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

aragonite relic preservation in jurassic calcite replaced bivalves shells of the aragonite bivalve neomiodon great estuarine group jurassic scotland replaced by coarse neomorphic calcite contain oriented relics of the original aragonite ultrastructure the presence of these relics in such old altered shells as well as the high sr content of the replacement calcite indicate that the process of calcite replacement of aragonite is not a cumulative slow process involving repeated alteration events but rather a rapid one step process aragonite relics once encased in neomorphic spar will survive as unequivocal evidence of original aragonite mineralogy barring total remobilization of the enclosing stable calcite a generally unlikely event the retention of this residual aragonite and high sr calcite supports recent isotopic studies which suggest that the multiple phases of alteration recrystallization invoked in earlier literature are unlikely events in the diagenesis of most undolomitized limestones retention of aragonite relics appears to be independent of whether alteration occurs in shallow meteoric or as in the case of our neomiodon material deeper burial environments pseudopleochroism of the replaced neomiodon shells appears to be due to organic largely graphitic relics not to the aragonite relics

carbonate recrystallization in shallow marine environments a widespread diagenetic process forming micritized grains abstract integrated morphologic petrographic and mineralogic analyses of sediment grains of the miliolid foraminifer archaias and the green alga halimeda from shallow marine environments in florida the bahamas and belize document pervasive syndepositional recrystallization in these grains scanning electron microscopy shows that original skeletal rods and needles recrystallize on the sea floor to a variety of equant micritic fabrics in thin section this textural alteration corresponds to progressive micritization with loss of the familiar golden brown color exhibited by fresh miliolids and halimeda and gradual development of gray cryptocrystalline carbonate x ray diffraction and electron microprobe studies show that this textural alteration may be accompanied by mineralogical changes from mg calcite to aragonite or from aragonite to mg calcite our findings support petrographic studies that reported syndepositional recrystallization in a wide variety of carbonate grains about thirty years ago but which have been largely ignored together these studies indicate that carbonate recrystallization is a widespread process of early diagenesis extensive recrystallization in shallow tropical seas challenges basic principles regarding the setting and timing of textural and mineralogic alteration of metastable carbonate grains in addition recognition of recrystallization as an important process of micritization contradicts prevailing theories that micritization results solely by infilling of microborings finally our findings raise fundamental questions concerning the nature of carbonate crystal structure mechanisms of crystal growth and driving forces for recrystallization answering these questions will require sedimentologists to step beyond traditional bounds into fields such as biomineralization and materials science

a terrestrial u th dated stable isotope record of the penultimate interglacial abstract here we present the first u series dated stable oxygen isotope record in continental europe that covers the entire tripartite penultimate interglacial i e marine isotope stages 7 5 to 7 1 this record was obtained from a u rich stalagmite from spannagel cave in the austrian alps which is largely devoid of kinetic isotope fractionation effects which comprised previously studied flowstone from this site composed of dense columnar calcite this speleothem apparently grew without significant interruption for ca 50 ka albeit at a very slow rate the age model was established based on 23 individual u th tims dates using a combination of a bayesian approach which includes additional information using stratigraphic constraints and the mixed effect regression model the resulting record shows three prominent maxima in 18 o mis 7 5 7 3 and 7 1 separated by a long earlier and a shorter later cold period mis 7 4 and 7 2 respectively the mid points of the transitions into the three warm phases occurred at 240 3 215 2 and 200 3 ka and the mis 7 6 transition was dated to 190 3 ka the timing of these climate transitions is supported by other samples from the same cave and agrees within analytical uncertainties with u th dated evidence from corals marine aragonitic sediments and submerged stalagmites as well as with orbitally tuned deep sea records good agreement was also found with new speleothem data from china as far as mis 7 1 and 7 5 are concerned whereas mis 7 3 apparently started earlier and mis 7 2 lasted longer than in the alps comparing the european speleothem data with antarctic ice cores reveals obvious differences in age the latter suggesting an earlier start and a generally shorter duration of the three warm episodes in essence this study underscores the great potential of speleothems as accurate and precise chronometers of pleistocene climate change and emphasizes the need for similar studies in other continents including submerged caves in order to improve the imperfect chronological framework of mis 7

calibration of the calcite water oxygen isotope geothermometer at devils hole nevada a natural laboratory abstract the 18 o of ground water 13 54 0 05 and inorganically precipitated holocene vein calcite 14 56 0 03 from devils hole cave 2 in southcentral nevada yield an oxygen isotopic fractionation factor between calcite and water at 33 7 c of 1 02849 0 00013 1000 ln calcite water 28 09 0 13 using the commonly accepted value of calcite water t of 0 00020 k 1 this corresponds to a 1000 ln calcite water value at 25 c of 29 80 which differs substantially from the current accepted value of 28 3 use of previously published oxygen isotopic fractionation factors would yield a calcite precipitation temperature in devils hole that is 8 c lower than the measured ground water temperature alternatively previously published fractionation factors would yield a 18 o of water from which the calcite precipitated that is too negative by 1 5 using a temperature of 33 7 c several lines of evidence indicate that the geochemical environment of devils hole has been remarkably constant for at least 10 ka accordingly a re evaluation of calcite water oxygen isotopic fractionation factor may be in order assuming the devils hole oxygen isotopic value of calcite water represents thermodynamic equilibrium many marine carbonates are precipitated with a 18 o value that is too low apparently due to a kinetic isotopic fractionation that preferentially enriches 16 o in the solid carbonate over 18 o feigning oxygen isotopic equilibrium

