The oxygen isotope composition of speleothems is a widely used proxy for past climate change. Robust use of this proxy depends on understanding the relationship between precipitation and cave drip ...water δ
O. Here, we present the first global analysis, based on data from 163 drip sites, from 39 caves on five continents, showing that drip water δ
O is most similar to the amount-weighted precipitation δ
O where mean annual temperature (MAT) is < 10 °C. By contrast, for seasonal climates with MAT > 10 °C and < 16 °C, drip water δ
O records the recharge-weighted δ
O. This implies that the δ
O of speleothems (formed in near isotopic equilibrium) are most likely to directly reflect meteoric precipitation in cool climates only. In warmer and drier environments, speleothems will have a seasonal bias toward the precipitation δ
O of recharge periods and, in some cases, the extent of evaporative fractionation of stored karst water.
Very little is known about Neanderthal cultures, particularly early ones. Other than lithic implements and exceptional bone tools, very few artefacts have been preserved. While those that do remain ...include red and black pigments and burial sites, these indications of modernity are extremely sparse and few have been precisely dated, thus greatly limiting our knowledge of these predecessors of modern humans. Here we report the dating of annular constructions made of broken stalagmites found deep in Bruniquel Cave in southwest France. The regular geometry of the stalagmite circles, the arrangement of broken stalagmites and several traces of fire demonstrate the anthropogenic origin of these constructions. Uranium-series dating of stalagmite regrowths on the structures and on burnt bone, combined with the dating of stalagmite tips in the structures, give a reliable and replicated age of 176.5 thousand years (±2.1 thousand years), making these edifices among the oldest known well-dated constructions made by humans. Their presence at 336 metres from the entrance of the cave indicates that humans from this period had already mastered the underground environment, which can be considered a major step in human modernity.
A multi-element study involving major alkaline-earth cations (Mg, Ca, Sr, Ba) and trace elements like Na, U, Mn, Y and Rare Earth Elements (REE) in calcite of a stalagmite from the Chauvet Cave (SE ...of France) was carried out using ICP-QMS analysis. This study focused on the Chau-stm6 stalagmite which displays a record of the Last Deglaciation until the end of the Younger Dryas with ages ranging from 33
kyr to 11.5
kyr BP. In this study, profiles of the alkaline-earth elements Sr and Ba show concentrations increasing sharply at the beginning of the deglaciation while Mg and U show a decreasing trend. REY (REE
+
Y) concentrations decrease sharply during early deglaciation. The clear record of the onset of the Younger Dryas by stable isotopes is not well marked by these elements. The absence of a significant correlation between REY and Mn suggests that REE were here not strongly bound to particulate–colloidal phases but were mainly controlled by limestone–groundwater interaction. Shale-normalized REE patterns in stalagmite, characterized by a negative Ce anomaly and HREE enrichment compared to LREE is thought to mainly arise from the dissolution of bedrock since Chau-stm6 patterns are similar to those of the bedrock. Chau-stm6 REY patterns are even more depleted in LREE than those of the bedrock, showing that part of the LREE were removed from groundwater upstream from the stalagmite. Some particular REY pattern changes were observed for the different climatic conditions: 1) glacial samples often display a more marked negative Ce anomaly (~
0.3) and a high Y/Ho ratio (~
0.6); 2) Bølling–Allerød and Younger Dryas samples display a variable and less pronounced anomaly (0.5–0.8) and a lower Y/Ho ratio (0.35–0.55). Climatic changes modified the rate of the stalagmite growth which likely caused a change in the properties of element incorporation in the calcite lattice. Consequently the concentration variations of Mg, Ca, Sr, Ba, U and REY would be directly controlled by ionic radii of each element.
► The Chau-stm-6 growth rate increases during the Last Deglaciation and remains high during the Younger Dryas. ► Concentrations of large ions increase while concentrations of small ions decrease during the Last Deglaciation. ► Changes in growth rate seem to be the first-order control on this record.
