late quaternary tephrochronology of sweden a review abstract studies of late quaternary sediments in south and central sweden have yielded a detailed tephrochronology for the last glacial interglacial transition lgit ca 15 000 10 000 cal yr bp and the holocene more than ten tephra layers have been detected and geochemically characterised the most widespread tephra from the lgit is the rhyolitic phase of the vedde ash ca 12 000 cal yr bp which has been found in lacustrine sediments and marine clays south of the younger dryas moraines in south sweden other horizons from the lgit identified to date include the borrobol tephra ca 14 400 cal yr bp the hasseldalen tephra ca 11 500 cal yr bp the 10 ka askja tephra ca 11 300 cal yr bp and the hogstorpsmossen tephra ca 10 200 cal yr bp the most significant holocene isochrones are hekla 4 ca 4260 cal yr bp hekla selsund kebister ca 3750 cal yr bp hekla 3 ca 3000 cal yr bp and askja 1875 two new late holocene tephra horizons the stomyren tephra ca 2100 cal yr bp and the gullbergby tephra ca 2700 cal yr bp were identified in single sites and are so far less valuable as marker horizons but are potentially important for the future

examination of late palaeolithic archaeological sites in northern europe for the preservation of cryptotephra layers we report the first major study of cryptotephra non visible volcanic ash layers on late palaeolithic archaeological sites in northern europe examination of 34 sites dating from the last termination reveals seven with identifiable cryptotephra layers preservation is observed in minerogenic and organic deposits although tephra is more common in organic sediments cryptotephra layers normally occur stratigraphically above or below the archaeology nearby off site palaeoclimate archives peat bogs and lakes 0 3 km distant were better locations for detecting tephra however in most cases the archaeology can only be correlated indirectly with such cryptotephras patterns affecting the presence absence of cryptotephra include geographic position of sites relative to the emitting volcanic centre the influence of past atmospherics on the quantity direction and patterns of cryptotephra transport the nature and timing of local site sedimentation sampling considerations and subsequent taphonomic processes overall while tephrostratigraphy has the potential to improve significantly the chronology of such sites many limiting factors currently impacts the successful application

bayesian analysis of radiocarbon chronologies examples from the european late glacial although there are many late glacial ca 15 000 11 000 cal yr bp proxy climate records from northwest europe some analysed at a very high temporal resolution decadal to century scale attempts to establish time stratigraphical correlations between sequences are constrained by problems of radiocarbon dating in an attempt to overcome some of these difficulties we have used a bayesian approach to the analysis of radiocarbon chronologies for two late glacial sites in the british isles and one in the adriatic sea the palaeoclimatic records from the three sites were then compared with that from the grip greenland ice core although there are some apparent differences in the timing of climatic events during the early part of the late glacial pre 14 000 cal yr bp the results suggest that regional climatic changes appear to have been broadly comparable between greenland the british isles and the adriatic during the major part of the late glacial i e between 14 000 and 11 000 cal yr bp the advantage of using the bayesian approach is that it provides a means of testing the reliability of late glacial radiocarbon chronologies that is independent of regional chronostratigraphical climatostratigraphical frameworks it also uses the full radiocarbon inventory available for each sequence and makes explicit any data selection applied potentially therefore it offers a more objective basis for comparing regional radiocarbon chronologies than the conventional approaches that have been used hitherto copyright 2004 john wiley sons ltd

some numerical considerations in the geochemical analysis of distal microtephra abstract the use of late quaternary tephra horizons as isochronous markers for high resolution correlation between records is of growing importance in a number of scientific fields particular advancements have been made through the identification of microtephra deposits very distal deposits of volcanic ash invisible to the naked eye the successful correlation of ash layers and volcanic eruptions depends on the acquisition of the major element chemistries of a tephra layer derived from microprobe analyses of individual glass shards this is particularly important for microtephras where aeolian fractionation has removed much of the mineral phase of the ash deposit which often aids tephra discrimination there are however difficulties in distinguishing precisely between different eruptions of the same volcano using major element composition and this may not always be resolved by the use of trace elements given the potential of tephrochronology as a correlative tool in many disciplines it is important to resolve this difficulty one way forward is to perform more robust statistical analyses on the geochemical data as in general analyses are confined to a series of bi plots of major elements here the authors explore some of the problems associated with dealing with microprobe data generated for individual tephras and pay particular attention to the unit sum problem using a subset of data generated as part of a eurodelta project on tephra distribution in the adriatic the authors demonstrate that this problem is detectable in major element data from tephras and have consequently applied the logratio method before further analyses of the data it is demonstrated that the use of logratios combined with discriminant functions analysis provides a more robust assessment of likely chemical correlations between tephras and are superior to the use of bi plots alone and obviate the need for any data normalization a particular point of contention between tephrochronologists

improved age modelling approaches as exemplified by the revised chronology for the central european varved lake soppensee abstract one of the key factors in understanding past climate change is the development of robust age models that have sufficient chronological precision for comparing different palaeoclimate archives while retaining accuracy recent developments in bayesian age modelling are applied here to the swiss varve lake soppensee we develop revised age models for this sequence using the available stratigraphic information to constrain the calibrated radiocarbon ages we begin by using stratigraphical order as the only constraint and then sequentially increase the information incorporated into the model using relative varve age sample depth and varying depositional models within this bayesian framework we develop internally robust models that significantly improve the dating precision and are applicable to both varved and non varved sequences we then compare the model output to wider chronological information such as the age of the laacher see tephra in order to test the model accuracy the results of this exercise suggest that these methods can be used to build very reliable improved age models in a variety of records

a laacher see eruption supplement to tephrabase investigating distal tephra fallout dynamics abstract tephrabase www tephrabase org is an online data repository and research tool for tephrochronological investigations in northern europe this paper presents and discusses an update to tephrabase that contains geographic and as far as available geochemical data on 452 data points for the widespread isochronous laacher see tephra this tephra is dated to c 12 920 calendar years bp and acts as an important chronostratigraphic marker for the lateglacial gi 1a late allerod chronozone in terrestrial and lacustrine palaeoenvironmental archives as well as in archaeological stratigraphies based on these data a revised map of the total tephra distribution is presented suggesting that the north eastern fallout lobe might contain a secondary fallout thickness maximum 230 340 km distant from the eruptive centre in addition new geochemical data from a series of distal tephra deposits spanning most of the north eastern fallout lobe are used to evaluate previous suggestions regarding the distribution of fallout from distinct eruption phases the aim of the study is that future tephrochronological investigations can use this database and the revised distribution map for effectively targeting sites for analysis