structural and host rock controls on the distribution morphology and mineralogy of speleothems in the castanar cave spain t he casta nar cave central western spain formed in mixed carbonate siliciclastic rocks of neoproterozoic age the host rock is finely bedded and shows a complex network of folds and fractures with a prevalent n150e strike this structure controlled the development and the maze pattern of the cave as well as its main water routes the cave formed more than 350 ka ago as the result of both the dissolution of interbedded carbonates and weathering of siliciclastic beds which also promoted collapse of the overlying host rock at present it is a totally vadose hypergenic cave but its initial development could have been phreatic the cave s speleothems vary widely in their morphology and mineralogy in general massive speleothems stalactites stalagmites flowstones etc are associated with the main fractures of the cave and bedding planes these discontinuities offer a fairly continuous water supply other branching fibrous mostly aragonite speleothems commonly occur in the steeper cave walls and were produced by capillary seepage or drip water detailed petrographical and isotope analyses indicate that both aragonite and calcite precipitated as primary minerals in the cave waters primary calcite precipitated in waters of low magnesium content whereas aragonite precipitated from magnesium rich waters differences in isotope values for calcite 5 2 for 18 oa nd 9 6 for 13 c and aragonite 18 oo f 4 5 and 13 co f 3 5 can be explained by the fact that the more unstable mineral aragonite tends to incorporate the heavier c isotope to stabilize its structure or that aragonite precipitates in heavier waters changes in the water supply and the chemistry and instability of aragonite caused 1 inversion of aragonite to calcite which led to the transformation of aragonite needles into coarse calcite mosaics 2 micritization which appears as films or crusts of powdery opaque calcite and 3 dissolution dolomite huntite magnesite and sepiolite were identified within moonmilk deposits and crusts moonmilk occurs as a soft white powder deposit on different types of speleothems but mostly on aragonite formations huntite and magnesite formed as primary minerals whereas dolomite arose via the replacement of both huntite and aragonite owing to its variety of speleothems and location in an area of scarce karstic features the casta nar cave was declared a natural monument in 1997 and is presently the target of a protection and research programme although the main products formed in the cave and their processes are relatively well known further radiometric data are needed to better constrain the timing of these processes for example it is difficult to understand why some aragonite speleothems around 350 ka old have not yet given way to calcite which indicates that the environmental setting of the cave is still not fully understood

start of the last interglacial period at 135 ka evidence from a high alpine speleothem a detailed study of growth periods of a flowstone from spannagel cave in the zillertal alps austria at 2500 m above sea level a site highly sensitive to climate changes offers unprecedented new insights into pleistocene climate change in central europe flowstone sample spa 52 has a high u content to 116 ppm analyses of this sample reveal that episodes of calcite deposition started at 204 3 ka 135 1 2 ka and 122 ka suggesting that at these times the mean air temperature at this high alpine site was within 1 5 c of the present day condition the beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 2 5 ka as deduced from the absolutely dated oxygen isotope curve in sediments from the bahamas as well as with recent coral evidence from barbados indicating a high sea level already by 135 8 0 8 ka this set of data supports evidence against northern hemisphere forcing of termination ii because the insolation maximum is at 127 ka

contrasting geochemical features of the central iberian zone shales iberian massif spain implications for the evolution of neoproterozoic lower cambrian sediments and their sources in other peri gondwanan areas abstract more than 90 samples of shales have been collected for geochemical purposes from neoproterozoic and lower cambrian sedimentary series in an extensive area of the central iberian zone ciz for similar sio2 and al2o3 abundances the neoproterozoic shales ns are characterized by relatively higher tio2 and zr abundances and by higher cr th and ti nb ratios by contrast the lower cambrian shales lcs have higher al2o3 tio2 rb zr la yb cn and th yb ratios diagrams such as al2o3 tio2 al2o3 tio2 ti nb tio2 zr tio2 zr nb and ti nb rb zr are useful to define two distinct fields that discriminate the neoproterozoic from the lower cambrian compositions these and other geochemical features suggest that these rocks were derived from different source compositions and that the lower cambrian shales lcs were chemically more fractionated than those of the neoproterozoic these distinctive chemical features are also recorded by neoproterozoic and cambrian fine grained rocks in other areas in the central iberian zone and in other zones within iberia published neodymium isotopic results consistently distinguish both compositions and together with the geochemical data support a relatively fractionated nature for the lower cambrian sediments compared to the neoproterozoic ones it is proposed that continental deposits derived from the interior orogens in north gondwana would have been the sources for neoproterozoic sediments in the iberian zones whereas the lower cambrian sediments in these zones would have been derived from older crust beneath those continental deposits thus the neoproterozoic lower cambrian stratigraphic succession in iberia reflects an inverse stratigraphy of the source area and contrasts with zones of central and western europe where equivalent sedimentary series record important coeval igneous contributions and show less fractionated geochemical characteristics finally the possible connection between the central iberian zone and the meguma zone mz in canada is discussed on the basis of certain sedimentological and geochemical features it is proposed that the sedimentary series of the central iberian zone and of the meguma zone represent respectively proximal and distal north gondwana derived sediments

