement with former studies thus the age difference between kebister and hekla 4 is estimated to be ca 400 40 varve years formally estimated to ca 200 c 14 years between hekla 3 and hekla 4 to ca 1135 55 varve years formally estimated to ca 1100 calibrated c 14 years and between hekla 3 and kebister 708 20 varve years less

thin tephra layers in peat revealed by x radiography x radiography has been found to provide a rapid economical non destructive method of locating very thin fine grained tephra of icelandic origin in scottish peats tephra layers form time parallel marker horizons or isochrones that are of great archaeological significance because they cover large areas offer precise chronological control for associated material and occur at times of significant cultural and environmental changes not all of the discrete deposits of recent volcanic fallout in scotland are sufficiently dense to show clearly on x radiographs but those which do provide particularly clear easily located marker horizons with many applications in palaeoenvironmental studies the tephra layer in caithness produced by fallout from a c 4000 by eruption of hekla provides a particularly good example of the use of x radiography to locate volcanic ash the method also reveals other structures of archaeological and palaeoenvironmental significance butler 1992 journal of archaeological science 19 151 161

towards a tephrochronology for the holocene of the north of ireland discrete layers of tephra have been found in both raised and blanket bogs in the north of ireland some of the layers have been identified to an icelandic source and in two cases specific eruptions of known radiocarbon age are suggested nine layers spanning the holocene are replicated in three lowland raised bogs one of the major layers has also been identified at a number of sites in two separate upland blanket peat systems and in a lake sediment

selective concentration and enumeration of tephra shards from lake sediment cores this paper describes a technique for the enumeration of tephra shards from lake sediment cores whereby approximately 85 of unwanted sediment fractions organic matter biogenic silica carbonates are removed by selective stepwise chemical attack the order of 100 samples can be prepared simultaneously in a modest sized water bath and the recovery rate of the technique is greater than 90 the procedure is appli cable to all lake sediment types

traces of volcanic ash from the mediterranean iceland and north america in a holocene record from south wales uk a tephra record is presented for a sediment core from llyn llech owain south wales spanning the early to mid holocene seven cryptotephra deposits are discovered with three thought to correlate with known eruptions and the remaining four considered to represent previously undocumented events one deposit is suggested to correlate with the 6 9 cal ka bp lairg a tephra from iceland whereas more distant sources are proposed as the origin for two of the tephra deposits a peak of colourless shards in early holocene sediments is thought to tentatively correlate with the 9 6 cal ka bp fondi di baia tephra campi flegrei and a second cryptotephra is tentatively correlated with the 3 6 cal ka bp aniakchak cfe ii tephra alaska the fondi di baia tephra has never been recorded beyond proximal sites and its discovery in south wales significantly extends the geographical distribution of ash from this eruption the remaining four cryptotephra deposits are yet to be correlated with known eruptions demonstrating that our current understanding of widespread tephra deposits is incomplete this new tephra record highlights the potential for sites at more southerly and westerly locations in northwest europe to act as repositories for ash from several volcanic regions

effects of volcanic activity on mire development case studies from hokkaido northern japan field stratigraphy and macrofossil composition of four mires in hokkaido northern japan were investigated to test whether tephra deposition induces long term vegetation shifts macroscopic tephras of known origin ranging from 0 5 to 25 cm in thickness were found in two or more of the study sites allowing correlation of the stratigraphic development of the mires major peat types and position of macroscopic mineral layers were determined in the field and selected cores were analysed by quantitative macrofossil analysis some macrofossil groups and the content of unidentifiable organic matter showed changes in the vicinity of tephra layers but they did not indicate a clear response pattern of the vegetation or the decomposition dynamics of plant material mosses were expected to be most strongly affected by tephra deposition but even in cases where tephra fell on sphagnum dominated vegetation no fundamental shifts to new plant communities were found this suggests that disturbance by widespread tep