constraints on the frequency and dispersal of explosive eruptions at sambe and daisen volcanoes south west japan arc from the distal lake suigetsu record sg06 core abstract accurately evaluating the tempo and magnitude of pre historic eruptions is essential for hazard assessments here we demonstrate the importance of integrating records from locations close to the volcano with those in distal regions to generate more comprehensive event stratigraphies the annually laminated varved and intensely radiocarbon dated lacustrine sediments of lake suigetsu sg06 core japan are used to place chronological constraints on the tempo of volcanism at two stratovolcanoes located favourably upwind of the lake along the south west japan arc sambe and daisen major and trace element glass compositions are used to assign visible ash tephra layers preserved in the sg06 sediment core to past explosive eruptions from these volcanoes integrating these stratigraphies confirm that the 150 ka long lake sequence records nine visible ash layers from daisen and five from sambe the sg06 record captures two periods of closely spaced eruptions at daisen volcano the first period begins at 61 1 ka with three explosive eruptions over 10 ka with two events separated by as little as 1 5 ka one layer sg06 4281 dated at 59 6 5 5 ka 95 4 probability relates to the large magnitude and widely dispersed daisen kurayoshi pumice dkp eruption the other period of frequent activity began at 29 837 96 intcal13 yrs bp 95 4 probability with five widely dispersed ash fall events associated with explosive eruptions separated by approximately 6 936 5 and 438 years the integrated proximal distal event stratigraphy and the high precision sg06 chronology provide unique insights into the timing and frequency of past explosive volcanism from daisen and sambe which has implications for the prediction of future eruption scenarios

ams radiocarbon dating and varve chronology of lake soppensee 6000 to 12000 14c years bp for the extension of the radiocarbon calibration curve beyond 10000 14c y bp laminated sediment from lake soppensee central switzerland was dated the radiocarbon time scale was obtained using accelerator mass spectrometry ams dating of terrestrial macrofossils selected from the soppensee sediment because of an unlaminated sediment section during the younger dryas 10000 11000 14c y bp the absolute time scale based on counting annual layers varves had to be corrected for missing varves the soppensee radiocarbon verve chronology covers the time period from 6000 to 12000 14c y bp on the radiocarbon time scale and 7000 to 13000 calendar y bp on the absolute time scale the good agreement with the tree ring curve in the interval from 7000 to 11450 cal y bp cal y indicates calendar year proves the annual character of the laminations the ash layer of the vasset killian tephra massif central france is dated at 8230 140 14c y bp and 9407 44 cal y bp the boundaries of the younger dryas biozone are placed at 10986 69 cal y bp younger dryas preboreal and 1212 86 cal y bp allerod younger dryas on the absolute time scale the absolute age of the laacher see tephra layer dated with the radiocarbon method at 10 800 to 11200 14c y bp is estimated at 12350 135 cal y bp the oldest radiocarbon age of 14190 120 14c y bp was obtained on macrofossils of pioneer vegetation which were found in the lowermost part of the sediment profile for the late glacial the offset between the radiocarbon 10000 12000 14c y bp and the absolute time scale 11400 13000 cal y bp in the soppensee chronology is not greater than 1000 years which differs from the trend of the u th radiocarbon curve derived from corals

stratigraphic evidence for a high marine shore line during the late weichselian deglaciation on the kullen peninsula southern sweden mineral magnetic properties and the carbon content of a sediment sequence in lake kullatorpssjon on the kullen peninsula in northwest scania southern sweden were investigated diatom and ostracod analyses were undertaken for palaeoecological reconstruction and a chronology was constructed from accelerator mass spectrometry ams radiocarbon dating of terrestrial plant remains and mosses five stratigraphical units were identified units 1 5 from oldest to youngest the two lowermost units consist of clay the lowest clay unit 1 is strikingly black 2 m thick and has magnetic properties dominated by high concentrations of authigenic greigite fe3s4 in contrast the overlying clay unit 2 is grey 1 18 m thick and has magnetic properties dominated by low concentrations of detrital magnetite fe3o4 a major palaeoecological change is reflected in the diatom flora and ostracod fauna at the transition from unit 1 to unit 2 the sediment stratigraphy geochemical mineral magnetic and palaeoecological analyses also point to a significant change in depositional environment at this transition which is proposed to represent the isolation of lake kullatorpssjon from the kattegat sea earlier investigations have determined the marine limit to ca 65 m a s l on the kullen peninsula the separate independent lines of evidence presented here however suggest that the late weichselian marine limit developed at 85 90 m a s l at the deglaciation ca 17 200 cal yr bp ca 14 500 yr bp this limit is ca 25 m higher than assumed previously lake kullatorpssjon formed ca 1000 cal yr later when the basin became isolated from the kattegat sea copyright c 1999 john wiley sons ltd less

optimising the use of marine tephrochronology in the north atlantic a detailed investigation of the faroe marine ash zones ii iii and iv abstract tephrochronology is central to the intimate 1 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

icelandic volcanic ash from the late glacial open air archaeological site of ahrenshoft la 58 d north germany abstract cryptotephra of icelandic origin from the open air archaeological site of ahrenshoft la 58 d kr nordfriesland schleswig holstein northern germany overlies a late glacial havelte lithic assemblage hitherto dated by 14 c and biostratigraphy to the earliest part of the late glacial interstadial gi 1e to gi 1c 3 peaks in ash shards are observed in two profiles major and minor element geochemistry indicates volcanic ash originating in the katla system precise correlation to previously described tephra is uncertain due to overlapping chemical characteristics the ahrenshoft 14 c determinations litho and bio stratigraphy encompass a broad age span for the cryptotephra bearing sediments from the end of the allerod to the preboreal the most plausible volcanic eruption correlates are the vedde ash younger dryas already known from the european mainland tephra af555 late younger dryas and the suduroy tephra preboreal boreal hitherto recorded only in the north atlantic region these three ash horizons have been dated to respectively 12 171 57 yr b2k in the ngrip ice core c 11 500 cal bp in scotland and c 8000 cal bp by radiocarbon from the faroe isles ongoing research on deposits from the type sites for the tephra layers may in the future differentiate these markers leading to better discrimination of the chemistries and a resolution of this question

evidence for the occurrence of vedde ash in sweden radiocarbon and calendar age estimates a tephra layer of rhyolitic composition has been recorded in sediments from lake madtjarn southwestern sweden geochemical analyses have shown that the tephra is identical to the rhyolitic component of the middle younger dryas vedde ash a series of ams radiocarbon measurements places the radiocarbon age of the tephra within a 14c plateau at 10 400 10 300 14c y bp based on a linear younger dryas sedimentation rate and assumptions about the apparent synchroneity of changes in lake sediments tree rings and ice core records the calendar year age of the tephra concentrations is estimated at 12 045 11 975 yr bp which accords well with the age of the equivalent tephra in the grip core 1998 john wiley sons ltd

rhyolitic and dacitic component of the askja 1875 tephra in southern and central finland first step towards a finnish tephrochronology tephra from icelandic volcanic eruptions is frequently dispersed to northern europe but so far tephra has not been detected in finnish sedimentary records we report the first finding of a cryptot

tephrostratigraphy of the last 160 ka in western limagne france the geocler 1 core extracted from the clermont crater lake sediments and surface studies made at several localities north of clermont provided numerous stratigraphic environmental and chronological data tl and radiocarbon which allow us to present a chronostratigraphy of the limagne for the past 160 ka 118 ash falls have been recorded in the crater lake sediments of the clermont maar they demonstrate that a basaltic phreatic activity developed along the western fault scarp of the limagne between 160 and 70 ka after which began the chaine des puys activity moreover several acid eruptions occured between 160 and 40 ka from older dryas to atlantic between 15 and 7 ka fourteen ash falls occured and in some cases the source volcanoes have been identified these include puy de la nugere puy de dome puy chopine kilian crater and puy de pariou which contribute mainly to the local tephra succession prospects for further prehistoric research in volcanic areas are outlined

