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Middle Holocene cultures have been widely studied around the Eastern-Mediterranean basin in the last 30 years and past cultural activities have been commonly linked with regional climate changes. However, in many cases such linkage is equivocal, in part due to existing climatic evidence that has been derived from areas outside the distribution of ancient settlements, leading to uncertainty from complex spatial heterogeneity in both climate and demography. A few high-resolution well-dated paleoclimate records were recently established using speleothems in the Central and Eastern-Mediterranean basin, however, the scarcity of such records in the western part of the Mediterranean prevents us from correlating past climate evolutions across the basin and deciphering climate-culture relation at fine timescales. Here we report the first decadal-resolved Mid-Holocene climate proxy records from theWestern-Mediterranean basin based on the stable carbon and oxygen isotopes analyses of two U/Th dated stalagmites from the Gueldaman GLD1 Cave in Northern Algeria. Comparison of our records with those from Italy and Israel reveals synchronous (multi) centennial dry phases centered at ca. 5600, ca. 5200 and ca. 4200 yr BP across the Mediterranean basin. New calibrated radiocarbon dating constrains reasonably well the age of rich anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated inside the cave, which allows the comparison between in situ evidence of human occupation and of climate change. This approach shows that the timing of a prolonged drought at ca. 4400-3800 yr BP blankets the onset of cave abandonment shortly after ca. 4403 cal yr BP, supporting the hypothesis that a climate anomaly may have played a role in this cultural disruption. [ABSTRACT FROM AUTHOR]

Middle Holocene cultures have been widely studied round the E-Mediterranean basin in the last 30 years and past cultural activities have been commonly linked with regional climate changes. However, in many cases such linkage is equivocal, in part due to existing climatic evidence that has been derived from areas outside the distribution of ancient settlements, leading to uncertainty from complex spatial heterogeneity in both climate and demography. A few high-resolution well-dated paleoclimate records were recently established using speleothems in the Central and E-Mediterranean basin, however, the scarcity of such records in the western part of the Mediterranean prevents us from correlating past climate evolutions across the basin and deciphering climate-culture relation at fine time scales. Here we report the first decadal-resolved Mid-Holocene climate proxy records from the W-Mediterranean basin based on the stable carbon and oxygen isotopes analyses of two U/Th dated stalagmites from the Gueldaman GLD1 Cave in N-Algeria. Comparison of our records with those from Italy and Israel reveals synchronous (multi) centennial dry phases centered at ca. 5600, ca. 5200 and ca. 4200 yrBP across the Mediterranean basin. New calibrated radiocarbon dating constrains reasonably well the age of rich anthropogenic deposits (e.g., faunal remains, pottery, charcoal) excavated inside the cave, which allows the comparison between in situ evidence of human occupation and of climate change. This approach shows that the timing of a prolonged drought at ca. 4400-3800 yrBP blankets the onset of cave abandonment shortly after ca. 4403 cal yrBP, supporting the hypothesis that a climate anomaly may have played a role in this cultural disruption. [ABSTRACT FROM AUTHOR]

The Bulnay earthquake of 23 July 1905 (Mw 8.3-8.5), in north-central Mongolia, is one of the world's largest recorded intracontinental earthquakes and one of four great earthquakes that occurred in the region during the twentieth century. The 375 km long surface rupture of the left-lateral, strike-slip, N095°E-trending Bulnay fault associated with this earthquake is remarkable for its pronounced expression across the landscape and for the size of features produced by previous earthquakes. Our field observations suggest that in many areas the width and geometry of the rupture zone is the result of repeated eaxthquakes; however, in those areas where it is possible to determine that the geomoiphic features are the result of the 1905 surface rupture alone, the size of the features produced by this single earthquake are singular in comparison to most other historical strike-slip surface raptures worldwide. Along the 80 km stretch, between 97.18° E and 98.33° E, the fault zone is characterized by several meters width and the mean left-lateral 1905 offset is 8.9 ± 0.6 m with two measured cumulative offsets that are twice the 1905 slip. These observations suggest that the displacement produced during the penultimate event was similar to the 1905 slip. Morphotectonic analyses carried out at three sites along the eastern part of the Bulnay fault allow us to estimate a mean horizontal slip rate of 3.1 ± 1.7 mm/yr over the Late Pleistocene-Holocene period. In parallel, paleoseismological investigations show evidence for two earthquakes prior to the 1905 event, with recurrence intervals of ~2700-000 yrs [ABSTRACT FROM AUTHOR]