Villars Cave is a typical shallow cave from South-West France (45.44°N; 0.78°E; 175 m asl) that has provided several speleothempalaeoclimatic records such as the millennial scale variability of the ...Last Glacial period and the Last Deglaciation. Monitoring theVillars cave environment over a 13-year period has helped in the understanding of the stable isotopic speleothem content and inthe hydrology. For example, it was demonstrated that most of the calcite CaCO3 carbon comes from the soil CO2, which explainsthe sensitivity of the δ13C to any vegetation and climatic changes. Drip rate monitoring, carried out under four stalactites from thelower and upper galleries, has shown a well marked seasonality of the seepage water with high flow rates during winter and spring.A time delay of about two months is observed between the water excess (estimated from outside meteorological stations) and thedrip rate in the cave. A great heterogeneity in the flow rate amplitude variations and in the annual quantity of water between twonearby stalactites is observed, confirming the complexity of the micro-fissure network system in the unsaturated zone. At a dailyscale, the air pressure and drip rates are anti-correlated probably because of pressure stress on the fissure network. Cave air CO2concentration follows soil CO2 production and is correlated with its δ13C content. Since the beginning of the monitoring, the cave airtemperature, in both lower and upper galleries, displays a warming trend of ~+0.4°C±0.1/10yrs. This might be the consequence ofthe outside temperature increase that reaches the Villars Cave galleries through thermal wave conduction. Chemistry monitoringover a few years has shown that the seepage water of the lower gallery stations is significantly more concentrated in trace and minorelements (i.e. Sr, Mg, Ba, U) than the upper stations, probably due to the 10-20 m depth difference between these galleries, whichimplies a different seepage pathway and different water/rock interaction durations. There is also, in the elemental concentration(i.e. Ca), a seasonal signal which causes variation in the speleothem growth rates. Modern calcite deposit experiments conductedfor several years have permitted the calculation of vertical growth rates, which are extremely high in Villars (i.e. 1.0 to 1.75 mm/yr). Pollen filter experiments in the cave have demonstrated that most of the pollen grain found in the cave comes from the air andnot from the water. The specificity of the Villars Cave records is that the climatic variations were well recorded in the calcite δ13Cwhereas the δ18O is usually used in such studies. Overall, these results are helpful for the interpretation of speleothem records forpalaeoclimatic reconstructions, but more work is needed, especially numerical modelling of the temperature, chemistry and hydrology.
Among the paintings and engravings found in the Chauvet-Pont d'Arc cave (Ardèche, France), several peculiar spray-shape signs have been previously described in the Megaloceros Gallery. Here we ...document the occurrence of strombolian volcanic activity located 35 km northwest of the cave, and visible from the hills above the cave entrance. The volcanic eruptions were dated, using 40Ar/39Ar, between 29 ± 10 ka and 35 ± 8 ka (2σ), which overlaps with the 14C AMS and thermoluminescence ages of the first Aurignacian occupations of the cave in the Megaloceros Gallery. Our work provides the first evidence of an intense volcanic activity between 40 and 30 ka in the Bas-Vivarais region, and it is very likely that Humans living in the Ardèche river area witnessed one or several eruptions. We propose that the spray-shape signs found in the Chauvet-Pont d'Arc cave could be the oldest known depiction of a volcanic eruption, predating by more than 34 ka the description by Pliny the Younger of the Vesuvius eruption (AD 79) and by 28 ka the Çatalhöyük mural discovered in central Turkey.
•Temperature variations (PIT) induced by atmospheric pressure dominate in caves.•After the transfer functions are determined, the PIT variations can be subtracted.•PIT corrected residual signals ...studied in four natural caves in France.•Temperature signals as small as 10−3 °C when visitors are present then observable.•Temperature signals associated with infiltration transients or resonances unveiled.