geoarchaeology the four dimensional 4d fluvial matrix and climatic causality abstract geoarchaeology is the application of geological and geomorphological techniques to archaeology and the study of the interactions of hominins with the natural environment at a variety of temporal and spatial scales geoarchaeology in the uk over the last twenty years has flourished largely because it has gone beyond technological and scientific applications over the same period our ability to reconstruct the 3 dimensional stratigraphy of fluvial deposits and the matrix of fluvial sites has increased dramatically because of a number of technological advances these have included the use of lidar laser imaging and radar to produce high resolution digital surface models the use of geophysics particularly ground penetrating radar and electrical resistivity to produce sediment depth models and the use of gis and data visualisation techniques to manipulate and display the data these techniques along with more systematic and detailed sedimentological recording of exposed sections have allowed the construction of more precise 3 dimensional volumetric models of the matrix of artefacts within fluvial deposits additionally a revolution in dating techniques particularly direct sediment dating by luminescence methods has enabled the creation of 4 dimensional models of the creation and preservation of these sites these 4 dimensional models have the ability to provide far more information about the processes of site creation preservation and even destruction and also allow the integration of these processes with independent data sources concerning cultural evolution and climatic change all improvements in the precision of dating fluvial deposits have archaeological importance in our need to translate events from a sequential or geological timeframe to human timescales this allows geoarchaeology to make a more direct contribution to cultural history through the recognition of agency at the individual or group level this data can then form a component of biocomplexity or agent based modelling which is becoming increasingly used in the natural sciences particularly ecology and geomorphology and which can be used to test scenarios including the impact on and response of hominins to abrupt or catastrophic environmental change whilst catastrophic events clearly represent the atypical they can be illuminating in revealing cognitive processes resulting in abandonment coping mitigation and innovation these points are exemplified using two in depth case studies one from the holocene geoarchaeological record of the river trent in central england and the other from the palaeolithic record from rivers in south west britain in the former the interaction between climate change and human activity is illustrated at the year to century timescale whilst in the other the timescale is millennial these case studies have deliberately been chosen to be as different as possible in temporal and spatial scale with the aim of examining the applicability of methodological and theoretical aspects of geoarchaeology lastly the paper considers the problem of scale in geoarchaeology and concludes it is process dependency which ultimately affects the questions we can ask and that questions of human response to climate change are fundamentally a product of materiality and cognitive processes this demands an in depth contextual approach to such questions rather than database driven assertions of causality

evidence for the presence of the vedde ash in central europe abstract as part of ongoing research to find distal tephra two lacustrine cores were analysed for the presence of volcanic ash layers not visible to the naked eye soppensee in switzerland and rotmeer in southern germany the laacher see tephra 12 900 ka bp is present as a visible layer in both sites in both cores we found a discrete tephra horizon with similar morphologies in the middle of the biostratigraphic units equivalent to the younger dryas stadial the vitreous components of these two tephra layers are geochemically identical comparison of the geochemical stratigraphical and chronological data from both sites strongly suggest that the tephra can be attributed to the icelandic vedde ash a widely distributed horizon found throughout the north atlantic and northern europe our results indicate that a precise and direct correlation between the greenland ice cores and central european sequences is now possible based on a co located tephra layer this means that there is now the potential to independently test climate synchronicity between greenland and europe as far south as the alps

late glacial climatic oscillations as recorded in swiss lake sediments regional pollen assemblage zones for the late glacial period of the swiss plateau are introduced and defined they include four major zones artemisia juniperus hippophae betula pinus paz with several subzones pollen and oxygen isotope analyses on lacustrine sediments from several lakes in the area reveal four distinct phases of climatic oscillation in the time period of 13 000 9500 yr bp the first oscillation termed the aegelsee fluctuation occurs shortly before 12 000 yr bp and varve counts suggest its duration was ca 100 yr it is characterised by a short decrease in the oxygen isotopes as well as a short increase in nap associated with a depression in birch pollen values the second oscillation which occurs in the 18o record shortly before the deposition of the laacher see tephra ca 11 000 yr bp is termed the gerzensee fluctuation it occurs during a pine dominated phase and its vegetational effects cannot be determined palynologically the most prominent regressive phase is the younger dryas biozone ca 10 700 10 000 yr bp characterised by an increase in heliophilous nap and low 18o values the younger dryas biozone can often be subdivided palynologically into two parts a first part rich in grasses and juniper and a second part with higher filipendula and birch values during the preboreal biozone another distinct oscillation is evidenced only in the oxygen isotope ratios comparison of the swiss oxygen isotope profiles with the greenland dye 3 record suggests that not only the three major shifts in the 18o curves but also the minor ones are closely comparable suggesting some common climatic control

the importance of independent chronology in integrating records of past climate change for the 60 8 ka intimate time interval this paper provides a brief overview of the most common dating techniques applied in palaeoclimate and palaeoenvironmental studies including four radiometric and isotopic dating methods radiocarbon 230th disequilibrium luminescence cosmogenic nuclides and two incremental methods based on layer counting ice layer varves for each method concise background information about the fundamental principles and methodological approaches is provided we concentrate on the time interval of focus for the intimate integrating ice core marine and terrestrial records community 60 8 ka this dating guide addresses palaeoclimatologists who aim at interpretation of their often regional and local proxy time series in a wider spatial context and therefore have to rely on correlation with proxy records obtained from different archives from various regions for this reason we especially emphasise scientific approaches for harmonising chronologies for sophisticated and robust proxy data integration in this respect up to date age modelling techniques are presented as well as tools for linking records by age equivalence including tephrochronology cosmogenic 10be and palaeomagnetic variations finally to avoid inadequate documentation of chronologies and assure reliable correlation of proxy time series this paper provides recommendations for minimum standards of uncertainty and age datum reporting

magnetic characterisation and correlation of a younger dryas tephra in north atlantic marine sediments a technique for identifying non visible basaltic tephra rich horizons of younger dryas yd greenland stadial gs 1 age in northeast atlantic sediments using rapid non destructive magnetic measurements is presented three high resolution marine sediment cores have been studied in an e w transect across the hebridean margin st kilda basin md95 2007 barra fan md95 2006 and rockall trough md04 2822 magnetic susceptibilities and remanent magnetisations were measured at contiguous 1 cm resolution on bulk sediments in all three cores an interval with higher proportions of hard magnetic minerals coincides with a clearly defined peak in basaltic tephra shard 250 m counts which can be constrained to the early part of the yd gs1 based on faunal climate proxies electron microprobe analyses of the magnetically distinct basaltic tephra interval in all three cores displays the same major element geochemistry as published for the vedde basaltic i tab 1 i e sourced from the icelandic volcano katla the identification of transitional alkalic basaltic tephras within marine sediments could potentially be facilitated by magnetic analysis as a useful chronostratigraphic screening tool copyright 2009 john wiley sons ltd

