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

drained shear strength parameters for analysis of landslides this paper presents recommendations for selecting the type and magnitude of drained shear strength parameters for analysis of landslides in particular the importance existence and use of the cohesion shear strength parameter is reviewed for slope stability analyses it is recommended that the shear strength be modeled using a stress dependent failure envelope or a friction angle that corresponds to the average effective normal stress acting on the slip surface passing through that particular material instead of using a combination of cohesion and friction angle to represent soil shear strength other recommendations for stability analyses include using an effective stress cohesion of zero for residual and fully softened strength situations to facilitate selection of shear strength parameters for landslide analyses empirical relationships for the drained residual and fully softened strengths are updated from the previous empirical relationships presented by stark and eid finally the paper presents torsional ring shear test results that indicate that pre existing shear surfaces exhibit self healing that results in increased shear resistance the magnitude of healing appears to increase with increasing soil plasticity and this increase could have implications for the size timing and cost of landslide remediation

a correlation between residual friction angle gradation and the index properties of cohesive soils this technical note proposes a new correlation between residual friction angle gradation and the index properties of cohesive soils the proposed correlation was obtained on the basis of laboratory tests performed on more than 20 sites along the autostrade spa motorway network in italy the test specimens were taken mostly from samples obtained from borings and test pits in the apennine silty clayey soils direct shear and ring shear tests were used to determine the residual shear strength the proposed correlation gives reliable qualitative indications when the input data for design cannot be obtained from an extensive laboratory test programme it has been included in a multi function database which contains all the available technical information required to design remedial measures in landslide areas trrl

micro x ray fluorescence μxrf line scanning on cretaceous rudist bivalves a new method for reproducible trace element profiles in bivalve calcite the reconstruction of palaeoclimate on a sub annual scale requires the measurement of chemical proxies in fossil material at a high spatial resolution while various methods for trace element analysis on the micrometre scale are available they are usually destructive to the sample or not widely accessible this study evaluates the performance of a table top micro x ray fluorescence scanner in obtaining reproducible trace element profiles on bivalve calcite standard calibration and repeatability tests demonstrate the robustness of results obtained with this new generation micro x ray fluorescence device that uses a comparatively high excitation energy of 30 w results show that elemental abundances measured using this fast readily accessible and non destructive analytical setup are reproducible on the g g level and therefore suitable for the analysis of the abundance of commonly studied elements in bivalve calcite for example sr mn and fe spectra obtained in this study show considerable improvement in terms of signal to noise ratio compared to earlier table top xrf studies reliability of the measurements is tested using a conservative detection and quantification limit count rates of ca are used to check for point measurements disturbed by irregularities on the sample surface furthermore the method allows semi quantitative two dimensional element mapping which is a convenient tool for the detection of diagenetic alteration in fossil samples the method reveals records of sr ca fe ca and mn ca ratios in a late campanian vaccinites vesiculosus shell with sr ca ratios showing a trend opposite to mn ca and fe ca resulting trace element records are discussed in terms of seasonal cyclicity in the late cretaceous and diagenetic alteration of the fossil shell this article is protected by copyright all rights reserved

trace element distribution in annual stalagmite laminae mapped by micrometer resolution x ray fluorescence implications for incorporation of environmentally significant species abstract stalagmite er78 from grotta di ernesto cave in ne italy displays clear annual lamination consistent with its shallow depth below a forest ecosystem subject to autumnal peaking of water infiltration synchrotron radiation scanning micro x ray fluorescence analyses of heavy elements at european synchrotron radiation facility beamline id22 and light elements at id21 with 1 3 m resolution has been combined with data from ion microprobe analyses to reveal chemical variability across the visible layers of these annual laminae a series of elements display a symmetrical peak centered around the thin dark layer at the top of each lamina the peak concentration is ordered y zn cu and pb p and br this hierarchy is thought to reflect the selectivity of transport of these elements possibly by organic colloids flushed from the soil zone during autumn infiltration ion microprobe analysis indicates na and f also increase as does h the latter reflecting increased microporosity sr displays a trough around the dark and thin autumn layer implying that its incorporation may be limited by competition with other elements mg and s show a different pattern of annual variation and fe displays none the trace metals br and y display peak abundance in the early 20th century which appears to reflect a period of tree felling rather than a climatic anomaly the results demonstrate the power of the high spatial resolution and low detection limits of the synchrotron technique and its ability to produce quantitative maps that allow distinction of layered structure from that of isolated particles or irregular inhomogeneities

seasonal variations in sr mg and p in modern speleothems grotta di ernesto italy sub annual variations in trace element chemistry and luminescence have recently been demonstrated from speleothems and offer the potential of high resolution palaeoclimatic proxies however no studies have yet examined microscopic trace element variations in relation to modern cave conditions in this study the spatial variations in trace element sr mg and p concentrations in speleothems a stalagmite and a soda straw stalactite from the alpine ernesto cave temperature 6 6 0 1 c in a forested catchment in ne italy have been studied using secondary ion mass spectrometry sims and compared with environmental parameters and waters in the modern cave an annual lamination exists in the stalagmite and soda straw stalactite in the form of clear calcite with narrow visible layers which are uv fluorescent and interpreted to contain soil derived humic fulvic acids washed into the cave during autumn rains microanalyses were undertaken of seven annual laminae probably deposited during the 1960s in the stalagmite and seven laminae in the 1990s for the stalactite the analysis results show that sr consistently has a trough and p a peak centred on the inclusion rich layer mg shows mainly a negative covariation with sr in laminae formed in the 1990s but a positive covariation in the stalagmite formed in 1960s the spatial scale of the main geochemical variations is the same as that of annual laminae of inclusion poor and inclusion rich couplets mass balance arguments are used to show that the p is inorganic in form and presumably occurs as individual phosphate ions within the calcite most drip waters show limited chemical variations but a summer peak in trace elements in 1995 and a decrease in mg ca in the following winter are notable more pronounced covariations in mg ca and sr ca are shown by a site with highly variable drip rates where ratios increase at slow drip rates the strongest seasonal variations are found in pool waters where ratios increase reflecting significant ca removal from the water into the calcite during the winter in response to seasonal pco2 variations in cave air thus the cave waters compositions tend to reflect climate conditions such that mg ca and sr ca are tentatively interpreted to be higher when climate conditions are dry combining results from the speleothems and cave water along with the behaviour of each trace species mg ca variations in the speleothems are considered to reflect their variation in the cave waters whereas sr incorporation is also dependent on precipitation rate in this case mainly controlled by temporal variations in pco2 in the cave and conceivably also by inhibitors such as phosphate p adsorption a fraction of which is subsequently incorporated within calcite depends on aqueous phosphate concentration and water flux both of which should increase during the autumn therefore multiple trace element profiles in speleothems reflect multiple aspects of environment seasonality and conditions and hence a calibration against weather records is desirable to establish their palaeoclimatological meaning the strong annual variation of trace elements and particularly p can provide chronological markers for high resolution studies of other climate proxies such as stable isotopes

