constraining the time span between the early holocene hasseldalen and askja s tephras through varve counting in the lake czechowskie sediment record poland we report the first findings of coexisting early holocene hasseldalen and askja s cryptotephras in a varved sediment record in lake czechowskie poland a time span of 152 11 8 varve years between the two tephras has been revealed by differential dating through varve counting this is in agreement within the uncertainties with calculations from radiocarbon based age models from the non varved hasseldala port record in southern sweden but shorter than assumed from the non varved lake record on the faroe islands we discuss possible reasons for the observed differences in duration between the two tephras and provide a revised absolute age for the askja s tephra of 11 228 226 cal a bp based on anchoring our floating varve chronology to the absolute timescale by using the hasseldalen tephra as dated in the hasseldala port sediments 11 380 216 cal a bp this age agrees with radiocarbon age models with larger uncertainty ranges but is slightly older than radiocarbon based age models with narrow uncertainty bands and is even 200 300 years older than the age reported from the faroe islands record in addition to these chronological issues we discuss the possible response of the czechowskie sediment record to the preboreal climate oscillation

tephrochronology and absolute centennial scale synchronisation of european and greenland records for the last glacial to interglacial transition a case study of soppensee and ngrip the tephrostratigraphy of soppensee switzerland is presented here for the first time with new geochemical data for four tephra layers derived from three volcanic centres the best available age estimates for the laacher see tephra and vedde ash layers are incorporated into a revision of the radiocarbon based bayesian age model for the last glacial to interglacial transition at soppensee which is used to explore synchronicity of climatic events between europe and the north atlantic local temperature changes recorded by biotic and abiotic proxies in soppensee appear to shift in phase with the oxygen isotope signal in greenland at the onset of the younger dryas however with the clarity of improved precision an apparent offset that likely results from a dating artefact is seen between records at the termination of the stadial event from a methodological standpoint the results clearly show that only by establishing detailed and independent chronological frameworks can abrupt climatic variability be compared between different regions with sufficiently high temporal precision to addresses the notion of hemispheric climatic synchronicity at the centennial scale in the late quaternary continuing to develop such approaches is therefore essential in order to understand how far in time and space the climate has behaved in such a way

younger dryas and allerod summer temperatures at gerzensee switzerland inferred from fossil pollen and cladoceran assemblages linear and unimodal based inference models for mean summer temperatures partial least squares weighted averaging and weighted averaging partial least squares models were applied to a high resolution pollen and cladoceran stratigraphy from gerzensee switzerland the time window of investigation included the allerod the younger dryas and the preboreal characteristic major and minor oscillations in the oxygen isotope stratigraphy such as the gerzensee oscillation the onset and end of the younger dryas stadial and the preboreal oscillation were identified by isotope analysis of bulk sediment carbonates of the same core and were used as independent indicators for hemispheric or global scale climatic change in general the pollen inferred mean summer temperature reconstruction using all three inference models follows the oxygen isotope curve more closely than the cladoceran curve the cladoceran inferred reconstruction suggests generally warmer summers than the pollen based reconstructions which may be an effect of terrestrial vegetation not being in equilibrium with climate due to migrational lags during the late glacial and early holocene allerod summer temperatures range between 11 and 12 c based on pollen whereas the cladoceran inferred temperatures lie between 11 and 13 c pollen and cladocera inferred reconstructions both suggest a drop to 9 10 c at the beginning of the younger dryas although the allerod younger dryas transition lasted 150 160 years in the oxygen isotope stratigraphy the pollen inferred cooling took 180 190 years and the cladoceran inferred cooling lasted 250 260 years the pollen inferred summer temperature rise to 11 5 12 c at the transition from the younger dryas to the preboreal preceded the oxygen isotope signal by several decades whereas the cladoceran inferred warming lagged major discrepancies between the pollen and cladoceran inference models are observed for the preboreal where the cladoceran inference model suggests mean summer temperatures of up to 14 15 c both pollen and cladoceran inferred reconstructions suggest a cooling that may be related to the gerzensee oscillation but there is no evidence for a cooling synchronous with the preboreal oscillation as recorded in the oxygen isotope record for the gerzensee oscillation the inferred cooling was ca 1 and 0 5 c based on pollen and cladocera respectively which lies well within the inherent prediction errors of the inference models

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

an application of hierarchical bayesian modeling to better constrain the chronologies of upper paleolithic archaeological cultures in france between ca 32 000 21 000 calibrated years before present abstract investigations of chronology play a key role in the majority of archaeological research endeavors and are particularly pertinent to examinations of culture environment relationships especially during periods characterized by rapid and marked climatic variability and environmental reorganization rigorous evaluations of available data and robust methods are required if one wishes to reconstruct reliable chronologies and this is especially the case when examining periods that are associated with a relatively few radiometric measurements such is the case for the upper paleolithic archaeological record documented in present day france from 32 000 to 21 000 calibrated years bp we take into account critically examined radiocarbon measurements from contextually secure archaeological contexts and employ a recently developed method of hierarchical bayesian modeling to reconstruct the chronology of archaeological cultures from the middle gravettian to the badegoulian the calculated chronological intervals for each typo technologically defined culture phase are compared to the greenland ice core climatic record and a terrestrial paleoenvironmental record from bergsee lake southern germany itself expressed in calendar years calculated with the same calibration curve employed in our age model thereby permitting each archaeological culture to be correlated accurately with documented paleoclimatic variability

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

lateglacial calendar year chronology based on annually laminated sediments from lake meerfelder maar germany abstract annually laminated sediments from lake meerfelder maar mfm in the eifel germany provide an independent calendar year timescale for the last glacial interglacial transition changes in varve thickness and varve facies reflect significant environment variations during this period the general micro facies pattern confirms that diatomaceous organic varves are favoured during warm climatic phases while cold periods generate higher allochthonous sediment fluxes an exception is the significant increase in diatom blooms at the beginning of the younger dryas six lateglacial biozones have been defined by litt and stebich quaternary international 1999 the sediment record comprises two tephra layers as chronomarkers the laacher see tephra 12 880 varve years bp is a continent wide correlation horizon while the ulmener maar tephra provides regional chronological links the beginning of the lateglacial warming is dated at 14 450 varve years vyrs bp which is regarded as the minimum age three abrupt cold spells interrupted the lateglacial interstadial at 13 800 vyrs bp oldest dryas 13 540 vyrs bp older dryas and 12 680 vyrs bp younger dryas the oldest dryas 130 years and the older dryas 190 years were rather short while the younger dryas lasted much longer 1090 years the mfm chronology was compared with ice core timescales from gisp2 and grip there is a good agreement between these timescales with the grip model age ss09 providing the best match to the mfm chronology