identification and definition of primary and reworked tephra in late glacial and holocene marine shelf sediments off north iceland nine tephra layers in marine sediment cores md99 2271 and md99 2275 from the north icelandic shelf spanning the late glacial and the holocene have been investigated to evaluate the effectiveness of methods to detect tephra layers in marine environments to pinpoint the stratigraphic level of the time signal the tephra layers provide and to discriminate between primary and reworked tephra layers in a marine environment these nine tephra layers are the borrobol like tephra vedde ash askja s tephra saksunarvatn ash and hekla 5 hekla 4 hekla 3 hekla 1104 and v1477 tephras the methods used were visual inspection magnetic susceptibility x ray photography mineralogical counts grain size and morphological measurements and microprobe analysis the results demonstrate that grain size measurements and mineralogical counts are the most effective methods to detect tephra layers in this environment revealing all nine tephra layers in question definition of the tephra layers revealed a 2 3 cm diffuse upper boundary in eight of the nine tephra layers and 2 3 cm diffuse lower boundary in two tephra layers using a multi parameter approach the stratigraphic position of a tephra layer was determined where the rate of change of the parameters tested was the greatest compared with background values below the tephra the first attempt to use grain morphology to distinguish between primary and reworked tephra in a marine environment suggests that this method can be effective in verifying whether a tephra layer is primary or reworked morphological measurements and microprobe analyses in combination with other methods can be used to identify primary tephra layers securely the study shows that there is a need to apply a combination of methods to detect define the time signal and discriminate between primary and reworked tephra in marine environments copyright 2011 john wiley sons ltd

volcanism and the greenland ice cores the tephra record abstract in recent years increased awareness of the considerable potential offered by tephrochronology in palaeoclimatic studies has fuelled a renewed interest in the tephra record preserved within the greenland ice cores this renewal has occurred in tandem with the development of continuous flow analysis techniques which provide high resolution volcanic aerosol records these chemical records are of considerable value for identifying tephra horizons composed of glass shards and also provide the basis for a new high precision ice core timescale thus allowing ages to be assigned to volcanic events tephra horizons of glass shards in the ice cores play a critical role for 1 testing and building chronological frameworks for the ice cores and other sequences 2 synchronising disparate palaeoclimatic sequences and testing phase relationships 3 atmospheric pathway reconstruction and 4 verifying the source of volcanic aerosol peaks here we review the results of over 25 years of research into tephra horizons in the grip gisp2 and ngrip cores we provide high precision ages for horizons based on recently developed timescales and draw together geochemical characterisations of the products of 45 volcanic events deposited on the greenland ice sheet and identified in the cores there is a clear disparity between the number of volcanic aerosol peaks and the number of tephra horizons of glass shards identified thus far however this synthesis highlights the critical role of the greenland ice cores firstly in the reconstruction of the history of icelandic volcanic eruptions and secondly the considerable value of some tephra horizons in facilitating the correlation of these key climatic archives to north atlantic marine sequences other noteworthy issues include the potential of these cores to preserve tephra horizons from more distal volcanic sources such as north america to resolve the debate surrounding the thera eruption and the observation that some tephra horizons are preserved within the ice without coeval volcanic aerosol signals

chironomid δ18o as a proxy for past lake water δ18o a lateglacial record from rotsee switzerland abstract we explored whether the stable oxygen isotope composition 18o of fossil chironomid remains can be used to reconstruct past variations in lake water 18o from lateglacial and early holocene sediments from rotsee switzerland a sediment core from the former littoral zone of the lake was examined since it contained both high concentrations of chironomid remains and abundant authigenic carbonates and therefore allowed a direct comparison of chironomid 18o with values measured on bulk carbonates since carbonate particles adhering to chironomid remains potentially affect 18o measurements we tested two methods to chemically remove residual carbonates trials with isotopically heavy and light acid solutions indicated that treatment with hydrochloric acid promoted oxygen exchange between chironomid remains and the water used during pretreatment in contrast a buffered 2 m ammonium chloride nh4cl solution did not seem to affect chironomid 18o to a significant extent fossil chironomid 18o was analyzed for the rotsee record both using standard palaeoecological methods and after pretreatment with nh4cl samples prepared using standard techniques showed a poor correlation with 18o of bulk carbonate r2 0 14 suggesting that carbonate contamination of the chironomid samples obscured the chironomid 18o signature samples pretreated with nh4cl correlated well with bulk carbonate 18o r2 0 67 and successfully tracked the well known lateglacial changes in 18o chironomid 18o indicated depleted lake water 18o during the oldest dryas period the aegelsee and gerzensee oscillations and the younger dryas whereas enriched 18o values were associated with sediments deposited during the lateglacial interstadial and the early holocene differences in the amplitude of variations in bulk carbonate and chironomid 18o are attributed to differential temperature effects on oxygen isotope fractionation during the formation of carbonates and chironomid head capsules or seasonal changes of lake water 18o potentially affecting 18o of these two substances to a different extent our results indicate that chironomid 18o can successfully reconstruct centennial to millennial scale changes in lake water 18o and that the method can be applied to carbonate rich records provided that care is taken to eliminate carbonate contamination from the samples

inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group the remit of the intimate project of the inqua palaeoclimate commission is to synthesise marine terrestrial andice core data for the north atlantic region during the last glacial interglacial transition lgit ca 13 10c kyr bp ca 15 11 5 ice core kyr bp a major problem however is the di culty of e ecting correlations at a temporal resolution that are adequate for de ning leads and lags between the polar ice terrestrial marine andatmospheric realms the limitations of the d ating andcorrelation method s currently employed are summarised and new quality assurance protocols are proposed these include recommendations on the contextual information that should accompany radiocarbon dates procedures for radiocarbon calibration the use of an eventstratigraphic approach in inter regional correlations andthe more widespreaduse of time parallel marker horizons basedon tephra layers oxygen isotope stratigraphy palaeomagnetic stratigraphy andradiocarbon wiggle matching to underpin the geochronology and correlation of events during the lgit these protocols will be adopted by the intimate project in future international collaborative research and are recommended to other groups working on this important time period 2001 elsevier science ltd all rights reserved

correlation and synchronisation of lateglacial continental sequences in northern central europe based on annually laminated lacustrine sediments abstract the present study focusses on correlation and synchronisation of weichselian lateglacial varved lake sediments from western germany meerfelder maar eifel region northern germany hamelsee lower saxony central poland lake go ci a z and eastern poland lake perespilno by using varve chronology tephrochronology palynostratigraphy and stable isotopes comparison of the several independent time scales shows that biotic and abiotic parameters respond abruptly and quasi synchronously within the errors of the different chronologies during the younger dryas preboreal transition moreover there is a consensus about the length of the younger dryas cold stage of 1100 1150 varve years in the allerod the prominent laacher see tephra 12 880 varve years bp can be used to fix floating varve chronologies the relative duration of this biozone has been determined in meerfelder maar and hamelsee at between 625 and 670 varve years in the meerfelder maar a combination of continuous varve counting and biostratigraphy has been possible for the almost entire lateglacial the comparison between continental limnic sequences and greenland ice core records should be made on the basis of independent chronologies in both archives it is more practicable to develop regional stratotypes on the continental regions instead of simply using ice cores as stratotypes for the lateglacial for terrestrial european records in this respect annually laminated lacustrine sequences have a great potential

tracing volcanic events in the ngrip ice core and synchronising north atlantic marine records during the last glacial period five basaltic tephra horizons have been identified in the ngrip ice core during the last glacial period geochemical analyses indicate that these tephras are of icelandic origin with one horizon identified as the faroe marine ash zone iii fmaz iii an important marker horizon in several marine records within the faroe islands margin the fmaz iii is a few millimetres thick and is constrained to 38 122 723 yr b2k before year ad 2000 according to the greenland ice core chronology gicc05 this event falls directly at the thermal peak of greenland interstadial 8 gi 8 and a marine ice correlation based on the position of this tephra suggests a close coupling of the marine and atmospheric systems at this time the remaining tephras originate from the eastern volcanic zone with the katla volcanic system pinpointed as the dominant source these are thought to represent previously unknown volcanic events which add considerably to our knowledge of icelandic volcanism during this period independent ages are assigned to these events and together with major element characterisation form the backbone of the tephrochronology framework presented here despite the identification of these tephras this study also demonstrates that the sulphate record may not always act as a suitable proxy for the identification of tephra horizons in ice core records