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

expanding the utility of uranium series dating of speleothems for archaeological and palaeontological applications uranium series u series dating of speleothems is frequently used for palaeoclimate studies but its archaeological and palaeontological applications are limited to stratigraphically significant speleothem formations such as flowstones to provide maximum and minimum temporal points this study targeted soda straw stalactites for u series dating in contrast to other speleothem formations soda straw stalactites are fragile have typically short life spans usually only years but rarely up to a few hundred years and are frequently incorporated into cave deposits results of thermal ionisation mass spectrometry tims u series dating of soda straw stalactites from palaeontological excavations at blanche cave south australia show that small dense clean straws tend to yield ages closest to the time of stratigraphic deposition a correlation between soda straw u series ages and radiocarbon ages of charcoal from the site is shown multiple soda straw age determinations for a single stratigraphic unit are required in order to verify age concordance in conjunction with other dating methods u series dating of soda straw stalactites may help to significantly constrain the age of stratigraphic units and associated archaeological and palaeontological deposits in order to provide more robust chronologies here we advocate the collection of soda straw stalactites at future excavations of limestone cave sites

calcite and aragonite precipitation under controlled instantaneous supersaturation elucidating the role of caco3 saturation state and mg ca ratio on calcium carbonate polymorphism abstract for many decades researchers have attempted to clarify the factors controlling the precipitation of calcium carbonate polymorphs and the incorporation of mg into calcite precipitating in natural systems in this study a novel experimental approach delineates the role of instantaneous supersaturation and solution mg ca ratio in calcium carbonate mineralogy and composition the results of this study show that in solutions with different mg ca ratios the transition between the aragonite and the calcite aragonite precipitation fields is controlled by a combination of the saturation state of the solution with respect to caco3 and the mg ca ratio in solution the data show that for increasing solution mg ca ratios progressively higher supersaturation level is required for calcite precipitation the predominance of aragonite at high solution mg ca and low supersaturations is attributed to a relative decrease in calcite growth rates as a result of increasing incorporation of mg2 in the calcite lattice at higher solution mg ca ratios as suggested by abundant experimental work increasing solution mg ca decreases the growth rate of calcite while aragonite growth rates stay unaffected our experiments do demonstrate that despite decreased growth rate the percentage of mgco3 in calcite increases with increasing solution mg ca ratio as calcite growth rates decrease aragonite growth rates stay constant and it becomes the dominant mineral phase in solutions with high mg ca ratio and low supersaturations these findings are relevant to present day mineralogical distributions in carbonate systems and might be the key to elucidate the environmental conditions responsible for mineralogic changes through geologic time the observed dependence of calcium carbonate mineralogy on solution composition and supersaturation suggests that carbonate mineralogy is controlled by kinetics of growth

the role of magnesium in the crystallization of calcite and aragonite in a porous medium abstract morphological development of calcite crystals is related to supersaturation conditions during growth crystallization of calcium carbonate calcite and aragonite as well as mg calcite was studied under controlled supersaturation conditions by the counter diffusion of ca2 and co32 ions through a porous transport medium a column of silica gel under our experimental conditions where ion transport is constrained to be diffusion controlled nucleation and growth take place under conditions of high supersaturation the actual threshold value of the supersaturation depending on the supersaturation gradient in the pure caco3 system calcite grows at lower supersaturation than aragonite the calcite develops relatively simple rhombohedra whil the aragonite grows as spherulites presence of mg2 in the interstitial fluid inhibits nucleation increasing the threshold supersaturation at which crystallization begins the resulting mg calcite crystals show a range of morphologies depending on the mg content and the supersaturation at the point of crystallization at high values of supersaturation up to 15 mol mgco3 is incorporated into the calcite and the crystals form spheres at lower supersaturations mg content decreases and morphologies change progressively through a well defined and reproducible sequence from spheres to dumbbell like forms to wheat sheaf like bundles and eventually single crystals with steep rhombohedral faces the crystals are compositionally zoned showing both sector and oscillatory zoning the compositional evol tion is related to the supersaturation and interface roughness during crystal growth

speleothem evidence for changes in indian summer monsoon precipitation over the last 2300 years speleothems from a well ventilated dolomitic cave in the pokhara valley central nepal preserve a mineralogic record of indian summer monsoon variability over the past 2300 yr annually deposited aragonite layers formed between 2300 and 1500 yr b p indicating reduced monsoon precipitation and increased cave aridity whereas alternating calcite aragonite laminae deposited after 1500 yr b p record elevated summer monsoon precipitation and increased cave humidity dense optically clear calcite layers deposited from 450 5 to 360 20 yr b p 1550 to 1640 a d indicate a less evaporative cave environment and suggest moister and or cooler conditions possibly related to climatic change associated with the onset of the little ice age

