advances in experimental investigation on hydraulic fracturing behavior of bentonite based materials used for hlw disposal bentonite based materials bbm in the form of blocks or rings have been commonly proposed as buffer materials for high level radioactive waste disposal in a real repository hydraulic fracturing is likely to be present when the ground water pressure exceeds to hydraulic resistance and the existence of technological gaps increases the risk of hydraulic fracturing based on the previous studies of hydraulic fracturing of bbm and technological interfaces the present work systematically analyzes the experimental achievements results show that the fracturing pressure of bbm and interfaces increases with hydration time initial dry density bentonite content and overburden pressure while it decreases with initial water content and gap thickness the temperature effect on hydraulic fracturing depends on the predominant cation of bentonite for na bentonite the higher temperature leads to the larger swelling pressure and thus the stronger hydraulic resistance tensile failure shear failure and synthesis failures are increasingly accepted for hydraulic fracturing mechanism the hydraulic fracturing of highly compacted bbm is mainly controlled by tensile failure while the initial shear failure can be found for bbm with a low enough density since hydraulic fracturing is expected to occur several times during the repository operation the long time monitoring of hydro mechanical behavior is of vital importance until the technological gaps are completely sealed furthermore the failure mechanism of hydraulic fracturing of bbm should be further researched as well as the sealing properties of interfaces under thermo hydro mechanically coupled conditions are proposed to be studied thoroughly

variations in the discharge and organic matter content of stalagmite drip waters in lower cave bristol six drip waters which were actively depositing stalagmites in lower cave bristol were analysed both for discharge and luminescence properties drip discharges were determined for two different years and show a complex response to surface precipitation variations inter annual variability in drip discharge is demonstrated to be significantly higher than intra annual variability and discharge was demonstrated both to increase and decrease non linearly with increased precipitation drip waters demonstrate a correlation between their luminescence intensity and drip discharge with increased luminescence in winter as more organic matter is flushed through the aquifer the strength of the relationship between luminescence intensity and discharge increases with increased discharge the results presented here have implications for the palaeoenvironmental interpretation of annual growth laminae and the growth rates of stalagmite samples 1997 john wiley sons ltd

climatic dependence of stable carbon and oxygen isotope signals recorded in speleothems from soil water to speleothem calcite abstract understanding the relationship between stable isotope signals recorded in speleothems 13 c and 18 o and the isotopic composition of the carbonate species in the soil water is of great importance for their interpretation in terms of past climate variability here the evolution of the carbon isotope composition of soil water on its way down to the cave during dissolution of limestone is studied for both closed and open closed conditions with respect to co 2 the water entering the cave flows as a thin film towards the drip site co 2 degasses from this film within approx 10 s by molecular diffusion subsequently chemical and isotopic equilibrium is established on a time scale of several 10 100 s the 13 c value of the drip water is mainly determined by the isotopic composition of soil co 2 the evolution of the 18 o value of the carbonate species is determined by the long exchange time t ex between oxygen in carbonate and water of several 10 000 s even if the oxygen of the co 2 in soil water is in isotopic equilibrium with that of the water dissolution of limestone delivers oxygen with a different isotopic composition changing the 18 o value of the carbonate species consequently the 18 o value of the rainwater will only be reflected in the drip water if it has stayed in the rock for a sufficiently long time after the water has entered the cave the carbon and oxygen isotope composition of the drip water may be altered by co 2 exchange with the cave air exchange times ex co 2 of about 3000 s are derived thus only drip water which drips in less than 3000 s onto the stalagmite surface is suitable to imprint climatic signals into speleothem calcite deposited from it precipitation of calcite proceeds with time constants p of several 100 s different rate constants and equilibrium concentrations for the heavy and light isotopes respectively result in isotope fractionation during calcite precipitation since t ex p exchange with the oxygen in the water can be neglected and the isotopic evolution of carbon and oxygen proceed analogously for drip intervals t d p the isotopic compositions of both carbon and oxygen in the solution evolve linearly in time the calcite precipitated at the apex of the stalagmite reflects the isotopic signal of the drip water for long drip intervals when calcite is deposited from a stagnant water film long drip intervals may have a significant effect on the isotopic composition of the dic in this case the isotopic composition of the calcite deposited at the apex must be determined by averaging over the drip interval such processes must be considered when speleothems are used as proxies of past climate variability

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

intensification of northern hemisphere glaciations in the circum atlantic region 3 5 2 4 ma ice rafted detritus evidence abstract records of ice rafted detritus ird from ocean drilling program sites 644 and 907 in the nordic seas and deep sea drilling program sites 610 and 607 in the north atlantic ocean are used to determine the growth and history of northern hemisphere glaciations spanning the interval from 3 6 to 2 4 ma the records document that the initiation of large scale glaciation in the circum atlantic region occurred stepwise between 3 5 and 2 4 ma with greenland leading the other areas the first major pulse of ird occurs at 3 3 ma suggesting a distinct expansion of the greenland ice sheet progressive increases in ird occur from 3 0 ma with a synchronous ice sheet development between the greenland scandinavian and north american regions starting around 2 72 2 75 ma the regional records of ird correspond to major trends in the oxygen isotope record suggesting a tight connection between the record of global ice volume and evidence for expanding glaciers in the northern hemisphere it appears as if widespread ird distribution occurs when the global ice volume surpasses certain thresholds similar to the late quaternary situation

speleothem based quaternary research in croatian karst a review abstract speleothems as secondary carbonate deposits precipitate in the cave environment from the water originally sourced from the ocean transferred via atmosphere through soil and epikarst into the cave system as such they archive valuable information on the ongoing changes in the atmosphere biosphere hydrosphere and lithosphere which may be used for palaeoenvironmental reconstructions especially for the quaternary period speleothem based quaternary research in croatia started in the 1960 s with the utilization of the flowstone and speleothems whose radiometric ages 14c and u th provided constrained chronological framework for underlying fossils or archaeological material mainly without any further palaeoenvironmental interpretations since the 1990 s several studies have used speleothems for the reconstruction of particular phases of speleogenesis while in the early 2000 s investigation on submerged speleothems started with the aim to reconstruct quaternary relative sea level changes along the eastern adriatic coast only after that thorough research on subaerial speleothems from the different regions of the croatian karst has been initiated usually associated with monitoring programs this paper gathers the most important speleothem based studies displaying potential of this still understudied but promising area in the terms of palaeoclimate and palaeoenvironmental changes in a wider european and global context

practical estimation of compression behavior of clayey silty sands using equivalent void ratio concept abstractclayey silty sands are widespread as naturally sedimentary soils such as marine deposits in estuaries and offshore locations they belong to a unique class of gap graded soils featuring a d

pliocene and early pleistocene glaciation and landscape evolution on the patagonian steppe santa cruz province argentina abstract at least seven late pliocene tills cap plateaus mesetas south of lago viedma just east of the andes in argentine patagonia chronologic constraints on the tills are provided by 40ar 39ar ages and magnetic polarities on associated basalt flows and sediments the tills were deposited by piedmont glaciers that reached at least 80 km east of the crest of the andes and flowed on a low relief surface sloping gently downward in that direction the oldest of the tills is about 3 6 ma old glacial deposits dating to the pliocene pleistocene transition are present at least 40 km beyond the east limit of the pliocene tills at lago viedma and tills of similar age occur at condor cliff in the rio santa cruz valley to the southeast a sequence of at least seven early pleistocene 2 1 1 1 ma tills is present between basalt flows in the cerro del fraile meseta south of lago argentino the glaciers that deposited these early pleistocene tills reached far beyond the marine isotope stage 2 limit in the rio santa cruz valley based on positions extents and ages of the un deformed basalt capped mesetas flanking lago viedma we conclude that the topography in this area was profoundly changed during the pleistocene the low to moderate relief pliocene surface was deeply incised by glaciers that became increasingly confined to and flowed within troughs the valley floors today are up to 1350 m below the late pliocene surface

effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation the late cenozoic closure of the seaway between the north andsouth american continents is thought to have caused extensive changes in ocean circulation and northern hemisphere climate1 2 but the timing and consequences of the emergence of the isthmus of panama which closed the seaway remain controversial1 2 3 4 5 here we present stable isotope and carbonate sand fraction records from caribbean sediments which when compared to atlantic and pacific palaeoceanographic records indicate that the closure caused a marked reorganization of ocean circulation starting 4 6 million years ago shallowing of the seaway intensified the gulf stream and introduced warm and saline water masses to high northern latitudes these changes strengthened deep water formation in the labrador sea over the next million years as indicated by an increased deep water ventilation and carbonate preservation in the caribbean sea and favoured early pliocene warming of the northern hemisphere the evaporative cooling of surface waters during north atlantic deep water formation would have introduced moisture to the northern hemisphere although the pronounced intensification of northern hemisphere glaciation between 3 1 and 2 5 million years ago substantially lagged the full development of north atlantic deep water formation we propose that the increased atmospheric moisture content was a necessary precondition for ice sheet growth which was then triggered by the incremental changes in the earth s orbital obliquity

oxygen and hydrogen isotopic variations between adjacent drips in three caves at increasing elevation in a temperate coastal rainforest vancouver island canada abstract the interpretation of speleothem paleoenvironmental records requires understanding of spatial temporal variations in vadose drip water chemistry and isotopic composition this study reports on intra and inter cave differences in d 18o and electrical conductivity using 18 monthly water samples from three adjacent drips all drips showed isotopic seasonal signals despite varied patterns of drip hydrology there was overlap in isotopic ranges at 1 sd between all three caves in contrast with the expected 18o depletion of 0 15 to 0 5 100 m of ascent observed in standard precipitation the isotopic seasonality was approximated with sine curves and compared to a gnip data set from victoria 300 km to the south the d and 18o drip isotopes lagged the victoria record by 155 26 days and 165 50 days respectively the longest lag was at the slowest drip sea level while the shortest lag 87 days for 18o 550 m asl implies a short residence time paradoxically from the drip with the highest mean electrical conductivity vadose residence time was less than one climatic year reflecting a combination of negligible matrix porosity in the host rock and super humid climatic conditions beneath the epikarst drip hydrology was evidently by simple piston flow phase shifted drip isotope records showed excellent agreement with sea level mean monthly air temperatures at the tahsis meteorological station over the study period the d and 18o drip amplitudes were damped on average 74 and 73 respectively compared to the victoria data the drips at 740 m asl are tightly aligned to the global mean meteoric water line gmwl and 18o depleted the drips at 550 m asl and at sea level plot along the gmwl or between it and the victoria lmwl with the exception of the slowest drip sea level which displays some seasonal evaporitic enrichment the findings quantify substantial intra and inter cave variation of d and 18o in drips having a wide range of drip type and volume of flow sufficient to mute the altitudinal isotopic lapse rate in this local coastal rainforest environment

a late holocene climate record in stalagmites from modric cave croatia few terrestrial holocene climate records exist from south eastern europe despite its important geographical position as a transitional climatic zone between the mediterranean and mainland continental europe here we present new petrographic and stable isotope data for two holocene speleothems from modric cave croatia 44 15 n 15 32 e a coastal adriatic site 120 m inland modern meteorological and cave conditions have been monitored for 2 years to understand the links between climate variability and stable isotope time series records in speleothems typical of a mediterranean type climate a negative water balance exists between april and september so that recharge of the aquifer is restricted to the winter months the weighted mean 18o of the rainfall is 5 96 2 2 83 and the weighted mean d h rainfall value is 36 83 2 19 95 slightly above the global meteoric water line but well below the mediterranean meteoric water line modern calcite from the tops of each stalagmite exhibits 18o values that are close to isotopic equilibrium with their respective drip water values unfortunately the relatively young ages and low uranium contents ca 50 p p b of both stalagmites hamper the use of u series dating radiocarbon dates have been used instead to constrain their chronology using a dead carbon correction apart from some isotope stage 3 material ca 55 ka both stalagmites were deposited during the late holocene climatic conditions during the late holocene are inferred to have been sufficiently wet to maintain stalagmite growth and any hiatuses appear to be relatively short lived inferred changes in the stalagmite diameters during deposition are linked to 13c and 18o variations indicating alternating periods of drier and wetter conditions drier conditions are inferred for the late roman ages warm period and the mid medieval warm period wetter conditions are associated with the little ice age copyright 2012 john wiley sons ltd