tephrochronology and the extended intimate integration of ice core marine and terrestrial records event stratigraphy 8 128 ka b2k the comparison of palaeoclimate records on their own independent timescales is central to the work of the intimate integrating ice core marine and terrestrial records network for the north atlantic region an event stratigraphy has been established from the high precision greenland ice core records and the integrated gicc05 chronology this stratotype provides a palaeoclimate signal to which the timing and nature of palaeoenvironmental change recorded in marine and terrestrial archives can be compared to facilitate this wider comparison without assuming synchroneity of climatic change proxy response intimate has also focussed on the development of tools to achieve this in particular the use of time parallel marker horizons e g tephra layers volcanic ash coupled with the recent temporal extension of the greenland stratotype as part of this special issue we present an updated intimate event stratigraphy highlighting key tephra horizons used for correlation across europe and the north atlantic we discuss the advantages of such an approach and the key challenges for the further integration of terrestrial palaeoenvironmental records with those from ice cores and the marine realm

dating synthesis and interpretation of palaeoclimatic records of the last glacial cycle and model data integration advances by the intimate integration of ice core marine and terrestrial records cost action es0907 since 2010 the intimate integration of ice core marine and terrestrial records network has been operating as a cost action designated es0907 this paper outlines the accomplishments of the intimate cost action in the context of how the intimate ideas have evolved during the network s twenty year life span and highlights a number of challenges that can guide further work in the second part of the paper the contributions that comprise this intimate special issue are introduced

tephra geochemistry a discussion of some persistent analytical problems distal tephrochronological studies are reliant upon precise and accurate geochemical quantitation this quantitation can involve difficulties not often encountered in more conventional petrology solving these problems is of particular importance in the holocene and late quaternary of northwest europe where numerous tephra layers of icelandic origin have been detected in peat bogs and lake and marine sediments electron probe microanalysis epma has proved the most applicable analytical technique when insufficient quantities of tephra are available for bulk analysis standard epma techniques require fine tuning to the tephra problem as the geochemical instability of glass is a common feature in many previous studies geochemical data of avoidably low quality have been produced and little attention appears to have been directed to modification of epma methods it is suggested that the black box approach to geochemical analysis should be avoided by the consideration of several factors these include

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

extending the limits of the borrobol tephra to scandinavia and detection of new early holocene tephras analyses of two infilled lakes in blekinge southeast sweden indicate the presence of at least three tephra horizons of termination 1 and early holocene age geochemical analyses confirm the presence of the borrobol tephra the askja tephra 10 000 14c yr b p and one previously unreported tephra of icelandic origin extending the limits of the borrobol tephra to scandinavia illustrates that this ash is far more widespread than previously realized and is therefore an important marker horizon for determining the rate and timing of the initial warming at the start of greenland interstade 1 gi 1 within europe the relatively unknown askja tephra and the newly discovered hasseldalen tephra are stratigraphically placed at the younger dryas preboreal transition this paper demonstrates the suitability and success associated with the extraction techniques for tracing microtephra horizons in areas distal to volcanic sources

north european last glacial interglacial transition lgit 15 9 ka tephrochronology extended limits and new events high precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change although radiocarbon is the traditional method for dating late quaternary sedimentary sequences particularly during the last glacial interglacial transition lgit 15 9 ka there are inherent problems with the method particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content an alternative method is the use of tephras that act as time parallel marker horizons within europe numerous volcanic centres are known to have erupted during the lgit providing considerable potential for high precision correlation independent of past radiocarbon fluctuations here we report the first identification of the vedde ash and askja tephra in ireland significantly extending the known provenance of these events we have also identified two new horizons the roddans port tephras a and b and tentatively recognise an additional horizon from vallensgard mose denmark that provide crucial additional chronological control for the lgit two phases of the laacher see tephra lst are reported the lower laacher see tephra llst and probably the c2 phase of the middle laacher see tephra mlst c2 indicating a more northeasterly distribution of this fan than reported previously copyright 2006 john wiley sons ltd

marine conditions in central sweden during the early preboreal as inferred from a stable oxygen isotope gradient the marine benthic fauna and the 18 oc of foraminifers and ostracods from six sites situated on a west east transect through central sweden have been analysed in order to estimate the palaeosalinity and palaeocirculation in this shallow marine environment the measurements have been undertaken on material from the early preboreal when the baltic basin was in contact with the north sea through straits in central sweden the 18 oc values have a more negative value towards the east indicating decreasing salinity this was the result of limited possibilities for marine water to penetrate into the baltic basin and the mixing with freshwater from the melting fennoscandian ice sheet four water masses existed in the area a surface layer of freshwater marine water from the north sea brackish marine intermediate water on the swedish west coast and brackish yoldia sea water in the baltic basin the chronology is based on radiocarbon dates of marine fossils and at one site on the occurrence of the vedde ash 10 400 10 300 14 c yr bp this is the first record from marine settings in sweden copyright 2001 john wiley sons ltd journal of quaternary science

climate oscillations and tephrochronology in eastern middle sweden during the last glacial interglacial transition abstract two sequences spanning the last glacial interglacial transition in southern o stergo t land eastern middle sweden have been investigated for high resolution vegetation change andtephrochronology organic carbon and pollen analysis indicates that the younger dryas pre boreal climatic transition was characterised by at least one well de ned oscillation or possiblytwo shorter climatic oscillations the vedde ash ca 12000 grip yr bp or ca 10300 14 cyrbp has been identi ed at both sites signi cantly increasing the known distribution of thismarker horizon in addition a previously unrecorded rhyolitic tephra of icelandic origin hasbeen identi ed at ca 9000 14 c yr bp the expansion of corylus into southern o stergo tland isestimated to be ca 9400 14 c yr bp copyright 1999 john wiley sons ltd keywords preboreal oscillation lacustrine records vedde ash last glacial interglacial transition expan sion of corylus introduction the last glacial interglacial transition 15 10 k cal yr bp was a period characterised by a succession of rapid extremeclimatic oscillations throughout the north atlantic the eventstratigraphy recently proposed by bjo rck

stratigraphic constraints for explosive activity in the past 100 ka at etna volcano italy the pyroclastic deposits of etna have been correlated over the whole volcanic edifice for the first time allowing the construction of a continuous record of tephra producing events which extends from approximately 100 ka to the present in this interval five main periods of explosive activity have been identified a 100 ka strombolian to subplinian activity b 80 to 100 ka plinian benmoreitic activity c 16 to 80 ka strombolian to subplinian from basaltic to mugearitic activity d 15 5 to 15 ka plinian benmoreitic activity accompanying the caldera forming eruptions of the ellittico volcano and e the most recent 13 ka basaltic explosive activity of strombolian and subplinian type of the present edifice that also includes the 122 b c plinian eruption this study results in a semi quantitative and in some cases quantitative definition of the intensity and chronology of the explosive activity at etna moreover this work gives a new significance to the volcanic hazards of etna a volcano generally considered to be the site of gentle effusive eruptions