Abstract: The capture and the storage of CO2 in deep geological media are proposed to reduce the emission of CO2 to the atmosphere. While the argillaceous formations have been extensively studied since more than two decades as potential host-rocks for nuclear waste disposal, only few studies have dealt with the potential degradation of their containment properties as caprocks induced by a CO2 attack. This paper focuses on the impact of a CO2-enriched fluid on the diffusive transport parameters of indurated argillaceous samples originating from the massif of Tournemire (Aveyron, France). Two through-diffusion experiments were carried out, the first one with a CO2-enriched fluid and the second one with an equilibrated fluid, chemistry of which is very close to that measured in-situ. Non-radioactive (deuterium and bromide) and radioactive tracers (tritium and Cl-36) were successively used. Throughout the duration of the experiments, the evolution of water chemistry was monitored by measuring pH, Ca, Na, Mg, K, Cl, SO4, TOC and alkalinity. The effect of the CO2 stress has been clearly evidenced. On the one hand, the tracer fluxes in the downstream reservoir of the cell having undergone CO2 attack were up to 3 times higher than in the reference cell, indicating a significant increase of the porosity and effective diffusion coefficient values (up to 100% for Cl-36 porosity and up to 300% for Cl-36 effective diffusion coefficient). On the other hand, the chemical monitoring showed that magnesium, calcium and carbonate concentrations in the collection reservoirs increased up to one order of magnitude, suggesting a possible dissolution of some carbonate minerals such as calcite, reacting with the acid fluid. [Copyright &y& Elsevier]

Abstract: Diffusion parameters for HTO, 36Cl− , and 125I− were determined on Upper Toarcian argillite samples from the Tournemire Underground Research Laboratory (Aveyron, France) using the through diffusion technique. The direction of diffusion was parallel to the bedding plane. The purpose of the present study was 3-fold; it was intended (i) to confirm the I− interaction with Upper Toarcian argillite and to verify the effects of initial I− concentration on this affinity, as previously observed by means of radial diffusion experiments, (ii) to highlight any discrepancy between Cl− and I− diffusivity, and (iii) to investigate the effect of an increase of the ionic strength of the solution on the anionic tracers’ diffusive behaviour. The results show that the effective diffusion coefficient (De ) and diffusion accessible porosity (εa ) values obtained with an ionic strength (I.S.) synthetic pore water of 0.01eqL−1 are: De =2.35–2.50×10−11 m2 s−1 and εa =12.0–15.0% for HTO, and De =14.5–15.5×10−13 m2 s−1 and εa =2.5–2.9% for 36Cl−. Because of anionic exclusion effects, anions diffuse slower and exhibit smaller diffusion accessible porosities than HTO, taken as a water tracer. The associated effective diffusion coefficient (De ) and rock capacity factor (α) obtained for 125I are: De =7.00–8.60×10−13 m2 s−1 and α =4.3–7.2%. Such values make it possible to calculate low 125I distribution ratios (0.0057< RD <0.0192mLg−1) which confirm the trend indicating that the 125I rock capacity factor increases with the decrease of the initial I− concentration. Additional through-diffusion experiments were carried out with a higher ionic strength synthetic pore water (I.S.=0.11eqL−1). No evolution of HTO diffusion parameters was observed. The anionic tracers’ effective diffusion coefficient increased by a factor of two but no clear evolution of their accessible porosity was observed. Such a paradox could be related to the particularly small mean pore size of the Upper Toarcian argillite of Tournemire. The most significant finding of this study is the large discrepancy (factor of two) between the values of the effective diffusion coefficient for 125I and 36Cl. Whatever the ionic strength of the synthetic solution used, 125I exhibited De values two times lower than those of 36Cl. A detailed explanation for this difference cannot be given at present even if a hypothesis based on ion-pairing or on steric-exclusion cannot be excluded. This makes questionable the assumption usually made for quantifying 125I sorption and postulating that 36Cl and 125I would diffuse in the same porosity. In other terms, at Tournemire, 125I sorption could be more pronounced than previously indicated. [Copyright &y& Elsevier]