linking the north atlantic to central europe a high resolution holocene tephrochronological record from northern germany a high resolution holocene tephrochronology for northern germany has been established based on systematic tephrostratigraphical analysis of three peat bogs microscopic volcanic ash layers have been traced and characterised petrographically and by the chemical composition of the glass shards at least 37 ash horizons representing 16 different explosive volcanic eruptions have been identified and many can be correlated between the three sites up to 100 km apart the tephra layers can be related to icelandic volcanic sources and some correlated to the eruptions of askja 1875 hekla 3 hekla selsund hekla 4 and hekla 5 as well as to unspecified eruptions of icelandic volcanic systems e g torfajokull the source volcanoes for some tephra layers remain unidentified some tephra layers were known previously from the north atlantic region e g sluggan glen garry others have not been recorded previously in the literature e g microlite tephra this study provides the first comprehensive holocene tephrostratigraphical record for northern germany complementing the north atlantic tephrostratigraphical dating framework effectively extending it into central europe the study shows that icelandic ash layers are even more widespread than hitherto thought copyright 2002 john wiley sons ltd

evolution of the late quaternary san gregorio magno tectono karstic basin southern italy inferred from geomorphological tephrostratigraphical and palaeoecological analyses tectonic implications the pantano di san gregorio magno is a 4 7 km 2 large tectono karstic basin located in the axial belt of the southern apennines an area affected by intense seismicity the basin was formed in the middle pleistocene and is presently undissected it is filled by lacustrine sediments clays silts and pyroclastic sands passing laterally into alluvial fan deposits geomorphological investigations were integrated with tephrostratigraphical palynological and palaeoecological analyses of a 61 m thick core not reaching the bedrock the multiproxy analysis of the s gregorio magno record shows that over the last 200k yr the basin hosted a freshwater lake with an oscillating level age constraints provided by the tephrostratigraphic record allowed estimation of the sedimentation rate which varied strongly through time evolution of the basin resulted from the complex combination of tectonic subsidence karst processes and changing amounts of sedimentary inputs the latter was influenced by allogenic contributions related both to primary and reworked volcanoclastic inputs and was climate driven the overall evidence which indicates that in the long term the accumulation rate substantially counterbalanced the accommodation space created by faulting suggests that the basin evolution was also modulated by changing subsidence rates copyright 2006 john wiley sons ltd

topogenous peat development and late flandrian vegetation history at a site in upland south wales three radiocarbon dated pollen diagrams were made from progressively shallower depths on a transect through an upland stream valley bog in south wales the peat ranges in age from approximately 400

determination and evaluation of saltwater intrusion on bafra plain joint interpretation of geophysical hydrogeological and hydrochemical data saltwater intrusion and its spatial distribution using a multidisciplinary approach were investigated on the northeast coast of bafra plain which is one of the most important delta plains in turkey intensive agricultural activity in the study area which supplies the local and international market with agricultural products is increasing the importance of this ecosystem even the groundwater potential and supply are high the main problem is the groundwater degradation due to salinization moreover local lithological tectonic and hydrological complexities increase the uncertainty in the interpretation of the collected chemical geophysical etc data providing an inaccurate geomodel specifically in the study area there are mixtures of freshwater saltwater aquifers and geological units containing clay lenses thin layers and fine grained alluvium at the same time these geological formations have similar resistivity responses and the ambiguity of the collected electric and electromagnetic geophysical data is high therefore a third geophysical method seismic refraction which is sensitive to different physical parameters to constrain the uncertainty in the interpretation was used in this study the salinization of bafra plain and complex aquifer system was revealed with the combined use of direct current resistivity and transient electromagnetic data constrained by seismic refraction data and guided by hydrogeological and hydrochemical data using information obtained from multidisciplinary study we inferred that the intrusion is monitored inland up to 3 5 km the intrusion is traced after approximately the first 10 m depth in the central part of the plain additionally in some areas it was concluded that the intrusion is interrupted by clay lenses also drainage channels constructed in the plain have brought soil salinization under control but have not completely succeeded in controlling the saltwater intrusion into the deeper aquifer the saltwater intrusion can move more inland if groundwater pumping is not controlled especially in areas close to the river