the use of microtephra horizons to correlate late glacial lake sediment successions in scotland evidence is presented to show that two measurable concentrations of microtephra particles can be detected in deposits of late devensian late glacial age in three sites in scotland one layer is attributed to the vedde ash a marker horizon within the younger dryas chronozone the second is a new tephra reported for the first time which we name the borrobol tephra this occurs consistently near the base of the late glacial interstadial organic sediments at each site and is thought to date to around 12 5 14c ka bp geochemical determinations using an electron microprobe confirm the identification of the vedde ash suggest the borrobol tephra to have an icelandic origin and demonstrate the consistency of the geochemical signals at all three sites 1997 john wiley sons ltd

evidence for phase locked changes in climate between scotland and greenland during gs 1 younger dryas using micromorphology of glaciolacustrine varves from glen roy there is a current need to develop annual decadal chronologies from periods of rapid climate change in order to understand the rate and timing of climate events and identify how other proxies either lead or lag this climate forcing annually laminated or varved sediments are key proxies for understanding environmental change at such a scale this paper presents the results of microscale analysis of glaciolacustrine varve sediments from scotland and develops a new index called varve group which ranks the number of pulses of sediment observed in the summer component of the varve the varve group index is compared with data from the greenland ice core record and correspondence can be observed between the oxygen isotope records from greenland during the latter part of gs 1 and the 515 year lochaber varve group index the processes that control the number of sediment pulses into the lake basin are discussed and we examine how these factors might control both the isotopic composition of the ice cores and varve group formation it is proposed that the position of the sea ice in the north atlantic may provide such a mechanism

was the 12 1 ka icelandic vedde ash one of a kind abstract the vedde ash is the most important volcanic event marker layer for the correlation of late quaternary palaeoenvironmental archives in europe and the north atlantic first defined from its type site localities near alesund western norway the vedde ash has now been traced across much of northern and central europe into northwest russia within north atlantic marine sediments and into the greenland ice cores the vedde ash is thought to derive from an eruption of the katla volcano in iceland that occurred midway through the younger dryas greenland stadial 1 gs 1 12 1 ka bp visible and cryptotephra deposits of the vedde ash have been found in numerous stratified sites with robust chronologies which allow its age to be constrained and its dispersal to be mapped the eruption must have been highly explosive however few proximal outcrops have been confirmed and this crucial ash layer remains almost exclusively distally described and characterised using major element glass compositions the widespread distribution stratigraphic associations and consistent major element glass chemistry have led the quaternary tephrochronological community to see the vedde ash as a robust and unique chronological marker layer for the last glacial to interglacial transition 10 18 ka bp here we present new glass analyses of the vedde ash from multiple sites around the dispersal area using a full suite of compositional analysis including for the first time single grain trace element data these data demonstrate the strong compositional coherence of vedde ash deposits however comparison with major minor and trace element compositional data from several other distally described icelandic tephras reveals that both before and after the younger dryas chronozone there were eruptions that generated widespread tephra layers that have comparable glass shard compositions to the vedde ash this implies that these numerous events not only hail from the same volcanic system but that the melts share similar crystallisation trends and mixing patterns prior to eruption it seems therefore that composition alone is insufficient for the correlation of some widespread tephra layers good stratigraphic information and or robust dating control are also essential

volcanic ash layers from the last glacial termination in the ngrip ice core the tephrochronological record of the 1400 1640 m depth 10 000 16 000 calendar ice core years before present of the ngrip ice core has been established by particle screening of selected samples ash was identified in 20 samples correlation with ice marine and terrestrial records from volcanic source regions in the northern hemisphere positively identifies the saksunarvatn ash and the vedde ash ash zone 1 major element chemistry of the remaining identified ash layers mainly points towards an icelandic origin this tephrochronological record provides new important marker horizons for correlating the timing of the climatic changes associated with the last glacial termination within the north atlantic region as well as outlining more details concerning the frequency and composition of volcanic eruptions occurring at this deglaciation copyright 2005 john wiley sons ltd

authigenic apatite formation and burial in sediments from non upwelling continental margin environments abstract evidence for precipitation of authigenic carbonate fluorapatite cfa in long island sound and mississippi delta sediments suggests that formation of cfa is not restricted to environments of active coastal upwelling we present porewater data suggestive of cfa formation in both these areas application of a sequential leaching procedure designed specifically to separate authigenic carbonate fluorapatite from other phosphorus containing phases including detrital apatite of igneous or metamorphic origin provides strong supporting evidence for authigenic apatite formation in these sediments the size of the authigenic apatite reservoir increases with depth indicating continued formation of cfa during early diagenesis this depth increase is mirrored by a decrease in solid phase organic p at both sites suggesting that cfa is forming at the expense of organic p mass balance considerations application of diagenetic models to interstitial water nutrient data and the saturation state of the interstitial water are consistent with this interpretation diagenetic redistribution of phosphorus among the different solid phase reservoirs is observed at both sites and results in near perfect retention of p by these sediments over the depth intervals sampled formation of cfa in continental margins which do not conform to the classically defined regions of phosphorite formation renders cfa a quantitatively more important sink than has previously been recognized including this reservoir as a newly identified sink for reactive p in the ocean the residence time of p in the modern ocean must be revised downward the implication for ancient oceans of cfa formation in continental margin sediments other than phosphorites is that phosphorite formation may be less a representation of episodicity in removal of reactive p from the oceans than of localized concentration of cfa in phosphatic sediments by secondary physical processes

extending the known distribution of the younger dryas vedde ash into northwestern russia the known distribution of wind blown vedde ash ca 10 3 ka bp has been extended to the karelian isthmus in northwestern russia this has been possible as the result of a density separation technique that separates the rhyolitic vedde ash shards from the minerogenic host sediment the vedde ash occurs in the middle of a pollen zone with high percentages of for example artemisia and chenopodiaceae suggesting that the younger dryas or gs i in the grip ice core event stratigraphy was cold and dry throughout its duration this is in agreement with sites in south sweden where the vedde ash also occurs in the middle of a pollen zone dominated by artemisia chenopodiaceae and cyperaceae copyright 2000 john wiley sons ltd

wind induced circulation in semienclosed homogeneous rotating basins the wind induced circulation over laterally varying bathymetry was investigated in homogeneous systems using the three dimensional regional ocean model system roms the investigation focused on the influence of the earth s rotation on the lateral distribution of the flow with particular emphasis on the transverse circulation along basin wind stress with no rotation caused a circulation dominated by an axially symmetric transverse structure consisting of downwind flow over the shoals and upwind flow in the channel along the whole domain transverse circulation was important only at the head of the system where the water sank and reversed direction to move toward the mouth the wind induced flow pattern under the effects of the earth s rotation depended on the ratio of the maximum basin s depth h to the ekman depth d the solution tended to that described in a nonrotating system as h d remained equal to or below 1 for higher values of h d the longitudinal flow was axially asymmetric maximum downwind flow was located over the right shoal in the northern hemisphere looking downwind the transverse component of velocity described three gyres the main gyre was clockwise looking downwind and occupied the entire basin cross section as expected from the earth s rotation and the presence of channel walls the other two gyres were small and localized and were linked to the lateral distribution of the along channel velocity component which in turn was dictated by bathymetry these results compared favorably with a limited set of observations and are expected to motivate future measurements