In underground cavities, temperature variations of the order of 10−3 °C are permanently induced by the variations of atmospheric pressure, even at great depths, with couplings of the order of 0.2 to 20 × 10−3 °C/hPa depending on frequency. In the first part of this study, we established the atmospheric pressure to temperature transfer function (TF) as a function of frequency from 8 × 10−7 to 8 × 10−4 Hz. Here, we use this TF to calculate the expected PIT variations, which, after being subtracted from the observed time-series, provide residual temperature time-series. We calculated such temperature residuals in four natural caves in France: Esparros, Aven d'Orgnac, Pech Merle and Chauvet-Pont d'Arc Caves, the last two containing unique prehistoric wall paintings. Temperature signals, as small as a few 10−3 °C, due to human presence, are then conspicuous, with evidence of relaxation longer than several days and long-term cumulative effects. In addition, we observe temperature signals suggesting non-stationary states characterized by several processes which are not necessarily easy to separate, such as transient air currents, due to barometric winds or locally semi-confined convection cells, transient infiltration, or energy dissipation by evaporation-condensation at the rock surface. This background thermal agitation displays a scale-free amplitude spectrum, from 2 × 10−5 to 4 × 10−4 Hz, of the form f−α, with α varying from 0.1 to 0.6 depending on the site. Furthermore, at the Chauvet Cave, a weak but unambiguous peak emerges during some months at a period of about 82.2 ± 0.8 minutes, suggesting a Helmholtz-type resonance. Small but significant temperature signals are therefore detected in underground cavities once the effect of atmospheric pressure variations is corrected for. These signals reveal subtle coupled processes whose knowledge is essential to evaluate preservation strategies and to establish conditions for resilience of underground systems under artificial or natural influence including climate change.
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•Temperature variations induced by atmospheric pressure variations visible in caves.•Frequency dependent transfer functions (TFs) studied in four caves in France.•TFs inferred from 8 × 10-7 to ...8 × 10−4 Hz, amplitude at 12 h from 2 to 14 × 10−3 °C/hPa.•Air to rock surface temperature TFs also evaluated at selected locations.•TF interpreted with a model including heat exchange, phase changes and air motion
According to thermodynamics, atmospheric pressure variations (APV) cause temperature variations in air. However, such variations are difficult to observe, except in thermally stable environments such as underground cavities. We have studied the properties of these temperature variations in four natural caves in France, where continuous time-series have been collected since 1998: Esparros, Aven d'Orgnac, Pech Merle and Chauvet-Pont d'Arc Caves, the last two containing unique prehistoric wall paintings. The pressure to air temperature transfer function (TF), evaluated from 8 × 10−7 to 8 × 10−4 Hz, strongly depends on frequency; its modulus, at the barometric tide S2 (12 h), varies from 2 to 14 × 10−3 °C/hPa. While the TFs show pluriannual stability, seasonal variations are observed when sufficiently long data sets are available. Rock surface temperature is also affected by APV and we extract the air to rock surface temperature TF at Esparros, Chauvet and Pech Merle Caves. The observed TFs are accounted for by an improved analytical model including gas adiabatic compressibility, heat exchange with the rock, heat diffusion in the rock, phase changes of water at the rock surface and an advective term due to barometric pumping motion in the air volume. This model has three free parameters: the effective rock surface to air volume ratio, the time constant of heat exchanges and the effective adiabatic coefficient of cavity air. It is sufficient to account for the various situations observed in natural caves. Using this model, the observed TFs can be interpreted; they reflect the type of thermodynamics active at a given location, in particular the presence of barometric winds, but the actual values of parameters remain difficult to predict. Thus, temperature variations induced by APV emerge as a fundamental tool to characterize underground environments, relevant in some cases for cave heritage preservation, illustrating the coupled processes active in the Critical Zone.