carbon and oxygen isotope study of the active water carbonate system in a karstic mediterranean cave implications for paleoclimate research in semiarid regions abstract in a semiarid climatic zone such as the eastern mediterranean region annual rainfall variations and fractionation processes in the epikarst zone exert a profound influence on the isotopic compositions of waters seeping into a cave consequently the isotopic compositions of speleothems depositing from cave waters may show complex variations that need to be understood if they are to be exploited for paleoclimate studies this is confirmed by a four year study of the active carbonate water system in the soreq cave israel the 18o smow values of cave waters range from 6 3 to 3 5 the highest 18o values occur at the end of the dry season in waters dripping from stalactites and reflect evaporation processes in the epikarst zone whereas the lowest values occur in rapidly dripping fast drip waters at the peak of the rainy seasons however even fast drip waters are about 1 5 heavier than the rainfall above the cave which is taken to reflect the mixing of fresh with residual evaporated water in the epikarst zone 13c pdb values of dissolved inorganic carbon dic vary from 15 6 to 5 4 with fast drip waters having lower 13c values mostly 15 6 to 12 and higher dic concentrations relative to pool and stalactite drip water the low 13c values of fast drip waters and their supersaturation with respect to calcium carbonate indicates that the seepage waters have dissolved both soil co2 derived from overlying c3 type vegetation and marine dolomite host rock the 18o pdb values of various types of present day low magnesium calcite lmc speleothems range from 6 5 to 4 3 and 13c values from 13 to 5 5 and are not correlated with speleothem type an analysis of 18o values of present day calcite rafts and pool waters shows that they form in oxygen isotope equilibrium similarly the measured ranges of 13c and 18o values for all types of present day speleothems are consistent with equilibrium deposition at cave temperatures the 13c 18o range of contemporary lmc thus reflects the variations in temperatures and isotopic compositions of the presentday cave waters the 10 variation in the 13c values in waters can be modeled by a simple rayleigh calculation of the carbon isotope fractionation accompanying co2 degassing and carbonate precipitation these variations may obscure the differences in the carbon isotopic composition of speleothems that could arise when vegetation cover changes from c3 to c4 type plants this consideration emphasizes that it is necessary to characterize the full range of 13c values associated with contemporaneous speleothems in order to clarify the effects of degassing from those due to differing vegetation types isotopic studies of a number of different types of fossil lmc speleothems show many of them to exhibit isotopic trends that are similar to those of present day lmc but others show both higher and lower 18o ranges in particular the higher 18o range has been shown by independent age measurements to be associated with a period of drier conditions the results of the study thus indicate that it is necessary to work on a well calibrated cave system in semiarid climates and that the fossil speleothem record should be obtained from different types of contemporaneous deposit in order to fully characterize the 18o 13c range representative of any given climatic period

holocene climatic conditions in the eastern adriatic recorded in stalagmites from strasna pec cave croatia abstract in the study we present results of stable isotope analysis 18o 13c of two stalagmites spd 1 and spd 2 from strasna pec cave situated on dugi otok island in the central adriatic region the growth interval of the speleothems based on u th dating covers the period from 4 4 ka to 1 5 ka both speleothems show frequent 18o and 13c fluctuations with similar average values 18o value of 4 for both speleothems and average value of 13c 8 5 and 8 8 respectively in order to reconstruct the holocene climatic conditions in the eastern adriatic the speleothem isotopic record is discussed and compared with other holocene records they reveal periods of drought which occurred at 4 3 4 ka and around 3 5 ka with relatively wet phases between from 3 ka there is a general trend towards dryness as evidentiated by the relatively high 18o values of 3 5 to 2 5 recorded in speleothem spd 1 there is distinct trend of drying during the roman warm period and further toward the dark age cold period dacp with shorter periods of wetter conditions these changes coincide well with the other records thus revealing regional events along the eastern adriatic

climate caving in to new chronologies speleothems formed in caves such as stalagmites can be dated precisely and are increasingly providing detailed and accurate records of past climates

evidence for obliquity forcing of glacial termination ii variations in the intensity of high latitude northern hemisphere summer insolation driven largely by precession of the equinoxes are widely thought to control the timing of late pleistocene glacial terminations however recently it has been suggested that changes in earth s obliquity may be a more important mechanism we present a new speleothem based north atlantic marine chronology that shows that the penultimate glacial termination termination ii commenced 141 000 2500 years before the present too early to be explained by northern hemisphere summer insolation but consistent with changes in earth s obliquity our record reveals that terminations i and ii are separated by three obliquity cycles and that they started at near identical obliquity phases

a global synthesis of the marine and terrestrial evidence for glaciation during the pliocene epoch abstract the pliocene climate is globally warm and characterised by high atmospheric carbon dioxide concentrations yet the terrestrial and marine scientific communities have gathered considerable evidence for substantial glaciation events in both the northern and southern hemisphere prior to the quaternary evidence on land is fragmentary but marine records of glaciation present a more complete history of pliocene glaciation here we present a global compilation of the terrestrial and marine glacial evidence for the pliocene and demonstrate four glaciation events that can be identified in the southern and or northern hemisphere prior to the latest pliocene intensification of northern hemisphere glaciation there are two globally recognisable glacial events in the early pliocene c 4 9 4 8 ma and c 4 0 ma one event around the early late pliocene transition c 3 6 ma and one event during marine isotope stage m2 c 3 3 ma long term climate cooling decreasing carbon dioxide concentrations in the atmosphere and high climate sensitivity in the pliocene probably facilitated each glaciation event however the mechanisms behind the early pliocene glacial events are unclear the global glaciation at c 3 3 ma may be caused by changes in ocean gateways whereas the decline in carbon dioxide concentrations is important for the latest pliocene intensification of northern hemisphere glaciation

late pliocene greenland glaciation controlled by a decline in atmospheric co2 levels it is thought that the northern hemisphere experienced only ephemeral glaciations from the late eocene to the early pliocene epochs about 38 to 4 million years ago and that the onset of extensive glaciations did not occur until about 3 million years ago several hypotheses have been proposed to explain this increase in northern hemisphere glaciation during the late pliocene here we use a fully coupled atmosphere ocean general circulation model and an ice sheet model to assess the impact of the proposed driving mechanisms for glaciation and the influence of orbital variations on the development of the greenland ice sheet in particular we find that greenland glaciation is mainly controlled by a decrease in atmospheric carbon dioxide during the late pliocene by contrast our model results suggest that climatic shifts associated with the tectonically driven closure of the panama seaway with the termination of a permanent el nino state or with tectonic uplift are not large enough to contribute significantly to the growth of the greenland ice sheet moreover we find that none of these processes acted as a priming mechanism for glacial inception triggered by variations in the earth s orbit

disequilibrium carbon and oxygen isotope fractionation in recent cave calcite comparison of cave precipitates and model data abstract speleothem proxy data provide important information in continental palaeo climate research due to their precise chronology and wide geographic distribution despite a continuously growing number of field and numerical studies designed to study stable isotope fractionation effects many aspects remain a matter of debate here carbon and oxygen isotope ratios from cave drip water and calcite precipitates sampled on watch glasses in the bunker cave western germany are compared with the values expected for isotopic equilibrium furthermore the field data are compared with the results of a numerical model simulating stalagmite growth and stable isotope ratios two drip sites with different drip rates were investigated drip site ts 1 is characterised by a high drip rate and drip water of this site is characterised by a high saturation index with respect to calcite ts 1 shows no evidence of prior calcite precipitation conversely drip site ts 8 shows a low drip rate and drip water from this site is characterised by a low saturation index ts 8 shows evidence of prior calcite precipitation whereas the mean 13 c dic values of the drip water are significantly different between the two drip sites the mean 18 o drip water values are similar calcite precipitation rates are higher at watch glass site u i corresponding to drip site ts 1 this is probably due to the higher si calcite and drip rate the 18 o and 13 c values of the calcite precipitated on watch glasses u iv corresponding to drip site ts 8 are significantly higher than those of the calcite collected on watch glasses u i calcite precipitation occurs close to isotopic equilibrium at watch glass site u i whereas the calcite precipitated at watch glass site u iv shows clear evidence of isotopic disequilibrium the results suggest that cave calcites precipitated at lower drip rates have higher 13 c and 18 o values than predicted by equilibrium precipitation furthermore our data show that stalagmites from the same cave which are fed by drip water with similar 18 o values may have different 18 o calcite values the 13 c and 18 o values predicted by the numerical model are generally lower by 1 9 and 0 8 respectively than those of the natural cave calcite nevertheless the first order trends observed in the cave data are well reproduced by the model the offset between cave and model data is probably due to the fractionation factors used in the model

rainfall and cave water isotopic relationships in two south france sites this article presents isotopic measurements 18o and d of precipitation and cave drip water from two sites in southern france in order to investigate the link between rainfall and seepage water and to characterize regional rainfall isotopic variability these data which are among the longest series in france come from two rainfall stations in south west france le mas 1996 2012 and villars 1998 2012 typically under atlantic influence and from one station in the south east orgnac 2000 2012 under both mediterranean and atlantic influence rainfall isotopic composition is compared to drip water collected under stalactites from the same sites villars cave four drip stations 1999 2012 in the south west and chauvet cave two drip stations 2000 2012 in the south east near orgnac the study of these isotopic data sets allows the following conclusions to be drawn about the rainfall drip water relationships and about rainfall variability 1 the cave drip water isotopic composition does not show any significant changes since the beginning of measurements in order to explain its isotopic signature it is necessary to integrate weighted rainfall 18o of all months during several years which demonstrates that even at shallow depths 10 50 m cave drip water is a mixture of rain water integrated over relatively long periods which give an apparent time residence from several months to up to several years these results have important consequences on the interpretation of proxies like speleothem fluid inclusions and tree ring cellulose isotopic composition which are used for paleoclimatic studies 2 in the villars cave where drip stations at two different depths were studied lower 18o values were observed in the lower galleries which might be due to winter season overflows during infiltration and or to older rain water with a different isotopic composition that reaches the lower galleries after years 3 local precipitation is characterized by local meteoric water lines lmwl with 18o d slopes close to 7 in both areas and correlations between air temperature and precipitation 18o are low at both monthly and annual scales even with temperature weighted by the amount of precipitation 4 the mesoscale climate model remoiso equipped with a water isotope module allows the direct comparison of modeled and observed long term water isotope records the model slightly overestimates rainfall 18o at the respective sampling stations however it simulates very well not only the seasonal rainfall isotopic signal but also some intra seasonal patterns such as a typical double peak 18o pattern in winter time

geomagnetic excursions and paleointensities in the matuyama chron at ocean drilling program sites 983 and 984 iceland basin 1 we report natural remanent magnetization nrm directions and geomagnetic paleointensity proxies for part of the matuyama chron 0 9 2 2 ma interval from two sites located on sediment drifts in the iceland basin at ocean drilling program sites 983 and 984 mean sedimentation rates in the late matuyama chron are 15 9 and 11 5 cm kyr 1 respectively for the older part of the record 1 2 ma oxygen isotope data are too sparse to provide the sole basis for age model construction the resemblance of the volume susceptibility record and a reference 18o record led us to match the two records to derive the age models this match based on site 983 984 susceptibility is consistent with available site 983 984 benthic 18o data paleointensity proxies were derived from the slope of the nrm versus anhysteretic remanent magnetization plot for alternating field demagnetization in the 30 60 mt peak field range paleointensity lows correspond to polarity reversals at the limits of the jaramillo olduvai cobb mountain and reunion subchrons and to seven excursions in nrm component directions magnetic excursions defined here by virtual geomagnetic polar latitudes crossing the virtual geomagnetic equator are observed at 932 1048 1115 1190 1215 cobb mountain subchron 1255 1472 1480 1567 1575 gilsa subchron and 1977 ka the results indicate that geomagnetic directional excursions associated with paleointensity minima are a characteristic of the matuyama chron and probably of polarity chrons in general