potential effects of alpha recoil on uranium series dating of calcrete abstract evaluation of paleosol ages in the vicinity of yucca mountain nevada at the time the site of a proposed high level nuclear waste repository is important for fault displacement hazard assessment uranium series isotope data were obtained for surface and subsurface calcrete samples from trenches and boreholes in midway valley nevada adjacent to yucca mountain 230 th u ages of 33 surface samples range from 1 3 to 423 thousand years ka and the back calculated 234 u 238 u initial activity ratios ar are relatively constant with a mean value of 1 54 0 15 1 which is consistent with the closed system behavior subsurface calcrete samples are too old to be dated by the 230 th u method u pb data for post pedogenic botryoidal opal from a subsurface calcrete sample show that these subsurface calcrete samples are older than 1 65 million years ma old enough to have attained secular equilibrium had their u th systems remained closed however subsurface calcrete samples show u series disequilibrium indicating open system behavior of 238 u daughter isotopes in contrast with the surface calcrete where open system behavior is not evident data for 21 subsurface calcrete samples yielded calculable 234 u 238 u model ages ranging from 130 to 1875 ka assuming an initial ar of 1 54 0 15 the mean value calculated for the surface calcrete samples a simple model describing continuous recoil loss predicts that the 234 u 238 u and 230 th 238 u ars reach steady state values 2 ma after calcrete formation potential effects of open system behavior on 230 th u ages and initial 234 u 238 u ars for younger surface calcrete were estimated using data for old subsurface calcrete samples with the 234 u loss and assuming that the total time of water rock interaction is the only difference between these soils the difference between the conventional closed system and open system ages may exceed errors of the calculated conventional ages for samples older than 250 ka but is negligible for younger soils

loss of primary texture and geochemical signatures in speleothems due to diagenesis evidences from castanar cave spain geochemical signals from speleothems are commonly used in the investigation of palaeoenvironments in most cases however little attention is paid to whether or not these signals are primary or altered by diagenesis the speleothems of the castanar cave caceres spain which are initially formed of calcite or aragonite have undergone a variety of meteoric diagenetic processes such as micritization and neomorphism inversion that collectively modify their primary features textures mineralogy geochemical signals the mean 13c and 18o values of the aragonites in the cave are 8 66 and 4 64 respectively whereas the primary calcites have mean 13c and 18o values of 9 99 and 5 77 respectively following the diagenetic process of micritization the aragonite isotopic signals averaged 7 63 13c and 4 74 18o and the calcite micrite signals 9 53 13c and 5 21 18o where inversion took place some secondary calcites after the aragonite show preserved aragonite whereas others do not the secondary calcites without aragonite relics show isotopic values slightly higher than those of the primary calcite due to the inheritance of the aragonite signal where aragonite relics are preserved the isotopic signatures are very similar to those of the aragonite micrite in addition the stable isotopic values and sr and mg contents of the speleothems became also modified by micritization and or inversion these diagenetic processes were driven by the changes in composition of the cave waters over time and space but also in the case of aragonite by its initial unstable mineralogy the present results highlight how important diagenesis is in caves and how the initial features of cave minerals may be lost these changes alter the geochemical signals shown by speleothems which may have an impact on the interpretation of the results obtained in palaeoenvironmental studies

determination of aragonite trace element distribution coefficients from speleothem calcite aragonite transitions the processes that govern the incorporation of trace elements into speleothems can often be linked to environmental changes although element incorporation into speleothem calcite is now reasonably well understood current knowledge regarding trace element variability in speleothem aragonite is very limited of particular interest is whether trace element distribution coefficients are above or below one in order to assess the extent to which prior aragonite precipitation has affected speleothem aragonite trace element records this study uses nine calcite to aragonite transitions in seven speleothems from diverse environmental settings to derive the first quantitative estimates of the distribution coefficients for several elements in speleothem aragonite dmg ar 9 7e 5 9 01e 5 dba ar 0 91 0 88 dsr ar 1 38 0 53 and du ar 6 26 4 54 1 sd for one speleothem from western germany the distribution coefficients are generally higher which is potentially related to the very low growth rates 11 m year of this sample in particular dsr ar appears to show a negative correlation with growth rate when growth rate is below 20 m year in summary our results demonstrate that speleothem aragonite dmg ar is below one du ar is considerably above one and dsr ar is above one or close to unity for dba ar reaching a similar conclusion is difficult due to the relatively high uncertainty enhanced prior aragonite precipitation will thus result in lower u and higher mg concentrations in speleothem aragonite although in many cases mg in speleothem aragonite is most likely dominated by other processes this result suggests that u concentrations in aragonitic stalagmites could serve as a very effective proxy for palaeo rainfall

high resolution mapping of uranium and other trace elements in recrystallized aragonite calcite speleothems from caves in the pyrenees france implication for u series dating abstract aragonite and calcite speleothems were sampled in the cave of pierre saint martin pyrenees atlantiques france these speleothems contain significant amounts of uranium and strontium which were measured spatially and chemically by nuclear microprobe analysis sr and u distributions are highly varied with a marked contrast between aragonite and calcite because the aragonite concentrates sr and u on the other hand zn is preferentially located in calcite and in layers of organic matter trapped in caco 3 sr contents ranged from 440 to 1100 g g in the calcite and 4900 to 18 500 g g in the aragonite u concentrations show remarkably high values from 11 to 19 g g in the calcite and 89 to 350 g g in the aragonite these u and sr concentrations are amongst the highest measured in supergene speleothems deposited by infiltrating meteoric waters x ray absorption experiments with synchrotron radiation suggested that uranium was incorporated in its hexavalent oxidation state in both aragonite and calcite recrystallization from aragonite into calcite was indicated by micromorphological observations for some of the samples this recrystallization process may explain the uranium loss in neogenic calcite deposits and consequently the opening of the geochemical system which can lead to errors in age dating with the u series dating method uranium loss in recrystallized calcite is one of the important aspects to be considered in u series dating and more generally for u geochemical stability in caco 3