impact of terrain attributes parent material and soil types on gully erosion abstract gully erosion is a worldwide matter of concern because of the irreversible losses of fertile land which often have severe environmental economic and social consequences while most of the studies on the gullying process have investigated the involved mechanisms either overland flow incision seepage or piping erosion only few have been conducted on the controlling factors of gully wall retreat an important if not the dominant land degradation process and sediment source in river systems in a representative 4 4 km 2 degraded area of the drakensberg foothills south africa the main objective of this study was to evaluate the relationship between the rate of gully bank retreat gbr and parent material soil types and selected terrain attributes elevation specific drainage area mean slope gradient slope length factor stream power index compound topographic index and slope curvatures the survey of gully bank retreat was performed during an entire hydrological year from september 2007 to september 2008 using a network of pins n 440 from 110 pits both the gully contours and pin coordinates were determined using a gps with a 0 5 m horizontal accuracy n 20 120 the information on the parent material and the soil types was obtained from field observations complemented by laboratory analysis while terrain attributes were extracted from a 20 m dem generated from 5 m interval contour lines the average gbr value for the 6512 m of gully banks found in the area was 0 049 0 0013 m y 1 which considering bank height and soil bulk density corresponded to an erosion rate of 2 30 ton ha 1 y 1 there was no significant difference in gbr between sandstone and dolerite and between acrisols and luvisols despite a weak one to one correlation with the selected terrain attributes r gbr was the highest at hillslope inflexion points profile and plan slope curvatures close to zero in the vicinity of the head cuts and for drainage areas up to 500 m 2 as both situations experience a high removal rate of the soil material produced from the gully bank collapse and protecting gullies from laterally retreating these results could be used to digitally map the more active gully banks for the improved implementation of preventive measures of gully growth if high resolution dems are available there remained however a certain amount of unexplained variability in the data that further research studies on the mechanisms and associated factors of control of gbr could help to address

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

rapid and widespread vegetation responses to past climate change in the north atlantic region ongoing anthropogenic perturbations to the atmosphere and biosphere increase the risk of future abrupt changes in the climate system and generate concern about the ability of natural ecosystems to respond to rapid climate change study of past climatic events and biotic responses can inform us about potential future change qualitatively fast local responses of plant taxa to abrupt late glacial climate oscillations have been reported from individual records and attributed to short migration distances in areas of high topographic relief by using quantitative time series analyses we show that vegetation responses to late glacial climate change around the north atlantic were rapid and widespread and occurred in areas of differing relief cross correlation analysis of 11 high resolution lacustrine records in eastern north america and europe indicates vegetation response times consistently of 200 yr and often 100 yr despite regional differences in physiography and species composition vegetation lags of 200 yr confirm theoretical predictions and the apparently tight coupling between vegetation and atmosphere suggests that recent climatic trends may already have begun to affect plant population abundances and distributions

tephra horizons contemporary with short early holocene climate fluctuations new results from the faroe islands the climate of the north atlantic region was relatively unstable after the last termination at least three cold events superimposed upon a general warming took place during the earliest part of the

late quaternary western mediterranean pollen records and african winds abstract late quaternary vegetation changes of regional and global significance in the mediterranean region are generally interpreted as being controlled by changes in the circulation patterns of north atlantic air masses however the possibility cannot be excluded that they may also be related to winds blowing from africa long pollen records from southwest europe show that cedrus pollen of northwest african provenance is found during the glacial periods and occasionally during abrupt deforestation events in the forest dominated periods of the interglacials a pollen concentration record from central italy shows that during the holocene the presence of cedrus pollen coincides with two abrupt deforestation events around 8 1 and 4 2 cal kyr bp these observations raise the question of a possible influence of eolian activity on arboreal vegetation during phases of climatic stress towards aridity and suggest the use of modern pollen monitoring as a strategy for revealing tendencies towards aridification in southwestern europe

pore pressure prediction in gas hydrate bearing sediments of krishna godavari basin india abstract predrill estimate of pore pressure pp is important for well design especially in areas containing gas hydrate bearing sediments here we report the pressure distribution in the gas hydrate bearing sediments in krishna godavari k g basin predicted from the seismic data along two lines passing through the site 10 of expedition 01 exp 01 conducted by the indian national gas hydrate programme nghp a series of elastic parameters namely p wave velocity vp s wave velocity vs density vp vs p impedance zp and s impedance zs were derived from seismic data using pre stack inversion first the pp estimated from a sonic transit time log was calibrated with pressure core measurements in the depth interval of 1060 1280 m its magnitude is found to be ranging from 10 5 to 12 9 mpa where the vertical stress varies from 10 7 to 13 4 mpa within the same depth interval this estimated pp was next treated as a target log desired output and seismic attributes resulting from pre stack seismic inversion were used as input parameters in the training of a multi layered feedforward network mlfn finally we use the trained network to generate a subsurface pp distribution map along two 2d multichannel seismic profiles line x and line y passing through nghp01 10 within a time interval of 1420 1620 ms corresponding to a depth interval of 1060 1280 m this corresponds to sedimentary column from 22 to 242 mbsf our results demonstrate that the pressure remains hydrostatic within the gas hydrate bearing sediments and is mostly above hydrostatic below the gas hydrate bearing zone

chironomid inferred late glacial air temperatures at whitrig bog southeast scotland this paper presents the first chironomid inferred mean july air temperature reconstruction for the late glacial in britain the reconstruction suggests that the thermal maximum occurred early in the interstadial with temperatures reaching about 12 degreesc there was then a gradual downward trend to about 11 degreesc punctuated by four distinct cold oscillations of varying intensity at the beginning of the younger dryas mean july temperatures fell to about 7 5 degreesc but gradually increased to about 9 degreesc before a rapid rise at the onset of the holocene the chironomid inferred temperature curve agrees closely both in general trends and in detail with the grip ice core oxygen isotope curve the reconstructed temperatures are 2 4 degreesc lower than coleopteran inferred temperatures but are closer to those inferred from plant macrofossils and glacial equilibrium line altitudes during the younger dryas copyright c 2000 john wiley sons ltd