distal deposition of tephra from the eyjafjallajokull 2010 summit eruption the 2010 eyjafjallajokull lasted 39 days and had 4 different phases of which the first and third 14 18 april and 5 6 may were most intense most of this period was dominated by winds with a northerly component that carried tephra toward europe where it was deposited in a number of locations and was sampled by rain gauges or buckets surface swabs sticky tape samples and air filtering in the uk tephra was collected from each of the phases 1 3 with a combined range of latitudes spanning the length of the country the modal grain size of tephra in the rain gauge samples was 25 mu m but the largest grains were 100 mu m in diameter and highly vesicular the mass loading was equivalent to 8 218 shards cm 2 which is comparable to tephra layers from much larger past eruptions falling tephra was collected on sticky tape in the english midlands on 19 20 and 21st april phase 2 and was dominated by aggregate clasts mean diameter 85 mu m component grains 10 mu m sem eds spectra for aggregate grains contained an extra peak for sulphur when compared to control samples from the volcano indicating that they were cemented by sulphur rich minerals e g gypsum caso4 center dot h2o air quality monitoring stations did not record fluctuations in hourly pm10 concentrations outside the normal range of variability during the eruption but there was a small increase in 24 hour running mean concentration from 21 24 april phase 2 deposition of tephra from phase 2 in the uk indicates that transport of tephra from iceland is possible even for small eruption plumes given suitable wind conditions the presence of relatively coarse grains adds uncertainty to concentration estimates from air quality sensors which are most sensitive to grain sizes 10 mu m elsewhere tephra was collected from roofs and vehicles in the faroe islands mean grain size 40 mu m but 100 mu m common from rainwater in bergen in norway 23 91 mu m and in air filters in budapest hungary 2 6 mu m a map is presented summarizing these and other recently published examples of distal tephra deposition from the eyjafjallajokull eruption it demonstrates that most tephra deposited on mainland europe was produced in the highly explosive phase 1 and was carried there in 2 3 days

a regional tephrostratigraphic framework for central and southern european climate archives during the last glacial to interglacial transition comparisons north and south of the alps abstract this paper summarises the results of tephrochronological investigations into a suite of central and southern european records which include rotmeer southern germany soppensee and rotsee central swiss plateau lago di lavarone and lago piccolo di avigliana italian southern alpine foreland these sites provide records of palaeoenvironmental changes for the last glacial to interglacial transition lgit at the boundary between north atlantic and mediterranean climatic influences chemical characterisation of glass shards in volcanic ash layers indicates that multiple volcanic sources have contributed to the central european tephra record amongst other volcanic markers the laacher see tephra originating from the eifel region of germany c 12 9 0 1 ka and the vedde ash from iceland c 12 1 0 1 ka are found co located within the sediments of rotmeer soppensee rotsee and lago piccolo di avigliana these key horizons which bracket the onset of the younger dryas stadial provide precise calendrically dated tie points around which a detailed picture of the timing of local and regional environmental transitions can be constructed using the co located tephra layers the re colonisation of northern italian catchment areas by quercus is shown to occur just prior to the deposition of the laacher see tephra layer whereas to the north of the alps quercus and other thermophilous trees do not reappear until several centuries after the deposition of the vedde ash furthermore the discovery of the vedde ash in lago piccolo di avigliana and lago di lavarone is indicative of atmospheric transport of polar air into southern europe during the younger dryas stadial matching evidence proposed for such transport of polar air during the last glacial maximum lgm

new evidence for the presence of changbaishan millennium eruption ash in the longgang volcanic field northeast china abstract the changbaishan millennium eruption ad 940s produced a widely distributed tephra layer around northeast asia this tephra layer serves as a marker bed in greenland ice cores and in marine lake archeological and tsunami sediments in japan and the surrounding region however little attention has been paid to the widespread sediments west of changbaishan volcano here we present new stratigraphic geochemical varve chronology and 14c geochronological data from the varved sediments in lake sihailongwan longgang volcanic field northeast china extending the westerly margin of this eruption the distinctive geochemical characteristic of volcanic glass ranging from trachyte to rhyolite similar to those of proximal and distal tephra confirmed the occurrence of changbaishan millennium eruption ash in the lake illustrating the westward dispersal fan of the ash deposits the position of the peak concentration of glass shards of this tephra was dated to 953 37 ad by varve chronology and the radiocarbon samples immediately above this tephra gave a date of 940 1020 ad overlapping the most recent ages for this eruption the occurrence of changbaishan millennium eruption ash in this lake enables a direct and precise synchronization with other high resolution archives in northeast asia such as maar lakes and peat and marine sediments thus providing an isochronous marker for a range of sedimentary contexts

petrogenesis of the solheimar ignimbrite katla iceland implications for tephrostratigraphy the solheimar ignimbrite was one of the largest eruptions from the katla caldera iceland and is important for tephra studies in the north atlantic because of its possible linkage with the vedde ash a compositionally bimodal tephra layer used for correlation of sedimentary records in the north atlantic and northern europe the composition of the solheimar ignimbrite extends from rhyolite to basaltic icelandite a trend that defines a coherent magma mixing line mixing is evident both in mingled textures seen in hand specimens and thin sections and as binary mixing trends in major and trace element and 87sr 86sr isotopes of the volcanic glasses the solheimar rhyolite is slightly more radiogenic than the basaltic icelandite in terms of sr isotopes which is inconsistent with generation of the rhyolite by fractionation of the basaltic icelandite alternatively the solheimar rhyolite may have been produced by partial melting of icelandic crust major and trace element modelling indicates that partial melting of icelandic tholeiite does not replicate the observed rhyolite composition in particular k2o is significantly lower in the modelled melt however partial melting of katla alkali basalt does produce a comparable melt we suggest a two stage model in which 30 40 melting of basalt generated a dacitic magma which underwent subsequent 30 fractionation of the observed phenocryst phases feldspar clinopyroxene spinel and feti oxide form rhyolite the eruption of the solheimar ignimbrite was triggered by the intrusion of basaltic icelandite magma which mixed with resident rhyolite magma during eruption the solheimar ignimbrite has been linked to the vedde ash lacasse et al 1995 a compositionally bimodal tephra layer used to link sedimentary records in the north atlantic and northern europe despite the importance of the vedde ash in late quaternary studies its provenance remains equivocal we demonstrate that vedde rhyolite glasses share the same major and trace element chemistry as the solheimar rhyolite carrying the implication that these deposits may be produced by the same eruption however the solheimar ignimbrite lacks the basaltic component that is sometimes associated with rhyolitic shards of the vedde ash at far distal locations therefore this correlation cannot be confirmed

synchronisation of palaeoenvironmental records over the last 60 000 years and an extended intimate event stratigraphy to 48 000 b2k the intimate protocol for the correlation of marine ice core and terrestrial records is here updated reflecting recent developments in palaeoclimate research originally focussed on last glacial to interglacial transition lgit 22 000 11 500 years b p the intimate group has now extended its study period back to 60 000 years as a first step the intimate event stratigraphy has now been extended to include 8000 48 000 b2k based on a combined ngrip and grip isotope profile against a gicc05 chronology and key tephra horizons from iceland and continental european volcanic sources in this lead article of this intimate special issue we introduce some of the recent achievements of the intimate community and discuss the challenges associated with extending the intimate approach back in time focussing in particular on the chronological problems inherent in comparing different proxy records the intimate approach has thus far been limited predominantly to the north atlantic and australasian regions and we also discuss the potential to extend the intimate protocol beyond these regions