daily response of drip water isotopes to precipitation in liangfeng cave guizhou province sw china abstract oxygen isotope 18o is one of the most commonly used palaeoclimate proxies and monitoring their modern evolutionary processes is very significant for palaeoclimate reconstruction in this study drip water samples are daily collected from two drip sites in liangfeng cave guizhou province sw china between june 2008 and june 2010 the stable hydrogen and oxygen isotopes of these samples and the contemporary precipitation samples are measured the relationships between the isotopes and the local air temperature precipitation and relative humidity are analysed the results show that the hydrogen and oxygen isotopic compositions of precipitation have obvious seasonal variations in the study area lower in the rainy season and higher in the dry season the local meteoric water line lmwl is d 8 64 18o 17 44 precipitation is the only source of cave drip water and its oxygen isotope signals are reflected in the two drip waters sd slower drip rate and previously called 1 and fd faster drip rate and previously called 5 however the amplitude of the drip water oxygen isotope variation is much smaller than that of the precipitation i e homogenization occurs to some extent however there are significantly different responses to precipitation between the two drip sites the response time of sd to precipitation is much longer than that of fd the amplitude of oxygen isotope variation in sd where the isotopic data deviate from the lmwl to a higher degree is much smaller than that in fd a comparison of these isotopic differences with previous research in the same cave indicates that the isotopic differences between the two drip waters result from different flow paths the oxygen isotope signal in cave drip water perhaps mainly reflects summer monsoon information in the study area the speleothems fed by drip waters e g fd with shorter response time to precipitation may be more suitable for high resolution palaeoclimate research moreover the d excess from speleothem fluid inclusion has the potential to be used as an indicator of relative humidity of local air

oxygen isotope variations in rainfall drip water and speleothem calcite from a well ventilated cave in texas usa assessing a new speleothem temperature proxy abstract measurements of the oxygen isotopic composition 18o value of rainfall drip water and associated calcite grown on artificial substrates and in a natural speleothem at multiple drip sites in a well ventilated cave in central texas were conducted to investigate the potential use of speleothem 18o for quantitative temperature reconstructions from 2009 to 2011 rainfall 18o varied by 11 5 10 5 to 1 0 v smow whereas drip waters had a much narrower range of 0 3 4 7 to 4 4 v smow this contrast indicates that mixing processes along flow paths in the vadose zone above the cave produce a well homogenized water reservoir that supplies drip water to the cave the 18o values for calcite grown on substrates over the same time period show seasonal variations summer 6 winter 3 that are strongly correlated with surface air temperatures ta at all three monitored sites r2 0 88 0 96 p

far flung moraines exploring the feedback of glacial erosion on the evolution of glacier length abstract over many glacial cycles the glacial erosion of alpine valleys can be sufficient to reduce the length of glaciers in the most recent cycles we document field cases illustrative of this erosional feedback and model the long term evolution of glacier lengths analytically and numerically the general feature we target is a moraine deposited well beyond the last glacial maximum lgm limit which we refer to as a far flung moraine firstly we assemble published observations to illustrate that far flung moraines are documented around the world the observations suggest that the downvalley distance to such far flung moraines can exceed the distance to lgm moraines by up to twofold secondly we address the problem analytically making several simplifying assumptions to demonstrate that glacier length scales linearly with erosion depth finally we employ a numerical model to test the analytical solution this 1d depth integrated flowline model includes i a depth averaged longitudinal coupling stress approximation ii prescribed winter and summer surface mass balance profiles iii evolving ice temperature calculated via the conventional heat equation and iv glacier sliding velocity parameterized as a function of basal ice temperature and spatially and temporally variable prescribed flotation fraction the simulated alpine landscape is modified through the competing processes of glacier erosion which is dependent on glacier sliding velocity and prescribed bedrock erodibility and prescribed uplift rate the climate controlling surface mass balance is prescribed by time series of air temperature and snowfall approximated by the sum of two sinusoidal cycles the recurrence statistics of these prescribed climate drivers closely match those of the marine isotopic record hence the prescribed climate drivers faithfully mimic observed long term climate drivers consistent with earlier landscape evolution studies we find that the primary effect of repeated glaciations is to flatten a valley floor and steepen its headwall effectively cutting a longitudinal notch in a fluvial valley profile analytical and numerical model results also demonstrate that far flung moraines are an inevitable consequence of repeated glaciations glaciers in tectonically inactive regions can sufficiently erode their valleys so that the earliest glaciations leave moraines many kilometers down valley from moraines left by the latest glaciations despite similar climates this suggests that a different landscape rather than a different climate is capable of explaining the early glacier extents as a corollary the long term drift toward reduced glacier length favors the survival of early moraines in the face of later glacial advances finally rock uplift can defeat this erosional feedback while rock subsidence enhances the feedback

epikarst hydrology and implications for stalagmite capture of climate changes at grotta di ernesto ne italy results from long term monitoring grotta di ernesto is a cave site well suited for palaeoclimate studies because it contains annually laminated stalagmites and was monitored from 1995 to the end of 2008 for microclimate hydrology and hydrochemistry long term monitoring highlighted that cave drips show three different hydrological responses to rainfall and infiltration 1 fast seasonal drips in the upper part of the cave which are mostly fed by fractures 2 slow seasonal drips located at mid depth in the cave characterized by mixed feeding and 3 slow drips mostly located in the deeper gallery which are fed by seepage flow from bulk porosity with a minor fracture fed component the slow drips display daily cycles during spring thaw monitoring also indicated that drip waters are only slightly modified by degassing within the soil zone and aquifer and by prior calcite precipitation hydrochemical studies show a clear seasonality in calcite saturation index which results in most cave calcite precipitation occurring during late autumn and winter with similar amounts of precipitated calcite on most stalagmites regardless of drip rate discharge differences drip rate and drip rate variability therefore has a minor role in modulating the amount of annual calcite formation in contrast drip rate when associated with moderate reduction in calcite saturation index clearly influences stalagmite morphology increasing drip rate yields a passage from candle to cone to dome shaped stalagmites very high drip rates feed speleothems with flowstone morphology in summary monitoring provides information about the karst aquifer and how hydrology influences those physical and chemical characteristics of speleothems which are commonly used as climate proxies copyright 2010 john wiley sons ltd

stratigraphy of the gorges moraine system mount kenya palaeosol and palaeoclimate record moraines marking an early pleistocene glaciation on mt kenya are known from several valleys along the eastern and southeastern flanks of the mountain the most prominent group of end moraines delimiting the lowermost extent of the early pleistocene gorges glaciation 2900 m above sea level overlie either older till or weathered bedrock the latter composed of thin pedostratigraphic remnants covered with locally derived aeolian sediments truncated by the ingress of ice the loess tills and interbedded palaeosols of the gorges glaciation crop out adjacent to the nithi river which drains the gorges valley and abut the upper timberline of montane forest the lowermost palaeosols at these sites were formed either in till predating the gorges glaciation or in weathered bedrock of trachytic textured lavas similar to the lithology forming the base of the mt kenya volcanic series of miocene or pliocene age palaeomagnetism and weathering characteristics are here used to refine the age of sediments assigned to the gorges glaciation these normally magnetized deposits carry a persistent reversed overprint suggesting that they were deposited during one of the normal subchrons within the matuyama reversed chron they are underlain either by a reversely magnetized till or by weathered bedrock and lower palaeosol the latter exhibiting normal magnetization gauss with reversed overprint matuyama the sediments of the gorges glaciation are overlain at all three sites by normally magnetized loesses and palaeosols presumably of brunhes age but carrying a high percentage of well weathered recycled grains the normal magnetization and reversed overprint recorded in sediments of the gorges glaciation most probably span a considerable portion of the olduvai subchron 1 78 1 950 ma which persisted for sufficient time to accommodate an extensive montane glaciation followed by a prolonged period of weathering and soil formation the importance of these sediments in global palaeoclimate reconstruction and insolation changes is discussed the stratigraphic evidence contradicts the cosmogenic exposure ages presented by previous workers attempting to obtain true ages of deposits using exhumed coarse clastic sediment without analysis of complex pedostratigraphic complexes supplementary materials tables 1s 5s are available at www geolsoc org uk sup18592

isotopic characterization of cave environments at varying altitudes on the eastern adriatic coast croatia implications for future speleothem based studies abstract an important step in the implementation of paleoclimate reconstructions from speleothems cave carbonate deposits is to evaluate the sensitivity of the host cave environment to regional climate accordingly we studied three caves at different altitudes 74 m 570 m and 1250 m a s l along a transect from the dalmatian islands to velebit mountain peaks in coastal croatia to characterize their environments in terms of each cave s suitability to host speleothems that would be capable of yielding robust paleoclimate reconstructions we conducted cave microclimate 2 years and dripwater 1 year monitoring and analysed the isotopic composition of precipitation cave dripwater and modern spelean calcite as for the water isotopic imprints the isotopic values of meteoric waters reaching the two lower altitude caves in spite of an altitude difference of 500 m lie on local meteoric water lines lmwls of similar slope and intercept 2 h 6 61 18 o 4 92 and 2 h 6 69 18 o 6 86 their slopes lower than that of gmwl indicate enhanced evaporation during the warm season as expected the lmwl of the highest cave region 2 h 7 83 18 o 14 45 resembles the slope of the gmwl but the values of deuterium excess obtained for all three caves between 15 2 and 16 6 match that of western mediterranean sourced waters 15 monthly d excess values suggest atlantic sourced air masses can reach the sites throughout the year but never dominate the rainfall composition the altitude effect was noted both in precipitation and in dripwater isotopic composition but with notably different 18 o 100 m gradients 0 33 and 0 11 respectively stable isotope variations of the dripwaters in all caves were attenuated in relation to the rainwater even those of the drip sites with fracture flow behaviour based on stable cave microclimate conditions relatively steady discharges and modern calcite apparently precipitated at or close to isotopic equilibrium with dripwater the two caves at lower altitudes show the greatest potential for future paleoclimate studies the cave at the highest altitude experiences large cave air temperature amplitudes 5 3 c and pronounced ventilation making the isotopic signal susceptible to kinetic fractionation which might preclude quantification of environmental changes but on the other hand it accentuates isotopic events making them easier to identify

strong influence of water vapor source dynamics on stable isotopes in precipitation observed in southern meghalaya ne india to calibrate 18o time series from speleothems in the eastern indian summer monsoon ism region of india and to understand the moisture regime over the northern bay of bengal bob we analyze the 18o and d of rainwater collected in 2007 and 2008 near cherrapunji india d values range from 18 5 to 144 4 while 18o varies between 0 8 and 18 8 the local meteoric water line lmwl is found to be indistinguishable from the global meteoric water line gmwl late ism september october rainfall exhibits lowest 18o and d values with little relationship to the local precipitation amount there is a trend to lighter isotope values over the course of the ism but it does not correlate with the patterns of temperature and rainfall amount 18o and d time series have to be interpreted with caution in terms of the amount effect in this subtropical region we find that the temporal trend in 18o reflects increasing transport distance during the ism isotopic changes in the northern bob surface waters during late ism and vapor re equilibration with rain droplets using an isotope box model for surface ocean waters we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern bob temporal variations in this source can contribute up to 25 of the observed changes in stable isotopes of precipitation in ne india to delineate other moisture sources we use backward trajectory computations and find a strong correlation between source region and isotopic composition palaeoclimatic stable isotope time series from northeast indian speleothems likely reflect changes in moisture source and transport pathway as well as the isotopic composition of the bob surface water all of which in turn reflect ism strength stalagmite records from the region can therefore be interpreted as integrated measures of the ism strength