effects of overconsolidation ratios on the shear strength of remoulded slip surface soils in ring shear the drained shear strength of clay soils is independent of stress history though there have been instances in the geotechnical literature of studies that have suggested some dependence of stress history on the drained shear strength accordingly the effect of artificial overconsolidation ratios ocr on the drained shear behaviour and shear strength of a high plasticity clay soil and a loess soil has been discussed from an experimental point of view the slip surface materials of two landslides were remoulded and consolidated from slurry and were subjected to drained shear tests four overconsolidation ratios ocr 1 ocr 2 ocr 4 and ocr 6 were tested under constant effective normal stress in a ring shear apparatus the overconsolidated specimens achieved peak friction coefficients at relatively lesser shear displacements in contrast to the normally consolidated specimens in the kamenose soil the fully softened friction coefficient and the residual friction coefficient showed stress dependency in the ocr 1 bloc of both soils however between the two soils although dissimilar patterns of variation of these two shear strength parameters in the overconsolidated state compared to the normally consolidated state was evident significant differences in the residual friction coefficient attributable to overconsolidation were not found

evaluation of common practice empirical procedures for residual friction angle of soils hawaiian amorphous material rich colluvial soil case study the residual strength of soils has received considerable attention after skempton suggested that the stability of reactivated landslides may be governed by residual strength in this respect numerous studies have been conducted to determine the factors affecting the residual strength of soils specifically research effort was focused on determining correlations between the residual friction angle of soils and soil indexes such as atterberg limits and clay fraction some of these researchers suggested that strong correlations exist with soil indexes other researchers claimed that there is no correlation between the soil index and the residual friction of soils thus there is a need to clarify whether there is a correlation between residual friction angle and soil index properties in this effort we describe general properties of landslides in hawaii with an emphasis on an active landslide followed by evaluating correlations between the residual strength and soil indexes the results of this study show that the existing empirical correlations for soil index properties and residual friction angle predict poorly the residual friction angle of colluvial soils that rich in amorphous materials however the results also show that a strong correlation between ll and pi and residual friction angle may exist depending on the soil mineral type

calcite fabrics growth mechanisms and environments of formation in speleothems from the italian alps and southwestern ireland five fabrics were identified in alpine and irish caves on the basis of morphological and microstructural characteristics and re lated to growth mechanisms and growth environment columnar and fibrous fabrics grow when speleothems are continuously wet and from fluids at near equilibrium conditions low supersaturation sicc 0 35 through the screw dislocation mechanism the highly defective microcrystalline fabrics form at the same supersaturation range as co lumnar fabric but under variable discharge and the presence of growth inhibitors dendritic fabrics which have the highest density of crystal defects develop in disequilibrium conditions high supersaturation un der periodic very low flow regime periods that result in prolonged out gassing cave calcareous tufa forms in disequilibrium conditions only the calcite crystals of fabrics formed at low supersaturation seem to precipitate near isotopic equilibrium conditions

trace elements in speleothems as recorders of environmental change speleothems are now established as important palaeoenvironmental archives and contain a number of suitable proxies although trace elements have been much less widely used than oxygen and carbon isotopes the complexity of the cave environment helps to explain this since the fluids from which speleothems form vary greatly in composition in space even within a cave chamber seasonally and over longer periods understanding the forcing factors for this variability is the key to decoding the significance of the trace element records a variety of techniques are available for trace element work and it is important to understand the strengths and limitations of each and also to seek an understanding e g by micro imaging techniques of whether the elements are associated with inclusions in the caco3 or are isolated within the crystal lattice for some elements there is a more or less predictable relationship between element ratios to ca in the water and in the calcite individual trace elements may be derived from atmospheric deposition superficial deposits or bedrock and can be recycled in soil processes before being transferred to the cave some components show an instantaneous response to water infiltration whereas others are only leached by slow flowing seepage waters changing in the proportion of water from fracture fed and seepage flow aquifer compartments is an important factor in influencing trace element supply high flows lead to higher fluxes of soil derived colloidally transported elements conversely under relatively dry conditions degassing of co2 results in prior calcite precipitation upflow of the site of speleothem deposition and leads to higher ratios of sr ca and mg ca some trace element variations in speleothems over time are induced during crystal growth whereby faster growth leads to a greater departure from equilibrium element partitioning despite the demonstrated temperature dependence of mg partitioning into calcite attempts at deriving palaeotemperature records from speleothems have been so far confounded by variations in solution mg ca and or crystallographic effects a number of case studies have effectively used trace elements such as speleothem mg as records of palaeo aridity using supporting arguments from modern monitoring or covariations with other parameters such as stable isotopes sr and u isotopes can also be indicators of palaeohydrology although sr isotope variations can also reflect varying aeolian input considerable progress has been made in decoding the meaning of annual trace element variations using criteria for understanding dripwater hydrology and ph this should lead in the future to more specific interpretations of how seasonality evolves through time

advancements in the use of speleothems as climate archives abstract speleothems have become a cornerstone of the approach to better understanding earth s climatic teleconnections due to their precise absolute chronologies their continuous or semicontinuous deposition and their global terrestrial distribution we review the last decade of speleothem related research building off a similar review by mcdermott 2004 in three themes i investigation of global teleconnections using speleothem based climate reconstructions ii refinement of climate interpretations from speleothem proxies through cave monitoring and iii novel technical methods of speleothem based climate reconstructions speleothem records have enabled critical insight into the response of global hydroclimate to large climate changes this includes the relevant forcings and sequence of climatic responses involved in glacial terminations and recognition of a global monsoon response to climate changes on orbital and millennial time scales we review advancements in understanding of the processes that control speleothem 13 c values and introduce the idea of a direct atmospheric pco 2 influence we discuss progress in understanding kinetic isotope fractionation which with further advances may help quantify paleoclimate changes despite non equilibrium formation of speleothems this feeds into the potential of proxy system modeling to consider climatic hydrological and biogeochemical processes with the objective of quantitatively interpreting speleothem proxies finally we provide an overview of emerging speleothem proxies and novel approaches using existing proxies most recently technical advancements made in the measurement of fluid inclusions are now yielding reliable determinations of paleotemperatures

