modification and preservation of environmental signals in speleothems speleothems are primarily studied in order to generate archives of climatic change and results have led to significant advances in identifying and dating major shifts in the climate system however the climatological meaning of many speleothem records cannot be interpreted unequivocally this is particularly so for more subtle shifts and shorter time periods but the use of multiple proxies and improving understanding of formation mechanisms offers a clear way forward

geochemistry of speleothems affected by aragonite to calcite recrystallization potential inheritance from the precursor mineral abstract formerly aragonite speleothems recrystallized to calcite result from solutions subsaturated in aragonite and supersaturated in calcite that infiltrate into the speleothem through the interconnected porosity in most cases the crystal replacement takes place through a thin solution film this diagenetic process can occur under open or semi closed geochemical conditions thus secondary calcite crystals record the composition of the fluid at the time of diagenesis affected by calcite partition coefficients and fractionation factors open system or partly inherit the composition of the primary aragonite semi closed system so whether or not recrystallized aragonite speleothems can record reliable geochemical signals from the time of speleothem primary deposition still is an open debate we studied a stalagmite from eagle cave spain predominantly composed of secondary calcite that replaced aragonite although a core of primary aragonite extending 45 mm along the growth direction was preserved at the base of the sample we obtained mg and sr compositional maps paired u th dating and 18 o and 13 c profiles across the diagenetic front additionally two parallel isotope records were obtained along the speleothem growth direction in the aragonite and calcite sectors our results support that recrystallization of this speleothem took place in open system conditions for 18 o 13 c mg and sr but in semi closed system conditions for u and th the recrystallization of this sample took place during one or several events likely after the younger dryas as a result of climate change influencing drip water composition based on compositional zoned patterns we suggest that the advance of diagenetic fronts in this speleothem had an average rate of 50 45 m yr such recrystallization rate can transform any aragonite speleothem into calcite within a few centuries we suggest that the volume of water interacting with the speleothem at the time of recrystallization is of critical importance for inheritance of different elements the volume of solution is controlled by 1 the discharge of water passing through the sample and 2 the lapse time between aragonite dissolution and calcite precipitation hydrology and hydrochemistry of the interacting solution together with the mineralogy and texture of the speleothem are the essential controls for the diagenesis of the speleothem recrystallization of aragonite speleothems does not follow stratigraphical levels of the sample but occurs along sites with preferential flow paths in any sector of the speleothem in these cases the relationship between age and distance from base is not preserved however alternation of periods of recrystallization with periods of aragonite precipitation causing speleothem accretion can result in recrystallized speleothems with coherent distance from the base age relationship thus early diagenesis of speleothems affected by seasonal or inter annual oscillation of drip waters supersaturated and subsaturated in aragonite may provide best scenario conditions for dating and preservation of paleoenvironmental records along recrystallized speleothems however even in this scenario the variable discharge and the diagenetic rate control the geochemical inheritance from the primary aragonite crystals

travertines associated with the alhama jaraba thermal waters ne spain genesis and geochemistry abstract freshwater carbonates are interesting archives in palaeoenvironmental reconstructions however more studies of those systems are needed to fully understand past environments in this work the actively forming travertines of the alhama jaraba thermal system were studied for the first time in order to evaluate the relationship between the geochemical and mineralogical composition and the environmental conditions during their formation with that aim a combination of petrographical mineralogical geochemical and stable isotope analyses were carried out these carbonates provide a natural laboratory for the study of the effect of different variables natural and anthropogenic on carbonate precipitation the results showed that there is a close relationship between the mineralogy of the solid precipitates and the formation temperature and only the samples formed from overheated waters 40 60 c show significant concentrations of aragonite aragonite bearing samples show higher concentrations in sr ba and u while calcitic solids are enriched in mg these differences could be attributed to mineralogy temperature or different precipitation rates the geochemical evaluation of the chemistry of both the solids and their parental waters suggests that differences in the rate of co 2 degassing and in some cases evaporation are the primary environmental controls on isotopic compositions in addition the results show that if strong evaporation and co 2 degassing are involved calcite precipitation occurs under conditions of isotopic disequilibrium with its parental water the results of our study are useful to interpret old depositional environments and palaeotemperatures

quantifying global warming from the retreat of glaciers records of glacier fluctuations compiled by the world glacier monitoring service can be used to derive an independent estimate of global warming during the last 100 years records of different glaciers are made comparable by a two step scaling procedure one allowing for differences in glacier geometry the other for differences in climate sensitivity the retreat of glaciers during the last 100 years appears to be coherent over the globe on the basis of modeling of the climate sensitivity of glaciers the observed glacier retreat can be explained by a linear warming trend of 0 66 kelvin per century

multi proxy speleothem record of climate instability during the early last interglacial in southern turkey abstract a stalagmite from dim cave in southern turkey contains a climate record documenting rapid and significant changes in amounts of precipitation between 132 ka and 128 ka during the penultimate glacial interglacial transition some u th dates have been compromised by carbonate dissolution but rigorous selection and tuning to 18o records from other speleothems has generated a robust age model growth rate was initially very slow but a rapid increase at 129 ka was accompanied by strong negative trends in 18o and 13c a combination implying the onset of much wetter conditions isotopic values at 129 ka suggest that groundwater recharge rates and biogenic activity in the soil zone exceeded those of the early holocene a significant isotopic enrichment event at 128 ka during which there was alternating aragonite and calcite deposition documents a strong drying event with a duration of 200 years a concurrent decrease in 87sr 86sr ratios indicates increased groundwater residence times and the cumulative evidence suggests amounts of rainfall fell from well above to slightly below present day levels similar 18o enrichment events are present in coeval speleothem records from southwest france and the northern alps and these together with pollen evidence from italy greece and the iberian margin of drier conditions at this time imply that a climate anomaly extended across the northern mediterranean borderlands the timing duration and structure of this episode are consistent with marine evidence of strong north atlantic cooling early in the last interglacial and there is a resemblance to the holocene 8 2 ka event recorded globally in many proxy climate archives

the influence of changing orbital parameters and surface boundary conditions on climate simulations for the past 18 000 years abstract general circulation model experiments at 3000 year intervals for the past 18 000 years were made to estimate the magnitude timing and pattern of the climatic response to prescribed changes of orbital parameters date of perihelion axial tilt eccentricity and glacial age lower boundary conditions ice sheets land albedo sea ice and sea surface temperature the experiments used the community climate model ccm of the national center for atmospheric research ncar the response of monsoon circulations and tropical precipitation to the orbitally produced solar radiation changes was much larger than the response to changes of glacial age boundary conditions the continental interior of eurasia was 2 4 k warmer in summer and summer monsoon precipitation of north africa south asia was increased by 10 20 between 12 000 and 6000 yr bp before present when perihelion occurred during northern summer rather than in winter as now and the earth s axial tilt was larger than now southern hemisphe

discovery of early holocene wood and peat on the forefield of the pasterze glacier eastern alps austria during recent years a number of fragments of pinus cembra and larix decidua as well as peat were found in front of the tongue of the pasterze glacier in the eastern alps these were washed out by the stream from under the present ice the wood originates from trees which reached ages of upto 400 years or more radiocarbon dating shows them to come from the early holocene they indicate that between cal bc 8100 and cal bc 6900 the pasterze glacier was smaller than at present the pasterze glacier advanced around cal bc 6900 a lump of peat shows that around cal bc 6300 at the latest the pasterze glacier was again smaller than today the radiocarbon age of the fulvic acid fraction of thepeat suggests that growth could have continued until cal bc 5430 5080 further wood samples dated to around cal bc 4800 and cal bc 3800 show that at these times the pasterze glacier was smaller than at present the pasterze glacier had a relatively limited extent over long periods inthe early holocene thus mostly favou