southern patagonian plateau basalts and deformation backarc testimony of ridge collisions abstract the distribution and volume of tertiary patagonian plateau basalts and the evolution of the patagonian fold and thrust belt between 46 and 49 s appear to be closely tied with ridge trench interactions along the continental margin to the west eocene plateau basalts south of 43 s are associated with a gap in the eocene arc and can be related to a proposed collision of the aluk farallon ridge against the trench at this time eruptions of late miocene to recent plateau basalts between 46 and 49 s can be related to time transgressive slab windows in the underlying mantle generated by the collision of segments of the chile ridge at 10 14 ma and 6 ma the principal deformation in the patagonian fold and thrust belt predates the eruption of the basalts and also appears to be related with late miocene ridge collision comparison of plateau basalts related to the collision of the three distinct ridge segments suggests that the volume of basalt erupted increases with the length of the collided ridge segment almost all eocene to recent plateau basalts between 46 and 49 s have oib like ocean island basalt trace element signatures showing that the mantle source region changed little with time plateau basalts with more arc like signatures appear to be contaminated by continental crust relative melting percentages inferred from the trace element chemistry of the plateau basalts correlate with volumes of erupted basalt implying spatial and temporal changes in temperatures in the mantle source that can be correlated with slab windows

the hydrochemical response of cave drip waters to sub annual and inter annual climate variability wombeyan caves se australia abstract a thorough understanding of cave seepage waters is necessary to interpret geochemical variations in speleothem calcite in terms of changing surface climatic conditions at a particular site here we present the hydrochemistry of ten cave drip waters from a karst system in se australia based on up to 5 5 years of monitoring discharge was continuously measured at six sites and manually at the other sites dripwater samples were analysed for ph electrical conductivity cations and anions at all sites at monthly or more frequent intervals each drip possesses a unique chemistry and not all drip waters responded to antecedent short term hydrological variations for example the hydrochemical behaviour of three adjacent drips at a bedrock depth of 45 m was completely different to that of shallower sites and was apparently un related to surface hydrology throughout the investigation based on modelled calcite precipitation vectors prior calcite precipitation was demonstrated at several sites but can only be linked directly to changes in surface recharge at the shallowest sites at extremely low flow shallow drip waters accessed a high mg sr and ba source thought to be the overlying soil high frequency sample collection allows for the calculation of predicted mg ca calcite and sr ca calcite values highlighting that the sites with the greatest potential to record high resolution palaeohydrological records are those situated at shallow depth longer temporal resolution palaeohydrological records may be recorded at deeper sites but longer term monitoring is required to identify probable time scales inherent system non linearities dissolution of secondary calcite in pore spaces of the aquifer changes in the source of trace elements and the presence of multiple reservoirs confirm the need for the use of multiple speleothems and a multi proxy approach to gain accurate palaeohydrological records from this site

unsaturated zone hydrology and cave drip discharge water response implications for speleothem paleoclimate record variability summary high frequency spatially dense discharge monitoring was conducted over fifteen months to characterise unsaturated zone flow at harrie wood cave hwc in the snowy mountains yarrangobilly se australia the cave was formed in the late silurian yarrangobilly limestone a fractured rock associated with very low primary porosity due to past diagenesis over our monitoring period we simultaneously measured rainfall soil moisture saturation and drip discharge rate at fourteen sites to characterise infiltration discharge relationships all drip discharge sites exhibited non gaussian distributions indicating long periods where low discharge predominates punctuated by short infrequent periods of high discharge however there was significant variability in discharge between sites and consequently no spatial correlation in the cave we investigated the depth discharge relationship at hwc and found a moderate relationship between depth and drip discharge lag response times to soil moisture content but only weak relationships between depth and mean and maximum discharge this highlights that the karst architecture plays an important role in controlling drip discharge dynamics principal component analysis pca and agglomerative hierarchal clustering ahc were used to classify similar drip types revealing five unique drip regimes two phase flow and non linear response to recharge behaviour were observed suggesting secondary porosity is controlling unsaturated zone flow in mature limestone environments with low primary porosity using the data presented here the first coupled conceptual and box hydrological flow model was developed this study highlights the heterogeneous nature of hydrological flow in karst and the need to understand unsaturated zone hydrology at the individual drip discharge level to inform speleothem studies for high resolution paleoclimate reconstruction

forcing of late cenozoic northern hemisphere climate by plateau uplift in southern asia and the american west geologic evidence indicates that net vertical uplift occurred on a large kilometer scale and at accelerating rates during the middle and late cenozoic in plateaus of southern asia and the american west based on this evidence general circulation model sensitivity tests were run to isolate the unique effects of plateau uplift on climate the experiments simulated significant climatic changes in many places some far from the uplifted regions the basic direction of most of these simulated responses to progressive uplift is borne out by changes found in the geologic record winter cooling of north america northern europe northern asia and the arctic ocean summer drying of the north american west coast the eurasian interior and the mediterranean winter drying of the north american northern plains and the interior of asia and changes over the north atlantic ocean conducive to increased formation of deep water the modeled changes result from increased orographic diversion of westerly winds from cyclonic and anticyclonic surface flow induced by summer heating and winter cooling of the uplifted plateaus and from the intensification of vertical circulation cells in the atmosphere caused by exchanges of mass between the summer heated and winter cooled plateaus and the mid latitude oceans disagreements between the geologic record and the model simulations in alaska and the southern rockies and plains may be related mainly to the lack of narrow mountain barriers in the model orography taken together the observed regional trends comprise much of the pattern of late cenozoic climatic deterioration in the northern hemisphere that culminated in the plio pleistocene ice ages the success of the uplift sensitivity experiment in simulating the correct pattern and sign of most of the observed regional climatic trends points to uplift as an important forcing function of late cenozoic climatic change in the northern hemisphere at time scales longer than orbital variations however the modest amplitude of the uplift induced cooling simulated at high latitudes indicates a probable need for additional climatic forcing

reply to discussion by kaya et al on swelling characteristics of bentonite in artificial seawater appears in canadian geotechnical journal 46 10 1236 1238 the authors are extremely grateful to drs kaya yukselenaksoy and oren for their valuable and constructive discussion we are aware that their discussion is as follows 1 it is known that calcium type bentonite has lower swelling potential than sodium type bentonite however the swelling pressure test results shown in fig 6 in komine et al 2009 contradict this 2 the authors of the discussion believe that the reported swelling pressures of bentonites are a coupled function of the water and montmorillonite content of bentonites for their evidence they show new figures by using the experimental data in komine et al 2009 thus from the presented data it is difficult to reach the conclusion that the influence of artificial seawater on the swelling characteristics of sodium type and artificial sodium type bentonites is low and the influence of artificial seawater on the swelling characteristics of calcium type bentonites is more slight than sodium type and artificial sodium type bentonites

infiltration of pb ii solution in compacted bentonite sand mixture under unconfined conditions compacted mixture of bentonite and sand has been proposed for using as buffer backfill material in the disposal of high level radioactive waste in many countries the hydraulic behaviors and deformation properties of this material can be influenced by the chemical composition of groundwater in the present work the infiltration test of pb ii solution was conducted on compacted gaomiaozi gmz bentonite sand mixture under unconfined conditions the moisture migration characteristics and swelling properties were analyzed results show that the moisture migrates more quickly in the gmz bentonite sand mixture infiltrated with pb ii solutions than that in the pure gmz bentonite hydrated with pure water for a same bentonite dry density this difference could be explained by the chemical influence of pb ii on the thickness of diffuse double layer for the bentonite sand mixture with high bentonite content its hydraulic conductivity depends on the bentonite dry density regardless of the influence of the sand content the hydration rate of the specimen is a function of the infiltration time and the distance from the wetting end the largest swelling deformation was observed at the wetting end at a given location the vertical displacement was larger than any unilateral one of both sides after the infiltration test the inductively coupled plasma emission spectrometer mercury intrusion porosimetry and environmental scanning electron microscope tests were conducted for investigation of the pb ii distribution and microstructural characteristics of the tested specimen results show that as the distance from the wetting end increases the pb ii content nonlinearly decreases from 4 48 to 0 07 mg g while the micro pore increases and the macro pore decreases

heat exchanges in the heterothermic zone of a karst system monlesi cave swiss jura mountains 1 subsurface ice accumulations in temperate karst environments are assumed to be highly sensitive to external climate forcing and therefore represent a favorable setting for studying processes controlling heat exchanges in the heterothermic zone of a karst system air rock water and ice temperatures were measured and complemented by airflow water discharge and cave air humidity data during a case study carried out between 2001 and 2006 at monlesi ice cave in the swiss jura mountains the energy balance of the system could be quantified for an annual cycle and results demonstrate that forced convection which is controlled by the temperature difference between the cave air and the external atmosphere is a driving force for the heat exchange between the cave and the surrounding environment therefore compared to the external mean annual conditions major thermal anomalies are to be expected in the entrance zone of a cave system since this heterothermic zone may extend over several hundreds of meters a better understanding of the mechanisms controlling the subsurface deposition environment represents a major prerequisite for high resolution paleoenvironmental reconstructions from cave deposits

isotope disequilibrium effects the influence of evaporation and ventilation effects on the carbon and oxygen isotope composition of speleothems a model approach abstract in order to improve the understanding of variations of speleothem 18o and 13c values in the context of palaeoclimate research it is important to quantify the isotope fractionation processes influencing the 18o and 13c values of stalagmites here we present an extended version of speleothem stable isotope model that accounts for evaporation and condensation effects during precipitation of calcite the isolution model allows to calculate the effect of evaporation on 18ocalcite and 13ccalcite values in dependence on relative humidity and wind velocity our results reveal that evaporation may have a significant effect on 18ocalcite and 13ccalcite due to the loss of h2o from the solution layer and the related increase of the ca2 concentration this leads to higher precipitation rates and consequently larger isotope fractionation effects the effect on speleothem 18ocalcite and 13ccalcite can be as high as changes caused by variations of temperature drip interval pco2 drip and pco2 cave furthermore the change of pco2 cave due to ventilation effects may also affect speleothem 18ocalcite and 13ccalcite values because of the effect of pco2 cave on the equilibrium concentrations of the co2 h2o caco3 system and thus the calcite precipitation rate the variability of other cave parameters temperature drip interval pco2 drip pco2 cave can have a comparable effect on 18ocalcite and 13ccalcite values depending on the magnitude of variability we validated the isolution model by modelling the 18ocalcite values from a cave analogue experiment and successfully reproduced the values for high temperatures

an extensive late cenozoic terrestrial record of multiple glaciations preserved in the tintina trench of west central yukon stratigraphy paleomagnetism paleosols and pollenthis is a companion paper to barendregt et al also in this issue geological survey of canada contribution 20100035 the tintina trench in west central yukon is a late miocene graben formed along the antecedent early tertiary tintina fault since its formation the trench has served as a sediment trap for alluvial and glacial deposits an extensive record of preglacial glacial and interglacial sediments spanning the late pliocene to late pleistocene has been preserved and is exposed today in modern landslide scars this sedimentary record comprises multiple sequences of tills outwash mudflows loess and paleosols the glacial sediments are the product of both local montane and regional cordilleran ice advances that channeled into the trench while loess and well developed paleosols brunisols and luvisols reflect nonglacial and interglacial conditions respectively the tintina trench exposures provide the most complete record of glaciations for the region paleomagnetism paleosols and palynology provide age constraints for the geological events a formal stratigraphic nomenclature is proposed for this region