the reset project constructing a european tephra lattice for refined synchronisation of environmental and archaeological events during the last c 100 ka this paper introduces the aims and scope of the reset project response of humans to abrupt environmental transitions a programme of research funded by the natural environment research council uk between 2008 and 2013 it also provides the context and rationale for papers included in a special volume of quaternary science reviews that report some of the project s findings reset examined the chronological and correlation methods employed to establish causal links between the timing of abrupt environmental transitions aets on the one hand and of human dispersal and development on the other with a focus on the middle and upper palaeolithic periods the period of interest is the last glacial cycle and the early holocene c 100 8 ka during which time a number of pronounced aets occurred a long running topic of debate is the degree to which human history in europe and the mediterranean region during the palaeolithic was shaped by these aets but this has proved difficult to assess because of poor dating control in an attempt to move the science forward reset examined the potential that tephra isochrons and in particular non visible ash layers cryptotephras might offer for synchronising palaeo records with a greater degree of finesse new tephrostratigraphical data generated by the project augment previously established tephra frameworks for the region and underpin a more evolved tephra lattice that links palaeo records between greenland the european mainland sub marine sequences in the mediterranean and north africa the paper also outlines the significance of other contributions to this special volume collectively these illustrate how the lattice was constructed how it links with cognate tephra research in europe and elsewhere and how the evidence of tephra isochrons is beginning to challenge long held views about the impacts of environmental change on humans during the palaeolithic

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

two terrestrial records of rapid climatic change during the glacial holocene transition 14 000 9 000 calendar years b p from europe two independent multidisciplinary studies of climatic change during the glacial holocene transition ca 14 000 9 000 calendar yr b p from norway and switzerland have assessed organism responses to the rapid climatic changes and made quantitative temperature reconstructions with modern calibration data sets transfer functions chronology at krakenes western norway was derived from calibration of a high resolution series of 14c dates chronologies at gerzensee and leysin switzerland were derived by comparison of 18o in lake carbonates with the 18o record from the greenland ice core project both studies demonstrate the sensitivity of terrestrial and aquatic organisms to rapid temperature changes and their value for quantitative reconstruction of the magnitudes and rates of the climatic changes the rates in these two terrestrial records are comparable to those in greenland ice cores but the actual temperatures inferred apply to the terrestrial environments of the two regions

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

rapid oceanic and atmospheric changes during the younger dryas cold period the younger dryas event which began approximately 12 900 years ago was a period of rapid cooling in the northern hemisphere driven by large scale reorganizations of patterns of atmospheric and oceanic circulation 1 3 environmental changes during this period have been documented by both proxy based reconstructions 3 and model simulations 4 but there is currently no consensus on the exact mechanisms of onset stabilization or termination of the younger dryas 5 8 here we present high resolution records from two sediment cores obtained from lake krakenes in western norway and the nordic seas multiple proxies from lake krakenes are indicative of rapid alternations between glacial growth and melting during the later younger dryas meanwhile reconstructed sea surface temperature and salinity from the nordic seas show an alternation between sea ice cover and the influx of warm salty north atlantic waters we suggest that the influx of warm water enabled the westerly wind systems to drift northward closer to their present day positions the winds thus brought relatively warm maritime air to northern europe resulting in rising temperatures and the melting of glaciers subsequent input of this fresh meltwater into the ocean spurred the formation of sea ice which forced the westerly winds back to the south cooling northern europe we conclude that rapid alternations between these two states immediately preceded the termination of the younger dryas and the permanent transition to an interglacial state the impact of freshwater pulses released from northern hemisphere ice sheets on the north atlantic meridional overturning circulation has been suggested as a likely mechanism for the younger dryas cooling 7 11 in addition a responsive sea ice cover has been proposed as a mechanism that could rapidly alter the heat exchange between the ocean and atmosphere during the last glacial period 12 13 the roles of the ocean and the atmosphere in triggering the climate shifts around the younger dryas are much discussed 9 these hypotheses are difficult to resolve partly because the temporal resolution of most palaeoclimate archives is too coarse to enable the anatomy of the younger dryas stadial to be adequately described 14 to address these questions we here present a lake sediment record at sub annual resolution together with new data on the sea surface conditions of the norwegian atlantic current nwac throughouttheyoungerdryasstadial fig 1

were last glacial climate events simultaneous between greenland and france a quantitative comparison using non tuned chronologies several large abrupt climate fluctuations during the last glacial have been recorded in greenland ice cores and archives from other regions often these dansgaard oeschger events are assumed to have been synchronous over wide areas and then used as tie points to link chronologies between the proxy archives however it has not yet been tested independently whether or not these events were indeed synchronous over large areas here we compare dansgaard oeschger type events in a well dated record from southeastern france with those in greenland ice cores instead of assuming simultaneous climate events between both archives we keep their age models independent even these well dated archives possess large chronological uncertainties that prevent us from inferring synchronous climate events at decadal to multi centennial time scales if possible comparisons between proxy archives should be based on independent non tuned time scales copyright 2009 john wiley sons ltd

the lateglacial quercus expansion in the southern european alps rapid vegetation response to a late allerod climate warming a pollen inferred vegetation shift from pioneer birch pine woodland to mixed pine summergreen oak forests in the southern alpine forelands is commonly attributed to a centennial scale warming that occurred between the gerzensee oscillation go and the younger dryas two microtephra layers bracketing the younger dryas onset the laacher see tephra and the vedde ash improve the chronology at lago piccolo di avigliana northern italy and allowed accurate correlation with central european records where the go is clearly detected we used pollen percentages pollen accumulation rates pars and plant macrofossils to assess the population dynamics of quercus and leaf cuticle analysis for a better taxonomic identification of quercus our results indicate that the species that was locally present was probably quercus robur pars suggest that the population expansion started as early as the bolling and followed an exponential increase through time we attribute this gradual shift to increasing summer temperatures and longer growing seasons which contrast with a gradually decreasing temperature trend as recorded in greenland ice cores and in central europe breaks or set backs in the par record may indicate the biotic response to minor lateglacial cooling events of different life history stages in the quercus population copyright 2011 john wiley sons ltd

cryptotephra from the 74 ka bp toba super eruption in the billa surgam caves southern india abstract the 74 ka bp youngest toba tuff ytt from the largest known quaternary volcanic eruption has been found for the first time as a non visible crypto tephra layer within the billa surgam caves southern india the occurrence of the ytt layer in charnel house cave provides the first calendrical age estimate for this much debated pleistocene faunal sequence and demonstrates the first successful application of cryptotephrochronology within a cave sequence the ytt layer lies 50 cm below a major sedimentological change which is related to global cooling around the mis 5 to mis 4 transition using this isochronous event layer the billa surgam cave record can be directly correlated with other archaeological sites in peninsular india and palaeoenvironmental archives across southern asia