quantifying sediment supply at the end of the last glaciation dynamic reconstruction of an alpine debris flow fan in this paper we quantify the sediment dynamics in the formerly glaciated zielbach catchment in the italian alps from the end of the last glacial maximum lgm until today as a basis for our quantification we use the stratigraphic record offered by a 3 5 km2 large fan that we explore with a seismic survey stratigraphic analyses of drillhole material and 14c ages measured on organic matter encountered in these drillings in addition we calculate past denudation rate variability in the fan deposits using concentrations of cosmogenic 10be we merge this information into a scenario of how the sediment flux has changed through time and how this variability can be related to climatic variations framed within well known paraglacial models the results document a highly complex natural system from the lgm to the very early holocene ice melted discharge and climate variability promoted a high sediment flux sedimentation rate up to 40 mm yr this flux then dramatically decreased toward interglacial values 0 8 mm yr at 5 4 calibrated kyr b p however in contrast to the trend of classic paraglacial models the flux recorded at zielbach shows secondary peaks at 6 5 ka and 2 5 ka with values of 13 mm yr and 1 5 mm yr respectively paleo denudation rates also decrease from 33 mm yr at the beginning of the holocene to 0 42 mm yr at 5 ka with peaks of 6 mm yr and 1 1 mm yr at 6 5 ka and 2 5 ka high amplitude climate change is the most likely cause of the secondary peaks but anthropogenic activities may have contributed as well the good correlation between paleo sedimentation and paleo denudation rates suggests that the majority of the deglaciated material destocked from the zielbach catchment is stored in the alluvial fan

a soil chronosequence study of the reno valley italy insights into the relative role of climate versus anthropogenic forcing on hillslope processes during the mid holocene abstract relatively few soil chronosequences with good age control exist for late pleistocene and holocene deposits in the mediterranean region of europe yet surface soils and their young buried counterparts can provide meaningful information about the timing and processes of landscape response to external forcing such as climate or anthropogenic change here we present the results of a study that examines a well dated chronosequence of nineteen soil exposures in surficial deposits ranging in age from hundreds of years to hundreds of thousands of years located in the reno river valley near bologna italy the soil forming climate of the reno valley sits on a threshold between that which facilitates the accumulation of caco 3 and that which facilitates the translocation and formation of clay minerals and iron oxides once formed secondary iron oxides are relatively immobile in oxidizing conditions in the soil profile and therefore consistently record age trends with feo fed ratios decreasing predictably with soil age for all soils in the chronosequence the morphology of secondary carbonate accumulation and its depth of leaching also vary predictably with soil age but only for soils younger than about 12 000 years in these young soils horizons that contain secondary carbonate progress from relatively shallow stage i bk horizons in late holocene aged soils to deeper stage iii bk horizons in latest pleistocene aged soils in soils older than approximately 12 000 cal ybp however carbonate dissolution during wetter climates and the addition of colluvium and or dust to terrace surfaces become important factors in the preservation of carbonate in the profile and carbonate content is not predictable by age alone without significant depositional additions these older soils become decalcified pedogenic carbonate precipitated during drier climates is susceptible to dissolution during wetter periods as evidenced by discontinuous carbonate coatings on grains in some soils therefore overall measurable pedogenic carbonate content is spatially and temporally variable as a function of input of fresh carbonate and locally controlled soil moisture conditions particle size does not decrease predictably with soil age for reno valley soils and appears to be strongly influenced by parent material variability in younger soils and by dust additions in older soils our detailed examination of soil stratigraphy in the reno valley revealed evidence of significant aggradation of colluvium and tributary fans in the middle holocene between 6000 and 4000 ybp this aggradation pre dates bronze age agricultural expansion and appears to be instead attributable to the climate conditions of the middle holocene that have been documented elsewhere in italy for this time period this study demonstrates that late pleistocene and holocene surface soils in the mediterranean region of europe can effectively help elucidate rates and processes of landscape evolution

climate and vegetation history of the midcontinent from 75 to 25 ka a speleothem record from crevice cave missouri usa four missouri stalagmites yield consistent overlapping records of oxygen and carbon isotopic changes and provide a climate and vegetation history with submillennial resolution from 75 to 25 thousand years ago ka the thorium 230 dated records reveal that between 75 and 55 ka the midcontinental climate oscillated on millennial time scales between cold and warm and vegetation alternated among forest savanna and prairie temperatures were highest and prairie vegetation peaked between 59 and 55 ka climate cooled and forest replaced grassland at 55 ka when global ice sheets began to build during the early part of marine oxygen isotope stage 3

u pb dating of a speleothem of quaternary age we demonstrate that u pb dating is a promising method for secondary carbonate materials of quaternary age and older by obtaining a 206pb 238u age for a speleothem with high u 10 g g 1 and very low pb 10 ng g 1 that is supported by an independent 230th age thermal ionisation mass spectrometry was used to determine the u and pb isotopic ratios and concentrations for subsamples of a stalactite from winnats head cave peak district uk we obtained 206pb 204pb ratios up to 50 and determined a 206pb 238u age of 248 10 ka which is within error of the 207pb 235u age of 333 79 ka and a spectrometric u th age of 255 ka for samples of tertiary and quaternary age the initial state of u series disequilibrium is an important consideration and as with most radiometric dating techniques the mineral must have remained closed to u th pb and all intermediate daughters we show that dense calcite speleothems are ideal in this respect and that no loss of rn has occurred unlike u series disequilibrium methods u pb dating has no upper limit and hence materials of quaternary age older than 0 6 ma can be analysed to investigate landscape development paleoclimate hominid evolution or hydrogeochemistry in carbonate terrains

elevated and variable values of 13c in speleothems in a british cave system 13c isotope variations in speleothems have been investigated for samples from the british isles where plants which use the hatch slack or c4 photosynthetic pathway are not present the range of 13c expected in speleothem carbonate formed in isotopic equilibrium with soil co2 derived from the overlying c3 vegetation should thus fall in the range 12 to 6 forty one actively growing speleothem samples from low discharge sites were analysed from stump cross caverns yorkshire england ten percent have 13c greater than 6 in addition a large range of 13c was observed 8 06 1 38 a 1 variability of 17 with adjacent samples having 13c differing by a maximum of 4 74 similar findings were obtained from a review of analyses of late quaternary speleothem samples from the british isles with 75 of flowstone samples and 57 of high flow stalagmite samples exhibiting elevated 13c three possible processes are proposed as possible causes of elevated 13c in speleothems firstly fractionation may occur between the stalactite and stalagmite due to evaporation or degassing secondly degassing of the groundwaters may have occurred within the aquifer before reaching the cave void allowing release of some co2 from the water whilst remaining saturated in calcium finally the elevated 13c may be due to short water residence times in the soil such that equilibrium between soil water and soil co2 is not reached evidence presented here demonstrates that any one of these mechanisms may be important in the karst areas of the british isles caution is needed before interpreting the 13c signal within speleothems in terms of palaeovegetation

duration of s1 the most recent sapropel in the eastern mediterranean sea as indicated by accelerator mass spectrometry radiocarbon and geochemical evidence slowly accumulated 5 cm kyr 1 and rapidly accumulated 5 20 cm kyr 1 sediments have been compared to define the initiation and termnation times of the most recent sapropel s1 in the eastern mediterranean sea the ba a1 ratio has been employed as a more persistent index of productivity than cg accelerator mass spectrometry radiocarbon dating of pelagic foraminifera indicates a maximum duration for increased ba a1 levels in s 1 from 9500 6000 uncorrected radiocarbon convention years b p in the rapidly accumulated sediments and 9500 5300 years b p in the slowly accumulated sediments this difference is ascribed to bioturbation affecting the slower accumulated s1 sediments in the two most rapidly accumulated s1 units from the adriatic and aegean seas there is a saddle of lower values centered on 7500 years b p in the corg and ba ai profiles so that the visual s 1 unit appears as a doublet geochemical evidence indicates that this intervening period is best interpreted as an episode of increased ventilation and bottom water oxygenation during the period of sapropel accumulation

