Review submerged speleothems and sea level reconstructions: A global overview and new results from the mediterranean sea

This study presents a global overview of the submerged speleothems used to reconstruct paleo sea levels and reports new results from two stalactites collected in the Mediterranean Sea. Coastal cave deposits significantly contributed to the understanding of global and regional sea-level variations during the Middle and Late Quaternary. The studied speleothems cover the last 1.4 Myr and focused mainly on Marine Isotope Stages (MIS) 1, 2, 3, 5.1, 5.3, 5.5, 7.1, 7.2, 7.3 and 7.5. The results indicate that submerged speleothems represent extraordinary archives that can provide detailed information on former sea-level changes. The two stalactites collected in the central Mediterranean Sea, at Favignana and Ustica islands (Sicily, Italy), are both characterized by continental, phreatic or marine layers. The U-Th and14C ages of the new speleothems provide results of great interest for relative sea-level changes over the last 1000 years

U-series and radiocarbon cross dating of speleothems from Nerja Cave (Spain): Evidence of open system behavior. Implication for the Spanish rock art chronology

Two stalagmites from Nerja cave (Andalusia, Spain) were studied. The cave is well known because of its long human occupation from the Upper Palaeolithic to the Chalcolithic and its abundant parietal prehistoric Art. The aims of this study were twofold: i) to compare uranium/thorium (Th/U) and Carbon-14 (C) ages obtained all along the growth axis of the stalagmites in order to understand the consequences of diagenetic processes on the validity of radiometric ages; ii) as one of the stalagmites contains black layers, attributed to combustion soot, to establish when these intense hearths were used and by which culture. Th/U and C ages were coupled with mineralogical studies using FTIR (Fourier-transform infrared spectroscopy) and thin section observations. The first stalagmite (GN16-9b) displays Th/U ages in stratigraphic order, and compatible with C ages corrected for a few percent of dead carbon. Homogeneous composition of aragonitic crystals characterized by their needle-like texture is observed throughout this speleothem. For the second stalagmite (GN16-7), in contrast, Th/U ages display large significant inversions and discordant results on the upper part and at the base of the stalagmite, suggesting a possible open system behavior for this chronometer. Interestingly, C ages are in stratigraphic order all along the stalagmite and are compatible with Th/U ages only in its central part. Mineralogical studies display evidence of aragonite to calcite transformation at the top and a complex mineralogical assemblage with interlayered silicates (possibly clays) and calcitic mineralogy for the base of GN16-7. In these parts, discordant Th/U ages were measured. In the middle part of the stalagmite, however, where the fibrous aragonite is well preserved, the C and Th/U ages agree. Our data suggest that in the case of aragonite to calcite transformation as shown here, Th/U ages are biased, but C ages seem to remain accurate, as already observed in aragonitic marine bio minerals. C ages obtained are used for the chronology of the soot layer, determined here between 7900 and 5500 years Cal BP, coherent with previous analysis of charcoals in the same sector of the cave. This study highlights the importance of working with at least two chronometers when stratigraphic age verification is not possible, as is the case of some parietal CaCO thin layers used for rock art dating. Recent Th/U ages published for carbonate deposits on Spanish parietal Art are discussed in light of this demonstration.This research was funded by ANR (grant number ANR-18-CE27- 0004, ApART project) and supported by the Paris Ile-de-France Region – DIM “matérieux Anciens et Patrimoniaux” for FTIR analysis. The authors thank LMC14 staff (Laboratoire de Mesure du Carbone-14), ARTEMIS national facility, for the results obtained with the Accelerator Mass Spectroscopy method, and the PANOPLY analytical platform. This research is part of the “Proyecto General de Investigación aplicada a la conservación de Cueva de Nerja” authorised by the Junta de Andalucía and financed by the Fundación de Servicios Cueva de Nerja. The authors also wish to thank the “Instituto de Investigación Cueva de Nerja” for supporting this research. M.A.Medina-Alcaide has a Postdoctoral Fyssen Grant; the results presented in this paper are included in the PID2019-107262GB-I00 and PDC2021-121501-I00 grants funded by MCIN/AEI/10.13039/501100011033

Methodological development for organic matter analysis in speleothems. Case study in urban areas (Paris, Lyon; France).

International audienceIn the current context of intense anthropization, the preservation of water resources and the limitation of pollutions are an environmental central issue. This is the aim of this project, which is in line with the sustainable development objectives defined by the United Nations for the year 2030 in the framework of the European directive 2000/60/EC of 23 October 2000. Speleothems are secondary carbonates deposited by dripping or flowing water and considered as archives of the water quality through time. Urban speleothems, from underground aqueducts, galleries and stone quarries, have already been employed to investigate the impact of urbanization on water using the content and isotopic composition of key elements (i.e. S, Pb , REE...) (Pons-Branchu et al; 2015, STOTEN, vol.518-519, 86-95). Their use to trace the organic pollution, including Polycyclic Aromatic Hydrocarbons (PAH), over the last centuries, is unprecedented and involves long and rigorous methodological development. To trace variations in quantity and quality of organic matter (OM) and PAH, we combine high-resolution (10 μm) UV-¬fluorescence imaging analyses on solid-phase with classical chemical analyses (extraction, chromatography and total organic carbon (TOC)) conducted on low weight samples

Methodological development for organic matter analysis in speleothems. Case study in urban areas (Paris, Lyon; France).