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

dolomite in caves recent dolomite formation in oxic non sulfate environments castanar cave spain abstract dolomite is a common mineral in the rock record but rare in recent superficial environments where it does occur it is related to anoxic sulfate rich environments and microbial activity the occurrence of some dolomite deposits in caves however indicates that dolomite formation is also possible in oxic non sulfate settings dolomite is forming at 17 c and in oxic vadose conditions on the host rocks and aragonite speleothems of the castanar cave caceres spain it appears as spheroids and dumbbells 50 300 m in diameter that internally consist of micron sized rhombic to rounded crystals initially this dolomite is ca rich non stoichiometric and poorly ordered mg rich solutions allow the precipitation of metastable mg rich carbonates such as huntite this soon transforms into this ca rich dolomite which later ages to form a more stoichiometric dolomite these dolomites show similarities to those grown under anoxic sulfate rich conditions and their presence in caves provides a different setting that may contribute to the understanding of the dolomite problem including their initial formation and later recrystallization processes

the little ice age and medieval warm period in the sargasso sea sea surface temperature sst salinity and flux of terrigenous material oscillated on millennial time scales in the pleistocene north atlantic but there are few records of holocene variability because of high rates of sediment accumulation holocene oscillations are well documented in the northern sargasso sea results from a radiocarbondated box core show that sst was approximately 1 degree c cooler than today approximately 400 years ago the little ice age and 1700 years ago and approximately 1 degree c warmer than today 1000 years ago the medieval warm period thus at least some of the warming since the little ice age appears to be part of a natural oscillation 39 refs 4 figs 1 tab

precipitation of barite by marine bacteria a possible mechanism for marine barite formation barite baso 4 is found throughout the ocean yet seawater is undersaturated with respect to barite and organisms that could account for the abundance of barite have not yet been identifi ed the mechanism for barite formation in seawater is not fully understood here we show that marine bacteria have the ability to precipitate barite through a metabolically mediated biomineralization process we precipitated barite in laboratory experiments in the presence of several strains of marine bacteria grown on yeast media enriched with barium ba barite did not precipitate under identical conditions in killed bacteria controls the crystals develop from amorphous phosphorous rich spherical precursors with fi brous internal textures common in bacterial mineral precipitation bacterial mediation of barite precipitation can explain the distribution of barite in the water column and the occurrence of barite crystals in organic rich sinking aggregates where bacteria are concentrated this fi nding has implications for the use of barite and ba proxies in paleoceanographic research

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

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

stable isotope composition alteration produced by the aragonite to calcite transformation in speleothems and implications for paleoclimate reconstructions abstract aragonite a mineralogical constituent of speleothems in cave environments is unstable and susceptible to inversion to calcite a diagenetic process that involves changes in the mineralogy texture and geochemistry of speleothems however the exact alterations of stable isotope compositions during such diagenesis have not been fully investigated in this study two aragonite stalagmites sn3 and sn15 from the shennong cave southeast china were found partially inverted to calcite as determined by x ray diffraction xrd and scanning electron microscopy sem analyses and thin section inspections under microscope the fiber relics and textural ghosts of aragonite preserved in coarse and equant mosaic calcite crystals clearly indicate that the calcite in these two stalagmites were inverted from aragonite the stable isotope compositions 13 c and 18 o given in per mil versus vpdb standard of primary aragonite and secondary calcite were analyzed and compared along both growth layers and growth axes the results show that along growth layers differences of 13 c values between aragonite and calcite are negligible 0 1 0 2 whereas differences of 18 o values between aragonite and calcite are significant 0 63 0 87 comparisons along growth axes show similar results i e differences of 13 c values are negligible 0 06 0 22 whereas differences of 18 o values are significant 0 85 0 29 most likely the aragonite in sn3 and sn15 were internally inverted by interactions of trace calcite crystallites and pore water within intercrystalline pore spaces by a dissolution reprecipitation process occurring in trapped pore water in the case of the inversion of aragonite to calcite in speleothems such as that observed in sn3 and sn15 the 13 c values could be used in paleoclimate and paleoenvironment reconstructions because they are inherited from those of primary aragonite although the 18 o values might be cross calibrated to those of primary aragonite if the aragonite calcite fractionation offset is known e g 0 85 0 29 in this study however the 18 o values of secondary calcite should be used with caution in such reconstructions as the 18 o offset value is not consistently invariable

influence of mg2 on the kinetics of calcite precipitation and calcite crystal morphology abstract the kinetics of calcite growth in the presence of mg2 has been studied by both a ph free drift method and by visual observation our experiments show that the calcite growth rate is reduced by the presence of mg2 the higher the mg ca ratio in the solution the lower the growth rate in a caco3 supersaturated solution the inhibition of calcite growth by the presence of mg2 is caused by mg2 being incorporated into the original calcite seed surfaces and developing new crystal surfaces the mg2 distribution on the calcite surfaces is not uniform as there is likely to be different mg2 densities on the newly developed surfaces than on the original surfaces of the calcite seeds this causes the calcite crystal morphology to change the significance of creating error in using the initial rate data rather than the equilibrium rate data for the prediction of the calcite precipitation kinetics is discussed