modern aragonite formation at near freezing conditions in an alpine cave carnic alps austria abstract aragonite is a common mineral in caves hosted in dolomitic bedrock and in particular in those from warm climate regions it is much less common in cold caves such as in the alps where the vast majority of speleothems consist of low mg calcite here we report the occurrence of modern aragonite at very low temperatures the first of its kind from an alpine cave in the interior part of obstanser eishohle a high alpine cave containing perennial ice in its near entrance zone aragonite forms stalactites and flowstones which coexist with calcite and locally also hydromagnesite precipitation of aragonite occurs at saturation indices between 0 4 and 0 6 at 1 0 0 4 c modern 230th dates of the youngest aragonite deposits demonstrate that aragonite formation is an ongoing process 13c values are high and overlap with those of the host rock a comparison between 18o values of aragonite and drip water showed that modern aragonite formation does not occur at isotopic equilibrium surprisingly no radiocarbon bomb peak was detected in these speleothems despite their young age in addition these samples are characterized by extremely high reservoir ages between 8800 and 10 100 yr the highest ever reported for a speleothem worldwide these data are best reconciled with a model of karst dissolution largely decoupled from the soil zone oxidation of disseminated pyrite in the dark gray host rock gives rise to acidic solutions driving carbonate dissolution the dolomitic nature of the bedrock prior calcite precipitation and ventilation enhanced degassing leads to high mg ca ratios in the drip water favoring aragonite formation these in situ observations confirm previous findings that temperature is not the dominant control on calcite versus aragonite formation in caves they also suggest that ancient aragonite speleothems should be examined carefully and ideally be compared to coeval calcite samples prior to interpreting their stable isotope data in terms of environmental climatic changes

quaternary paludal tufas from the ben younes spring system gafsa southwestern tunisia interactions between tectonics and climate abstract tufa deposits that can be fit into a single depositional model are restricted to relatively few publications in the geological literature this paper presents a detailed sedimentological study of quaternary early holocene paludal tufas partly exposed in the ben younes piedmont field data reveal five main paludal lithofacies phytoherm framestones sapropelitic tufa microdetrital tufa microbial laminites and lime muds radiocarbon dating of residual organic matter in tufa shows that the tufa ranges in age from 8790 50 to 3230 60 bp most tufa deposits appear to remain preserved during the different stages of their development lithification and diagenetic modifications of tufa show two major trends an increase in the average carbonate grain size and non selective dissolution of the fabric where deposits are exposed to meteoric diagenesis the studied tufas are water limited and the importance of climate in their formation is as major as implied in other mediterranean equivalents the predominance of paludal conditions in this area is controlled by the flat substrate the spring locations and the water supply the gafsa strike slip fault aside its tectonic role acts as a major regional sill that controlled paleoflow directions discharge locations content volume rate and fluctuations of the water supply

hydrochemical controls on aragonite versus calcite precipitation in cave dripwaters abstract despite the paleoclimatic relevance of primary calcite to aragonite transitions in stalagmites the relative role of fluid mg ca ratio supersaturation and co 3 2 concentration in controlling such transitions is still incompletely understood accordingly we have monitored the hydrochemistry of 50 drips and 8 pools that are currently precipitating calcite and or aragonite in el soplao and torca ancha caves n spain investigating the mineralogy and geochemistry of the caco 3 precipitates on the corresponding natural speleothem surfaces the data reveal that apart from possible substrate effects dripwater mg ca is the only obvious control on caco 3 polymorphism in the studied stalagmites and pools where calcite and aragonite precipitating dripwaters are separated by an initial i e at stalactite tips mg ca threshold at 1 1 mol mol within the analyzed ranges of ph 8 2 8 6 co 3 2 concentration 1 6 mg l supersaturation si aragonite 0 08 1 08 si calcite 0 23 1 24 drip rate 0 2 81 drops min and dissolved zn 6 90 g l we observe no unequivocal influence of these parameters on caco 3 mineralogy despite the almost complete overlapping supersaturations of calcite and aragonite precipitating waters the latter are on average less supersaturated because the waters having mg ca above 1 1 have mostly achieved such high ratios by previously precipitating calcite both calcite and aragonite precipitated at or near oxygen isotopic equilibrium and mg incorporation into calcite was consistent with literature based predictions indicating that in the studied cases caco 3 precipitation was not significantly influenced by strong kinetic effects in the studied cases the calcites that precipitate at 11 c from dripwaters with initial mg ca approaching 1 1 incorporate 5 mol mgco 3 close to the published value above which calcite solubility exceeds aragonite solubility suggesting that aragonite precipitation in high relative humidity caves is favored from a solubility viewpoint we also show that unaccounted caco 3 precipitation in intermediate sampling containers and splash effects may in cases result in underestimating dripwater ca concentration and alkalinity potentially leading to incorrect conclusions regarding the role of fluid mg ca ratio and supersaturation on caco 3 mineralogy a simple way to elude the first effect is by taking water samples directly from stalactites and by titrating alkalinity in the same containers used to collect dripwaters

growth and development of notch speleothems from cayman brac british west indies response to variable climatic conditions over the last 125 000 years abstract the spectacular wave cut notch on cayman brac which is 6 m above sea level formed during marine isotope stage 5e highstand 128 000 to 116 000 years ago on cayman brac the notch is commonly decorated with speleothems mostly stalactites that are formed of calcite aragonite and micrite these notch speleothems are characterized by numerous growth zones that are delimited by minor and major hiatal surfaces u th dating indicates that the major growth phases which took place 73 000 to 59 000 years ago 46 000 to 49 000 years ago and 4000 to 1000 years ago were separated by periods when erosion and minimal precipitation were the norm the 18ovpdb values range from 6 5 to 0 3 with a mode between 2 and 4 and an average of 3 1 whereas the 13cvpdb values range from 10 5 to 1 9 with one mode between 2 0 and 3 0 a second mode between 7 0 and 8 0 and an overall average of 6 1 the 18o and 13c values co vary the 18ovpdb and 13cvpdb values are similar to those from the young 125 000 years cave speleothems today with the little evidence of active speleothem growth in the notch or caves cayman brac is characterized by dry sub tropical forest and shrubland with xeric components on the elevated eastern end of the island available data indicate that most of the speleothem growth took place during the transitions from marine isotope stage mis 5a to 4 and mis2 to 1 these transitional periods which define the onset and termination of glaciation in the northern latitudes were probably characterized by higher rainfall and development of tropical rainforests it is evident that notch speleothems like those from cayman brac are valuable archives of the paleoclimate conditions that have existed since the highstand associated with mis5e

holocene climate variability in europe evidence from δ18o textural and extension rate variations in three speleothems time series o isotope profiles for three u th dated stalagmites have revealed that for much of the holocene a site on the atlantic seaboard sw ireland exhibits first order 18o trends that are almost exactly out of phase with coupled 18o curves from two southern european sites se france and nw italy in the irish stalagmite cc3 from crag cave sw ireland low 18o at 10 000 cal yr bp reflects cool conditions by the early to mid holocene 9000 6000 cal yr bp 18o had increased reflecting the onset of warmer conditions on the atlantic seaboard this shift to higher 18o was accompanied by a marked increase in the stalagmite extension rate reinforcing our interpretation that this was a period of relative warmth except for an episode of increased extension rate about 5500 yr ago 18o in the crag stalagmite exhibits a gradual decrease accompanied by declining extension rates between 7800 and 3500 cal yr bp interpreted as a cooling trend there is evidence for increases in both 18o and stalagmite extension rate in the period from 3500 cal yr bp to the present day suggesting a return to warmer conditions on the atlantic seaboard in the stalagmite from nw italy er76 grotta di ernesto trentino province the early holocene c 9200 7800 cal yr bp is characterised by high 18o probably indicative of warm and or dry conditions exceptionally low 18o from 7800 to 6900 cal yr bp at this site reflects a well defined wet phase cerin wet phase in the last three millennia this stalagmite exhibits a shift to lower 18o interpreted as some combination of cooler and or wetter conditions unlike the irish stalagmite the italian sample does not show a correlation between 18o and extension rate instead its extension rate correlates roughly with 13c presumably reflecting a climate driven vegetation change in the early holocene 18o in the french stalagmite cl26 grotte de clamouse herault province se france was low relative to its holocene average for much of the period since c 3500 cal yr bp this stalagmite exhibits higher 18o than in the early holocene suggesting warmer conditions like the irish stalagmite the french sample exhibits a well defined correlation between 18o and extension rate had drip water availability been the dominant control on 18o at this semi arid site then higher 18o would have been accompanied by lower not higher extension rates this suggests strongly that temperature rather than rainfall amount was the dominant control at this site while conclusions regarding the patterns of climate variability on a continent scale must remain tentative because of the limited number of stalagmites studied we argue that early holocene warm conditions on the atlantic seaboard irish site coincided with relatively cool conditions at the clamouse site by c 3500 yr ago the pattern appears to have been reversed