International audienceIn the current context of intense anthropization, the preservation of water resources and the limitation of pollutions are an environmental central issue. This is the aim of this project, which is in line with the sustainable development objectives defined by the United Nations for the year 2030 in the framework of the European directive 2000/60/EC of 23 October 2000. Speleothems are secondary carbonates deposited by dripping or flowing water and considered as archives of the water quality through time. Urban speleothems, from underground aqueducts, galleries and stone quarries, have already been employed to investigate the impact of urbanization on water using the content and isotopic composition of key elements (i.e. S, Pb , REE...) (Pons-Branchu et al; 2015, STOTEN, vol.518-519, 86-95). Their use to trace the organic pollution, including Polycyclic Aromatic Hydrocarbons (PAH), over the last centuries, is unprecedented and involves long and rigorous methodological development. To trace variations in quantity and quality of organic matter (OM) and PAH, we combine high-resolution (10 μm) UV-¬fluorescence imaging analyses on solid-phase with classical chemical analyses (extraction, chromatography and total organic carbon (TOC)) conducted on low weight samples

Methodological development for organic matter analysis in speleothems. Case study in urban areas (Paris, Lyon; France).

International audienceIn the current context of intense anthropization, the preservation of water resources and the limitation of pollutions are an environmental central issue. This is the aim of this project, which is in line with the sustainable development objectives defined by the United Nations for the year 2030 in the framework of the European directive 2000/60/EC of 23 October 2000. Speleothems are secondary carbonates deposited by dripping or flowing water and considered as archives of the water quality through time. Urban speleothems, from underground aqueducts, galleries and stone quarries, have already been employed to investigate the impact of urbanization on water using the content and isotopic composition of key elements (i.e. S, Pb , REE...) (Pons-Branchu et al; 2015, STOTEN, vol.518-519, 86-95). Their use to trace the organic pollution, including Polycyclic Aromatic Hydrocarbons (PAH), over the last centuries, is unprecedented and involves long and rigorous methodological development. To trace variations in quantity and quality of organic matter (OM) and PAH, we combine high-resolution (10 μm) UV-¬fluorescence imaging analyses on solid-phase with classical chemical analyses (extraction, chromatography and total organic carbon (TOC)) conducted on low weight samples

Comment on: “Uranium–thorium dating method and Palaeolithic rock art” by Sauvet et al. (2015, in press)

International audienceSauvet et al. (in press) present a partial description of the Uranium-series or 230Th/234U dating method, which leads them to criticize this dating tool and claim that this method provides “an extremely wide range of uncertainty providing a weak base upon which to build scientific reasoning”. In this comment, we discuss three concepts introduced by these authors that could lead to a misunderstanding of the method and its application in the archaeological community and in the scientific debate about rock art chronology. The first misconception concerns the claim that “speleothems stopped during much of the Upper Palaeolithic”. A brief review of the literature demonstrates that this affirmation is not quite exact as a large number of studies document speleothem growth in Europe and circum-Mediterranean regions (as well as in other regions) during the upper Paleolithic. Secondly, Sauvet et al. claim that when age corrections are applied due to the possible presence of initial 230Th, the ages should be considered with caution or they should be rejected. However, this is not entirely correct, as this detrital fraction can be determined using several methods (and not merely assumed to be a “mean earth value”). Thirdly, with respect to their claim that “Loss of uranium or input of230Th leads to anomalously old ages and sometimes to the impossibility to calculate an age when230Th/234U > 1”, we present a classical figure of 230Th/234U evolution vs 234U/238U that can be drawn using the U-series equations demonstrating that 230Th/234U ratios can in fact be >1 and permit a valid age determination

Methodological development for organic matter analysis in speleothems. Case study in urban areas (Paris, Lyon; France).

International audienceIn the current context of intense anthropization, the preservation of water resources and the limitation of pollutions are an environmental central issue. This is the aim of this project, which is in line with the sustainable development objectives defined by the United Nations for the year 2030 in the framework of the European directive 2000/60/EC of 23 October 2000. Speleothems are secondary carbonates deposited by dripping or flowing water and considered as archives of the water quality through time. Urban speleothems, from underground aqueducts, galleries and stone quarries, have already been employed to investigate the impact of urbanization on water using the content and isotopic composition of key elements (i.e. S, Pb , REE...) (Pons-Branchu et al; 2015, STOTEN, vol.518-519, 86-95). Their use to trace the organic pollution, including Polycyclic Aromatic Hydrocarbons (PAH), over the last centuries, is unprecedented and involves long and rigorous methodological development. To trace variations in quantity and quality of organic matter (OM) and PAH, we combine high-resolution (10 μm) UV-¬fluorescence imaging analyses on solid-phase with classical chemical analyses (extraction, chromatography and total organic carbon (TOC)) conducted on low weight samples