land ice teleconnections of cold climatic periods during the last glacial interglacial transition independent calendar year chronologies are a basic requirement for the establishment of high resolution land ice teleconnections the annually laminated meerfelder maar record provides both an independent chronology established by varve counting and high resolution lithological proxy data for the period of the last glacial interglacial transition these data reveal a series of four periods of climatic deterioration coinciding with negative isotopic deviations in the grip record signal thus demonstrating the synchronicity of environment changes in western germany and temperature shifts in greenland the terrestrial data supports a further sub division of the event stratigraphy based on the grip core by introducing the cold event gi 1c2 between 13 500 and 13 400 calendar years bp multiproxy analyses reveal that the environmental response at meerfelder maar was not linear throughout the lateglacial but was modified by local processes a change in the response of the lake environment to climate deterioration was observed during sub stage gi 1b gerzensee oscillation the only event with gradual rather than abrupt transitions the two fold character of the younger dryas as seen in the grip record is more pronounced in the meerfelder maar record this lithological signal occurred with a delay of 60 years to the grip signal and has been linked to a shift in the catchment it is proposed that the trigger for this shift was a trend towards a more humid second half of the younger dryas

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

sedimentology dating and palaeoclimatic interpretation of a 76 3 ka record from lago grande di monticchio southern italy abstract detailed sedimentological and microstratigraphical investigations of lacustrine sediments from lago grande di monticchio southern italy provide a time scale based on rates of sedimentation obtained from annual laminations although not annually laminated throughout a time scale covering the last 76 3 ka is available by interpolation of sedimentation rates results of this chronology agree with radiocarbon dates and with ar ar dates on tephra layers from the same lacustrine sediment sequence occurrence of varves in combination with physical and geochemical properties are related to variations in the trophic state of the lake and to changing runoff both controlled by palaeoclimatic conditions water depth was relatively shallow with dominating bioturbation and only few varves preserved for most of the pleniglacial a marked increase in precipitation and related runoff characterises the early last glacial maximum when water depth reached a maximum and clastic varves were deposited subsequently water depth was shallower again a drastic change towards nutrient rich conditions occurred at the pleistocene holocene transition during the holocene organic varves were deposited two periods with higher organic productivity were recognised prior to the last glacial maximum around 50 ka and 73 ka these intervals are interpreted as the result of interstadial conditions the oldes of the two events shows laminations comparable to those at the glacial holocene transition the periods with increased minerogenic influx may be characterised as stadial conditions lasting from 14 40 ka and from 50 73 ka

a new lateglacial chronostratigraphic tephra marker for the south eastern alps the neapolitan yellow tuff nyt in langsee austria in the context of a regional biostratigraphy and palaeoclimate langsee is a small meromictic lake in carinthia se alps with partially varved lateglacial sediments the langsee tephra correlates to the neapolitan yellow tuff nyt an eruption from the campanian volcanic province italy this tephra provides a lateglacial chronostratigraphic time marker from central italy across the adriatic sea to the southeastern alps the langsee tephra is discussed in the context of pollen geochemical and microstratigraphical data from a profundal sediment core from langsee the age of 14 120 cal yr bp for the nyt has been accepted from the monticchio chronology the timescale for the lateglacial in the langsee record is based on laminae counts and has been linked to calendar year ages using the nyt tephrachronological marker consequently the mass expansion of betula has been dated at 14 270 cal yr bp the expansion of p sylvestris started concurrent with the nyt and about 180 yr later at 13 940 cal yr bp p sylvestris forests were established the younger dryas biozone at langsee is characterized only by a slight increase in non arboreal pollen and dominated by pine with visible variations only in pine pollen types differentiation of pine pollen types allowed the recognition of three minor fluctuations during the lateglacial interstadial two of these oscillations tentatively have been correlated with the aegelsee and gerzensee oscillations in switzerland as well as with vegetation changes in nw germany

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

varve microfacies and varve preservation record of climate change and human impact for the last 6000 years at lake tiefer see ne germany the holocene sediment record of lake tiefer see exhibits striking alternations between well varved and non varved intervals here we present a high resolution multi proxy record for the past 6000

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

slope process change and colluvium deposition in swaziland an sem analysis electron microscope analysis of sixty samples taken from six colluvium sites in swaziland has shown that the quartz grains exhibit marked edge abrasion in the uppermost beds of exposures this edge abrasion is lacking in the lower beds in all sections examined and indicates slope process change during colluvium deposition a model of slope evolution is provided in which slope erosion progressively brings about more channelling and causes greater surface roughness because of the exhumation of more core stones and differentially weathered rock this roughness causes increased edge abrasion

regional synthesis of mediterranean atmospheric circulation during the last glacial maximum atmospheric circulation leaves few direct traces in the geological record making reconstructions of this crucial element of the climate system inherently difficult we produced a regional mediterranean synthesis of paleo proxy data from the sea surface to alpine altitudes this provides a detailed observational context for change in the three dimensional structure of atmospheric circulation between the last glacial maximum lgm 23 000 to 19 000 years ago and the present the synthesis reveals evidence for frequent cold polar air incursions topographically channeled into the northwestern mediterranean anomalously steep vertical temperature gradients in the central mediterranean imply local convective precipitation we find the lgm patterns to be analogous though amplified to previously reconstructed phases of enhanced meridional winter circulation during the maunder minimum the little ice age

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

late glacial chironomid based temperature reconstructions for lago piccolo di avigliana in the southwestern alps italy chironomid headcapsules were used to reconstruct late glacial and early holocene summer temperatures at lago piccolo di avigliana lpa two training sets northern sweden north america were used to infer temperatures the reconstructed patterns of temperature change agreed well with the grip and ngrip 18o records inferred temperatures were high during the bolling ca 19 c slowly decreased to ca 17 5 c during the allerod reached lowest temperatures ca 16 c during the younger dryas and increased to ca 18 5 c during the preboreal the amplitudes of change at climate transitions i e oldest dryas bolling 3 c allerod younger dryas 1 5 c and younger dryas preboreal 2 5 c were smaller than in the northern alps but similar to those recorded at another site in northeastern italy our results suggest that 1 allerod temperatures were higher in the southern alps and 2 higher during the preboreal 1 c than during the allerod these differences might provide an explanation for the different responses of terrestrial vegetation to late glacial and early holocene climatic changes in the two regions other sites on both sides of the alps should be studied to confirm these two hypotheses