residual strength of clays and correlations using atterberg limits various attempts have been made to correlate the residual strength friction angle of soils to their index parameters either the particle size or the atterberg limits the first correlation attempt was that of skempton 1964 relating the residual strength friction angle to clay fraction followed by a number of others the best known probably being lupini et al 1981 mesri and cepe da diaz 1986 colotta et al 1989 and stark et al 1994 the purpose of this paper is to reconsider these correlation attempts and to make some general comments about the use of atterberg limits for correlation purposes a

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

a new method for the correlation of residual shear strength of the soil with mineralogical composition mineralogical composition measured with x ray diffraction for soil specimens collected from more than 80 natural disaster areas show smectite kaolinite mica feldspar and quartz as major constituent minerals based on the results of more than 35 mixtures of smectite kaolinite and quartz in different proportions a new correlation method was proposed for estimation of the residual friction angle r with the proportion of the minerals the mineralogical compositions of the natural samples were used to estimate the r based on the proposed triangular model the estimation method resulted in values as close as 90 to the measured r and as close as 80 to the case of 53 samples tested by other researchers the paper incorporates the correlation of r with the liquid limit the plasticity index the clay fraction the specific surface area and the proportion of smectite various ranges are proposed according to the influence of the constituent clay minerals in addition the applicable range

controls on trace element sr mg compositions of carbonate cave waters implications for speleothem climatic records abstract at two caves clamouse s france and ernesto ne italy cave drip and pool waters were collected and sampled at intervals over a 2 3 year period mg ca and sr ca concentration ratios corrected for marine aerosols are compared with those of bedrocks and in some cases aqueous leachates of soils and weathered bedrocks cave waters do not lie along mixing lines between calcite and dolomite of bedrock carbonate but typically show enhanced and covarying mg ca and sr ca four factors are considered as controlling processes 1 the much faster dissolution rate of calcite than dolomite allows for the possibility of increase of mg ca if water rock contact times are increased during drier conditions a theoretical model is shown to be comparable to experimental leachates 2 prior calcite precipitation along a flow path is a powerful mechanism for generating enhanced and covarying mg ca and sr ca ratios this mechanism requires the solution to lose co 2 into pores or caverns 3 incongruent dolomite dissolution has only limited potential and is best regarded as two separate processes of dolomite dissolution and calcite precipitation 4 selective leaching of mg and sr with respect to ca is shown to be important in leachates from ernesto where it appears to be a phenomenon of calcite dissolution in general selective leaching can occur whenever ca is sequestered into precipitates due to freezing or drying of soils or if there is derivation of excess sr and mg from non carbonate species the ernesto cave has abundant water supply which in the main chamber is derived from a reservoir with year round constant p co 2 of around 10 2 4 and no evidence of calcite precipitation in the karst above the cave two distinct but overlying trends of enhanced and covarying mg ca and sr ca away from the locus of bedrock compositions are due to calcite precipitation within the cave and at a variable drip site due to enhanced selective leaching at slow drip rates mg enhancement in the first chamber is due to a more dolomitic bedrock and longer residence times the clamouse site has a less abundant water supply and presents geochemical evidence of prior calcite precipitation both in the cave and in overlying porous dolomite dedolomitized limestone bedrock initial p co 2 values as high as 10 1 are inferred experimental incubations of clamouse soils which generated enhanced p co 2 and precipitated caco 3 had compositions similar to the karst waters calcite precipitation is inferred to be enhanced in drier conditions hydrological controls on cave water chemistry imply that the trace element chemistry of speleothems may be interpretable in palaeohydrological terms drier conditions tends to promote not only longer mean residence times enhancing dolomite dissolution and hence mg ca but also enhances degassing and calcite precipitation leading to increased mg ca and sr ca

intra and inter annual uranium concentration variability in a belizean stalagmite controlled by prior aragonite precipitation a new tool for reconstructing hydro climate using aragonitic speleothems aragonitic speleothems are increasingly utilised as palaeoclimate archives due to their amenability to high precision u th dating proxy records from fast growing aragonitic stalagmites precisely dated to annual timescales can allow investigation of climatic events occurring on annual or even sub annual timescales with minimal chronological uncertainty however the behaviour of many trace elements such as uranium in aragonitic speleothems has not thus far been as well constrained as in calcitic speleothems here we use uranium concentration shifts measured across primary calcite to aragonite mineralogical transitions in speleothems to calculate the distribution coefficient of uranium in aragonitic speleothems derived du 3 74 1 13 because our calculated du is considerably above 1 increased prior aragonite precipitation due to increased karst water residence time should strongly control stalagmite aragonite u ca values consequently uranium concentrations in aragonitic speleothems should act as excellent proxies for effective rainfall we test this using a high resolution icp ms derived trace element dataset from a belizean stalagmite yok g is an aragonitic stalagmite from yok balum cave in belize with an extremely robust monthly resolved chronology built using annual 13c cycles we interpret seasonal u ca variations in yok g as reflecting changes in the amount and seasonality of prior aragonite precipitation driven by variable rainfall amounts the u ca record strongly suggests that modern drying has occurred in belize and that this drying was primarily caused by a reduction in wet season rainfall this is consistent with published stable isotope data from yok g also very strongly suggesting modern rainfall reductions previously interpreted as the result of southward itcz displacement our results strongly suggest that u ca values in aragonitic speleothems are excellent proxies for rainfall variability this new tool combined with the exceptional chronological control characteristic of aragonitic stalagmites and the high spatial resolution afforded by modern microanalytical techniques should facilitate the construction of new exquisitely resolved rainfall records providing rare insights into seasonality changes as well as long term changes in local recharge conditions