an inter laboratory comparison of the electron probe microanalysis of glass geochemistry abstract tephrochronology commonly relies upon grain discrete analysis of glass shards to reveal the subtle geochemical differences between tephras from past explosive volcanic eruptions the use of electron probe microanalysis for this purpose is widely accepted by tephrochronologists it is widely recognised that both precision and accuracy must be maximised and that rigorous standardisation procedures must be followed in this paper the performances of seven northern european electron microprobe centres are compared using a geochemically homogeneous obsidian secondary standard the results reveal that a number of tephra oriented probe centres could benefit from exercises similar to the programme outlined within in particular it is evident that a number of these centres undertaking tephrochronological investigations have generated geochemical data that may be inadequate in terms of distinguishing between tephras inaccuracy in the determination of sodium is seen to be the main difficulty in recent years the application of distal tephrochronology to stratigraphical problems in the northern european quaternary record has become increasingly common geochemical standardisation is essential at an early stage in the development of a regional tephrochronological framework and we hope exercises such as presented here will encourage the production of reliable tephra geochemical data

identification and dating of tephra layers from quaternary sedimentary sequences of inner anatolia turkey abstract results presented here are part of a research programme to investigate the environmental evolution in central anatolia during the pleistocene in this study tephra are used as chronostratigraphical markers between lacustrine sequences studied in cores or in sections surrounding eruptive centres of the central anatolian province at different locations in the konya plain and cappadocia tephra have been identified characterized and linked to eruptions of the nearby volcanoes seven different tephra have been clearly identified in lacustrine sequences of the konya plain 14 c dates on shells or organic matter as well as 230 th 234 u ages on gypsum give a chronological framework to the tephra layers in addition the study of the sediment fill of the eski acigol maar near nevsehir has allowed the recognition of several eruptions during late glacial and holocene in the vicinity of acigol the results show the first tephra to be identified in lacustrine sequences of anatolia they also show the cappadocian volcanism to be very young 35 ka this young volcanism is often of a basaltic type and does not include thick differenciated pyroclastic deposits

widespread dispersal of icelandic tephra how does the eyjafjoll eruption of 2010 compare to past icelandic events widespread dispersal of icelandic tephra how does the eyjafjoll eruption of 2010 compare to past icelandic events

a new and less destructive laboratory procedure for the physical separation of distal glass tephra shards from sediments abstract tephrochronology a key tool in the correlation of quaternary sequences relies on the extraction of tephra shards from sediments for visual identification and high precision geochemical comparison a prerequisite for the reliable correlation of tephra layers is that the geochemical composition of glass shards remains unaltered by natural processes e g chemical exchange in the sedimentary environment and or by laboratory analytical procedures however natural glasses particularly when in the form of small shards with a high surface to volume ratio are prone to chemical alteration in both acidic and basic environments current techniques for the extraction of distal tephra from sediments involve the cleaning of samples in precisely such environments and at elevated temperatures the acid phase of the cleaning process risks alteration of the geochemical signature of the shards while the basic phase leads to considerable sample loss through dissolution of the silica network here we illustrate the degree of alteration and loss to which distal tephras may be prone and introduce a less destructive procedure for their extraction this method is based on stepped heavy liquid flotation and which results in samples of sufficient quality for analysis while preserving their geochemical integrity in trials this method out performed chemical extraction procedures in terms of the number of shards recovered and has resulted in the detection of new tephra layers with low shard concentrations the implications of this study are highly significant because i the current database of distal tephra records and their corresponding geochemical signatures may require refinement and ii the record of distal tephras may be incomplete due to sample loss induced by corrosive laboratory procedures it is therefore vital that less corrosive laboratory procedures are developed to make the detection and classification of distal glass tephra more secure

cryptotephra as a dating and correlation tool in archaeology a new development in archaeological chronology involves the use of far travelled volcanic ash which may form discrete but invisible layers within a site s stratigraphy known as cryptotephra these horizons can provide isochrons for the precise correlation of archaeological records at single moments in time removing or at least significantly reducing temporal uncertainty within inter site comparisons when a tephra can be dated elsewhere its age can be imported between records providing an independent check on other dating methods in use and valuable age estimates for difficult to date sequences the use of cryptotephra layers to date and correlate palaeoenvironmental archives is well established and there exists a wealth of tephra compositional data and regional tephrostratigraphic frameworks from which archaeological cryptotephra studies can benefit greatly existing approaches to finding and analysing cryptotephra are easily adapted to archaeological sequences so long as the often complex nature of archaeological stratigraphies and sediment taphonomy are borne in mind

integrating the intimate records using tephrochronology rising to the challenge little has challenged our understanding of climate change more so than the abruptness with which large scale shifts in temperature occurred during the late quaternary the causal mechanisms driving

tephrochronology of last termination sequences in europe a protocol for improved analytical precision and robust correlation procedures a joint scotav intimate proposal the precise sequence of events during the last termination 18 000 9000 ka 14 cy r bp and the extent to which major environmental changes were synchronous are difficult to estab lish using the radiocarbon method alone because of serious distortions of the radiocarbon time scale as well as the influences of site specific errors that can affect the materials dated attention has there fore turned to other methods that can provide independent tests of the chronology and correlation of events during the last termination with emphasis on european sequences we summarise here the potential of tephrostratigraphy and tephrochronology to fulfil this role recent advances in the detection and analysis of hidden tephra layers cryptotephra indicate that some tephras of last termination age are much more widespread in europe than appreciated hitherto and a number of new tephra deposits have also been identified there is much potential for developing an integrated tephrochronological framework for europe which can help to underpin the overall chronology of events during the last termination for that potential to be realised however there needs to be a more systematic and robust analysis of tephra layers than has been the practice in the past we pro pose a protocol for improving analytical and reporting procedures as well as the establishment of a centralised data base of the results which will provide an important geochronological tool to support a diverse range of stratigraphical studies including opportunities to reassess volcanic hazards although aimed primarily at europe the protocol proposed here is of equal relevance to other regions and periods of interest copyright 2004 john wiley sons ltd

late pleistocene eifel eruptions insights from clinopyroxene and glass geochemistry of tephra layers from eifel laminated sediment archive sediment cores

deposition models for chronological records abstract long term sedimentary sequences provide a wealth of useful information for research into the palaeo environment especially in relation to past climate change shorter records provide similar information in many archaeological contexts however if such records are to be used to provide precise timing of events and more critically the relative timing between different records methods are needed to provide accurate and precise age depth models for these sequences given the imprecision of individual calibrated radiocarbon determinations it is necessary to use the information we have about the deposition process to refine our chronologies and also to provide interpolation between dated levels in any sequence even with layer counted chronologies the uncertainties are sometimes hard to quantify this paper outlines a range of bayesian models for deposition which have been implemented in the computer programme oxcal these models can be used to combine information from the sediments themselves with radiocarbon or other direct dating information such models have the potential to integrate information between different records and provide a coherent chronology on which to base environmental or archaeological research