the atmospheric winter circulation during the younger dryas stadial in the atlantic european sector the younger dryas yd stadial signified an interruption of the warming during the transition from the last glacial to the present interglacial the mechanism responsible for this cooling is still uncertain so valuable information concerning climate variability can be obtained by numerical simulation of the yd climate we performed four experiments on the younger dryas climate with the hamburg atmospheric general circulation model here we use the results of these experiments which differed in prescribed boundary conditions to characterize the atmospheric winter circulation during the yd stadial in the north atlantic european sector the 10 year means of the following variables are presented sea level pressure 500 hpa geopotential heights and 200 hpa winds in addition we used daily values to calculate an index to assess the occurrence of blocking and strong zonal flow and to compute storm tracks our results show that the yd cooling in europe was present with a strong and stable westerly circulation without blocking this is in conflict with an earlier study suggesting frequent easterly winds over nw europe in our experiments the sea ice cover in the north atlantic ocean was the crucial factor forcing this specific yd circulation moreover the jet stream over the north atlantic was strengthened considerably causing an enhanced cyclonic activity over the eurasian continent the yd winter circulation was different from the circulation found in most simulation studies on the last glacial maximum since no glacial anticyclones were present and no split of the jet stream occurred

the significance of maar volcanoes for palaeoclimatic studies in china abstract the sediments of maar lakes often provide paleoenvironmental records which are highly suitable for palaeoclimatic studies the main advantages of the records from maar lakes compared with other lacustrine records are as follows first the presence of varves annually laminated layers and tephra layers as well as other materials like terrestrial plant macrofossils charcoals organic carbon organic shells suitable for isotopic dating like ams 14c 210pb 137cs 238u 230th 40ar 39ar provides the possibility of developing several independent chronologies enabling the development of robust high resolution chronologies second maars and maar lakes can provide continuous sedimentary records spanning tens of thousands of years tianyang maar in china is hosted the longest known record spanning at least 400 kyr bp that are ideal for the investigation of climate change on different timescales including orbital millennial centennial and annual decadal third recent studies of biomarkers based on long chain alkenones lcas and glycerol dialkyl glycerol tetraethers gdgts have demonstrated the potential of maar lakes for quantitative paleotemperature reconstruction in this study we review some of the more significant achievements of palaeoclimatic research based on maar lake sediment sequences from china with the focus on chronology multiple timescales and quantitative paleoclimatic reconstruction

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

tephrostratigraphy study for the last 18 000 14 c years in a deep sea sediment sequence for the south adriatic abstract a detailed tephrostratigraphy supported by accelerator mass spectrometry ams 14c dating and isotopic and geochemical analyses has been carried out for a deep sea core collected from the southern adriatic sea which spans the last 18 14c kyr fourteen ash layers have been recognized in the marine core and the origin was determined by comparing their age and geochemistry with tephra detected in terrestrial deposits the geochemical signatures of marine ash layers indicate a prevailing campanian and subordinate etnean and eolian provenances collectively they are attributed to sources in the phlegraean fields lam lagno amendolare ln1 ln2 gm1 c 2 nyt neapolitan yellow tuff c 1 agnano pomici principali ams pf agnano monte spina ast astroni somma vesuvius l9 pomici di base l8 greenish mount etna et1 y1 biancavilla ignimbrite lipari e 1 gabellotto fiumebianco and palinuro seamount pal 1 some of these eruptions have been detected for the first time in marine cores astroni lam l9 l8 and three were detected and dated by marine tephra ln1 ln2 and pal 1 providing new more precise stratigraphic markers for the last 18 kyr in the south adriatic marine record

identification of cryptotephra horizons in a north east atlantic marine record spanning marine isotope stages 4 and 5a 60 000 82 000 a b2k abstract tephrochronology is one of the few techniques that offer considerable but as yet largely unrealised potential for the correlation of north atlantic palaeoclimatic archives spanning the mis 4 and 5a substage period a phase of pronounced global cooling during the initiation of the last glacial period in this investigation two previously unidentified rhyolitic tephra horizons believed to be sourced from iceland were isolated within the giant piston core md04 2822 retrieved from the rockall trough north east atlantic one horizon was deposited at the beginning of greenland stadial 19 70 150 a b2k and the other around the cooling transition at the end of greenland interstadial 20 75 320 a b2k density separation epma and la icp ms techniques were utilised for the identification of these cryptotephra within the fine fraction sediment

tracing the laacher see tephra in the varved sediment record of the trzechowskie palaeolake in central northern poland abstract tephrochronological studies of partly varved sediments of trzechowskie palaeolake in central northern poland led to the finding of the late allerod laacher see tephra lst from the eifel volcanic field for the first time in a very distal site ca 840 km ene from its volcanic source the detection of glass shards of the lst involved a comprehensive combination of techniques i e biostratigraphical constrains high resolution xrf core scanning and areal xrf mapping of impregnated sediment slabs as well as detailed visual inspection of sediments the major element chemistry of volcanic glass confirmed the laacher see tephra composition in trzechowskie palaeolake sediments suggesting a deposition from the middle laacher see tephra mlst c or upper laacher see tephra ulst dispersal fans the finding of the lst in this palaeolake enables direct synchronisation with other high resolution archives in north central europe i e lake meerfelder maar rehwiese palaeolake to investigate regional variations of environmental responses at the onset of the younger dryas along a west east transect through north central europe

hydrological effects of buried palaeosols in eroding landscapes a case study in south africa abstract palaeosols have long been studied as valuable records of past climate and landscape changes the influence of palaeosols on the functioning of present day landscapes is receiving closer attention due to the relevance of palaeosols on long term hydrological processes and the future hydrological and erosive response of catchments this study describes a sequence of interbedded colluvial sedimentary deposits and buried palaeosols exposed by gully erosion in the drakensberg escarpment foothills in kwazulu natal province south africa model simulations are presented that explore present day hydrological effects of pedogenetic and textural differentiation under conditions of groundwater lowering caused by gully erosion at 14 sites the results suggest that the colluvial deposits and palaeosols cause a significant increase in total annual drainage from most of the 14 studied sites compared with similar sites without texturalor structural differentiation in the simulations sediment deposition not palaeosol formation has the most profound influence on the present day hydrological functioning of the catchment a true deposystem service effects of the limited palaeosol development on soil water holding capacity and actual soil water storage appear to be negligible