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We measure the factors that determine growth rate (temperature, drip rate, calcium ion concentration) for 31 waters that feed stalagmites within six cave systems throughout Europe. Water samples were ...collected at a frequency of at least 1 month, to permit the modelling of both inter- and intra-annual growth rate variations, utilising the theory of Wolfgang Dreybrodt (Chem. Geol. 29 (1980) 89–105; Chem. Geol. 32 (1981) 237–245; Dreybrodt, W., 1988. Processes in Karst Systems. Springer-Verlag, Berlin 288 pp.). Inter-annual growth rates were measured using the stalagmites that were associated with the analysed water samples; growth rate was determined from annual lamina counting, specific time markers within the stalagmites, and location of bomb
14C. When compared to theoretically predicted values, a good agreement between theoretical and measured stalagmite growth rates is observed (
R
2=0.69). When compared to site climate and geochemical parameters, a good correlation is observed between measured growth rate and mean annual temperature for five sites (
R
2=0.63) and dripwater calcium content (
R
2=0.61), but not drip rate (
R
2=0.09). The good correlation with both calcium and temperature is due to soil CO
2 production being primarily determined by surface temperature and soil moisture. However, when we compare our data to that in the Grotte de Clamouse, a site that has little soil cover, we observe that the growth rate–temperature relationship breaks down due to either the lack of soil CO
2 production or prior calcite precipitation. Intra-annual data demonstrates that maximum growth rate occurs when calcium concentrations are high, and that this occurs under different seasons depending on the hydrology of each site. Our results demonstrate a stronger dependence of intra-annual stalagmite growth rate on dissolved calcium ion concentrations than drip rate for the range of drip rates investigated here (0.01<
t<2drip s
−1), but for lower drip rates, this factor becomes important in controlling growth rate. We suggest that for well-monitored and -understood sites, stalagmite growth rate variations can provide useful information for palaeoclimate reconstruction.
The study of drip rate and seepage water electrical conductivity (hereafter called conductivity) under one stalactite in the Pere Noel cave (Belgium), with data produced from an automatic station ...since 1991, demonstrates several previously unobserved features: (1) measurement of drop volume shows that, for 94% of the time series, drop volume is constant (= 0.14 ml), but when discharge exceeds 48.2 drips min(-1), drop volume decreases, probably because of secondary drop formation; (2) the interannual drip rate variation is correlated to the annual water excess and its correlant, rainfall (R2 = 0.98; exponential model); this result introduces a new improvement in the understanding of the previously investigated relationships between stalagmite annual laminae thickness and mean annual rainfall; (3) the drip rate shows a well marked seasonality: it increases abruptly in late fall or early winter and decreases slowly during spring, summer and fall. Increased discharge is accompanied by an increase in conductivity, which suggests that the flushed water is more mineralized and was stored in the karst aquifer for several months. (4) superimposed on these seasonal variations, there are two kinds of flow regimes which are driven by the atmospheric pressure: (i) a "wiggles regime". whose duration is 1-7 days in length and which is inversely proportional to the air pressure wiggles, it is explained by either a "shut-off faucet" process due to the rock formation stress, or to a change in the two-phases flow component proportions (air/water); (ii) an "unstable regime" characterized by abrupt switches (< 2 h) or oscillations with variable periodicities, from a few minutes to a few hours. These occur when the drip rate reaches a threshold (i.e. 240 drops 10 min(-1)); the chaotic behaviour of this phenomenon is discussed.
Annually laminated speleothems: a review Baker, Andy; Smith, Claire; Jex, Catherine ...
International journal of speleology,
01/2008, Letnik:
37, Številka:
3
Journal Article
Recenzirano
Odprti dostop
This review of annually laminated speleothems firstly considers the four types of annual laminae found within speleothems: fluorescent laminae formed by annual variations in organic matter flux; ...visible or petrographic laminae, formed by annual variations in calcite texture or fabric; calcite-aragonite couplets; and finally trace element laminae. The methods available to confirm the annual nature, or otherwise, of lamina deposition are reviewed. We consider the use of annual laminae in chronology building, with particular relevance to palaeoclimate reconstructions. Finally, the use of annual lamina width as a palaeoclimate proxy is reviewed.
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