40ar 39ar and k ar chronology of pleistocene glaciations in patagonia during the pleistocene east of lago buenos aires argentina at 46 5 s at least 19 terminal moraines were deposited as piedmont glaciers from the patagonian ice cap advanced onto the semi arid high plains adjacent to the southern andes exceptional preservation of these deposits offers a rare opportunity to document ice cap fluctuations during the last 1 2 m y 4 0 ar 3 9 ar incremental heating and unspiked k ar experiments on four basaltic lava flows interbedded with the moraines provide a chronologic framework for the entire glacial sequence the 4 0 ar 3 9 ar isochron ages of three lavas that overlie till 90 km east of the cordillera at lago buenos aires and another 120 km from the andes along rio gallegos at 51 8 s that underlies till strongly suggest that the ice cap reached its greatest eastward extent ca 1100 ka at least six moraines were deposited within the 256 k y period bracketed by basaltic eruptions at 1016 10 ka and 760 14 ka similarly six younger more proximal moraines were deposited during an 651 k y period bracketed by an underlying 760 14 ka basalt and the 109 3 ka cerro volcan basalt flow that buried all six moraines coupled with in situ cosmogenic surface exposure ages of moraine boulders the 109 ka age of cerro volcan implies that moraines deposited during the penultimate local glaciation correspond to marine oxygen isotope stage 6 further westward toward lago buenos aires six additional moraines younger than the cerro volcan basalt flow occur surface exposure dating of boulders on these moraines combined with the 1 4 c age of overlying varved lacustrine sediment indicates deposition during the last glacial maximum lgm 23 16 ka although antarctic dust records signal an important patagonian glaciation at 60 40 ka moraines corresponding to marine oxygen isotope stage 4 are not preserved at lago buenos aires apparently these were overrun and obliterated by the younger ice advance at 23 ka notwithstanding the overall pattern of glaciation in patagonia is one of diminishing eastward extent of ice during successive glacial advances over the past 1 m y we hypothesize that tectonically driven uplift of the patagonian andes which began in the pliocene yet continued into the quaternary in part due to subduction of the chile rise spreading center during the past 2 m y maximized the ice accumulation area and ice extent by 1 1 ma subsequent deep glacial erosion has reduced the accumulation area resulting in less extensive glaciers over time

pliocene near trench magmatism in southern chile a possible manifestation of ridge collision eight shallow level intrusions and an ophiolite complex have recently been discovered in a remote region along the pacific coast of southern chile known as the taitao peninsula the magmatic rocks are found only 10 to 15 km from the buried extension of the peru chile trench the ophiolite body includes serpentinized ultramaflc rocks gabbro dikes and an interbedded sequence of volcanic and marine sedimentary rocks more regionally distributed granodiorite plutons and porphyritic stocks and sills intrude pre late jurassic basement as well as tertiary marine sequences of the south american forearc k ar ages of 3 5 to 4 0 ma of the ophiolite and other intrusions suggest that these rocks represent a short lived pulse of pliocene magmatism directly seaward of the taitao peninsula a segment of the chile rise bounded by the tres monies and taitao fracture zones collided with the chilean forearc and was subducted about 2 5 to 4 0 ma because of this good spatial and temporal correlation the magmatic activity of the taitao peninsula is likely to be a direct result of ridge subduction

magnetic polarity and fission track chronology of a late pliocene pleistocene paleoclimatic proxy record in the tropical andes abstract two sections exposing a late pliocene pleistocene sedimentary sequence in the marginal valleys of the bogota basin colombian andes south america were sampled for paleomagnetic analysis magnetostratigraphy and fission track dates of tephra beds provide a detailed geochronologic calibration for the sedimentary basin measurements of magnetic susceptibility complement the regional environmental record provided by lithological and palynological evidence sedimentation in the bogota basin started in the early part of the gauss chron at ca 3 2 myr the oldest recorded sediments belong to the guasca member of the upper tilata formation they were deposited in a lacustrine paludal environment near the end of the tectonic uplift in the bogota area and or under pliocene climatic conditions that were warmer than today repeated climate cooling associated with glaciations in the surrounding mountains resulted in the deposition of a fluvial lacustrine complex referred to as the subachoque formation the first glaciation is placed near the gauss matuyama polarity reversal at 2 6 myr a lithologic change in the subachoque formation marked by coarser grained fluvial deposits and a possible increase in amplitude of the magnetic susceptibility signal occurs near the matuyama brunhes boundary at 0 8 myr indicating a shift toward higher magnitude climate oscillations

stress state permeability relationships for fine grained soils this technical note investigates the possibility that stress state permeability relationships might be developed for clays within the framework of generalisations already made in the analysis and prediction of soil behaviour consolidation and permeability tests carried out on red brown black cotton and bentonite soils chosen for their varying liquid limits are described the results are presented and interpreted for a given void ratio the experimental and predicted permeability coefficients showed a good correlation the interchangeability of stress state and permeability is discussed

seismic responses to ridge transform subduction chile triple junction the first local seismic network established in the remote region bordering the chile triple junction monitored earthquakes at a rate of three per day with magnitudes m 0 to m 4 far smaller than any recorded previously from that region focal mechanisms were obtained by the adaptation of the relative amplitude method to local earthquakes epicentral locations define a lineament corresponding to the active segment of a subducted transform fault and events corresponding to the predicted position of a subducted ridge show extensional mechanisms with the exclusion of thrusting and trench parallel mechanisms these data suggest that oceanic spreading and seismic activity continue in the subducted ridge transform system extension in the slab influences the overlying crust giving rise to dextral transtension over the past 10 m y the locus of ridge subduction has migrated northward we postulate that the pattern through time of extension and basin development in the overlying crust has mirrored this

spatial variability in cave drip water hydrochemistry implications for stalagmite paleoclimate records the identification of vadose zone hydrological pathways that most accurately transmit climate signals through karst aquifers to stalagmites is critical for accurately interpreting climate proxies contained within individual stalagmites a three year cave drip hydrochemical study across a spectrum of drip types in crag cave sw ireland reveals substantial variability in drip hydrochemical behaviour stalagmites fed by very slow drips 2 ml min sites apparently unconnected with local meteorological events water from these drips was typically undersaturated with respect to calcite and thus did not result in calcite deposition data presented here suggest that drips in this flow regime also experience flow re routing and blocking and that any stalagmites developed under such drips are unsuitable as mid to high resolution paleoclimate proxies most drip sites demonstrated seasonal ca2 and mg2 variability that was probably linked to water excess prior calcite precipitation along the flowpath affected the chemistry of slowly dripping sites while dilution predominantly controlled the water chemistry of the more rapidly dripping sites this research underscores the importance of understanding drip hydrology prior to selecting stalagmites for paleoclimate analysis and before interpreting any subsequent proxy data

atmospheric co2 decline during the pliocene intensification of northern hemisphere glaciations 1 several hypotheses have been put forward to explain the onset of intensive glaciations on greenland scandinavia and north america during the pliocene epoch between 3 6 and 2 7 million years ago ma a decrease in atmospheric co2 may have played a role during the onset of glaciations but other tectonic and oceanic events occurring at the same time may have played a part as well here we present detailed atmospheric co2 estimates from boron isotopes in planktic foraminifer shells spanning 4 6 2 0 ma maximal pliocene atmospheric co2 estimates gradually declined from values around 410 atm to early pleistocene values of 300 atm at 2 0 ma after the onset of large scale ice sheets in the northern hemisphere maximal pco2 estimates were still at 2 5 ma 90 atm higher than values characteristic of the early pleistocene interglacials by contrast pliocene minimal atmospheric co2 gradually decreased from 310 to 245 atm at 3 2 ma coinciding with the start of transient glaciations on greenland values characteristic of early pleistocene glacial atmospheric co2 of 200 atm were abruptly reached after 2 7 ma during the late pliocene transition this trend is consistent with the suggestion that ocean stratification and iron fertilization increased after 2 7 ma in the north pacific and southern ocean and may have led to increased glacial co2 storage in the oceanic abyss after 2 7 ma onward

hydraulic conductivity of bentonite sand mixtures the use of bentonite alone or amended with natural soils for construction of liners for water retention and waste containment facilities is very common the importance of bentonite content in reduc

can glacial erosion limit the extent of glaciation kaplan m r hein a s hubbard a 2009 can glacial erosion limit the extent of glaciation geomorphology 103 2 172 179

monitoring bunker cave nw germany a prerequisite to interpret geochemical proxy data of speleothems from this site summary monitoring cave environments is important to understand processes in karst systems if stalagmites from a specific cave are used as archives of past climate variability a quantitative understanding of the soil karst speleothem system is crucial the monitoring program performed in bunker cave nw germany which includes monthly collection of climatological data as well as air and water samples from the cave and the overlying soil since 2006 is a prerequisite for the interpretation of speleothem data from the cave in terms of climate variability the results show that bunker cave is a homogeneously ventilated cave with rather low pco2 values of 580 1200 ppmv which lacks strong seasonal variations the 18o value of cave drip water reflects the mean annual composition of the rain water and the seasonal variability is strongly attenuated indicating a well mixed karst aquifer hence stalagmites from bunker cave should be well suited to record interannual decadal climate trends seven drip sites in two cave chambers show three different types of discharge behaviour including slow seasonal drip fast seasonal drip and seepage flow the drip rate patterns of most drip sites are consistent with the main infiltration events taking into account a delay of several months an instantaneous response to precipitation i e piston flow is not observed for any drip site indicating a specific water capacity threshold in the soil karst aquifer prior calcite precipitation pcp was also identified especially during times of low discharge though pcp is not as pronounced at bunker cave as in other caves it probably has an influence on the mg ca ratios of the stalagmites

speleothem calcite farmed in situ modern calibration of δ18o and δ13c paleoclimate proxies in a continuously monitored natural cave system abstract understanding the relationships between speleothem stable isotopes 13 c 18 o and in situ cave forcing mechanisms is important to interpreting ancient stalagmite paleoclimate records cave studies have demonstrated that the 18 o of inorganically precipitated low temperature speleothem calcite is systematically heavier than the 18 o of laboratory grown calcite for a given temperature to understand this apparent offset rainwater cave drip water groundwater and modern naturally precipitated calcite farmed in situ were grown at multiple locations inside hollow ridge cave in marianna florida high resolution micrometeorological air chemistry time series and ventilation regimes were also monitored continuously at two locations inside the cave supplemented with periodic bi monthly air gas grab sample transects throughout the cave cave air chemistry and isotope monitoring reveal density driven airflow pathways through hollow ridge cave at velocities of up to 1 2 m s 1 in winter and 0 4 m s 1 in summer hollow ridge cave displays a strong ventilation gradient in the front of the cave near the entrances resulting in cave air that is a mixture of soil gas and atmospheric co 2 a clear relationship is found between calcite 13 c and cave air ventilation rates estimated by proxies pco 2 and 222 rn calcite 13 c decreased linearly with distance from the front entrance to the interior of the cave during all seasons with a maximum entrance to interior gradient of 13 c caco3 7 a whole cave hendy test at multiple contemporaneous farming sites reveals that ventilation induces a 1 9 0 96 13 c offset between calcite precipitated in a ventilation flow path and calcite precipitated on the edge or out of flow paths this interpretation of the hendy test has implications for interpreting 13 c records in ancient speleothems calcite 13 c caco3 may be a proxy not only for atmospheric co 2 or overlying vegetation shifts but also for changes in cave ventilation due to dissolution fissures and ceiling collapse creating and plugging ventilation windows farmed calcite 18 o was found to exhibit a 0 82 0 24 offset from values predicted by both theoretical calculations and laboratory grown inorganic calcite unlike 13 c caco3 oxygen isotopes showed no ventilation effects i e 18 o caco3 appears to be a function of growth temperature only although we cannot rule out a small effect of unmeasured gradients in relative humidity evaporation accompanying ventilation our results support the findings of other cave investigators that water calcite fractionation factors observed in speleothem calcite are higher that those measured in laboratory experiments cave and laboratory calcite precipitates may differ mainly in the complex effects of kinetic isotope fractionation combining our data with other recent speleothem studies we find a new empirical relationship for cave specific water calcite oxygen isotope fractionation across a range of temperatures and cave environments 1000 ln 16 1 10 3 t 1 24 6 with a fractionation temperature dependence of 18 o t 0 177 c lower than the currently accepted 0 206 c