a high precision age estimate of the holocene plinian eruption of mount mazama oregon usa the climactic eruption of mount mazama in oregon north america resulted in the deposition of the most widespread holocene tephra deposit in the conterminous united states and south western canada the tephra forms an isochronous marker horizon for palaeoenvironmental sedimentary and archaeological reconstructions despite the current lack of a precise age estimate for the source eruption previous radiocarbon age estimates for the eruption have varied and greenland ice core ages are in disagreement for the mazama tephra to be fully utilised in tephrochronology and palaeoenvironmental research a refined precise and accurate age for the eruption is required here we apply a meta analysis of all previously published radiocarbon age estimations n 81 and perform bayesian statistical modelling to this data set to provide a refined age of 7682 7584 cal yr bp 95 4 probability range although the depositional histories of the published ages vary this estimate is consistent with that estimated from the gisp2 ice core of 7627 150 yr bp zdanowicz et al 1999

dating the glen garry tephra a widespread late holocene marker horizon in the peatlands of northern britain the distal icelandic tephra known as the glen garry layer has been dated by ams 14c at eight ombrotrophic peat bogs from northern england and scotland the geochemistry of all the tephra layers is consistent with there being only one glen garry tephra rather than two or more from eruptions of the same volcanic source at seven of the sites all in scotland the tephra layer was bracketed by 1 cm contiguous samples below at and above the horizon at the one english site walton moss cumbria a suite of 16 ams dates was applied to a 116 cm section of a peat core containing the tephra the resulting dates were calibrated and wiggle matched using the bcal and bpeat programmes to give an estimated age for the glen garry tephra of 2176 cal bp with a 2 range of 2210 1966 cal bp this 244 year range is an improvement on the 410 years calibrated date range for the date without the wiggle match this age estimate will allow future work on peat profiles and other sediments containing the tephra to use the date as a pinning point in age depth models and obviate the need for radiocarbon dating at this period

assessing the impact of icelandic volcanism on vegetation systems in the north of ireland in the fifth and sixth millennia bc the lairg tephras comprise two of the three most abundantly represented tephra layers in irish holocene peat sequences the impact of these tephras on the vegetation at two lowland raised bogs in northern ireland is investigated through high resolution pollen percentage and concentration studies the palynological response of mire and dryland taxa to the tephra falls is assessed no significant palynological response to either tephra event is recorded

simulating the impacts of distal volcanic products upon peatlands in northern britain an experimental study on the moss of achnacree scotland the potential impact of prehistoric volcanism on distal areas has been the subject of some discussion in both ecology and archaeology an experimental approach is used here to examine the potential effects of distant volcanism on a peatland environment simulations of different tephra and acidity loading designed to approximately replicate the prehistoric hekla 4 ashfall were monitored over 2 years impacts on the peatland ecosystem were assessed by qualitative observations of plant health and abundance semi quantitative observations of flowering measurements of peat ph humification and testate amoebae community composition plots with higher acid loading showed immediate and lasting impacts on plants although other treated plots were less affected changes in testate amoebae and peat humification were inconsistent both within and between plots the experiment demonstrates the potentially severe effects of high acid loading on peatland plants although some responses remain unclear

holocene comment and reply hekla 4 ash the pine decline in northern ireland and the effective use of tephra isochrones a comment on hall pilcher and mccormac in response to a paper by blackford et al 1992 which showed a coincidence between the deposition of hekla 4 tephra and a decline of pinus pollen in two northern scottish sites hall et al 1994 investigated the tephra pine pollen relationship at two sites in northern ireland we argue that their sites are inappropriate for such comparison because pine was effectively absent from co antrim long before the deposition of hekla 4 the opportunity is taken to make some additional points concerning the irish data and the wider use of tephra isochrones

snapshots in time precise correlations of peat based proxy climate records in scotland using mid holocene tephras mid holocene tephra layers have been located and geochemically analysed from seven ombrotrophic bogs in scotland the tephras found in these scottish peats occur as stratigraphically discrete horizons not visible to the naked eye and originate from volcanic activity in iceland identifying and geochemically typing the tephra layers can enable precise correlations between sites on regional scales depending on the spatial extent of the airfall events dispersal of both the glen garry and hekla 4 tephras is excellent over scotland enabling snapshot views of the past at the time of these tephra depositions palaeoecological analyses have also been undertaken on these bogs providing detailed reconstructions of past changes in bog vegetation and surface wetness a proxy for past climates correlations between the ombrotrophic bogs at the time of the glen garry tephra revealed significant differences between the proxy climate records in the north and the south of scotland suggesting asynchronous changes between northern scotland and the rest of great britain