timing and hydrological conditions of sapropel events in the eastern mediterranean as evident from speleothems soreq cave israel this paper explores the connection between the timing of sapropel events in the eastern mediterranean sea and the time of low 18o events in speleothems of the soreq cave israel a new well dated 18o and 13c profile of the soreq cave speleothems for the last 140 kyr reveals five prominent low 18o events dated at 124 to 119 kyr with the main peak at 122 kyr event v 108 to 100 kyr with peaks at 107 and 102 kyr event iv 85 to 79 kyr with peak at 80 kyr event iii 55 to 52 kyr with a peak at 54 kyr event ii and 8 5 to 7 kyr with peaks at 8 5 and 7 kyr event i these events are characteristic of period of enhanced rainfall in the eastern mediterranean area particularly so for events v and i where the marked decrease in 18o and the correspondingly marked increase in 13c indicate very wet conditions the chronology of the low 18o events v iv iii and i match the ages estimated for the formation of sapropels s5 s4 s3 and s1 which are also associated with high hydrological activity thus it is suggested that the low 18o events in the soreq cave speleothems constrain the maximum duration of the sapropel formation pollen data from the sapropel layers and the isotopic pattern of the speleothems indicate that sapropels s5 and s1 were deposited during very wet periods when there were major decrease in the sea surface salinity coupled with frost free winters and drought free summers sapropels s4 and s3 were formed during periods of increased precipitation but ones in which the general climate was mediterranean semi arid

warm period growth of travertine during the last interglaciation in southern germany abstract late quaternary travertine at two sites near stuttgart formed entirely during interglacial periods the travertine contains structures from growth induced by bacteria and such structures have been dated by 230th u mass spectrometry the resulting ages from both sites imply growth episodes of short duration with growth rates up to 5 mm yr 1 at 99 800 1300 yr b p 2 n 8 and 105 900 1300 yr b p 2 n 7 these episodes were likely part of marine isotope stage mis 5 3 deposition of silt interrupted travertine growth at one of the sites 105 000 yr b p likely correlatives of this silt are the st germain i b stade recorded in the grand pile peat bog and a cold episode 1000 yr long recorded by 18o values in the grip ice core travertine also formed during stage 5 5 115 000 yr and during the early holocene we found no evidence for travertine accumulation in stages 2 3 4 and 5 1 at both sites the sr u ratio and the initial 234u 238u activity ratio resemble those of modern spring water however the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation

aragonite calcite relationships in speleothems grotte de clamouse france environment fabrics and carbonate geochemistry abstract in grotte de clamouse france aragonite forms in a variety of crystal habits whose properties reflect the conditions of formation prolonged degassing and evaporation yield needle aragonite which is more enriched in 18o and 13c than aragonite ray crystals which form near isotopic equilibrium at present aragonite ray crystals form at the tops of stalagmites at very low discharge 0 00035 ml min and when fluid mg ca ratio is 1 1 temperature and evaporation do not seem to have a significant role in their formation the presence of aragonite in stalagmites should be indicative of a decrease in drip rate related to either dry climate conditions or local hydrology fossil aragonite was in part replaced by calcite in a time frame 13c signal and u content and preserved aragonite relicts up to 16 weight the isotope signal of different aragonite habits may reflect conditions of formation rather than climate parameters the real extent of aragonite to calcite transformation may be underestimated when replacement calcite inherits both textural and chemical properties of the precursor

influence of the subducting plate velocity on the geometry of the slab and migration of the subduction hinge abstract geological observations indicate that along two active continental margins east asia and mediterranean major phases of overriding plate extension resulting from subduction hinge retreat occurred synchronously with a reduction in subducting plate velocity in this paper results of fluid dynamical experiments are presented to test the influence of the velocity of the subducting plate on the hinge migration velocity and on the geometry of the slab results show that hinge retreat decreases with increasing subducting plate velocity in addition phases of hinge retreat alternate with phases of hinge advance for relatively high subducting plate velocities due to interaction of the slab with the bottom of the box simulating the upper lower mantle discontinuity such slab kinematics could explain the episodic behaviour of back arc opening observed in convergent settings the geometry of the slab and the kinematics of subduction are significantly affected by the velocity of the subducting plate three subduction modes with accompanying slab geometry can be recognized a relatively low subducting plate velocity is accompanied by relatively fast hinge retreat with backward sinking of the slab and a backward draping slab geometry with increasing subducting plate velocity hinge migration is relatively small resulting in subvertical sinking of the slab and a folded slab piling geometry for a very high velocity the hinge migrates forward resulting in forward oriented subduction vectors and a forward draping slab geometry

the gisp2 δ18o climate record of the past 16 500 years and the role of the sun ocean and volcanoes measured 18o 16o ratios from the greenland ice sheet project 2 gisp2 ice core extending back to 16 500 cal yr b p provide a continuous record of climate change since the last glaciation high resolution annual 18o 16o results were obtained for most of the current millennium a d 818 1985 and record the medieval warm period the little ice age and a distinct 11 yr 18o 16o cycle volcanic aerosols depress central greenland annual temperature 1 5 c maximally and annual 18o 16o for about 4 yr after each major eruptive event on a bidecadal to millennial time scale the contribution of solar variability to holocene greenlandic temperature change is 0 4 c the role of thermohaline circulation change on climate problematic during the holocene is more distinct for the 16 500 10 000 cal yr b p interval analogous to 14c age calibration terminology we express time in calibrated cal yr b p a d 1950 0 cal yr b p the oldest dryas bolling older dryas allerod younger dryas sequence appears in great detail bidecadal variance in 18o 16o but not necessarily in temperature is enhanced during the last phase of lateglacial time and the younger dryas interval suggesting switches of air mass transport between jet stream branches the branched system is nearly instantaneously replaced at the beginning of the bolling and holocene at 14 670 and 11 650 cal yr b p respectively by an atmospheric circulation system in which 18o 16o and annual accumulation initially track each other closely thermodynamic considerations of the accumulation rate temperature relationship can be used to evaluate the 18 o 16o temperature relationship the gisp2 ice layer count years of major gisp2 climate transitions also support the use of coral 14c ages for age calibration

late cretaceous synorogenic low angle normal faulting along the schlinig fault switzerland italy austria and its significance for the tectonics of the eastern alps abstract the schlinig fault at the western border of theotztal nappe eastern alps previously interpreted as a west directed thrust actually represents a late cretaceous top se to ese normal fault as indicated by sense of shear criteria found within cataclasites and greenschist facies mylonites normal faulting postdated and offset an earlier cretaceous age west directed thrust at the base of theotztal nappe shape fabric and crystallographic preferred orientation in completely recrystallized quartz layers in a mylonite from the schlinig fault record a combination of 1 top east southeast simple shear during late cretaceous normal faulting and 2 later north northeast directed shortening during the early tertiary also recorded by open folds on the outcrop and map scale offset of the basal thrust of theotztal nappe across the schlinig fault indicates a normal displacement of 17 km the fault was initiated with a dip angle of 10 to 15 low angle normal fault domino style extension of the competent late triassic hauptdolomit in the footwall was kinematically linked to normal faulting the schlinig fault belongs to a system of east to southeast dipping normal faults which accommodated severe stretching of the alpine orogen during the late cretaceous the slip direction of extensional faults often parallels the direction of earlier thrusting top w to top nw only the slip sense is reversed and the normal faults are slightly steeper than the thrusts in the western austroalpine nappes extension started at about 80 ma and was coeval with subduction of piemont ligurian oceanic lithosphere and continental fragments farther west the extensional episode led to the formation of austroalpine gosau basins with fluviatile to deep marine sediments west directed rollback of an east dipping piemont ligurian subduction zone is proposed to have caused this stretching in the upper plate