the upper cenozoic white river tillites of southern alaska subaerial slope and fan delta deposits in a strike slip setting the white river tillites crop out over 8 km 2 either side of the totschunda fault in the northern foothills of the wrangell mountains in southern alaska and record glacially influenced slope and fan delta deposition in a high relief basin close to an active volcano between 10 and 2 7 ma two measured sections 1 200 and 450 m thick show diamictite and conglomerates interbedded with augite andesite lavas facies range from massive diamictites deposited subaerially as debris flows to crudely stratified sandstones and conglomerates formed by sheet flow processes on alluvial fans and well stratified and normally graded sandstones and conglomerates that accumulated subaqueously as turbidites large scale southward dipping foresets as much as 17 m high identify a fan delta that prograded into a temporary lake the white river succession is identified as a valley infill complex consisting of subaerial slope and lacustrine fan delta deposits there are no in situ primary glacial deposits present in the succession the glacial component of sedimentation was limited to the supply of coarse grained debris identified by the presence of glacially striated and faceted clasts the white river deposits may be typical of glacial sequences preserved as isolated local basin fills in high relief areas such as occur in convergent or strike slip plate margin settings they provide only a limited and fragmentary record of paleoenvironmental changes compared to coeval glacially influenced marine rocks preserved in the yakataga formation 5 km thick along the gulf of alaska coast

glacial interglacial history of the skaftafell region southeast iceland 0 5 ma volcanic strata in the skaftafell region southeast iceland record a sequence of at least 16 glacial and interglacial intervals since 5 ma two composite sections of 2 to 2 8 km thickness have been constructed from multiple overlapping cliff profiles the timing of alternating sequences of subaerial lava flows pillow basalts and hyaloclastite deposits is provided by magnetostratigraphic mapping and k ar radiometric dating we find that the frequency and intensity of glaciations increased significantly at ca 2 6 ma and particularly since 0 8 ma amplifying topographic relief in this area from

hydraulic conductivity and compressibility of mixtures of nagoya clay with sand or bentonite in this study a series of incremental loading oedometer tests and microscopic observations is carried out in order to investigate the influence of sand bentonite fractions on hydraulic conductivity and compressibility if sand particles do not form a skeletal structure and each particle is independent in the clay matrix an additive fraction of sand causes a decrease in the compressibility however it does not affect the hydraulic conductivity under the same consolidation pressure the additive fraction of bentonite contributes to a decrease in the hydraulic conductivity even for clayey materials in addition the relationship between the pore size parameter which represents the pore entrance size distribution and the hydraulic conductivity is discussed using a probabilistic model known as the general capillary model

a latest pliocene age for the earliest and most extensive cordilleran ice sheet in northwestern canada abstract the klondike gravel is a widespread glaciofluvial gravel marking the earliest and most extensive cordilleran ice sheet cis in nw north america new terrestrial cosmogenic nuclide tcn burial ages indicate this gravel was emplaced 2 64 0 20 0 18 ma 1 coupled with previously interpreted paleomagnetic stratigraphy this numerical age constrains the timing of the earliest cis to the late gauss chron and provides a minimum age for the upper white channel gravel a significant placer gold source in the yukon this implies the first cis glacial maximum pre dates the maximum extent of the laurentide ice sheet indicating that during the initial stages of northern hemisphere glaciation the most extensive glaciers were present in the relatively cold and high elevation northern cordillera our results verify the cis as a likely source of persistent coeval ice rafted debris in the northern pacific and suggest that the first cis formed as a response to the establishment of the northern pacific halocline and emergence of the 41 ka obliquity cycle during the plio pliocene transition

paleomagnetic evidence for multiple late cenozoic glaciations in the tintina trench west central yukon canadathis article is a companion paper to duk rodkin et al also in this issue the tintina trench in west central yukon has preserved an extensive record of late cenozoic preglacial glacial and interglacial deposits these deposits comprise multiple sequences of tills outwash loesses and paleosols the sediments that were laid down directly by ice tills are of both local montane and regional cordilleran provenance the tintina trench area was impacted repeatedly by montane ice from the southern ogilvie mountains to the northwest 2500 m above sea level asl and also repeatedly along its southern extent by cordilleran ice from the selwyn mountains to the east 2759 m asl the latter forming the continental divide in this region we report here the magnetostratigraphy of three sections rock creek 64 13 n 139 07 w west fifteenmile river 64 29 n 139 55 w and east fifteenmile river 64 23 n 139 48 w the majority of the units identified at these sections record late pliocene to mid pleistocene glaciations although relatively thin surficial sequences of late mid

late pleistocene holocene sea level rise and the pattern of coastal karst inundation records from submerged speleothems along the eastern adriatic coast croatia in order to reconstruct the late pleistocene holocene sea level rise along the eastern adriatic coast eight speleothems were collected from three submerged caves along the croatian coast from depths of 38 5 to 17 m the marine biogenic overgrowth layer and the youngest and the oldest parts of the speleothems were dated by the 14c method their stable isotope 13c 12c and 18o 16o contents were also measured from the measured 14c activity of the marine overgrowth and using the model of alessio et al 1992 risultati preliminari relativi alla datazione di speleotemi sommersi nelle fasce costiere del tirreno centrale giornale di geologia ser 3 54 2 165 193 the start of overgrowth i e the time of flooding by seawater was determined to be 10 185 cal bp at 36 m 9160 cal bp at 34 m and 7920 cal bp at 23 m our results partially match the sea level curves reconstructed for adjacent areas tyrrhenian coast and french mediterranean coast however the start of the marine overgrowth on speleothems in pit caves indicates strong dependence on the steepness of the terrain on steep extensively karstified coasts marine overgrowths on speleothems coincided with the submersion of the speleothems due to the relatively short distance between the pit and the open sea and fast penetration of seawater into the pit in contrast marine overgrowths on speleothems in pits in the flat terrains occurred later because speleothem growth ceased due to flooding with fresh groundwater later the fresh water was replaced by seawater due to the greater distance of the inland pits to the former coast

a 53 year seasonally resolved oxygen and carbon isotope record from a modern gibraltar speleothem reconstructed drip water and relationship to local precipitation abstract the response of a climate proxy against measured temperature rainfall and atmospheric circulation patterns at sub annual resolution is the ultimate test of proxy fidelity but very few data exist showing the level of correspondence between speleothem climate proxies and the instrumental climate record cave sites on the gibraltar peninsula provide a unique opportunity to calibrate speleothem climate proxies with the longest known available precipitation isotopes and instrumental records an actively growing speleothem sampled from new st michaels cave in 2004 is composed of paired laminae consisting of light columnar calcite and a darker microsparitic calcite stable isotope analysis of samples micromilled in 100 m steps at the equivalent of bi monthly intervals reveals fabric correlated annual cycles in carbon isotopes oxygen isotopes and trace elements responding to seasonal changes in cave microclimate hydrology and ventilation patterns calcite 13 c values reach a minimum in the light columnar fabric and evidence from trace element behaviour and cave monitoring indicates that this grows under cave winter conditions of highest p co 2 whereas the dark microsparitic calcite characterised by elevated 13 c and 18 o values grows under low summer p co 2 conditions drip water 13 c dic reaches a minimum in march april at which time the attenuated 18 o signal becomes most representative of winter precipitation an age model based on cycle counting and the position of the 14 c bomb carbon spike yields a precisely dated winter oxygen isotope proxy of cave seepage water for comparison with the gnip and instrumental climate record for gibraltar the 18 o characteristics of calcite deposited from drip water representing winter precipitation for each year can be derived from the seasonally resolved record and allows reconstruction of the 18 o drip water representing winter precipitation for each year from 1951 2004 these data show an encouraging level of correspondence r 2 0 47 with the 18 o of rainfall falling each year between october and march and on a decadal scale the 18 o of reconstructed winter drip water mirrors secular change in mean winter temperatures

climate controls on rainfall isotopes and their effects on cave drip water and speleothem growth the case of molinos cave teruel ne spain the interpretation of stable isotopes in speleothems in terms of past temperature variability or precipitation rates requires a comprehensive understanding of the climatic factors and processes that influence the 18o signal in the way through the atmosphere to the cave where carbonate precipitates acquiring its final isotopic composition this study presents for the first time in the iberia peninsula an integrated analysis of the isotopic composition of rainfall 18op during 2010 2012 years and through a detailed monitoring survey the transference of the primary isotopic signal throughout the soil and epikarst into the molinos cave teruel ne spain both air temperature and amount of precipitation have an important effect on 18op values clearly imprinting a seasonal variability modulated by an amount effect when rainfall events are more frequent or intense air mass history and atmospheric circulation influences are considered through the study of weather types synoptic scale climate patterns and large scale atmospheric circulation indexes north atlantic oscillation and western mediterranean oscillation revealing a dominant source effect on 18op values in this region where tropical north atlantic and western mediterranean are the two moisture source regions a delay of 2 3 months occurs between the dripwater oxygen isotopic composition 18od respect to 18op values as a consequence of large residence time in the epikarst limited calcite precipitates are found from winter to spring when 18od values are less negative and dripwater rates are constant this study suggests that ne iberian 18ocalcite proxy records are best interpreted as reflecting a combination of parameters not just paleotemperature or paleorainfall and if extending present day situation towards the recent past a biased signal towards winter values should be expected in molinos speleothem records

seasonal isotopic imprint in moonmilk from caverne de l ours quebec canada implications for climatic reconstruction moonmilk which is often seen coating walls in temperate caves is a porous secondary calcite deposit com posed of an aggregate of microcrystalline calcite and water this study based on moonmilk deposits found in caverne de l ours ottawa valley region proposes a model for its formation based on the calcite and water isotope chemistry and evaluates its use as a climatic proxy in caverne de l ours non calcitic mineral inclusions protrude from the bed rock grenville marble into the moonmilk while others are entirely enclosed within the moonmilk this observation suggests a mechanism of bedrock dissolution and reprecipitation for the formation of moonmilk which is controlled by the changing seasonal climate in the cave the 18 o of the moonmilk interstial water indicates that the condensation of water vapour occurs mostly in winter and spring the condensation of water vapour on the surface of the walls allows for the dissolution of the grenville marble and releases ions necessary for the precipitation of moonmilk the 18 o and 13 c of calcite and 18 o of the moonmilk interstitial water indicate that precipitation of moonmilk occurs during sum mer and fall during these seasons the relative humidity in the cave decreases resulting in moonmilk growth through the slow evaporation of calcite saturated water a comparison of the 18 o record of moonmilk from caves in gaspesie canada and from aven d orgnac france shows that this material retains temperature information valuable for paleoclimatic reconstructions