temperature dependent residual shear strength characteristics of smectite bearing landslide soils this paper presents experimental investigations regarding the effect of temperature on the residual strength of landslide soils at slow to moderate shearing velocities we performed ring shear tests on 23 soil samples at temperatures of 6 29 c the test results show that the shear strength of smectite rich soils decreased when temperatures were relatively low these positive temperature effects strength losses at lower temperatures observed for smectite bearing soils are typical under relatively slow shearing rates in contrast under relatively high shearing rates strength was gained as temperature decreased as rheological properties of smectite suspensions are sensitive to environmental factors such as temperature ph and dissolved ions we inferred that temperature dependent residual strengths of smectitic soils are also attributed to their specific rheological properties visual and sem observations of ca bentonite suggest that slickensided shear surfaces at slow shearing rates are very shiny and smooth whereas those at moderate shearing rates are not glossy and are slightly turbulent indicating that platy smectite particles are strongly orientated at slow velocities the positive temperature effect is probably due to temperature dependent micro friction that is mobilized in the parallel directions of the sheet structure of hydrous smectite particles on the contrary the influence of micro viscous resistance which appears in the vertical directions of the lamination is assumed to increase at faster velocities our results imply that if slip surface soils contain high fractions of smectite decreases in ground temperature can lead to lowered shear resistance of the slip surface and trigger slow landslide movement

residual strength of kaolin and bentonite the influence of their constituent pore fluid the residual strength of clays is affected by their mineral composition and by the nature of their constituent pore fluid in principle both factors may influence either strength parameters or stresses but it is not yet completely clear how this influence works previous publications have elucidated some aspects of clay residual strength behaviour this paper investigates further the roles of minerals and pore fluid composition on the residual strength of clayey soils it describes and analyses tests on kaolin bentonite and their mixtures exposed to distilled water and sodium choride solutions with given concentrations the results show that the shear strength of kaolin is not affected by the solutions used whereas the residual strength of bentonite varies greatly because of the inward salt diffusion towards the clay further for the clay mixtures with any of the pore fluids considered the weaker component has the greater influence on the behaviour of the mixture la resistance residuelle des argile

lake level history of lake tanganyika east africa for the past 2500 years based on ostracode inferred water depth reconstruction assemblages of ostracodes from sediment cores illuminate lake level history at decadal to centennial timescales during the late holocene at lake tanganyika east africa the ostracode based lake level curves for several cores resemble both each other and the only previously published lake level record of comparable resolution for lake tanganyika during this interval successfully reconstructing known highstands improving the chronology of known lowstands and contributing new information on late holocene lake level variability at this important tropical african location in agreement with other late holocene records from east africa the surface level at lake tanganyika reflects predominantly arid conditions throughout this interval interrupted by relatively brief episodes of higher precipitation and lake level the most pronounced lowstand in the record occurs at v200 0 bc with other significant lowstands dating to the intervals v200 500 ad v700 850 ad the medieval warmperiod mwp v1050 1250 ad at lake tanganyika and the latter part of the little ice age lia v1550 1850 ad the most important wet intervals in the lake level record are centered on v500 ad v1500 ad and v1870 ad the highstands and lowstands reported here for lake tanganyika appear to be fairly coherent with other records of rainfall throughout east africa during the mwp and the lia prior to the mwp paleoclimate records are apparently less coherent although this may be a reflection of the resolution and abundance of recent paleoclimatic data available for this climatically complex region

controls on trace element partitioning in cave analogue calcite abstract we report trace element data from a series of carbonate growth experiments in cave analogue conditions in the laboratory with the goal of better understanding environmental controls on trace element incorporation in stalagmites the experimental setup closely mimics natural processes e g precipitation driven by co2 degassing low ionic strength solution thin solution film but with a tight control on growth conditions temperature pco2 drip rate calcite saturation index and the composition of the initial solution calcite is dissolved in deionized water in a 20 000 ppmv pco2 environment with trace elements li na mg co sr cd ba u at appropriate concentrations to mimic natural cave drip waters this solution is dripped onto glass plates coated with seed calcite in a lower pco2 environment at 7 15 25 and 35 c and drip rates of 2 6 and 10 drips per minute d sr was shown to be statistically invariant over the full range of temperature and growth rate studied no relationship between sr ca and growth rate is therefore expected in stalagmite samples over comparable growth rates d mg has a relationship with temperature defined by d mg 0 01e0 02 0 006 t but temperature is not expected to be the dominant control on mg ca in cave calcite due to the larger impact of calcite precipitation on mg ca over short timescales in conditions where temperature is well buffered the fraction of calcium remaining in solution f is likely to be the dominant control on mg ca and other trace element ratios but differences in the response of trace elements to f and t may allow their combined use to assess past cave conditions high cd castalagmite is particularly indicative of low amounts of prior calcite precipitation and cd ca would be a useful addition to trace element studies of natural stalagmites significant scatter is observed in trace element ratios during the laboratory experiments which cannot be explained by simple rayleigh distillation this scatter is well explained by solution mixing and by the mixing of calcite with different fractions of calcite growth accounting for the effects of mixing on trace element concentrations or ratios may help to achieve more robust interpretations of stalagmite chemistry as part of a multi proxy approach to assessment of past environments

the avaatech xrf core scanner technical description and applications to ne atlantic sediments abstract x ray fluorescence xrf core scanning provides rapid high resolution down to 1 mm records of chemical composition on split sediment cores the measurements are non destructive and require very limited sample preparation the new avaatech xrf core scanner operational since 2002 covers the atomic mass range from al to u instrument parameters especially tube voltage can be adjusted to provide optimum settings for selected elements or sets thereof owing to the nature of the surface of split sediment cores particularly effects resulting from sample inhomogeneity and surface roughness results are semiquantitative yet provide reliable records of the relative variability in elemental composition downcore selected case studies from diverse sedimentary settings in the ne atlantic ocean illustrate a range of applications of xrf logging data these include preliminary stratigraphic interpretations glacial interglacial cycles provenance studies of the terrigenous sediment fraction lithological characterization early diagenetic processes and distinction between carbonate phases aragonite v calcite

