RESUMEN

A hydrogeochemical and isotopic study has been carried out to understand the hydrogeological functioning of a small alluvial aquifer in central Chile in a context of mega-drought and intensive exploitation of its waters. Additionally, two mine tailings dams from porphyry copper mining are situated in the area. The prolonged mega-drought, which has lasted for over thirteen years, has resulted in a significant decrease in rainfall recharge and a drop of up to 50 m in piezometric levels, although no serious groundwater contamination problems have yet been detected, except for a rise in nitrate contents (ranging between 23 and 45 mg/L NO3) attributed to return irrigation. Groundwaters are calcium-bicarbonate and calcium-sodium-bicarbonate in composition. The values of δ18O and δ2H of the alluvial aquifer indicate fractionation by evaporation that would be explained by the recirculation of water that occurs in the agricultural areas of the basin, where the excess irrigation water that go back to the aquifer presents fractionation by evaporation. The δ34S and δ18O of dissolved sulfate point to pyrite oxidation, which could be related to the pyrite present in the copper porphyry and recognized in the Andes Cordillera. The 87Sr/86Sr isotopic values of the alluvial aquifer waters are close to the isotopic fingerprint of the volcanic rocks of the Abanico Formation. However, the water from the wells located further downstream in the basin and close to the tailing dams show δ34S and δ18O of dissolved sulfate and 87Sr/86Sr consistent with Miocene intrusive mineralogies of the copper porphyry type. The groundwater chemistry does not show water seepage from the tailings dam. Therefore, a minor contribution of minerals related to the intrusive rocks is proposed, which would originate from the movement of fine particles by the wind from the dams to the valley floor. The 14C activities indicate that groundwater is recent.

RESUMEN

Within post-conflict communities, attempts to identify and repatriate unidentified and missing individuals poses a difficult task. As current forensic strategies commonly lack the capacity to provide region of origin assessments, forensic anthropologists/investigators are often unable to identify sources of DNA for kinship analysis. Using Thermal Ionization Mass Spectrometry (TIMS), hair samples from 10 volunteers were used to assess the variation in strontium isotope ratios (87 Sr/86 Sr) between extant people in Guatemala City and Coban; with a leach (external) and digest (dietary) signal analyzed for each sample. A two-way anova demonstrated that the difference between 87 Sr/86 Sr of Guatemala City and Coban was statistically significant (F [1, 16] = 259.839, p < 0.05), with no statistically significant differences observed between leach and digest 87 Sr/86 Sr (F [1,16] = 4.319, p = 0.054). Overall, individuals from Coban demonstrate 87 Sr/86 Sr comparable to previously recorded baseline values, demonstrating a minimal change in diet which is reflected in associated surveys. Volunteers from Guatemala City, however, show a marked shift in 87 Sr/86 Sr away from predicted values highlighting the potential influence of imported goods. The results here highlight the applicability of 87 Sr/86 Sr in hair to serve as a potential tool to support the identification of unknown individuals in Guatemala in a forensic context.

Asunto(s)

RESUMEN

Northern Chile, NW Argentina, and SW Bolivia, ("the lithium triangle"), represent a world class reservoir of lithium, but this extraordinary enrichment is still controversial, and different processes have been invoked over the years, including, geothermal waters associated with active volcanism, leaching of soluble salts from volcanic rocks and leaching of lithium-rich clays. The Salar de Atacama (SDA) represents one of the richest reservoirs of Li in northern Chile and has been extensively studied during the past years. Most of the studies have been focused in the southern and southeastern portions, where the highest lithium concentrations have been reported. However, a comprehensive model of water recharge at SDA is still imprecise. We used a combination of isotopic methods, including δ7Li, δ11B and 87Sr/86Sr ratios, with their chemical composition of a set of water samples from salt lakes, geothermal manifestations, groundwaters and surficial diluted waters (rivers and streams with low salinity). This study explores the hydrogeochemical processes controlling the water composition and solute distribution of the SDA. Our data confirm that weathering of the ignimbrites constitutes one of the most important processes in relation of solute origin in the region, where deep water-rock interactions would operate at high temperature, enhancing leaching of Li and other solutes. We determine that groundwater flow entering the SDA has undergone pre-enrichment processes (e.g., leak from Altiplano salt lakes; evaporite dissolution, among others) associated with salt inputs in the Western Cordillera. Our results provide a step forward to a comprehensive understanding of the processes that govern brine formation and lithium enrichment in a hyperarid environment, contributing to a sustainable exploration and exploitation of lithium in these environments.

Asunto(s)

RESUMEN

OBJECTIVES: This article addresses evidence of violence imbedded in both soft and hard tissues from early populations of hunters, fishermen, and gatherers, known as the Chinchorro culture, who lived between 10,000 and 4,000 cal yr BP, along the coast of the Atacama Desert, one of the driest environments on Earth. Our study is aimed to test two hypotheses (a) that interactions and violent behaviors increased through time as population density and social complexity augmented; and (b) that violence was more prevalent between local Chinchorro groups and groups from other inland locations. MATERIAL AND METHODS: Two lines of data were analyzed: (1) bioarchaeology, through the quantification of physical traces of interpersonal violence in skeletons and mummies from a sample of 136 adult individuals and, (2) isotopic chemical analysis (strontium) of individuals with traces of trauma in order to determine their local or foreign origin. RESULTS: Violence among Chinchorro populations was ubiquitous and remained invariant over time, with a remarkable skew to male (about 25% above female across the complete sample). Moreover, the chemical signature of individuals with traces of violence was not of foreign origin. DISCUSSION: The violence exerted by the Chinchorro groups was not related to increased population size, nor social complexity and was mostly restricted to individuals coming from the same coastal habitat. That is, our data suggest that violence was constant across the Archaic period among the Chinchorro, implying that violent behavior was part of the sociocultural repertory of these populations, likely associated to mechanisms to resolve conflicts and social tensions.