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

cenozoic glaciation in the southern hemisphere with the end of glaciation in gondwana in early permian time a prolonged interval began when the earth was without ice sheets though not necessarily free of mountain glaciers not until sometime during the tertiary era did ice sheets build up once more first in antarctica and later in the northern hemisphere the fundamental cause of the cooling that led to the formation of the antarctic ice sheet and eventually to major glaciation in lower latitudes is generally held to have been the increasing thermal isolation of antarctica as australia and later south america separated from it allowing zonal oceanic circulation to develop rifting between australia and antarctica began between 1 10 and 90 m y ago cande mutter 1982 but not until much later probably sometime between 30 and 25 m y ago had it progressed far enough for deep circulation to begin as the south tasman rise cleared north victoria land kennett et a1 1974 kennett 1977 weissel et ai 1977 however antarctica did not reach its present high level of thermal isolation until south america had separated from it enabling the antarctic circumpolar current to become established savin et ai 1975 according to barker burrell 1977 1982 coherent spreading between the antarctic peninsula and tierra del fuego started about 29 m y ago and deep circulation began 23 5 2 5 m y ago thereafter increasing in volume the initial ice fields and ice caps that later expanded to become the

hydrology of cave drip waters at varying bedrock depths from a karst system in southeastern australia the study of how cave drip water discharge responds to recharge events is fundamental to evaluating the potential of actively forming speleothems as high resolution climate archives most previous research has focused on caves of the northern hemisphere middle latitudes where recharge is strongly seasonal few studies have explored drip water behaviour from regions where the expected seasonal rainfall pattern is significantly perturbed on an irregular basis by changing regional atmospheric circulation patterns here we report the results of a 4 year study of cave drip water climate relationships from two caves in eastern australia the discharge of 10 drip sites located beneath bedrock thicknesses of 12 22 and 45 m was monitored either continuously using automated infrared sensors or at discrete approximately monthly intervals and compared with local rainfall and water balance data the study period traversed two major droughts including the severe 2002 2003 el nino drips at 12 and 22 m depths responded almost simultaneously to individual recharge events although the time lag between individual events varied according to the volume of recharge and pre event storage overall a steady decline in discharge is evident through the moisture deficit period with increased flows through phases of positive water balance speleothems growing at these and similar shallow chamber sites have potential for reconstructing palaeo rainfall trends at high resolution although the highly variable nature of year to year recharge would make it difficult to obtain data on a calendrical time scale drips at 45 m depth did not respond consistently to individual recharge events and displayed hydrological behaviour markedly dissimilar to one another and to the near surface drip sites indicating great complexity in karst architecture and the absence of fissure flow although speleothems at this depth may well preserve information on longer term rainfall trends their potential to encode a palaeo rainfall variability signal at interannual resolution is poor copyright 2007 john wiley sons ltd

neogene patagonian plateau lavas continental magmas associated with ridge collision at the chile triple junction extensive neogene patagonian plateau lavas 46 5 to 49 5 s southeast of the modern chile triple junction can be related to opening of asthenospheric slab windows associated with collisions of chile rise segments with the chile trench at 12 ma and 6 ma support comes from 26 new total fusion whole rock 40ar 39ar ages and geochemical data from back arc plateau lavas in most localities plateau lava sequences consist of voluminous tholeiitic main plateau flows overlain by less voluminous 2 to 5 million year younger alkalic postplateau flows northeast of where the ridge collided at 12 ma most lavas are syncollisional or postcollisional in age with eruptions of both sequences migrating northeastward at 50 to 70 km ma plateau lavas have ages from 12 to 7 ma in the western back arc and from 5 to 2 ma farther to the northeast trace element and isotopic data indicate main plateau lavas formed as larger percentage melts of a garnet bearing oceanic island basalt oib like mantle than postplateau lavas the highest percentage melts erupted in the western and central plateaus in a migrating slab window model main plateau lavas can be explained as melts that formed as upwelling subslab asthenosphere which flowed around the trailing edge of the descending nazca plate and then interacted with subduction altered asthenospheric wedge and continental lithosphere alkaline postplateau lavas can be explained as melts generated by weaker upwelling of subslab asthenosphere through the open slab window thermal problems of high pressure melt generation of anhydrous mantle can be explained by volatiles h2o and co2 introduced by the subduction process into slab window source region s an oib like rather than a mid ocean ridge basalt morb like source region and the lack of magmatism northeast of where ridge collision occurred at 13 to 14 ma can be explained by entrainment of weak plume s or regional variations in an ambient oib like asthenosphere

hydrological uncertainties in the modelling of cave drip water δ18o and the implications for stalagmite palaeoclimate reconstructions abstract in this paper we review our current understanding of karst drip water hydrology emphasising the extent of non linear and non stationary process dynamics that render stalagmite palaeoclimate reconstructions using a statistical pseudo proxy approach difficult to implement we outline an approach to attribute the uncertainty that arises specifically as a consequence of variable water routing through the overlying soil epikarst and karst aquifer this is based upon the development of a monthly lumped parameter karst hydrological model which we use to demonstrate the range of modelled drip water discharges possible from a single climate input refinement of the model to include precipitation 18 o enables us to determine the theoretical range in drip water and stalagmite 18 o for three sites with contrasting climates northern temperate nw scotland monsoonal ethiopia and mediterranean gibraltar for actual climate monthly mean temperature monthly total precipitation monthly mean precipitation 18 o we compare model simulations of karst groundwater storage and drip water 18 o to demonstrate our ability to model different climate regimes realistically we also investigate the 18 o variability associated with specific karst water reservoirs that differ in their capacity and drainage mechanisms 18 o variability is then compared to stalagmite 18 o record from the three regions for the last 45 years we conclude by reviewing the implications of our hydrological model for stalagmite 18 o quaternary palaeoclimate reconstructions over different timescales and sampling resolutions

constraints on hydrological and paleotemperature variations in the eastern mediterranean region in the last 140 ka given by the δd values of speleothem fluid inclusions abstract speleothem fluid inclusions potentially provide vital data on the paleohydrological conditions in glacial and interglacial periods we show here that d analyses of fluid inclusions from speleothems in three caves in the eastern mediterranean region israel provide a basis for understanding hydrological and temperature variations in the last 140 ka using measured d fluid inclusion values and temperature ranges constrained by the present day mediterranean meteoric water line mmwl and the global mwl we show a strong compatibility between the land and marine temperature records with the highest land temperatures occurring at 120 130 ka 17 22 c and the present 18 c and the lowest temperatures during the lgm about 10 c lower than present interglacial waters are constrained to follow the mmwl and most glacial waters also plot close to the mmwl with a slight shift towards the mwl however during two remarkable brief periods at the termination of the lgm the waters plot on the mwl suggesting that both sharp cooling and an increase in relative humidity above the em sea reduced d excess values to those of the global system

sea level change during mis 5a based on submerged speleothems from the eastern adriatic sea croatia abstract two stalagmites were collected from below sea level in u vode pit on the krk island eastern adriatic sea at elevations of 14 5 and 18 8 m they exhibit a growth history indicating a double high sea level stand during marine isotope stage mis 5a 87 77 ka thin layers of halite and gypsum were found to be associated with hiatuses in speleothem growth probably caused by seawater inundation during sea level highstands these mineral deposits are likely to have been precipitated during marine regression phases under evaporitic conditions we constrain the age of the speleothem growth below and above growth hiatuses and hence timing of possible marine incursions using multi collector inductively coupled plasma mass spectrometry mc icpms u th techniques age estimates indicate that during mis 5a relative sea level elevations were greater than 14 5 m from 87 to 82 ka and 18 8 m from 77 to 64 ka and constrained to be lower than 18 8 m from 93 to 90 ka 82 to 77 ka and 64 to 54 ka assuming no tectonic adjustment however present speleothem depths could indicate long term regional tectonics

origin and type of rainfall for recharge of a karstic aquifer in the western mediterranean a case study from the sierra de gador campo de dalias southeast spain isotope signatures in precipitation from the global network for isotopes in precipitation around the mediterranean basin and literature data are compared with isotopic data from a large karstic aquifer in southeast spain to explain the origin and type of the precipitation events dominating recharge analysis of the deuterium excess d at the scale of the mediterranean basin and at the regional scale allows us to understand the isotopic context of the study area campo de dalias and the sierra de gador almerfa province the origin of precipitation can be determined from its d value the d value changes as a function of the initial evaporation condition it depends on the relative humidity and temperature during the evaporation producing the water vapour of the clouds the water vapour which dominates the study area is generated in two areas the atlantic ocean d 10 parts per thousand and the western mediterranean basin d 15 parts per thousand with increasing precipitation volume the western mediterranean character dominates these heavier storms contribute mainly to recharge as illustrated by the d value of 13 6 parts per thousand in deep groundwater of the campo de dalias weighted d values increase with the volume of precipitation giving a significant relationship for the southern and eastern coasts of the iberian peninsula this selectivity of d to monthly precipitation was used to estimate the return period of precipitation leading to aquifer recharge at 0 9 4 9 years moderate rainfall which occurs more frequently still represents similar to 60 90 of the total precipitation one of the challenges to meet ever growing water demands is to increase recharge from moderate events yielding intermediate quantities per event but forming the bulk of the annual precipitation copyright c 2006 john wiley sons ltd

decadal scale rainfall variability in ethiopia recorded in an annually laminated holocene age stalagmite an annually laminated uranium series dated holocene stalagmite from southeast ethiopia has been analysed for growth rate and 13c and 18o variations at annual to biennial resolution in order to provide the first long duration proxy record of decadal scale rainfall variability in this climatically sensitive region our study site 10 n is climatically influenced by both summer june august and spring march may rainfall caused by the annual movement of the inter tropical convergence zone itcz and modulated by large scale anomalies in the atmospheric circulation and in ocean temperatures here we show that stalagmite growth episodic throughout the last 7800 years demonstrates decadal scale 8 25 yr variability in both growth rate and 18o a hydrological model was employed and indicates that this decadal variability is due to variations in the relative amounts of rainfall in the two rain seasons our record unique in its combination of length a total of 1000 years annual chronology and high resolution 18o shows for the first time that such decadal scale variability in rainfall in this region has occurred through the holocene which implies persistent decadal scale variability for the large scale atmospheric and oceanic driving factors

response of a modern cave system to large seasonal precipitation variability abstract speleothems are capable of providing information on the response of middle and low latitude terrestrial environments to global climate change during the pleistocene and holocene multiproxy speleothem studies however have demonstrated that complex interactions can occur in cave settings between processes that are directly and indirectly related to climate change thorough and extended monitoring of modern cave environments is necessary in order to fully understand how each cave responds to these processes on seasonal and interannual timescales and how environmental signals are preserved in speleothem carbonate regular environmental monitoring began at black chasm cavern in the sierra nevada foothills california during the winter of 2006 2007 monthly measurements of cave air temperature humidity and p co 2 in black chasm demonstrate that the cave is ventilated in the winter months when cold dense surface air sinks into the cave cave drip water flow nearly ceases during the late summer and autumn increases substantially during the winter and spring and responds within hours to storm events during the height of the rainy season rainwater and drip water 18 o and 2 h are controlled by variations in surface air temperature and moisture source while rainfall source influences rainwater isotopes through individual storm events it has less influence on drip water isotopic composition due to mixing of recharge waters delivered by different rainfall events in the epikarst variations in drip water chemistry 13 c mg ca and sr ca indicate that the greatest level of calcite precipitation upflow from the drip water collection site prior calcite precipitation occurs during the autumn october november when drip rates are slow and cave air p co 2 is low the least prior calcite precipitation occurs during the summer july august when drip rates are slow but cave air p co 2 is at a maximum while p co 2 is a primary control on prior calcite precipitation during all seasons the predominant influence of drip rate variability on prior calcite precipitation is evident when considering only those seasons winter spring and autumn characterized by low cave air p co 2 thus drip rate variability and in turn rainfall amount should provide the primary control on trace element variations ultimately captured in speleothem calcite the isotopic and chemical variability observed in black chasm drip waters supports previous interpretations of speleothem paleoclimate proxy records from a nearby cave where such monitoring is not feasible observations of the modern cave environment at black chasm provide a reference point for the interpretation of stalagmite proxy records from similar seasonal mediterranean climates