seasonal trace element and stable isotope variations in a chinese speleothem the potential for high resolution paleomonsoon reconstruction abstract we report the presence of clear annual cycles in trace element mg ca sr ca ba ca and u ca and stable isotope 18o and 13c composition in an annually banded stalagmite from heshang cave hubei province china 30 44 n 110 42 e through a combination of micromilling and in situ analysis la mc icpms we measured geochemical variations across 16 annual growth bands to assess their potential as seasonal resolution paleomonsoon proxies to facilitate comparison with modern climatic and environmental data we created composite annual cycles for each proxy by stacking 6 well defined years speleothem 18o variations 10 8 to 8 5 are controlled by seasonal variations in temperature and drip water 18o which lead to maximum values during may around the time of summer monsoon onset this provides a chronological marker which can be used to constrain the timing of the other geochemical cycles the composite cycles reveal a strong positive correlation between mg ca sr ca ba ca and 13c values in the micromilled section r2 0 65 0 98 with minimum values occurring around may maximum u ca values occur at the same time we present simple models which show that these correlations as well as the observed ranges of mg ca 14 1 to 22 4 mmol mol sr ca 0 2 to 0 4 mmol mol and 13c 12 5 to 10 7 may be fully explained by progressive co2 degassing and calcite precipitation from an initially saturated solution using realistic initial conditions for heshang cave t 18 c mg casolution 0 84 mol mol sr casolution 0 69 mmol mol 13ctdic 16 75 we find that the observed relationships can be produced by using dmg 0 016 and dsr 0 30 within the range of expected values the model suggests that the fraction of ca removed from the solution ranges from 0 to 30 to produce the observed seasonal cycles this variation may be due to two related processes which occur during drier periods 1 increased prior precipitation of calcite in the epikarst or on the cave ceiling and or 2 a greater degree of co2 degassing and calcite precipitation on stalagmite surfaces when drip rates are lower both mechanisms would have the effect of enriching speleothem mg ca sr ca ba ca and 13c values during drier periods past variations in heshang carbonate chemistry may therefore be useful as seasonal resolution proxies for past rainfall

mg sr and sr isotope geochemistry of a belgian holocene speleothem implications for paleoclimate reconstructions in this study variations in mg ca sr ca and 87sr 86sr ratios in a holocene belgian speleothem cave secondary carbonate deposit are interpreted in terms of changes in water residence time and changes in weathering processes possibly induced by changes in west european climate a stalagmite from the pere noel cave belgium was dated with the tims u th method and was deposited between 13 and 2 ka bp the 1000 mg ca ratio varies between 4 9 and 26 and displays short term changes but no significant long term trend the 1000 sr ca ratio varies between 0 09 and 0 31 and displays both short term changes and a long term decreasing trend from 12 9 to 3 5 ka in parallel the sr isotopic composition of the speleothem decreases from 0 7090 at 12 9 ka to 0 7088 at 3 5 ka the sr isotope ratio is higher than expected from the overlying limestone 87sr 86sr 0 7081 which implies an external source of radiogenic sr most probably from a silicate phase short term and long term changes in mg ca sr ca as well as long term changes of 87sr 86sr ratios can be explained by changes in the dissolution and precipitation processes of the host limestone these processes are controlled by changes in water residence times linked to changes in the water excess precipitation minus evapo transpiration c 2000 elsevier science b v all rights reserved

calibration of xrf core scanners for quantitative geochemical logging of sediment cores theory and application abstract on line analysis of split sediment cores by xrf core scanners has become increasingly popular in the past decade because it allows nondestructive extraction of near continuous records of element intensities from sediment cores with a minimum of analytical effort a disadvantage of xrf core scanning relative to conventional geochemical analysis is the problematic conversion of core scanner output to element concentrations the main reason for this long standing problem is the poorly constrained measurement geometry attributable to inhomogeneity of the specimens e g variable water content and grain size distribution irregularities of the split core surface and in some setups spatial variations in thickness of an adhesive pore water film which forms directly below a protective foil covering the core surface we propose a log ratio calibration model for xrf core scanners derived from a combination of xrf spectrometry theory principles of compositional data analysis and empirical evidence the log ratio calibration model provides accurate and precise predictions of sediment composition element concentrations from xrf core scanner output with a limited number of parameters namely 2 d 1 where d equals the number of chemical elements whose concentrations are to be estimated the model can accommodate the inherent non linearity of the relation between relative intensities and concentrations which is apparent from the fact that it provides unbiased estimates an immediate corollary of our results is that log ratios of element intensities which are related to log ratios of element abundances by a simple linear transformation provide the most easily interpretable signals of relative changes in chemical composition consistent use of log ratios of element intensities or concentrations should minimise the risk of drawing erroneous conclusions from geochemical proxies the relative standard deviation precision of predicted element concentrations in core geob7920 is less than 2 stochastic simulations indicate that this level of precision can be attained with 40 randomly selected calibration specimens improved control over input errors and development of robust goodness of fit statistics allows xrf core scanning to be developed into a rigorous quantitative measurement technology the log ratio calibration equation derived in this study may be adapted to inter laboratory and inter instrument calibration as well

tropical seasonality in the late campanian late cretaceous comparison between multiproxy records from three bivalve taxa from oman abstract geochemical proxy records from calcite shells of bivalves constitute an important archive for the reconstruction of palaeoenvironmental conditions on sub annual timescales however the incorporation of these trace element and stable isotope proxies into the shell is influenced by a multitude of physiological and environmental factors that need to be disentangled to enable reliable reconstruction of palaeoclimate and palaeoenvironment in this study records of multiple proxies in three bivalve taxa from the same late campanian locality in oman are used to study the expression of various geochemical proxies in relation to each other and to the palaeoenvironment micro x ray fluorescence mapping allows the localization discussion and evasion of diagenetically altered parts of the fossil shells x ray fluorescence line scanning calibrated with laser ablation inductively coupled plasma mass spectrometry is used to measure trace element profiles through well preserved calcitic parts of the shells records of stable carbon and oxygen isotope ratios of shell calcite are combined with these high resolution trace element concentration profiles to study sub annual variations in shell chemistry and reconstruct changes in the palaeoenvironment of the bivalves on a seasonal scale spectral analysis routines are used to detect cyclicity in stable isotope 18o and 13c and trace element mg ca sr ca s ca and zn ca records differences in seasonal expression between these chemical proxies and between individual shells are discussed in terms of the relative influence of palaeoenvironment and potential species specific physiological effects stable oxygen isotope ratios between shells suggest a local palaeotemperature seasonality of 8 c around an annual mean of 28 c with the shell of the rudistid torreites sanchezi milovanovici yielding slightly higher average temperatures the discussion of the application of various mg ca palaeotemperature calibrations on mg ca records in these bivalve species emphasizes the complexity of using trace element proxies in extinct bivalve species it shows that long term changes in mg ca ratios in ocean water need to be taken into account and that mg ca ratios in bivalves might be influenced by vital effects sr ca and s ca ratios in these fossil taxa are likely controlled by growth and metabolic rates of the shell although an influence of local salinity on strontium to calcium ratios cannot be excluded sub annual variations in zinc concentrations in shell calcite may reflect seasonal variations in palaeoproductivity and redox conditions in the water column