uranium series dating applications in natural environmental science uranium series u series analyses are an essential component of many research projects in earth and environmental science oceanography hydrology and science based archaeology topics range from magma chamber evolution and volcanic hazard prediction global climatic change through dating of authigenic carbonate deposits human evolution through dating of bone to the study of groundwater evolution the u series decay chains contain many elements that can be fractionated in environmental and geological processes half lives of radioactive isotopes of such elements range from seconds to many millennia and application depends on the natural timeframe of the process or the elapsed time this review will be limited to some aspects of the 238u 234u 230th 226ra system with half lives of 245 kyr 76 kyr and 1 6 kyr respectively in environmental systems fractionation of uranium and thorium is a very efficient process because thorium is extremely insoluble while hexavalent uranium in oxidising conditions is relatively soluble many authigenic precipitates of calcite contain virtually no thorium and inorganic precipitates have u ca ratios very similar to the ratio of dissolved uranium and calcium almost no radiogenic 230th in the precipitate means that the radiogenic clock starts effectively at zero however pure authigenic precipitates are rare and many contain some allogenic material mostly silicate with 238u in secular equilibrium with significant 230th some of the characteristics of different types of samples and various methods to accommodate or correct for inherited 230th will be discussed authigenic material should remain a closed system with respect to the relevant isotopes but that requirement is sometimes difficult to maintain because radioactive decay results in damage to the crystal lattice of the host mineral consequences of this recoil effect and correction schemes will be discussed dating archaeological bone based on the systematics of diffusion and adsorption to effectively model open system behaviour is also included

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

stalagmite growth and palaeo climate the numerical perspective abstract the growth of stalagmites can be approximated by a simple mathematical model which depends on growth rate and equilibrium radius these two parameters are controlled by the climate temperature variations derived from ice and deep sea core data together with models for changes in precipitation and soil cover are used to derive stalagmite stratigraphies which reflect the palaeo climate variations imposed in general stalagmite growth is strongly correlated to temperature and the amount of carbon dioxide available in the soil furthermore precipitation is correlated to the stalagmite diameter however several assumptions need to be made i a functional relationship between temperature on the one hand and precipitation and soil cover on the other needs to be established ii the kinetics of calcite dissolution and precipitation needs to be assigned either under soil and epikarst conditions open to the atmosphere or under fractured rock conditions closed from the atmosphere these assumptions are difficult to access from field data and therefore a stalagmite stratigraphy can be ambiguous and not easily converted back into an unknown palaeo climate signal

pleistocene speleothems of mallorca implications for palaeoclimate and carbonate diagenesis in mixing zones the pleistocene speleothems of sa bassa blanca cave mallorca are excellent indicators of palaeoclimate variations and are samples that allow evaluation of the products and processes of mixing zone diagenesis in an open water cave system integrated stratigraphic petrographic and geochemical data from a horizontal core of speleothem identified two main origins for speleothem precipitates meteoric marine mixing zone and meteoric vadose zone mixing zone precipitates formed at and just below the water air interface of cave pools during interglacial times when the cave was flooded as a result of highstand sea level mixing zone precipitates include bladed and dendritic high mg calcite microporous bladed calcite with variable mg content and acicular aragonite their presence suggests that calcium carbonate cementation is significant in the studied mixing zone system fluid inclusion salinities 13c and 18o compositions of the mixing zone precipitates suggest that mixing ratio was not the primary control on whether precipitation or dissolution occurred rather the proximity to the water table and degassing of co2 at the interface were the major controls on precipitation thus simple two end member mixing models may apply only in mixing zones well below the water table meteoric vadose speleothems include calcite and high mg calcite with columnar and bladed morphologies vadose speleothems precipitated during glacial stages when sea level was lower than present progressive increase in 13c and 18o of the vadose speleothems resulted from cooling temperatures and more positive seawater 18o associated with glacial buildup such covariation could be considered as a valid alternative to models predicting invariant 18o and highly variable 13c in meteoric calcite glacio eustatic oscillations of sea level are recorded as alternating vadose and mixing zone speleothems short term climatic variations are recorded as alternating aragonite and calcite speleothems precipitated in the mixing zone fluid inclusion and stable isotope data suggest that aragonite as opposed to calcite precipitated during times of reduced meteoric recharge

effect of aragonite to calcite transformation on the geochemistry and dating accuracy of speleothems an example from castanar cave spain aragonite speleothems are increasingly being used as high resolution climate proxies however aragonite is unstable and susceptible to diagenetic transformation into calcite leading to mineralogical textural and geochemical alterations that have not been fully investigated to provide some insights to these modifications this study combines stable isotope geochemistry and u series dating with petrological observations and empa elemental analyses to characterize a stalagmite from castanar cave caceres spain that shows primary aragonite diagenetically altered and with reverse ages the diagenetic processes include recrystallization to calcite micritization and dissolution characterization and interpretation of the chemistry and nature of the waters from which the aragonite precipitated and of the ones that subsequently formed the calcite indicates that both polymorphs formed from the same fluids these fluids hydrochemically evolved from an aragonite mode to a calcite mode along a diagenetic path within the sample the results show that during transformation the system stayed close in one of the stages and open in the other with the same textural result reverse ages are found either in the recrystallized areas or in the primary aragonite caused by two different u remobilization mechanisms u leaching due to flowing waters on the surface and u loss during the transformation process these results highlight the complex behavior of speleothems during diagenesis and the impact on the geochemical information of the primary and secondary phases and thus the importance of petrological and geochemical characterization of speleothems for paleoclimatic studies