climatic and environmental controls on speleothem oxygen isotope values variations in speleothem oxygen isotope values d 18 o result from a complicated interplay of environmental controls and processes in the ocean atmosphere soil zone epikarst and cave system as such the controls on speleothem d 18 o values are extremely complex an understanding of the processes that control equilibrium and kinetic fractionation of oxygen isotopes in water and carbonate species is essential for the proper interpretation of speleothem d 18 o as paleoclimate and paleoenvironmental proxies and is best complemented by study of site specific cave processes such as infiltration flow routing drip seasonality and saturation state and cave microclimate among others this review is a process based summary of the multiple controls on d 18 o in the atmosphere soil epikarst and speleothem calcite illustrated with case studies primary controls of d 18 o in the atmosphere include temperature and relative humidity through their role in the multiple isotope effects variability and modifications of water d 18 o values in the soil and epikarst zones are dominated by evaporation mixing and infiltration of source waters the isotopically effective recharge into a cave system consists of those waters that participate in precipitation of caco3 resulting in calcite deposition rates which may be biased to time periods with optimal dripwater saturation state recent modeling experimental and observational data yield insight into the significance of kinetic fractionation between dissolved carbonate phases and solid caco3 and have implications for the hendy test to assist interpretation of speleothem d 18 o time series quantitative and semi quantitative d 18 o climate calibrations are discussed with an emphasis on some of the difficulties inherent in using modern spatial and temporal isotope gradients to interpret speleothems as paleoclimate proxy records finally several case studies of globally significant speleothem paleoclimate records are discussed that show the utility of d 18 o to reconstruct past climate

stable isotope variations in modern tropical speleothems evaluating equilibrium vs kinetic isotope effects applications of speleothem calcite geochemistry in climate change studies require the evaluation of the accuracy and sensitivity of speleothem proxies to correctly infer paleoclimatic information the present study of harrison s cave barbados uses the analysis of the modern climatology and groundwater system to evaluate controls on the c and o isotopic composition of modern speleothems this new approach directly compares the 18 o and 13 c values of modern speleothems with the values for their corresponding drip waters in order to assess the degree to which isotopic equilibrium is achieved during calcite precipitation if modern speleothems can be demonstrated to precipitate in isotopic equilibrium then ancient speleothems suitable for paleoclimatic studies from the same cave environment may also have been precipitated in isotopic equilib rium if modern speleothems are precipitated out of isotopic equilibrium then the magnitude and direction of the c and o isotopic offsets may allow specific kinetic and or equilibrium isotopic fractionation mechanisms to be identified carbon isotope values for the majority of modern speleothem samples from harrison s cave fall within the range of equilibrium values predicted from the combined use of 1 calcite water fractionation factors from the literature 2 measured temperatures and 3 measured 13 c values of the dissolved inorganic carbon of drip waters calcite samples range from 0 8 higher to 1 1 lower than predicted values the 13 c depletions are likely caused by kinetically driven departures in the fractionation between hco3 aq and caco3 from equilibrium conditions caused by rapid calcite growth 13 c enrichments can be accounted for by rayleigh distillation of the hco3 aq reservoir during degassing of 13 c depleted co2 modern speleothems from harrison s cave are not in o isotopic equilibrium with their corresponding drip waters and are 0 2 to 2 3 enriched in 18 o relative to equilibrium values 18 o variations in modern calcite are likely controlled by kinetically driven changes in the fractionation between hco3 aq and caco3 from equilibrium conditions to nonequilibrium conditions consistent with rapid calcite growth in contrast to 13 c 18 o values of modern calcite may not be affected by rayleigh distillation during degassing because co2 hydration and hydroxylation reactions will buffer the o isotopic composition of the hco3 aq reservoir if the effects of rayleigh distillation manifest themselves in the o isotopic system they will result in 18 o enrichment in the hco3

an alternative suggestion for the pliocene onset of major northern hemisphere glaciation based on the geochemical provenance of north atlantic ocean ice rafted debris abstract the onset of abundant ice rafted debris ird deposition in the nordic seas and subpolar north atlantic ocean 2 72 millions of years ago ma is thought to record the pliocene onset of major northern hemisphere glaciation nhg due to a synchronous advance of north american laurentide scandinavian and greenland ice sheets to their marine calving margins during marine isotope stage mis g6 numerous marine and terrestrial records from the nordic seas region indicate that extensive ice sheets on greenland and scandinavia increased ird inputs to these seas from 2 72 ma the timing of ice sheet expansion on north america as tracked by ird deposition in the subpolar north atlantic ocean however is less clear because both europe and north america are potential sources for icebergs in this region moreover cosmogenic dating of terrestrial tills on north america indicate that the laurentide ice sheet did not extend to 39 n until 2 4 0 14 ma at least 180 ka after the onset of major ird deposition at 2 72 ma to address this problem we present the first detailed analysis of the geochemical provenance of individual sand sized ird deposited in the subpolar north atlantic ocean between mis g6 and 100 2 72 2 52 ma ird provenance is assessed using laser ablation lead pb isotope analyses of single ice rafted 150 m feldspar grains to track when an ice rafting setting consistent with major nhg first occurred in the north atlantic ocean during the pliocene intensification of nhg inhg we investigate when the pb isotope composition 206pb 204pb 207pb 204pb 208pb 204pb of feldspars deposited at dsdp site 611 first resembles that determined for ird deposited at this site during mis 100 2 52 ma the oldest glacial for which there exists convincing evidence for widespread glaciation of north america whilst quaternary magnitude ird fluxes exist at site 611 during glacials from 2 72 ma we find that the provenance of this ird is not constant instead we find that the pb isotope composition of ird at our study site is not consistent with major nhg until mis g2 2 64 ma we hypothesise that ird deposition in the north atlantic ocean prior to mis g2 was dominated by iceberg calving from greenland and scandinavia we further suggest that the grounding line of continental ice on northeast america may not have extended onto the continental shelf and calved significant numbers of icebergs to the north atlantic ocean during glacials until 2 64 ma

workability compressibility and hydraulic conductivity of zeolite amended clayey soil calcium bentonite backfills for slurry trench cutoff walls soil bentonite slurry trench cutoff walls using backfill consisting of on site sandy soil and na bentonite are extensively used as engineering barriers for the purpose of achieving relatively low hydraulic conductivity the amendments such as zeolite to backfill are considered to improve the contaminant sorptive capacity at some sites local clayey soil ca bentonite and natural zeolite may be available for an alternate backfill however studies on the workability in terms of slump compressibility and hydraulic conductivity of such zeolite amended clayey soil ca bentonite backfills for the cutoff walls are very limited this paper presents a comprehensive laboratory investigation on the workability compressibility and hydraulic conductivity of fine grained zeolite amended clayey soil ca bentonite backfills using several series of slump and oedometer tests kaolin is used as the model clayey soil and it is amended with various amounts of ca bentonite 7 8 8 4 and zeolite 10 40 to prepare zeolite amended kaolin bentonite backfills the test results are compared with previous studies on zeolite amended sandy soil na bentonite backfills as well as compacted zeolite bentonite liners to assess the effects of zeolite content and zeolite grain size on the compressibility and hydraulic conductivity the results indicate that the water content required to achieve a target slump 100 150 mm for the backfills increases with increasing zeolite content liquid limit can be a useful index for a preliminary estimation of the water content required to achieve the target slump for the backfills presented in this study and zeolite amended sandy soil na bentonite backfills reported in previous studies the results reveal that the hydraulic conductivity of the zeolite amended clayey soil ca bentonite backfills with void ratio ranging from 0 54 to 1 45 is generally lower than the typical regulatory limit 10 9 m s the addition of fine grained zeolite has insignificant influence on the compressibility and hydraulic conductivity of both clayey soil ca bentonite and sandy soil na bentonite backfills a proposed empirical method based on the framework of kozeny carman equation can predict the hydraulic conductivity of zeolite amended clayey soil ca bentonite backfills values within the range of 1 3 to 3 times those calculated from the oedometer tests the proposed method is also shown to estimate the hydraulic conductivity of the compacted zeolite bentonite liners from previous studies with reasonable accuracy additional research is recommended to evaluate the proposed zeolite amended backfill using tap water and also by direct measurement of hydraulic conductivity using falling head or constant head testing method

monitoring of selected caves as a prerequisite for the speleothem based reconstruction of the quaternary environment in croatia abstract quaternary palaeo environmental changes that have taken place in croatia are likely to be recorded in speleothems secondary carbonate deposits precipitated in caves confident interpretation of well dated speleothem proxy records relies on modern monitoring programs which we provided in three regionally different caves parallel monitoring of the surface and cave air temperature and relative humidity precipitation and cave drip intensity as well as stable isotope modification of meteoric and drip water was carried out in order to estimate the most reliable stalagmites for the interpretation of quaternary landscape history in all three caves nova grgosova 239 m a s l t cave 11 2 c in central croatia lokvarka 780 m a s l t cave 7 5 c in the mountainous part of croatia and modric 32 m a s l t cave 16 6 c in coastal croatia we selected the parts of the caves where the ambient cave conditions appeared to be appropriate for equilibrium deposition of calcite in terms of constant air temperature seasonal amplitudes of 0 73 0 38 and 0 45 c respectively and relative humidity 100 both atlantic and mediterranean moisture influences were detected in all three caves but of different intensities cave hydrological settings governed by karst aquifer properties were resolved by the comparison of the precipitation intensities and drip site responses to the rain events and generally seasonal rainwater isotopic signal was almost completely attenuated except for one drip site such homogenized drip water and stable cave environmental settings give confidence for calcite deposition under equilibrium conditions especially for modric and nova grgosova caves where speleothems inner structures also look promising for potentially quality dating results and stable isotopic profiles the fracture flow drip regime of selected drip sites in lokvarka cave and uncompleted homogenization of the water in the epikarst might point to speleothem samples that are unsuitable for resolving multi annual quaternary climate changes this view is supported by the high porosity internal structure of some lokvarka speleothems so further monitoring sampling and the thorough speleothem examination is therefore necessary for adequate interpretations of palaeo environmental changes

stable isotope study of cave percolation waters in subtropical brazil implications for paleoclimate inferences from speleothems we analyze the interannual monthly variability of oxygen isotope ratios in data from iaea stations along the atlantic coast of south america between 238 and 348 s to evaluate the influence of parameters such as temperature rainfall amount and moisture source contribution on meteoric water recharging two karst systems in subtropical brazil in addition a 2 year monitoring program performed on soil and cave drip and rimstone pool waters from sampling sites with contrasting discharge values and located at 100 and 300 m below the surface in the santana cave system 24831v s 48843v w is used to test the influence of hydrologic and geologic features on the temporal variations of seepage water d 18 o interannual monthly variations in d 18 o of rainfall reflect primarily regional changes in moisture source contribution related to seasonal shifts in atmospheric circulation from a more monsoonal regime in summer negative values of d 18 o to a more extratropical regime in winter positive values of d 18 o variations in groundwater d 18 o indicate that the climatic signal of recent rainfall events is rapidly transmitted through the relatively deep karst aquifer to the cave drip waters regardless of location of collection in the cave in addition the data also suggest that water replenishment in the system is triggered by the increase in hydraulic head during periods when recharge exceeds the storage capacity of the soil and epikarst reservoirs significant perturbations in the groundwater composition characterized by more positive values of d 18 o are probably connected to an increased atlantic moisture contribution associated with extratropical precipitation this implies that the d 18 o of speleothems from caves in this region may be a suitable proxy for studying

modelling the shrinkage curve of soil clay pastes the shrinkage properties of soil require an understanding of the volumetric changes to swelling clays the presence of non swelling minerals like silt and sand and the soil volume occupied by cracks and other voids it is natural to consider first the matrix of clay particles only the objective of this work is the further development of a basic model of the shrinkage curve of a soil clay based on its microstructure the specific goals include developments of a relation between the saturation degree and pore size distribution a physical condition determining the shrinkage limit of a soil clay paste the points of the basic model the major concepts definitions assumptions simple formulas and results that are relevant to these goals are preliminarily briefly summarized application of the points supplemented by the above developments allows one to reduce the number of independent macroparameters of clay paste that were introduced in the basic model to express the residual water content shrinkage limit and shrinkage curve of clay paste through the reduced number of its macroparameters to show additional interconnection between micro and macroparameters of the clay paste microstructure besides those indicated in the basic model comparison between model estimates and relevant available data on characteristic points of the shrinkage curve of soil clay pastes gives arguments in favour of the basic model supplemented here that enables one to predict the total shrinkage curve of a clay paste including the residual water content shrinkage and liquid limits