paleoclimate reconstruction in the levant region from the geochemistry of a holocene stalagmite from the jeita cave lebanon dated oxygen and carbon isotopic profiles from a holocene stalagmite 11 9 1 1 ka from the jeita cave lebanon are compared to variations in crystallographic habit stalagmite diameter and growth rate the profiles show generally high 18o and 13c values during the late glacial period low values during the early holocene and again high values after 5 8 ka on the basis of the good correlation between the morphological and crystallographic aspect of the stalagmite and its isotopic records as well as the isotopic response of speleothems from central and northern israel we relate high 18o and 13c values to drier conditions between 6 5 and 5 8 ka an increase in isotopic values a decrease in growth rate and stalagmite diameter suggest a transition from wet conditions in the early holocene towards drier conditions in the mid holocene the transition occurred in two steps first a progressive change to drier conditions started at 6 5 ka but was interrupted by a short 100 years return to wetter conditions followed by an equally rapid 200 years change to drier conditions

the residual shear strength of tropical soils the paper discusses the residual shear strength of tropical soils ring shear tests have been performed with tropical soils from southern brazil using the bromhead apparatus the data from the study are compared with data obtained in a comprehensive literature review of the subject the residual friction angle of tropical residual soils from sedimentary formations decreases with increasing plasticity index following a general trend presented in the literature most of the residual soils described herein have also shown this trend however some of these residual soils particularly basalt saprolitic soils have shown quite low residual friction angles despite having low plasticity index and clay fraction values it has been confirmed that the residual shear strength of tropical soils depends chiefly on mineralogy particle size distribution effective stress parent rock weathering degree pedogenetic evolution and when partly weathered minerals are present degradation upon shearing the substantial

residual strength of smectite dominated soils from the kamenose landslide in japan the residual strength of smectite dominated soils from the main slip surfaces of the kamenose landslide japan was measured by ring shear test and the relations of the residual strength to the clay fraction content and clay particle orientation were studied the residual angles of shearing resistance were estimated assuming that the residual cohesion is zero the magnitude of the residual angle of shearing resistance was dependent on the 2 m clay fraction content cf and on the effective normal stress because of curved strength lines at equivalent to the overburden pressures the soils had of 6 8 these residual angles of shearing resistance were fitted on the cf line for sand bentonite mixtures and exhibited the sliding shear mode the orientation of smectite particles on shear surfaces showing slickensides was assessed by x ray diffraction technique the orientation of smectite particles was found to reduce the residual strength considerably and this orientation effect was revealed more

benchtop μxrf as a tool for speleothem trace elemental analysis validation limitations and application on an eemian to early weichselian 125 97 ka stalagmite from belgium abstract variations of trace element e g mg sr ba fe zn etc concentrations along a speleothem s growth axis constitute important paleoclimate proxies the use of laboratory micro x ray fluorescence spectrometry as a fast and cheap alternative for conventional mass spectrometry techniques for trace element analysis on speleothems has been explored in the past and yielded satisfactory results however within the speleothem community there is need for an in depth investigation of the full potential of this analytical technique compared to other types of paleoclimate archives benchtop xrf analysis on speleothems is analytically more challenging because of the high crystalline speleothem matrix and the low abundance of the elements of interest in this study several speleothem samples with differences in mineralogy calcite versus aragonite and composition are investigated various instrumental parameters are tested and recommendations are made for future studies applying xrf analysis to speleothems quantification based on a multiple standard calibration and an assessment of the error is carried out through validation with mass spectrometry techniques it is confirmed that benchtop xrf devises are able to generate speleothem trace element records successful results were obtained for sr mg and fe while zn and ba were quantified in samples characterized by high concentrations nevertheless caution has to be taken when interpreting the results due to the presence of diffraction caused by the crystallinity of the samples the elements which provide reliable results are sample specific and depend on the type of matrix and elemental abundance these findings are applied on an eemian to early weichselian stalagmite from the han sur lesse cave belgium time series were constructed for mg and sr creating a multiproxy dataset together with previously obtained stable isotope 13c and 18o ratios growth rate and stalagmite morphology it appears that mg and sr are not primarily controlled by prior calcite precipitation but rather by changes in vegetation activity above the cave

climate and cave control on pleistocene holocene calcite to aragonite transitions in speleothems from morocco elemental and isotopic evidence the occurrence of aragonite in speleothems has commonly been related to high dripwater mg ca ratios because mg is known to be a growth inhibitor for calcite laboratory aragonite precipitation experiments however suggested a more complex array of controlling factors here we present data from pleistocene to holocene speleothems collected from both a dolostone and a limestone cave in northern morocco these stalagmites exhibit both lateral and stratigraphic calcite to aragonite transitions aragonite fabrics are well preserved and represent primary features in order to shed light on the factors that control alternating calcite and aragonite precipitation elemental mg sr ba u p y pb al ti and th abundances were measured using la icp ms and analysed with principal component analysis samples were analyzed at 100 200 m resolution across stratigraphic and lateral transitions carbon and oxygen isotope ratios were analysed at 100 m resolution covering stratigraphic calcite to aragonite transitions results show that the precipitation of aragonite was driven by a decrease in effective rainfall which enhanced prior calcite precipitation different geochemical patterns are observed between calcite and aragonite when comparing data from the grotte de piste and grotte prison de chien this may be explained by the increased dripwater mg ca ratio and enhanced prior aragonite precipitation in the dolostone cave versus lower dripwater mg ca ratio and prior calcite precipitation in the limestone cave a full understanding for the presence of lateral calcite to aragonite transitions is not reached trace elemental analysis however does suggest that different crystallographic parameters ionic radius amount of crystal defect sites adsorption potential may have a direct effect on the incorporation of sr mg ba al ti th and possibly y and p