some physical and chemical properties of sediments exposed in a gully donga in northern kwazulu natal south africa and their relationship to the erodibility of the colluvial layers abstract gullies locally termed dongas are a characteristic feature of the landscape in central kwazulu natal and are highly associated with widespread stratified colluvial sediments and the buried palaeosols that have formed in this material research objectives were to find out which sediment property or properties contribute most to the vulnerability of the colluvium to gully erosion to study the erosion susceptibility of the sequence of buried stratigraphic layers and palaeosols and to improve understanding of the relationship between erosion susceptibility of the colluvial layers and palaeosols and their disposition in the landscape materials from several colluvial layers and palaeosols exposed in the donga sidewall of the dabekazi donga 13 km north of nqutu in central kwazulu natal were subjected to chemical and mineralogical analyses several dispersion and erodibility tests and were characterized physically exchangeable sodium percentages esp ranged from 0 to 23 and the dispersivity and erodibility tests revealed a range of dispersion potential and erodibility across the sequence of colluvial layers and palaeosols however a poor correlation was found between the results of different dispersion tests as well as between dispersion tests and dispersion related properties dispersion tests showed significant correlation with silt content an erodibility test using a flume showed very strong correlation with electrical conductivity ec and sodium adsorption ratio sar of the saturated paste extract and esp values the plasticity index ranged from 0 to 0 23 and estimated hydraulic conductivities ranged from 33 to 0 7 m day high correlation with esp and ec suggests that dispersion plays an important role in the erodibility of the materials under conditions of short duration turbulent water flow however colluvium in which deep gullying occurs is not necessarily strongly sodic also the degree of erodibility of the materials differs depending on the test used illustrating the complexity of the interactions that govern dispersion and erosion the erodibility of the colluvial layers and palaeosols from the dabekazi donga and properties with relevance to dispersion differ considerably down the profile indicating that geomorphic threshold conditions and position in the landscape with respect to surface runoff hydrology also codetermine donga erosion hydraulic conductivity estimates of the investigated materials are relatively high and do not differ sufficiently to enable lateral subsurface flow through and piping of these materials to be the main causes of donga formation

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

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

a younger dryas ash bed in western norway and its possible correlations with tephra in cores from the norwegian sea and the north atlantic abstract a bed of volcanic ash up to 23 cm thick is found in lacustrine and marine sediments in western norway it is formally mamed the vedde ash bed and its age is approximately 10 600 yr b p i e mid younger dryas the bed consits of pure glass having a bimodal basaltic and rhyolitic somposition the geochemistry of the glass shards suggests an icelandic source by means of stratigraphic position and geochemistry the ash is correlated with ash zones found in cores from the continental shelf the norwegian sea and the north atlatic

a late younger dryas early holocene tephrostratigraphy for fosen central norway a number of rapid climate oscillations occur during the lateglacial early holocene 15 8 ka bp period and a well developed tephrostratigraphy in association with these oscillations increases the po

three new distal tephras in sediments spanning the last glacial interglacial transition in scotland three new microtephras are reported from a number of lake sites from the inner hebrides and scottish mainland one occurs stratigrapically in the middle of greenland interstadial 1 gi 1 and has been named the penifiler tephra it is rhyolitic and possesses a geochemical signature that is very similar to that of the borrobol tephra which also occurs in three of the sequences reported here but which lies close to the lower boundary of gi 1 the second occurs stratigraphically in the early holocene below the saksunarvatn ash and is named the ashik tephra this tephra is geochemically bimodal with a rhyolitic component comparable to the an druim tephra that occurs later in the holocene and a basaltic component which is similar to the saksunarvatn ash a third tephra occurs stratigraphically above the saksunarvatn ash and is provisionally named the breakish tephra the consistent inter site correlation demonstrated for these new tephras at several sites enhances the regional tephrostratigraphic framework and increases the potential for correlating palaeoenvironmental events during gi 1 and the early holocene however the occurrence of multiple tephras with similar geochemistry in close stratigraphic and temporal proximity has implications for the rigour with which tephrostratigraphic investigations must be performed copyright 2006 john wiley sons ltd

the palaeoenvironmental interpretation of colluvial sediments and palaeosols of the late pleistocene hypothermal in southern africa colluvial deposits reaching thicknesses of more than 10 m mantle the pediment slopes and choke the streams and river valleys of an area covering about 20 of africa south of the zambezi the sediments are usually deeply incised by gully systems termed dongas which have exposed abundant archaeological remains in the form of stone tools dating from the african middle stone age while the bedrock types in the different areas exhibiting colluvium vary greatly the range in present mean annual rainfall is very narrow being between 600 and 800 mm the grain size characteristics of 55 samples of colluvium show a broad similarity in the percentages of sand silt and clay sized material in the majority of cases the percentage of sand ranges from 45 to 65 silt from 15 to 25 and clay from 10 to 35 the 14c ages of palaeosols in the sediments in swaziland natal and zululand based upon the dating of calcium carbonate nodules and charcoal from cave sediments containing identical stone tool assemblages indicate that colluviation took place between about 30 000 and 12 000 years ago the palaeosols and colluvial sediments of southern africa are indicative of semi arid conditions in which the regolith was stripped from poorly vegetated hill slopes and laid down on gently inclined pediment slopes the age of the deposits supports the contention of several recent workers that the area experienced dry climatic conditions during the last glacial maximum as a result of restricted circulation and reduced sea surface temperatures in the southern ocean

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

towards a european tephrochronological framework for termination 1 and the early holocene the record of deposition of tephras in europe and the north atlantic during the period 18 5 8 0 14 c ka bp the last termination and early holocene is reviewed altogether 34 tephras originating from four main volcanic provinces iceland the eifel district the massif central and italy have been identi ed so far in geological sequences spanning this time interval most of the records have been based until very recently on observations of visible layers of tephras here we report on the potential for extending the areas over which some of the tephras can be traced by the search for layers of micro tephra which are not visible to the naked eye and on the use of geochemical methods to correlate them with known tephra horizons this approach has greatly extended the area in northern europe over which the vedde ash can be traced the same potential exists in southern europe which is demonstrated for the rst time by the discovery of a distinct layer of micro tephra of the neapolitan yellow tu in a site in the northern apennines in italy far to the north of the occurrences of visible records of this tephra the paper closes by considering the potential for developing a robust european tephrostratigraphy to underpin the chronology of records of the last termination and early holocene thereby promoting a better understanding of the nature timing and environmental e ects of the abrupt climatic changes that characterized this period