relationships between colour and diagenesis in the aragonite calcite speleothems in basajaun etxea cave spain abstract basajaun etxea cave north spain contains a wide morphological and colour variety of speleothems most of them are composed of aragonite but calcite speleothems are also found their most common colour is white but there are also pink green and turquoise speleothems in different areas of the cave mg rich dissolution waters from the cave s crystalline dolostone and magnesite host rock favour aragonite precipitation and drive important diagenetic changes in this paper we will discuss how diagenesis modifies speleothem texture mineralogy and geochemistry causing significant changes in the colour we also discuss how speleothems that have undergone diagenesis may also be useful indictors of paleoclimatic conditions our work shows that diagenesis changes the colour of the speleothems because of the mobility of the chromophore elements during this process along with this elemental alteration comes the loss of the primary isotopic signals of speleothems detailed petrological studies of speleothems should precede their analysis for palaeoclimatic reconstruction so that influence of areas affected by diagenesis can be eliminated in addition diagenetic signals also contain valuable information on the changes of the waters within the cave and the overall evolution of speleothems and the cave itself

aragonite calcite speleothems identifying original and diagenetic features despite the increasing use of speleothems as high resolution archives of past climate proxies few efforts have been made to improve understanding of diagenetic pathways affecting this material and to assess the degree of postdepositional transformation of initial features including associated geochemical signatures to provide criteria for distinguishing primary spelean growth history and secondary spelean diagenetic history features this study documents a process based approach combining mineralogical textural and geochemical data at different scales to characterize various diagenetic processes undergone by aragonite and calcite speleothems from the pont de ratz cave herault s france results show that the initial precipitation of carbonate minerals forming the stalagmites vadose precipitation is represented alternatively by aragonite and calcite and consists of two types of primary aragonite and a primary columnar calcite four different types of growth interruption and inclusion horizons are evident and attest to the discontinuous growth of stalagmites in this cave postdepositional diagenetic processes include void filling calcite cementation selective dissolution of either aragonite or calcite and recrystallization recrystallization processes include 1 textural change of original aragonite precipitates isomineralogical recrystallization and 2 two distinct types of aragonite to calcite recrystallization these results highlight the diversity of potential synformational and postformational processes controlling the formation and evolution of speleothems and their impact on the geochemical properties of the primary and secondary carbonate phases and the potential importance in paleoclimatic interpretation

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

geochemistry and petrology of recycled orogen derived sediments a case study from upper precambrian siliciclastic rocks of the central iberian zone iberian massif spain abstract two areas of upper precambrian siliciclastic rocks separated from each other by 150 km were selected in the central iberian zone ciz for a petrological and geochemical study the petrology of the coarser grained rocks indicates the absence or scarcity of igneous clasts the presence of extrabasinal and intrabasinal clasts and homogeneous features of sandstones ranging from very fine to fine grained the modal data of these rocks plot close to the qt l and qm lt sides of qtfl and qmflt triangular diagrams suggesting provenance from a recycled orogen the geochemical data on the shales and sandstones from the two areas studied are very uniform both groups of rock show similar ranges of relevant major element ratios such as al 2 o 3 tio 2 17 46 21 51 17 46 21 34 for shale and sandstone respectively al 2 o 3 feo t 2 40 3 79 2 18 3 33 and feo t feo t mgo 0 71 0 77 0 68 0 76 together with parallel average rare earth element ree patterns and similar values for some key trace element ratios la th th yb th u zr hf sm nd and cr sc other trace element ratios la sc th sc cr th and cr zr are uniform in the shales group and also in the sandstones group although minor differences become apparent when both groups are compared these differences are probably related to the quartz dilution effect affecting the relative abundance of phyllosilicates in these rocks and indirectly the sc and cr contents given their covariations with al2o3 the zr yb zr y and zr th ratios of the shales are uniform the sandstones show higher and more variable values and there is no correlation between zr abundance and any of these ratios in the shales or sandstones together with the parallel ree patterns shown by both groups of rock these results suggest the absence of heavy mineral fractionation during the transport of detrital material and or the relative importance of other minerals probably phyllosilicates in the control of yb y and th abundances apparently all the groups of rocks show a remarkable geochemical homogeneity despite the distance between the sampling areas thus the petrological and chemical data are consistent and point to a very extensive homogeneous and stable source region as the most plausible contributor to the upper precambrian siliciclastic rocks in the ciz the possible relationship between this zone and n gondwana is also discussed

replacement of aragonite by calcite in sediments from the san cassiano formation italy abstract the fossils of the patch reefs of the san cassiano formation triassic northern italy still preserve aragonite in their shell the explanation for the persistence of the metastable polymorph of caco3 has been believed to be the lowering of the porosity and permeability of the sediment by early cementation and the presence of marls scherer 1977 the transmission electron microscope tem adds to the understanding of the replacement mechanism recrystallization occurs primarily along crystal defects suggesting that the kinetics of the replacement are controlled mainly by the microstructure of aragonite at least under conditions of slow diagenetic alteration the replacive calcite in the san cassiano fossils and the calcite crystals of the cement show a pervasive modulated microstructure when observed with the tem this can be attributed either to compositional variations calcite contains mg and fe to stacking disorder or to positional disorder of anions we believe that these modulations account mainly for the metastability of the san cassiano calcite this study further demonstrates that transmission electron microscopy is a powerful technique in investigations of sedimentary rocks and their diagenesis