development and optimization of microbeam x ray fluorescence analysis of sr in speleothems abstract trace metal abundances and ratios sr ca mg ca ba ca in speleothems can be indicators of the hydrogeochemical processes active in overlying epikarst and serve as valuable proxies for precipitation amount and source water residence time and vegetation cover however conventional methods of trace element acquisition can be expensive time consuming and destructive a semi portable xrf system is compared to other methods as it is non destructive rapid and has the capacity to provide high quality datasets a suite of test scans was performed in order to define the appropriate methodology for the application of xrf in trace metal analysis of speleothems statistical analyses were performed on an experimental dataset in order to assess the precision with which data were obtained and determined that there is no evidence for time dependent behavior within the data and there is no evidence that the data do not follow a poisson distribution the optimal count time varies from sample to sample as it was determined to be a function of the desired level of analytical uncertainty sr results for a speleothem obtained through la icp oes show a high degree of comparability to results obtained through xrf and demonstrate the suitability of this non destructive method sr counts can also be converted to concentration ppm via x ray tube dependent calibration curves

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

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

environmental variability between the penultimate deglaciation and the mid eemian insights from tana che urla central italy speleothem trace element record abstract a trace element record mg sr ba al si p y zn covering the ca 133 ka to ca 124 ka time interval was acquired from a flowstone core from tana che urla cave central italy it was compared with stable isotope data to investigate the environmental evolution in response to regional and extra regional climate changes in the period corresponding to the latter part of the penultimate deglaciation and the first part of the last interglacial eemian trace element geochemical changes on centennial and millennial time scales responded to changes in hydrological input variations in the supply and transport of catchment erosion products to the cave including those linked to intense rainfall events and to the state of the overlying soil and vegetation abrupt increases in precipitation and the progressive development of soil and vegetation occurred at ca 132 ka in response to the development of the global deglacial phase the major changes in trace element composition are coherent with the previous hydrological interpretation of speleothem oxygen stable isotope composition 18o as predominantly a rainfall amount proxy however reduced growth rate persisted until ca 130 ka suggesting still depressed temperatures an abrupt event of climatic deterioration with marked decrease in precipitation and soil degradation is apparent between ca 131 and 130 ka cool wet conditions between ca 132 and 131 ka and the subsequent dry period may represent the local hydrological response to an interval of north atlantic cooling and ice rafted debris ird deposition known as heinrich event 11 h11 after 129 6 ka there was a rapid recovery according to all of the studied speleothem properties indicating the onset of full interglacial conditions a minor amplitude event of reduced precipitation is recorded within the lig at ca 127 ka the record highlights the growing regional evidence for a complex penultimate deglacial climate involving major reorganization of oceanic and atmospheric patterns

the chemical and mineralogical controls upon the residual strength of pure and natural clays recent work has shown that the residual strength of clays is to a large extent determined by the type of clay minerals and the chemistry of the constituent pore water changes in either of these factors cause corresponding alterations in residual shear strength the findings have important implications for the seasonal reactivation of landslides and may also provide an explanation for the long term weathering and shear strength reduction of clay slopes results are presented here to demonstrate the separate effects of clay mineralogy and pore water chemistry upon the residual strength of pure and natural clays explanations are sought to identify the controls of these factors upon residual strength based on brief reviews of the shear strength and physico chemical behaviour of clays the findings strongly suggest that residual strength should be considered a dynamic property with increases or decreases in strength occurring in response to environmental change des etudes recentes ont montre que la resis

a stratigraphic framework for abrupt climatic changes during the last glacial period based on three synchronized greenland ice core records refining and extending the intimate event stratigraphy due to their outstanding resolution and well constrained chronologies greenland ice core records provide a master record of past climatic changes throughout the last interglacial glacial cycle in the north atlantic region as part of the intimate integration of ice core marine and terrestrial records project protocols have been proposed to ensure consistent and robust correlation between different records of past climate a key element of these protocols has been the formal definition and ordinal numbering of the sequence of greenland stadials gs and greenland interstadials gi within the most recent glacial period the gs and gi periods are the greenland expressions of the characteristic dansgaard oeschger events that represent cold and warm phases of the north atlantic region respectively we present here a more detailed and extended gs gi template for the whole of the last glacial period it is based on a synchronization of the ngrip grip and gisp2 ice core records that allows the parallel analysis of all three records on a common time scale the boundaries of the gs and gi periods are defined based on a combination of stable oxygen isotope ratios of the ice 18o reflecting mainly local temperature and calcium ion concentrations reflecting mainly atmospheric dust loading measured in the ice the data not only resolve the well known sequence of dansgaard oeschger events that were first defined and numbered in the ice core records more than two decades ago but also better resolve a number of short lived climatic oscillations some defined here for the first time using this revised scheme we propose a consistent approach for discriminating and naming all the significant abrupt climatic events of the last glacial period that are represented in the greenland ice records the final product constitutes an extended and better resolved greenland stratotype sequence against which other proxy records can be compared and correlated it also provides a more secure basis for investigating the dynamics and fundamental causes of these climatic perturbations

a high resolution absolute dated late pleistocene monsoon record from hulu cave china oxygen isotope records of five stalagmites from hulu cave near nanjing bear a remarkable resemblance to oxygen isotope records from greenland ice cores suggesting that east asian monsoon intensity changed in concert with greenland temperature between 11 000 and 75 000 years before the present yr b p between 11 000 and 30 000 yr b p the timing of changes in the monsoon as established with 230th dates generally agrees with the timing of temperature changes from the greenland ice sheet project two gisp2 core which supports gisp2 s chronology in this interval our record links north atlantic climate with the meridional transport of heat and moisture from the warmest part of the ocean where the summer east asian monsoon originates