Hydrochemistry (major and trace elements) of Lake Malawi (Nyasa), Tanzanian Northern Basin: local versus global considerations

International audienceThis paper presents the first inventory of dissolved minor and trace element (F, Al, Fe, Mn, Ba, Cd, Cr, Cu, Pb, Mo, Bi, Sr, Zn) concentrations in Lake Malawi, the second largest African lake. Sampling was carried out during 1993 dry season in the northern part of the lake. Trace metal concentrations were measured, together with Ca, Mg, Na, K, Cl, SO4, Alkalinity and Si, along three profiles in the lake northern extremity, in five tributaries and two on-land hydrothermal springs. Water profiles show similar elemental distributions and concentrations that are influenced by lake physical-chemical stratification. Stratification, assessed using temperature, conductivity, Si and Mn profiles, is characterised by two boundaries: the thermocline (70-90 m) and the oxicline (150-190 m). Elemental water concentrations are discussed using simple covariance analyse. Epilimnetic concentrations and distribution are also influenced by atmospheric deposition and river diving. Comparison of dissolved concentrations for potentially polluting elements with World Health Organisation Guidelines and those reported for other East African lakes shows that this reservoir is uncontaminated despite an increasing human stress. Major element behaviour is assessed through a 3 boxes model. In this model Cl and K are conservative elements whereas Si is removed from the solution by diatom productivity and sedimentation. Ca, Na, Mg and alkalinity show low reactivity. Evaporation is one of the controlling factors of lake element concentration that superimposes on the watershed control. Hydrothermal activity, not evidenced in the lake, controls the chemistry of one of the main northern tributary. Chemical comparison between Northern rivers and other tributaries characterises the geographical and geological specificity of studied northern watershed. Moreover the lake annual chemical budget shows that northern watershed generates the main elemental input to the lake, illustrating the dual importance of this area in terms of water and ionic recharge to the lake

Seismic Hazards Implications of Uplifted Pleistocene Coral Terraces in the Gulf of Aqaba

International audienceThe Gulf of Aqaba transform plate boundary is a source of destructive teleseismic earthquakes. Seismicity is concentrated in the central sub-basin and decreases to both the north and south. Although principally a strike-slip plate boundary, the faulted margins of the Gulf display largely dip-slip extensional movement and accompanying footwall uplift. We have constrained rates of this uplift by measurements of elevated Pleistocene coral terraces. In particular the terrace that formed during the last interglacial (~125 ka) is found discontinuously along the length of the Gulf at elevations of 3 to 26 m. Global sea level was ~7 m higher than today at 125 ka indicating net maximum tectonic uplift of ~19 m with an average rate of ~0.015 cm/yr. Uplift has been greatest adjacent to the central sub-basin and like the seismicity decreases to the north and south. We suggest that the present pattern of a seismically active central region linked to more aseismic areas in the north and south has therefore persisted for at least the past 125 kyr. Consequently the potential for future destructive earthquakes in the central Gulf is greater than in the sub-basins to the north and south

Rare earth and alkali elements in stalagmites, as markers of Mediterranean environmental changes during Termination I

International audienceSpeleothems represent a key source of information on climate variations in continental environments as they enable high temporal resolution reconstructions. The stalagmite salam3 presented in this study comes from the Salamandre Cave (SE France, Gard region). Its growth period, determined by 230Th/234U chronology and MOD-AGE extrapolation, falls between 10.91 ± 1.00 kyr BP and 13.43 ± 0.25 kyr BP, which corresponds to the transition between the last glacial period and the Holocene. This period is essential for the understanding of past and future climate variations.In this study, trace elements were measured along the growth axis of this stalagmite and results were compared with the elementary composition of bedrock and soil above the cave. Three periods were identified with high Li, Rb, Cs, Th and rare earth element (REE) concentrations, between 13.43 ± 0.25 and 13.11 ± 0.27, between 12.70 ± 0.34 and 12.30 ± 0.15 kyr, and between 11.31 ± 0.86 and 11.15 ± 0.87 kyr.Our results suggest that the alkali metals (alkalis) studied are either associated in the detrital phase with the clay and particle fraction (correlation with Th), or with the organic matter and colloids as complexed ligands (correlation with Mn). To attribute the origin of REE measured within the stalagmite, we compared their pattern with those of soil and bedrock, and two sources were deduced: i) periods with an enrichment in light REE and no cerium anomaly corresponding to mobilization from soil during weathering episodes such as the Bölling-Alleröd period; ii) from bedrock during a longer residence time of water in the epikarst such as during the Younger Dryas and the Holocene. Thus, as illustrated in this study, combined analysis of REE and alkalis can provide key information on soil weathering linked to climate/environmental change