speleothem evidence from oman for continental pluvial events during interglacial periods growth periods and stable isotope analyses of speleothems from hoti cave in northern oman provide a record of continental pluvial periods extending back over the past four of earth s glacial interglacial cycles rapid speleothem growth occurred during the early to middle holocene 6 10 5 ka b p 78 82 ka b p 120 135 ka b p 180 200 ka b p and 300 325 ka b p the speleothem calcite deposited during each of these episodes is highly depleted in 18 o compared to modern speleothems the d 18 o values for calcite deposited within pluvial periods generally fall in the range of 24 to 28 relative to the vienna peedee belemnite standard whereas modern speleothems range from 21 to 23 the growth and isotopic records indicate that during peak interglacial periods the limit of the monsoon rainfall was shifted far north of its present location and each pluvial period was coincident with an interglacial stage of the marine oxygen isotope record the association of continental pluvial periods with peak interglacial conditions suggests that glacial boundary conditions and not changes in solar radiation are the primary control on continental wetness on glacial interglacial time scales

a depositional model for hydromagnesite magnesite playas near atlin british columbia canada this study formulates a comprehensive depositional model for hydromagnesite magnesite playas mineralogical isotopic and hydrogeochemical data are coupled with electron microscopy and field observations of the hydromagnesite magnesite playas near atlin british columbia canada four surface environments are recognized wetlands grasslands localized mounds metre scale and amalgamated mounds composed primarily of hydromagnesite mg co oh 4ho which are interpreted to represent stages in playa genesis water chemistry precipitation kinetics and depositional environment are primary controls on sediment mineralogy at depth average 2 m ca mg carbonate sediments overlay early holocene glaciolacustrine sediments indicating deposition within a lake post deglaciation this mineralogical change corresponds to a shift from siliciclastic to chemical carbonate deposition as the supply of fresh surface water for example glacier meltwater ceased and was replaced by alkaline groundwater weathering of ultramafic bedrock in the region produces mg hco groundwater that concentrates by evaporation upon discharging into closed basins occupied by the playas an uppermost unit of mg carbonate sediments hydromagnesite mounds overlies the ca mg carbonate sediments this second mineralogical shift corresponds to a change in the depositional environment from subaqueous to subaerial occurring once sediments emerged from the water surface capillary action and evaporation draw mg hco water up towards the ground surface precipitating mg carbonate minerals evaporation at the water table causes precipitation of lansfordite mgco 5ho which partially cements pre existing sediments forming a hardpan as carbonate deposition continues the weight of the overlying sediments causes compaction and minor lateral movement of the mounds leading to amalgamation of localized mounds radiocarbon dating of buried vegetation at the ca mg carbonate boundary indicates that there has been ca 8000 years of continuous mg carbonate deposition at a rate of 0 4 mm yr the depositional model accounts for the many sedimentological mineralogical and geochemical processes that occur in the four surface environments elucidating past and present carbonate deposition

a 3000 year high resolution stalagmitebased record of palaeoclimate for northeastern south africa high resolution stable isotope variations and growth structure analyses of the last three millennia of a 6600 year stalagmite record at cold air cave makapansgat valley south africa are presented growth layers which are measurable over the last 250 years are shown to be annual the correlation between the width of growth layers and precipitation is strongly positive changes in 18o and 13c are positively correlated and inversely correlated to changes in the colour of the growth layers in the stalagmite variations in colour are directly correlated with mean annual temperature dark colouration is the product of increased temperature and mobilization of organic matter from the soil and is associated with wetter summers and enhanced growth of c4 grasses darker colouring and enriched 18o and 13c reflect a warmer wetter environment whereas lighter colouring and depleted isotopic values are indicative of cooler drier conditions the dominant episode in the 3000 year record is the cool dry 500 year

environmental controls on the petrology of a late holocene speleothem from botswana with annual layers of aragonite and calcite abstract a carbonate stalagmite from drotsky s cave in northwestern botswana consists of alternating layers of calcite and aragonite layer counts and radiocarbon ages indicate that the calcite aragonite pairs are annual layers representing about 1500 years of deposition the annual layering probably resulted from highly seasonal rainfall comparison of the uppermost layers of the speleothem with meteorological records shows that precipitation of caco3 in drotsky s cave was controlled by climate thickness of calcite layers correlates with rainfall suggesting that calcite precipitation was largely dependent on the quantity of water supplied to the speleothem by contrast thickness of aragonite layers correlates with temperature although variation in temperature cannot explain greater aragonite abundance on the sides of the speleothem compared to its center mg ca ratios in calcite layers increase upward to the bases of overlying aragonite layers and analyses of cave waters suggest that fluid mg ca ratios reach levels sufficient to cause aragonite precipitation increasing evaporation which caused greater ionic strength and supersaturation resultant increasing mg ca ratios in the fluid and perhaps increasing temperature probably combined to cause aragonite precipitation detailed petrographic analysis suggests that each annual cycle of caco3 precipitation began with relatively intense fluid flow sometimes sufficient to dissolve some of the underlying aragonite before precipitation of calcite calcite precipitation under a thick fluid layer allowed euhedral crystals to form at first but thinning of the fluid to a film allowed only flatly terminated calcite crystals by season s end as fluid flow diminished increasing evaporation increasing mg ca ratios in the fluid and perhaps increasing temperature combined to cause aragonite precipitation to begin particularly on the sides of the speleothem in some years fluid flow diminished to the point that dust accumulated on aragonite surfaces before the onset of the next year s precipitation p

directly dating geologic events u pb dating of carbonates 1 carbonates are ubiquitous forming in a variety of settings including caves soils the oceans during burial from hydrothermal fluids and along faults u pb dating of carbonates is applicable to almost the entire geologic time scale with results from pleistocene speleothems showing great promise for dating records 1 ma old here we review studies of u pb dating of carbonates from a range of depositional and diagenetic environments and consider published results with regard to stratigraphic associations and the behavior of u and pb in various fluids we detail the steps required to select suitable samples summarize current laboratory techniques and provide directions for improvement of analytical protocols the u pb dating of carbonates has tremendous potential for dating events of geologic interest and is virtually untapped

cyclic variations of uranium concentrations and oxygen isotopes in tufa from the middle miocene barstow formation mojave desert california uranium concentrations of 42 to 169 ppm in fibrous calcite from spring deposited tufa in the middle miocene barstow formation california are among the highest reported for calcite fission track maps of multiple bands of uniformly dull luminescent fibrous calcite show that the concentration of u increases in the outward growth direction of the calcite of each individual band homogeneous dull luminescence in the fibrous calcite indicates no change in redox conditions of the fluid from which the calcite was precipitated it is proposed that the cyclic pattern of increase in u concentration reflects a cyclical change in the u ca ratio in the fluid episodic mixing between ca rich spring water with a low u ca ratio and ca poor saline alkaline lake water with a high u ca ratio could produce the episodes of formation of fibrous calcite with increasing u concentrations the spring water supplies the ca for calcite precipitation and the u concentrations increase with the decreasing fraction of spring water and increasing fraction of lake water these cycles reflect a variable recharge of groundwater into the lake by springs the large variation in u concentrations suggests mixing of 0 to 45 spring water with the lake while the narrow range in 18 o of 6 37 to 6 87 limits the variation of the proportions of spring and lake water to 5

late quaternary paleoclimate in semiarid northeastern brazil from u series dating of travertine and water table speleothems abstract fossil travertine and subaqueous speleothems in presently dry caves suggest periods of enhanced ground water recharge during the quaternary period in semiarid northeastern brazil travertine deposits and water table speleothems were dated by the 230 th 234 u technique yielding new evidence for the timing of past periods of increased rainfall the travertine was deposited in two distinct phases extensive in situ deposits during marine isotope stage 2 and fragmentary indurated deposits dating to ca 400 000 yr b p possibly marine isotope stage 10 or 12 dating of water table speleothems showed that the regional water table was 13 1 m above the present level at the last glacial maximum a second site yielded ages suggesting a still higher water table during marine isotope stage 6 these new data demonstrate that northeastern brazil did not follow the general pattern of a dry last glacial maximum as suggested by other continental records in amazonia and southeastern brazil and as depicted in recent general circulation model gcm simulations our results thus indicate that significant variability in regional rainfall patterns occurred in the area during glaciations and caution against overgeneralization of paleoclimate patterns