cryptic diagenesis and its implications for speleothem geochronologies abstract speleothems are usually considered as one of the most amenable palaeoclimate archives for u series dating a number of studies in recent years however report cases of diagenetic alteration which compromises the use of u series systematics in speleothems resulting in inaccurate u th ages here we present the results of a high resolution u th dating study of a stalagmite cc26 from corchia cave in italy where we document a number of departures from an otherwise well defined age depth model and explore potential causes for these outliers unlike examples illustrated in previous studies cc26 contains no visible evidence of neomorphism and appears at least superficially ideally suited to dating good reproducibility obtained between multi aliquot u th analyses removes any possibility of analytical issues contributing to these outliers furthermore replicate analyses of samples from the same stratigraphic layer yielded ages in stratigraphic sequence implying very localized open system behavior uranium loss is suggested as a causative mechanism on account of the fact that all the outliers are older than their assumed true age a limited number of micro voids were observed under micro ct analyses and it is proposed that these were pathways for u loss uranium loss modelling allows us to constrain the possible timing of diagenetic alteration and indicates that the precursor for the outlier with the largest age discrepancy 309 must have been aragonite this study indicates that visibly unaltered speleothems may still contain small domains that have experienced post depositional alteration such cryptic diagenesis as recorded in this stalagmite has implications for the constancy of accuracy of the u series dating technique and suggests a need for careful examination of speleothems prior to dating particularly in low resolution u th studies

annual trace element cycles in calcite aragonite speleothems evidence of drought in the western mediterranean 1200 1100 yr bp each of two calcitic stalagmites from grotte de clamouse herault southern france displays a discrete aragonite layer dated at around 1100 yr bp the layer of fanning aragonite ray crystals is immediately preceded by calcite with mg and sr compositions that are uniquely high for the past 3 kyr trace element compositions close to the boundary between original aragonite and calcite are consistent with quasi equilibrium partitioning of trace elements between the phases study of modern dripwaters demonstrates that pronounced covariation of mg ca and sr ca ratios in dripwater occurs owing to large amounts of calcite precipitation upflow of the drips that fed the stalagmites trace element to ca ratios are enhanced during seasonally dry periods ion microprobe data demonstrate a pronounced covariation of trace elements including mg and sr in calcite and sr u and ba in aragonite the mean peak spacing is close to the long term mean of annual growth rates determined by differences in u series ages and so the trace element peaks are interpreted as annual the trace element chemistry of the stalagmites on annual to inter annual scales thus directly reflects the amounts of prior calcite precipitation interpreted as an index of aridity the longer term context is a multi decadal period of aridity 1200 1100 yr bp possibly correlated with an analogous episode in central america the arid period culminated in the nucleation of aragonite but within a decade was followed by a return to precursor conditions copyright 2005 john wiley sons ltd

diagenesis of speleothems and its effect on the accuracy of 230th u ages abstract speleothems can be precisely dated by u series disequilibrium methods one basic assumption of the 230th u dating method is that the system remains closed and u and th isotopes are neither lost nor added after deposition for stalagmites this requirement is usually fulfilled due to their protected environment in caves however undersaturated drip water may lead to diagenesis of speleothem caco3 and altered 230th u ages here we present a detailed petrographic investigation using thin sections and 230th u ages of a stalagmite from the riesenberghohle northern germany which grew during marine isotope stages 5e c and a the occurrence of a mosaic fabric in large parts of the stalagmite in combination with several age inversions is a clear indication for diagenetic alteration we discuss the potential diagenetic processes and quantitatively model their influence on the 230th u ages post depositional u loss leads to increasing 230th 238u activity ratios and thus apparently older ages in contrast post depositional addition of u results in decreased 230th 238u activity ratios and apparently younger ages comparison with our modelling results suggests that diagenesis occurred early after deposition initial and post depositional detrital contamination probably played a minor role for the observed age inversions

u th isotope systematics from the soreq cave israel and climatic correlations precise 230 th 234 u ages were obtained on thirty one growth laminae in speleothem samples which are self consistent with the detailed layer stratigraphy samples with low 232 th 238 u ratios give ages with analytical uncertainties of 40 years at 2 ky and 1000 years at 90 ky some growth zones with high but variable 232 th 238 u were dated by intermal isochrons this permits the determination of the initial 230 th 232 th assuming equilibrium of 232 th and 238 u series in the source of the high 232 th component this shows initial 230 th 232 th in activity units of from 1 3 to 2 9 the calculated atomic ratios of 232 th 238 u for the high 232 th component range from 1 08 to 2 4 which is well below the average crustal value speleothem materials with high 232 th 238 u are found to exhibit clear correlations of 232 th with si al and fe while 238 u correlates with sr and ba analyses of soreq cave drip waters show that the particulates in the waters have high 232 th concentrations and a 232 th 238 u ratio much lower than that found in the high 232 th component in speleothems but with 230 th 232 th 1 0 to 2 4 we infer that the trapped high th component in speleothems is from particulate matter in water with a large concentration of adsorbed u and not simply from detrital material the speleothems have only small234u excess the initial 234 u 238 u 0 show a range of 1 02 to 1 14 that was found to correlate with age over the past 25 ky the youngest samples have values in the same range as the modern drip waters there appears to be a correlation of 234 u 238 u 0 with the 18 o values there is a drop of 18 o in the time interval 20 to 15 ky which then remains relatively constant to recent times as the high 18 o values have been related to rainfall and associated climatic conditions we suggest that the 234 u 238 u in the speleothem reflects the effects of rainfall and soil weathering conditions on drip water composition and may provide a proxy for climate change