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

platy layer silicate minerals for controlling residual strength in landslide soils of different origins and geology we use a ring shear apparatus to examine the relationship between the residual strength and mineralogical properties of landslide soils and find a significant relation between the residual strength parameter r and the total content of layer silicate minerals prone to preferred orientation within the bulk soil in this context the total content of smectite vermiculite chlorite and mica in the sub 425 m soil fraction is a suitable mineralogical parameter for estimating the magnitude of r plotting r as a function of total mineral content forms a chair shaped curve based on which we classify landslide soils into three groups in the first group of soils sliding appears to be controlled by minerals such as quartz feldspar calcite dolomite and layer silicate minerals other than smectite vermiculite chlorite and mica and their r is almost constant at 32 in the second group of soils the controlling mineralogical factor for sliding quickly shifts from nonpreferred orientation minerals to preferred orientation minerals and r decreases from 30 to 10 in the third group of soils sliding is well controlled by preferred orientation layer silicate minerals and r gradually decreases from 10 to 5 the results show that the relationship can be used for predicting r of a wide range of landslide soils that differ in geology soil type mineralogical properties and shear strength

characterizing the eemian weichselian transition in northwestern europe with three multiproxy speleothem archives from the belgian han sur lesse and remouchamps cave systems abstract interglacial to glacial transitions represent the most drastic turnovers in the quaternary climate system yet millennial scaled climate variability and stochastic internal variability that result in inter glacial transitions remain poorly understood here three speleothems from two different cave systems in belgium are investigated to characterize the eemian to early weichselian transition the speleothems show high reproducibility for 13c interpreted as a proxy for past vegetation activity controlled by type of vegetation above the cave all three speleothems show a drastic increase in 13c between 118 and 117 ka reflecting a rapid change in vegetation from last interglacial temperate tree species towards glacial open grass vegetation this transition shows a strong affinity with the late eemian aridity pulse leap at 118 1 ka previously identified in pollen records from western germany an age of 117 7 0 5 ka is determined for the start of this transition in the belgian speleothems the speleothem records show a distinct transition in the proxies between eemian optimum conditions and increased variability during the glacial inception and therefore the eemian weichselian transition is set at 117 7 0 5 ka in the speleothem records high resolution trace element analysis shows that the transition is initiated by a cooling pulse followed by a decrease in precipitation through comparison with other archives including north atlantic sedimentary records it is proposed that the transition at 117 7 ka constitutes an internal climate response caused by a substantial input of freshwater from degraded ice sheets by the end of the eemian 120 118 ka

high resolution synchrotron x ray fluorescence investigation of calcite coralloid speleothems elemental incorporation and their potential as environmental archives synchrotron high resolution and micro x ray fluorescence elemental mapping of two coeval coralloid speleothems from lamalunga cave italy are complemented with petrographic morphological and microstratigraphic studies the importance of these speleothems relies on their direct and indirect association with a complete neanderthal skeleton altamura man found inside the cave the coralloids grew discontinuously between 64 6 ka and the holocene and reveal exceptionally high concentrations of mg sr and si particularly on convex surfaces where evaporation is more intense the incorporation of trace elements depends on several factors including location shape and geometrical evolution during their growth as well as climate and environmental parameters this resulted in calcite precipitation with sr compositions from 100 to 1200 ppm and an average concentration of 7000 ppm mg an unusually high si content up to 16 is possibly derived from volcanic ash transported as particulate and in solution inside the cave the most common fabrics observed consist of non fluorescent elongated columnar calcite forming clean isopachous bands and fluorescent fibre like crystals associated with laminated lenticular bands high in sr mg and si variability in sr mg and si concentrations appears to induce fabric changes in the coralloids elongation and lattice distortion of the crystals was found to coincide with high mg concentrations the transition from compact elongated to open to fibre like is here interpreted as due to high concentrations of si and sr which are preferentially incorporated in the speleothem at crystal boundaries and intra laminae it is here inferred that coralloid fabric changes and their elemental content potentially record local rainfall variations through time with the clean compact calcite marking high infiltration and open fibre like and micrite fabrics recording dry periods

precise dating of dansgaard oeschger climate oscillations in western europe from stalagmite data the signature of dansgaard oeschger events millennial scale abrupt climate oscillations during the last glacial period is well established in ice cores and marine records but the effects of such events in continental settings are not as clear and their absolute chronology is uncertain beyond the limit of 14 c dating and annual layer counting for marine records and ice cores respectively here we present carbon and oxygen isotope records from a stalagmite collected in southwest france which have been precisely dated using 234u 230th ratios we find rapid climate oscillations coincident with the established dansgaard oeschger events between 83 000 and 32 000 years ago in both isotope records the oxygen isotope signature is similar to a record from soreq cave israel and deep sea records indicating the large spatial scale of the climate oscillations the signal in the carbon isotopes gives evidence of drastic and rapid vegetation changes in western europe an important site in human cultural evolution we also find evidence for a long phase of extremely cold climate in southwest france between 61 2 0 6 and 67 4 0 9 kyr ago

residual strength of clays in landslides folded strata and the laboratory the post peak drop in drained shear strength of an overconsolidated clay may be considered as taking place in two stages first at relatively small displacements the strength decreases to the fully softened or critical state value owing to an increase in water content dilatancy second after much larger displacements the strength falls to the residual value owing to reorientation of platy clay minerals parallel to the direction of shearing if the clay fraction is less than about 25 the second stage scarcely comes into operation the clay behaves much like a sand or silt with angles of residual shearing resistance typically greater than 20 degrees conversely when the clay fraction is about 50 residual strength is controlled almost entirely by sliding friction of the clay minerals and further increase in clay fraction has little effect the angles of residual shearing resistance of the three most commonly occurring clay minerals are approximately 15 degrees for kaolinite 10 degrees for illite or clay mica and 5 degrees for montmorillonite when the clay fraction lies between 25 and 50 there is a transitional type of behaviour residual strength being dependent on the percentage of clay particles as well as on their nature the post peak drop in strength of a normally consolidated clay is due only to particle reorientation measurements of strength on natural shear surfaces agree within practical limits of variation with values derived from back analysis of reactivated landslides this field residual strength can be recovered by multiple reversal shear box tests on cut plane samples but in high clay fraction materials it is typically somewhat higher than the strength measured in ring shear tests residual strength is little affected by variation in the slow rates of displacement encountered in reactivated landslides and in the usual laboratory tests but at rates faster than about 100 mm min qualitative changes take place in the pattern of behaviour a substantial gain in strength is followed with increasing displacement by a fall to a minimum value in clays and low clay fraction silts this minimum is not less than the slow or static residual but in clayey silts with clay fractions around 15 25 according to tests currently in progress the minimum can be as low as one half of the static value author trrl