laacher see tephra a widespread isochronous late quaternary tephra layer in central and northern europe a late quaternary tephra layer widespread in central and northern europe resulted from explosive plinian and phreatomagmatic eruptions of the laacher see volcano 11 000 yr b p the tephra is distinguished from other late quaternary andesitic rhyolitic airfall tuff layers in northern europe and from basaltic or trachytic tuff deposits in southern europe by its phonolitic composition and abundance of sanidine plagioclase clinopyroxene amphibole and sphene the proximal tephia sequence at laacher see is divided into three main deposits the predominantly plinian deposits of lower and middle laacher see tephra llst and mlst and phreatomagmatic deposits of the upper laacher see tephra ulst the mlst member is further subdivided into beds a b and c1 c2 and c3 the chemical composition of the magma is highly differentiated phonolite in the llst to mlst b sections but mafic phonolite in the mlst c1 to ulst sections all deposits are considered to be isochronous the frequency maximum of 16 radiocarbon datings indicating an eruption about 11 000 50 yr b p distal ash was deposited in three main fans directed to the northeast lst traced up to 1 100 km distance south lst traced up to 600 km and southwest lst traced up to 100 km tephrostratigraphic correlation of the distal ash deposits is based on a the major element composition of glass shards b lithology and c heavy mineral analyses the northeastern fan consists of deposits from llst mlst b and mlst c1 eruptive phases the southern fan comprises mlst a mlst c2 and ulst deposits and the southwestern fan consists exclusively of ash from the ulst eruptive phase northeastern transport of ash during eruptive phases with high plinian eruption columns but southern and southwestern transport of ash along phases of relatively low eruption columns are interpreted in terms of prevailing southwesterly paleowinds at high altitudes tropopause level but northerly winds dominating in the lower atmosphere the laacher see eruption columns were emplaced into an atmosphere vertically zoned with respect to paleowind directions which also explains the near vent shifting of llst mlst b and mlst c1 iso pach axes from east southeast to northeast within the first 20 km of transport

a compilation of western european terrestrial records 60 8 ka bp towards an understanding of latitudinal climatic gradients terrestrial records of past climatic conditions such as lake sediments and speleothems provide data of great importance for understanding environmental changes however unlike marine and ice core records terrestrial palaeodata are often not available in databases or in a format that is easily accessible to the non specialist as a consequence many excellent terrestrial records are unknown to the broader palaeoclimate community and are not included in compilations comparisons or modelling exercises here we present a compilation of western european terrestrial palaeo records covering entirely or partially the 60 8 ka intimate time period the compilation contains 56 natural archives including lake records speleothems ice cores and terrestrial proxies in marine records the compilation is limited to include records of high temporal resolution and or records that provide climate proxies or quantitative reconstructions of environmental parameters such as temperature or precipitation and that are of relevance and interest to a broader community we briefly review the different types of terrestrial archives their respective proxies their interpretation and their application for palaeoclimatic reconstructions we also discuss the importance of independent chronologies and the issue of record synchronization the aim of this exercise is to provide the wider palaeo community with a consistent compilation of high quality terrestrial records to facilitate model data comparisons and to identify key areas of interest for future investigations we use the compilation to investigate western european latitudinal climate gradients during the deglacial period and despite of poorly constrained chronologies for the older records we summarize the main results obtained from nw and sw european terrestrial records before the lgm

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

synchronisation of palaeoenvironmental events in the north atlantic region during the last termination a revised protocol recommended by the intimate group abstract the north atlantic intimate group of the inqua palaeoclimate commission has previously recommended an event stratigraphy approach for the synchronisation of records of the last termination using the greenland grip isotopic record as the regional stratotype and intcal98 for the calibration of radiocarbon dates lowe j j hoek w intimate group 2001 inter regional correlation of palaeoclimatic records for the last glacial interglacial transition a protocol for improved precision recommended by the intimate project group quaternary science reviews 20 1175 1187 here we present a revised protocol for time stratigraphic correlation in the north atlantic region over a more extended time period 30 8 ka this employs the new ngrip isotopic record and associated greenland ice core chronology 2005 gicc05 as the regional stratotype intcal04 for the calibration of radiocarbon dates bayesian based statistical procedures for the construction of age models and tephrochronology to validate correlations between regional site records

climate and environment during the younger dryas gs 1 as reflected by composite stable isotope records of lacustrine carbonates at torreberga southern sweden climatic and environmental changes during the younger dryas stadial gs 1 and preceding and following transitions are inferred from stable carbon and oxygen isotope records obtained from the sediments of ancient lake torreberga southern sweden event gs 1 is represented in the sediment sequence by 3 5 m of clay containing lacustrine carbonates of various origins comparison of isotopic records obtained on mollusc shells ostracod valves and chara encrustations precipitated during specific seasons of the year supports estimates of relative changes in both lake water and mean annual air temperatures variations in soil erosion rates can also be estimated from a simple isotope mass balance model to separate allochthonous and autochthonous carbonate contributions to the bulk carbonate content of the sediments the well known rapid climatic shifts characterising the last termination in the north atlantic region are clearly reflected in the isotopic data as well as longer term changes within gs 1 following maximum cooling shortly after the allerod younger dryas gi 1 gs 1 transition a progressive warming and a slight increase in aquatic productivity is indicated at the younger dryas preboreal gs 1 pb transition mean annual air temperature rapidly increased by more than 5 c and summer lake water temperature increased by ca 12 c the subsequent preboreal oscillation is characterised by an increase in soil erosion and a slight decrease in mean annual air temperature these results are in harmony with recent findings about large scale climate dynamics during the last termination copyright 1999 john wiley sons ltd

geochronology of betula extensions in pollen diagrams of alpine late glacial lake deposits a case study of the late glacial deposits of the gasserplatz soil archives vorarlberg austria pollen diagrams of alpine late glacial calcareous lake deposits show several extensions of betula the geochronology of these extensions cannot be based on radiocarbon dating due to reservoir effects of such lakes on the radiocarbon ages a robust geochronology can be based on the oxygen isotope stratigraphy additionally recognition of 12 920 calbp lst in the sediment cores provides a secure time marker the combined results of pollen macro remains and stable isotope analyses of the gasserplatz cores point to a correlation of the betula extensions with the oscillations in the oxygen isotope curve and are related to global climatic oscillations this is sustained by the correlation of the gasserplatz isotope oscillations with the oscillations as registered in the greenland ice cores comparison of the results of the gasserplatz cores with the results of similar alpine lake deposits makes clear that the fluctuations in the betula curve are not a local but a regional phenomenon