transition from near surface thrusting to intrabasement decollement schlinig thrust eastern alps west directed thrusting along the schlinig thrust amounts to a minimum displacement of 45 km a discrete plane of brittle thrusting is observed in the frontal part where the otztal unit overrides the sediments of the engadine dolomites both shortening of the more ductile lower and middle triassic and very substantial stretching by domino type normal faults in the brittle upper triassic dolomites are contemporaneous with and caused by thrusting extension is related to extrusion of parts of the sediments in the footwall of the schlinig thrust a relatively rapid transition into an intrabasement shear zone which is as much as 2 km thick occurs farther to the east in a region where a paleotemperature of 300 c is indicated for cretaceous metamorphism still farther to the east localized shearing is transformed into a wider area affected by large scale folding this second transition corresponds to estimated temperatures in excess of 550 c since the changes in structural style and deformation mechanisms toward the hinterland go hand in hand with increasing metamorphic grade we regard thrusting as contemporaneous with metamorphism this view is supported by geochronological data the age of thrusting and metamorphism 90 ma indicates very rapid heating after the deposition of the youngest sediments cenomanian involved in cretaceous deformation our data suggest that localized detachment along a discrete thrust plane and within broader mylonite zones cannot always be traced indefinitely to greater depth the transformation of localized shearing into large scale folding indicates a fundamentally different deformational style for lower crustal levels

mediterranean pluvial periods and sapropel formation over the last 200 000 years abstract three mediterranean deep sea cores have been studied to reconstruct the hydrological conditions at the time of deposition of interglacial and glacial sapropels during the time interval 200 60 kyr bp the isotopic and sea surface temperature records of planktonic foraminifera were used to estimate the oxygen isotopic composition of surface water w in the tyrrhenian sea and levantine basin our results show a strong w salinity decrease in both basins associated with each sapropel these w decreases reflect a drastic change in the local freshwater budget and were comparable to that observed during the last sapropel s 1 centred at ca 8 kyr bp a strong precipitation increase transformed the whole mediterranean sea into a non concentration basin the low surface salinity was responsible for the water column stratification while nutrients brought in by the runoff enhanced productivity it resulted in a significant reduction in the rate of deep water oxygenation and sapropel formation in the eastern basin in addition the mediterranean sea 18 o record is very similar to that of the bay of bengal as the latter is very sensitive to the summer monsoon rain this similarity suggests that both glacial and interglacial sapropels result from enhanced monsoon like precipitation due to an increase in summer insolation driven by precession variations

evidence for increased cool season moisture during the middle holocene isotopic analyses of three stalagmites from cold water cave northeast iowa united states reveal nearly identical 13 c trends from ca 7 to 2 ka however 18 o patterns differ by as much as 3 from 5 7 to 3 2 ka these disparate 18 o values reflect evaporative 18 o enrichment in meteoric water prior to infiltration suggesting that previously calculated temperatures based on a single cold water cave stalagmite overestimated middle holocene warming the coincidence of elevated middle holocene growth rates in the stalagmites with the lowest oxygen isotopic compositions indicates that the middle holocene was marked by a predominance of coolweather precipitation during a period of increased overall aridity

500 ka precipitation record from southeastern australia evidence for interglacial relative aridity 230 th 234 u dating of speleothems from southeastern australia documents changes in effective precipitation over the past 500 k y at a temporal resolution not previously achieved results show that the highest effective precipitation for the southeastern interior of australia occurred during stadials and cool interstadials of the past four glacial cycles interglacials and warm interstadials as well as glacial maxima are comparatively arid we suggest that lower regional temperatures over the continent and changes in atmospheric circulation stronger walker circulation produced the observed periods of increased effective precipitation

duration and structure of the past four interglaciations reanalysis and additional dating of the devils hole 18o paleotemperature record confirm that the last interglaciation in the great basin the continental analog of marine isotopic substage 5e lasted 22 000 yr consistent with the vostok paleotemperature record which suggests a duration of 19 000 yr for this event in antarctica the three preceding interglaciations in the devils hole record analogs of marine isotopic substages 7e 9c and 11c range from 20 000 to 26 000 yr in duration a 20 000 yr duration for the last interglaciation is consistent with tims uranium series dated sea level high stands thus the widely held view that interglaciations were of 11 000 to 13 000 yr duration and constituted only about 10 of mid to late pleistocene climatic cycles needs reexamination the warmest portion of each interglaciation in the devils hole time series is marked by a 18o plateau signifying apparent climatic stability for periods of 10 000 to 15 000 yr duration

origin and migration of the alpine iceman the alpine iceman provides a unique window into the neolithic copper age of europe we compared the radiogenic strontium and lead and stable oxygen and carbon isotope composition of the iceman s teeth and bones as well as 40ar 39ar mica ages from his intestine to local geology and hydrology and we inferred his habitat and range from childhood to adult life the iceman s origin can be restricted to a few valleys within 60 kilometers south east of the discovery site his migration during adulthood is indicated by contrasting isotopic compositions of enamel bones and intestinal content this demonstrates that the alpine valleys of central europe were permanently inhabited during the terminal neolithic

temperature and salinity records of the tyrrhenian sea during the last 18 000 years abstract we have used the modern analogue technique to derive sea surface temperature sst records of the last 18 000 years from two well dated deep sea cores recovered in the tyrrhenian sea results show two major cooling events synchronous with the european and north atlantic oldest and younger dryas events a later cooling of lower amplitude is observed between about 8000 and 4500 yr bp tyrrhenian ssts were similar to those of the upper holocene only during the bolling allerod event and at the beginning of the holocene we compared the sst and the planktonic foraminiferal oxygen isotope records to estimate the surface salinity variations our reconstruction shows that salinity decreased in the tyrrhenian sea during the three cold events whereas high ssts correlate with high salinities during most of the last 18 000 years tyrrhenian sea salinity variations were similar to those of the north atlantic ocean near the entrance of the mediterranean sea the salinity gradient between the two basins was thus constant indicating that the western mediterranean circulation pattern and the freshwater budget were not significantly different from the modern one the case was however different during the middle holocene when the strong salinity decrease associated with the sapropel deposit in the eastern mediterranean basin had no equivalent in the north atlantic ocean this peculiar event can only be explained by a local climatic change and an increase of precipitation

age and isotopic constraints on pleistocene pluvial episodes in the western desert egypt abstract north africa has undergone drastic climatic changes over the past several hundred thousand years the timing of humid intervals called pluvials was investigated by uranium series disequilibrium dating of travertines from the kurkur oasis western desert egypt the youngest and best dated travertines 70 160 ka are found in wadi kurkur and include spring and lacustrine units exposed as 2 to 3 m high terraces travertines having an age of approximately 191 220 ka are exposed by differential erosion as linear mounds produced by spring systems over fracture zones in ancient wadis the oldest travertines having ages 260 ka are extensive cap limestone units above the oasis and were deposited in paludal and lacustrine environments oxygen isotope ratios were measured for the wadi travertines 18o values ranging from 16 7 to 19 1 smow and for spring mound travertines 18 5 20 5 equilibrium oxygen isotope fractionation calculations indicate that the kurkur travertines were deposited from waters having 18o values similar to ancient western desert groundwaters 11 sonntag et al 1978a b thorweithe 1990 sultan et al 1996 the ages of the travertines correspond to times of monsoonal maxima eustatic sea level high stands and interglacial maxima rainfall producing these groundwaters and travertines was significantly fractionated during atmospheric transport in contrast to modern meteoric waters 2 09 joseph et al 1992 implying a distant source for the pluvial waters increased precipitation recharge of western desert groundwaters and resultant travertine deposition are interpreted to be consequences of milankovitch insolation cycle forcing through enhanced atlantic and indian ocean monsoons during interglacial time periods