icelandic volcanic ash and the mid holocene scots pine pinus sylvestris pollen decline in northern scotland a volcanic ash layer in peat from northern scotland has been identified and coincides exactly with an abrupt decline in pinus sylvestris l scots pine pollen frequencies this provides an isochrone time equivalent marker horizon with which to investigate the timing of the holocene pine decline furthermore two possible causes of the southward shift of the range of pinus in scotland c 4000 bp are suggested a direct effect of acid pollution by chemicals produced by the eruption of hekla h 4 or a volcanically induced climatic perturbation these possibilities have wider implications for the influence of volcanism on postglacial environmental change

irish tree rings santorini and volcanic dust veils there has recently been renewed interest in the dating of the violent eruption of the aegean island of santorini in the second millennium bc both by its possible effects on tree ring growth in the united states1 suggesting a date of 1628 1626 bc and by acidity peaks in ice cores from south greenland2 suggesting 1645 bc we now show that oak trees growing on bogs in northern ireland produce significant concentrations of extremely narrow rings within a few periods less than 20 years long and that these periods correspond to the dates suggested by other methods for major volcanic eruptions in particular one of them corresponding to a short period beginning in 1628 bc was probably caused by santorini this date is qualitatively better than those derived from carbon 14 or ice cores because it is based on an absolute tree ring chronology

tephrochronological studies in northern england tephrostratigraphic investigations of two upland blanket bogs in northern england show that micro scopic layers of tephra are present their geochemistry shows that they are identical to two icelandic tephra layers of known age found at sites in scotland and the north of ireland the work extends the regional tephro chronology of the mid holocene for the british isles

an outline tephrochronology for the holocene of the north of ireland geochemically typed thin layers of icelandic holocene tephras form a tephrochronology for the north of ireland tephrochronology construction is based on geochemical linkage with dated historic icelandic eruptions and high precision multisample radiocarbon dating comparison with geochemically typed holocene layers at sites throughout scotland and northern england shows that some layers are widespread throughout much of the northern british isles other layers of known historic date have so far been detected only in ireland

paleoceanographic changes and calcium carbonate dissolution in the central fram strait during the last 20 ka article i nfo article history received 31 october 2011 available online xxxx a deep sea sediment core covering thelast20 ka and located between thepolar and thearctic fronts in themar ginal ice zone miz of the central fram strait has been investigated for changes in paleoceanography and calcium carbonatepreservation the reconstructionisbased on the distribution patternsofplankticforaminifera mean shell weight and the degree of fragmentation of their shells stable isotopes and other geochemical and sedimentological data the results show that the planktic foraminifera shells are poorly preserved throughout most of the record only the intervals comprising the early holocene from 10 8 to 8 cal ka bp and the last 800 yr show improved preservation of caco3 the dissolution correlated with the extent of arctic water and the associated marginal ice zone miz and high organic productivity dissolution of planktic foraminifera is generally high during the late deglaciation mid and late holocene prior to 800 cal yr bp the abundance of small subpolar species increases in the surface sediments dating from the last century which could be interpreted as a large and significant surface water warming however this apparent high magnitude warming seems to be overestimated due to preservation changes in the youngest sediments

icelandic volcanic ash and the mid holocene scots pine pinus sylvestris decline in the north of ireland no correlation tephra linked pollen and dendrochronological studies were performed on mid holocene subfossil peats and pines and two lowland raised bogs in the north of ireland the results demonstrated that at these sites contrary to recent findings in the north of scotland there was no temporal link between the decline in pine pollen and tephra from the eruption of the icelandic volcano hekla h4

geochemical stability of fine grained silicic holocene tephra in iceland and scotland this paper tests two assumptions fundamental to the use of fine grained silicic tephras from iceland for creating chronological frameworks in northwest europe it is shown firstly that glass shards can retain their overall chemical integrity on at least a four millennial time scale in contrasting depositional environments in iceland and scotland and secondly that an acid digestion process the most practical method for extracting tephra from peat does not significantly bias the results of major element analysis by electron microprobe the implication is that there is great potential and an appropriate method for developing both the resolution and the spatial coverage of chronologies based on silicic icelandic tephras in northwest europe