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

an abrupt wind shift in western europe at the onset of the younger dryas cold period the younger dryas cold reversal during the last glacial termination is one of the most abrupt climate change events observed in the northern hemisphere analyses of varved lake sediments from western germany suggest that storminess in the north atlantic region increased within a single year at this time providing a mechanistic link between a decrease in the meridional overturning circulation and western european cooling the younger dryas cooling 12 700 years ago is one of the most abrupt climate changes observed in northern hemisphere palaeoclimate records1 2 3 4 annually laminated lake sediments are ideally suited to record the dynamics of such abrupt changes as the seasonal deposition responds immediately to climate and the varve counts provide an accurate estimate of the timing of the change here we present sub annual records of varve microfacies and geochemistry from lake meerfelder maar in western germany providing one of the best dated records of this climate transition5 our data indicate an abrupt increase in storminess during the autumn to spring seasons occurring from one year to the next at 12 679 yr bp broadly coincident with other changes in this region we suggest that this shift in wind strength represents an abrupt change in the north atlantic westerlies towards a stronger and more zonal jet changes in meridional overturning circulation alone cannot fully explain the changes in european climate6 7 we suggest the observed wind shift provides the mechanism for the strong temporal link between north atlantic ocean overturning circulation and european climate during deglaciation

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

lgm and late glacial fluctuations in the eastern alps abstract studies of glacier development in the eastern alps around the last glacial maximum lgm for more than a hundred years have created a reasonably well based knowledge of glacier extent sedimentation and palaeoclimate as well as chronology this was obtained from broad and detailed mapping palynological investigations and radiocarbon dating despite a very cold climate between 31 and 21 ka bp topographical constraints meant that glacier extent was limited to tributary valleys of the main trenches until about 24 ka bp then rapid ice build up in the main longitudinal valleys led to extended ice streams and to piedmont glaciers in the foreland this build up virtually ended at ca 21 ka bp according to radiocarbon dates obtained from organic matter embedded in the outwash and periglacial gravels niederterrasse the lgm possibly lasted 3000 4000 years and shows a short maximalstand and a more prolonged hochstand both connected with outwash deposits the ice decay was apparently very fast and the glaciers vanished from the longitudinal valleys probably within some hundreds of years this retreat was interrupted by two short oscillations of active glaciers in contact with huge masses of inactive ice occupying the main valley floors before these became totally ice free these events at the beginning of the oldest dryas ca 16 ka bp were followed by a distinct glacier readvance gschnitz marked by end moraines and outwash fans according to some radiocarbon dates this occurred around 14 ka bp during the bolling interstade the valleys became almost ice free the next two glacier readvances daun and egesen were limited to cirques and the higher parts of the valleys and are dated to the older and younger dryas stades respectively

tephrostratigraphy of a deep sea sediment sequence off the south chilean margin new insight into the hudson volcanic activity since the last glacial period abstract a detailed tephrostratigraphy study supported by accelerator mass spectrometry ams 14 c dating stable isotope 18 o and geochemical analyses has been carried out from a deep sea core collected offshore the chonos taitao archipelago southern chile close to the main andean volcanic centres of the southern volcanic zone svz counting of glass shards in the drill core revealed the occurrence of twelve ash layers over the last 22 ka bp their provenance was determined by comparing the 14 c age and major element geochemistry of glass shards with tephra recovered in terrestrial fallout deposits from the southern south volcanic zone ssvz four cryptotephra layers in the uppermost part of the studied core 1 9 16 1 ka bp can be confidently correlated to the corresponding cerro hudson volcanic eruptive events hw7 hw3 hw2 and hw1 for the eight remaining tephra layers deposited between 16 1 ka and 20 ka bp no direct correlation is possible with onland volcanic products however the major element geochemistry of the glass shards strongly suggests the cerro hudson as the volcanic source for these tephra on the other hand the lack of two of the largest hudson holocene eruptions 3 6 and 7 5 ka bp in the uppermost part of deep sea core may be linked to changes in the position of the southern westerlies wind belt sww as a response to the climate variability in northern patagonia during the holocene

connection between south mediterranean climate and north african atmospheric circulation during the last 50 000 yr bp north atlantic cold events abstract high resolution clay mineralogical analyses were performed on sediment deposited during the last 50 000 yr in the alboran sea odp site 976 the clay mineral record is compared with pollen assemblages and with annual precipitation pann and mean temperatures of the coldest month mtco reconstructed with the modern analog technique mat enhanced contribution of palygorskite a typical wind blown clay mineral characterizes the north atlantic cold climatic events coeval development of the semi arid vegetation artemisia rich associated with a drastic fall of reconstructed precipitations and temperatures suggest cold and arid continental conditions in the west mediterranean area during north atlantic cold events the clay mineral association especially the palygorskite content and the illite to kaolinite ratio indicate western morocco as one of the major source of the clay size fraction during the north atlantic cold events the maximum abundance of artemisia associated with the presence of argania pollen both indicate morocco as the main origin for pollen during these cold periods the comparison of these pollen and clay mineral specific features allows us to pinpoint western morocco as the dominant source of wind blown particles during north atlantic cold events these specific mineralogical composition and palynological assemblages reveal enhanced aridity over north africa and intensification of winds favouring dust erosion and transport from north africa toward the alboran sea during the north atlantic cold events according to atmospheric models such a meridian transport 1 likely results from the development of strong and stable anticyclonic conditions over the tropical atlantic and north africa similar to today s summer meteorological configuration and 2 implies a northward position of the westerly winds during north atlantic cold events finally the synoptic situation over the west mediterranean during the north atlantic cold events is compared with the north atlantic oscillation nao suggesting that during the cold atlantic events weather regimes over europe and north africa may have been systematically shifted towards a positive nao situation

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

the detailed tephrostratigraphy of a core from the south east black sea spanning the last 60 ka one visible volcanic ash layer and 21 non visible cryptotephra horizons have been identified in the m72 5 25 gc1 core from the south east black sea that spans the last 60 ka glass chemistry suggests that the tephras derive from italian hellenic and turkish sources the visible tephra layer is trachytic in composition and has been correlated to the 39 ka campanian ignimbrite super eruption from campi flegrei caldera italy two cryptotephra layers are associated with eruptions from acigol volcano turkey around the last glacial maximum another is linked to activity at erciyes dagi in the early holocene perikartini or karagullu and a cryptotephra layer near the top of the core correlates to the 3 6k cal a bp minoan marine z2 tephra from santorini thera greece this extends the known dispersal area for all these volcanic ash units many other calc alkaline rhyolite layers preserved in the core are likely to be from central anatolian sources but the lack of detailed proximal data for many of the volcanoes in the region prohibits further correlations the tephrostratigraphy and glass compositional data presented here allow the tephra layers to be used to correlate sedimentary archives across the region and help to extend the mediterranean tephrochronology framework towards the east

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