the nature of annual lamination in carbonate flowstones from non karstic fractures vinschgau northern italy abstract the vinschgau is an inneralpine valley in the southern alps whose steep flanks are composed of strongly sheared gneisses and schists affected by deep seated gravitational slope deformations fractures generated by these movements host a groundwater system characterised by high amounts of dissolved solids which reflect long residence times and water rock interactions driven by sulphide oxidation this in combination with high air and soil temperatures on the south facing slope sonnenberg of the valley favoured the deposition of calcite and aragonite flowstone in shallow parts of this fractured non karstic aquifer about 5 of these speleothems exhibit well developed regular lamination whose annual origin was confirmed by radiometric dating a stable isotope petrographic and trace element study combined with u th dating was undertaken to disentangle the processes controlling lamina formation a succession of darker and lighter laminae forms distinct macroscopic couplets 0 2 2 mm wide in three of the samples while one sample comprises alternating white and translucent laminae microscopically the darker and white laminae show a higher abundance of opaque particles whose organic origin is confirmed by their strong epifluorescence the crystal fabric is dominated by the fascicular optic type the calcite shows regular 18 o oscillations with an amplitude of up to 1 2 with the exception of one sample 13 c lacks such a regular pattern and only shows smaller variations which do not correlate with 18 o in a consistent way all samples exhibit regular low amplitude mg sr ba and u cycles in three samples mg shows oscillations similar to the 18 o cycles in their frequency but opposite in phasing 18 o and mg oscillations are primarily attributed to surface temperature variations that are transmitted to the shallow subsurface by thermal conduction low amplitude trace element cycles mg sr ba and u are most probably driven by intra annual variations in the degree of prior aragonite precipitation in the seepage path which relates to seasonal changes in evaporation

carbonate speleothems in the dry inneralpine vinschgau valley northernmost italy witnesses of changes in climate and hydrology since the last glacial maximum abstract an interesting association of slope breccia inactive and active tufa deposits and speleothems is present in the central vinschgau valley italy the occurrence of abundant carbonate cements in fractures and voids of crystalline basement rocks is unexpected considering the fact that this valley is among the driest spots in the entire alps low annual precipitation of 440 530 mm coupled with frequent wind give rise to a semiarid climate and steppe vegetation along the south facing slopes of the valley springs in this area are mostly supersaturated with respect to calcite and carbonate precipitation occurs locally as tufas and less well known because of lack of accessibility as speleothems in the shallow subsurface the majority of the tufa deposits and speleothems however are fossil speleothems are composed of low mg calcite and calcite aragonite respectively delicate growth textures including presumable annual lamination caused by pronounced changes in fluorescence intensity are preserved in both calcite and aragonite most calcite is a primary precipitate but small amounts of secondary calcite replacing aragonite are common in most aragonite bearing samples the highly radiogenic sr isotope composition as well as high concentrations of u fe sr and mg indicate that the groundwater from which these carbonates precipitated experienced intensive interaction with the host crystalline rocks the very low tritium concentrations and the lack of a seasonal o isotope variation in modern spring waters as well as their rather constant hydrochemical composition also support this suggestion s isotope data for dissolved sulfate and ca and mg sulfate precipitates indicate a sulfide source i e oxidation of sulfide ore minerals in the aquifer resulting in elevated sulfate and fe concentrations th u dating of speleothem samples using thermal ionization mass spectrometry yielded ages between 13 710 and 378 yr bp with most ages falling in the early to middle holocene although no isotopic dates are available for the tufa deposits field evidence strongly suggests that speleothems tufa deposits and carbonate cements in the slope breccia were closely related we therefore interpret the existence of these terrestrial carbonates as evidence of changes in climate since the middle holocene their presence suggests a higher annual rainfall during the first half of the holocene possibly because of enhanced moisture transport from the mediterranean

temperature and salinity variations of mediterranean sea surface waters over the last 16 000 years from records of planktonic stable oxygen isotopes and alkenone unsaturation ratios alkenone unsaturation ratios and planktonic d18o records from sediment cores of the alboran ionian and levantine basins in the mediterranean sea show pronounced variations in paleo temperatures and salinities of surface waters over the last 16 000 years average sea surface temperatures ssts are low during the last glacial averages prior to 13 000 years 11 15 c vary rapidly at the beginning of the holocene and increase to 17 18 ca t all sites during s1 formation dated between 9500 and 6600 calendar years the modern temperature gradient 2 3 c between the mediterranean sub basins is maintained during formation of sapropel s1 in the eastern mediterranean sea after s1 ssts have remained uniform in the alboran sea at 18 c and have fluctuated around 20 c in the ionian and levantine basin sites the d18o of planktonic foraminifer calcite decreases by 2 from the late glacial to s1 sediments in the ionian basin and by 2 8 in the levantine basin in the alboran sea the decrease is 1 7 of the 2 8 decrease in the levantine basin the evect of global ice volume accounts for a maximum of 1 05 and the temperature increase explains only a maximum of 1 3 the remainder is attributed to salinity changes we use the temperature and salinity estimates to calculate seawater density changes they indicate that a reversal of water mass circulation is not a likely explanation for increased carbon burial during s1 time instead it appears that intermediate and deep water formation may have shifted to the ionian sea approximately 2000 years before onset of s1 deposition because surface waters were as cold but saltier than surface water in the levantine basin during the younger dryas sapropel s1 began to form at the same time when a significant density decrease also occurred in the ionian sea 2000 elsevier science b v all rights reserved

stable isotope microsampling of speleothems for palaeoenvironmental studies a comparison of microdrill micromill and laser ablation techniques three different techniques are currently in use to microsample speleothem and tufa specimens at moderate to high spatial resolution manual microdrilling using a dentist drill semi automated micromilling and laser ablation while a separate handling step is involved in the first two techniques transferring the sample powder to an on line carbonate preparation system linked to an isotope ratio mass spectrometer the laser is directly interfaced with the mass spectrometer via a gas preparation device in this study we compare stable c and o isotope results obtained by these three preparation techniques using continuous he flow mass spectrometry on the same speleothem samples the overall consistency of the results is satisfactorily high in particular between the micromill and the laser data although the precision of the laser data is slightly lower than analyses obtained by the other two methods in particular with respect to 18o the speed of acquisition renders laser ablation a useful reconnaissance technique for rapidly analyzing long sections of speleothems micromilling is the method of choice to obtain highly spatially resolved isotope data of high analytical precision while microdrilling is still an low cost alternative for sampling at comparably low resolution e g of fast growing stalagmites

the eastern mediterranean paleoclimate as a reflection of regional events soreq cave israel the climate of the eastern mediterranean region of the last 60 ky was determined by a high resolution study of the oxygen and carbon isotopic composition 1500 measurement pairs of speleothems from the soreq cave israel with chronology provided by 53 precise 230 th 234 u tims ages the high precision of the speleothem tims ages permits us to determine the timing of regional climatic events in the eastern mediterranean region and to see if they correlate with global events during the period from 60 to 17 ky the 18 o and 13 c values were generally 2 2 5 higher than during the period from 17 ky to present this is consistent with the climatic transition from glacial to interglacial within the 60 to 17 ky period the soreq cave stable isotope profile includes four cold peaks at 46 35 25 and 19 ky and 2 warm peaks at 54 and 36 ky in addition the period 17 ky has two more cold peaks at 16 5 and from 13 2 to 11 4 ky the ages of four of the six cold peaks correlate well with the ages of three heinrich events h1 h2 h5 and with the age of the younger dryas however the other two heinrich events are not reflected in the soreq cave record several other isotope peaks which appear during the last 7 ky are contemporaneous with regional climatic events in the middle east and north africa in addition to the drop in 18 o and 13 c observed between the last glacial and the holocene sharp simultaneous drops in 234 u 238 u 0 ratios sr concentrations and in 87 sr 86 sr are also observed suggesting that the latter are climate related these variations are interpreted in terms of major changes in the temperature the mean annual rainfall and its isotopic composition the isotopic composition of the mediterranean vapor source the soil moisture conditions and in the mixing proportions of sources with different 87 sr 86 sr ratios sea spray dust particles and dolomitic host rock

the calcareous tufa in the tadrart acacus mt sw fezzan libya an early holocene palaeoclimate archive in the central sahara article i nfo the palaeoclimatic signi cance of calcareous tufa deposits found in the presently hyperarid tadrart acacus massif central sahara sw libya is discussed on the basis of u th datings stable isotope analyses and the regional hydrogeological context these deposits formed mostly between c 9600 and 8100 yr bp the isotopic signature 18 o and 13 c of this tufa indicates that the water forming these carbonates originated as isotopically depleted rainwater as a result of the northward expansion of the sw african monsoon system during the early holocene carbonate sedimentation in the tadrart acacus decreased shortly before c 8000 yr bp attributed to a drop in precipitation in the course of the well known 8 2 kyr event a correlation between tufa development and climate change in n and e africa and in the mediterranean basin during the early holocene is discussed the effect of early holocene climate change on both the landscape and the dwellers living in the tadrart acacus region is also evaluated

last glacial to holocene vegetation succession recorded in polyphase slope failure deposits on the malenik ridge outer western carpathians abstract structural settings and palaeoenvironmental reconstruction of a polyphase late pleistocene deep seated landslide at the malenik ridge in the eastern part of the czech republic are presented the deep seated rotational landslide is about 480 m long and 1540 m wide and it is a part of much larger landslide complex the depositional record of two generations of former near scarp depressions revealed a multiple deep seated landslide activity during the last quaternary climatic cycle with the minimum age of 47704 2346 cal b2k the landslide belongs among the oldest dated landslides in the outer western carpathians and carpathian foredeep in the czech republic the younger reactivation started at 12662 73 cal b2k during younger dryas the palaeobotanical and depositional record from the landslide brought unique palaeoenvironmental data for two time intervals of the last quaternary climatic cycle the reconstructed mis 3 forest vegetation with the predominance of stone pine larch pinus cembra larix taiga with pinus sylvestris and betula pendula pubescens are the first evidences of the forest vegetation for the gs13 to gi12 transition in outer western carpathians similarly documented events of mis 3 landslide activity from outer western carpathians are rather rare the late glacial to holocene record from the younger near scarp depression revealed vegetation and landscape changes during the pleistocene holocene transition the evidenced oldest parts of the landslide at the malenik ridge had to originate during more humid interpleniglacial conditions the geomorphological evidence for landslide activity from this period has almost completely disappeared from the ground surface topography due to intensive periglacial processes operating later during the last glacial maximum and subsequent fluvial and anthropogenic processes of the holocene the cold and relatively dry period of the pleniglacial is considered as a time when deep seated mass movements use to be halted and overprinted by shallow solifluction of the active layer masking former deep seated landslide features

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

environmental controls of speleothem mineralogy in a karstic dolomitic terrain soreq cave israel pleistocene speleothems of the soreq cave beth shemesh israel situated within karstic cretaceous dolomitic rocks consist of two major mineralogical types 1 monomineralic low magnesium calcite lmc 0 5 and 7 5 mol mgco 3 straw stalactites stalagmites helictites and pool deposits 2 mineralogically heterogeneous deposits in the form of conical stalactites flowstones and cave corals produced from thin flowing solution films or sprays in which lmc alternates with high magnesium calcite hmc 13 to 33 mol mgco 3 dolomite 33 50 mol mgco 3 and lmc laminations a unique feature of the type 2 is the continuous 0 50 mol range of mgco 3 sem and delta 18 o studies show that all calcites and dolomites grew by direct precipitation from local groundwater solutions lmc formation represents equilibrium precipitation from dripping water solution with mg ca 2 whereas hmc and dolomite precipitation occurred from solution films enriched in mg as the result of prior clos

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years

a new model for the origin of type b and fluffy type a cais analogies to remelted compound chondrules abstract in the scenario developed here most types of calcium aluminum rich inclusions cais formed near the sun where they developed wark lovering rims before being transported by aerodynamic forces throughout the nebula the amount of ambient dust in the nebula varied with heliocentric distance peaking in the cv ck formation location literature data show that accretionary rims which occur outside the wark lovering rims around cais contain substantial 16o rich forsterite suggesting that at this time the ambient dust in the nebula consisted largely of 16o rich forsterite individual sub millimeter size compact type a cais each surrounded by a wark lovering rim collided in the cv ck region and stuck together in a manner similar to that of sibling compound chondrules the ctas were mixed with small amounts of 16o rich mafic dust and formed centimeter size compound objects large fluffy type a cais after experiencing minor melting in contrast to other types of cais centimeter size type b cais formed directly in the cv ck region after gehlenite rich compact type a cais collided and stuck together incorporated significant amounts of 16o rich forsteritic dust on the order of 10 15 and probably some anorthite and experienced extensive melting and partial evaporation enveloping compound chondrules formed in an analogous manner in those cases where appreciably higher amounts of 16o rich forsterite on the order of 25 and perhaps minor anorthite and pyroxene were incorporated into compound type a objects prior to melting centimeter size forsterite bearing type b cais b3 inclusions were produced type b1 inclusions formed from b2 inclusions that collided with and stuck to melilite rich compact type a cais and experienced high temperature processing

hypogene speleogenesis in dolomite host rock by co2 rich fluids kozak cave southern austria a growing number of studies suggest that cave formation by deep seated groundwater hypogene is a more common process of subsurface water rock interaction than previously thought fossil hypogene caves are identified by a characteristic suite of morphological features on different spatial scales in addition mineral deposits speleothems may provide clues about the chemical composition of the paleowater which range from co2 rich to sulfuric acid bearing waters this is one of the first studies to examine hypogene cave formation in dolomite kozak cave is a fossil cave near the periadriatic lineament an area known for its abundance of co2 rich springs the cave displays a number of macro meso and micromorphological elements found also in other hypogene caves hosted in limestone marble or gypsum including cupolas cusps laughohle type chambers and notches the existance of cupolas and cusps suggests a thermal gradient capable of sustaining free convection during a first phase of speleogenesis while triangular cross sections laughohle morphology indicate subsequent density driven convection close to the paleowater table notches mark the final emergence of the cave due to continued rock uplift and valley incision very narrow shafts near the end of the cave may be part of the initial feeder system but an epigene vadose overprint cannot be ruled out vadose speleothems indicate that the phreatic phase ended at least about half a million years ago drill cores show no evidence of carbon or oxygen isotope alteration of the wall rock this is in contrast to similar studies in limestone caves and highlights the need for further wall rock studies of caves hosted in limestone and dolomite

a strontium and sulfur isotopic study of permo triassic evaporites in the northern calcareous alps austria pervasively deformed permian and to a lesser extent triassic evaporites of the northern calcareous alps form a tectonic melange collectively known as alpine haselgebirge isotopic compositions of s and sr and trace element concentrations of sr and ba in ca sulfate minerals were investigated in terms of their stratigraphic and paleoenvironmental significance the majority of the samples yielded 34s values ranging from 9 8 to 13 8 indicating precipitation from late permian seawater with local modifications due to bacterial sulfate reduction bsr 87sr86sr ratios of these samples range widely from 0 7070 to 0 7098 but most samples show sr isotope values between 0 7070 and 0 7074 overlapping with the accepted late permian seawater values comparison of both s and sr isotopic compositions of individual samples reveals distinct trends of isotopic enrichment and depletion that can be linked to early diagenetic bsr mixing with continental surface or groundwaters and burial diagenesis concentrations of sr tend to be lower and ba values show a tendency toward values higher than those reported from marine evaporites implying variable diagenetic alteration triassic evaporites are volumetrically less important in the haselgebirge than their permian counterparts and are characterized by marine upper scythian to lower anisian s and sr isotope values in three localities hitherto unknown inclusions of these triassic evaporites were identified within the haselgebirge melange