Asunto(s)

RESUMEN

Human provenance studies employing isotopic analysis have become an essential tool in forensic and archaeological sciences, with multi-isotope approaches providing more specific location estimates compared to single isotope studies. This study reports on the human provenancing capability of neodymium isotopes (143Nd/144Nd), a relatively conservative tracer in the environment. Neodymium isotope ratios have only recently been determined on human remains due to low concentrations in human dental enamel (ppb range), requiring thermal ionisation mass spectrometry (TIMS) using 1013â€¯Ω resistors. Dental elements (third molars) from 20 individuals born and raised in the Netherlands were analysed for Nd concentration (n = 12) and Nd isotope ratios (n = 15). The geological control on Nd isotope composition was examined using coupled Nd-Sr isotope analysis of the same third molar. Teeth from different geological environments were also analysed (Caribbean, Columbian, and Icelandic, n = 5). Neodymium elemental concentrations in dental elements ranged between 0.1 and 7.9 ppb (median 0.5 ppb). The Dutch 143Nd/144Nd ratios of the provinces of Limburg and Friesland were between 0.5118 and 0.5121, with Dutch 87Sr/86Sr ratios in agreement with the previously established local range (0.708-0.710). The current findings were compared to previously published results on Nd concentration and composition from Dutch individuals. The concentration of Nd and 143Nd/144Nd ratios were weakly correlated (R2 = 0.47, n = 17) in Dutch human dental enamel. The majority (n = 25, 83.3%) of individuals had Nd and Sr isotope values isotopically indistinguishable from the geological environment in which their third molars formed and mineralised. However, the Nd isotope ratios of the Icelandic individual and several Dutch individuals (n = 4) suggested that Nd in enamel is not solely influenced by geological environment. In order for neodymium isotopes to be quantitatively applied in forensic and archaeological settings further analyses of individuals from various geographical regions with well-defined dietary Nd isotope data are required.

Asunto(s)

RESUMEN

A review of the bioarchaeological collections from the site Morro de Arica in northern Chile allowed the identification of two cases of human polydactyly. Both cases are from the Chinchorro culture, hunters, fishers, and gatherers with a maritime orientation who inhabited the coast of the Atacama Desert (9000-3400 BP). Additionally, the analyses of 75 rock art sites in the area, from the Formative to Late Intermediate Periods (3000-550 BP), allowed the identification of hands and feet with six digits. Given the bioarchaeological record of polydactyly, it is highly probable that the rock art images were based on real individuals with polydactyly. However, the Sr chemical signal in a juvenile with polydactyly is the same as the Sr chemical signal in the rest of the individuals buried in the same site, proving that all the individuals were born and lived on the coast. We discuss the idea that, although these anomalies could have been the result of genetic mutations, endogamy and exposition to ecotoxic environments could also be at play within the Chinchorro groups.

Asunto(s)

RESUMEN

In the coastal multilayer aquifer system of a highly urbanized southern city (Recife, Brazil), where groundwaters are affected by salinization, a multi-isotope approach (Sr, B, O, H) was used to investigate the sources and processes of salinization. The high diversity of the geological bodies, built since the Atlantic opening during the Cretaceous, highly constrains the heterogeneity of the groundwater chemistry, e.g. Sr isotope ratios, and needs to be integrated to explain the salinization processes and groundwater pathways. A paleoseawater intrusion, most probably the 120 kyB.P. Pleistocene marine transgression, and cationic exchange are clearly evidenced in the most salinized parts of the Cabo and Beberibe aquifers. All (87)Sr/(86)Sr values are above the past and present-day seawater signatures, meaning that the Sr isotopic signature is altered due to additional Sr inputs from dilution with different freshwaters, and water-rock interactions. Only the Cabo aquifer presents a well-delimitated area of Na-HCO3 water typical of a freshening process. The two deep aquifers also display a broad range of B concentrations and B isotope ratios with values among the highest known to date (63-68.5‰). This suggests multiple sources and processes affecting B behavior, among which mixing with saline water, B sorption on clays and mixing with wastewater. The highly fractionated B isotopic values were explained by infiltration of relatively salty water with B interacting with clays, pointing out the major role played by (palaeo)-channels for the deep Beberibe aquifer recharge. Based on an increase of salinity at the end of the dry season, a present-day seawater intrusion is identified in the surficial Boa Viagem aquifer. Our conceptual model presents a comprehensive understanding of the major groundwater salinization pathways and processes, and should be of benefit for other southern Atlantic coastal aquifers to better address groundwater management issues.

RESUMEN

Paleomobility has been a key element in the study of the expansion of ancient states and empires, including the Tiwanaku polity of the South Central Andes (AD 500-1000). We present radiogenic strontium and oxygen isotope data from human burials from three cemeteries in the Tiwanaku-affiliated Middle Horizon archaeological site complex of Rio Muerto in the Moquegua Valley of southern Peru. At Rio Muerto, archaeological human enamel and bone values range from (87) Sr/(86) Sr = 0.70657-0.72018, with a mean of (87) Sr/(86) Sr = 0.70804 ± 0.00207 (1σ, n = 55). For the subset of samples analyzed for oxygen isotope values (n = 48), the data ranges from δ(18) Ocarbonate(VSMOW) = +18.1 to +27.0‰. When contextualized with other lines of archaeological evidence, we interpret these data as evidence for an archaeological population in which the majority of individuals had "local" origins, and were likely second-generation, or more, immigrants from the Tiwanaku heartland in the altiplano. Based on detailed life history data, we argue a smaller number of individuals came at different ages from various regions within the Tiwanaku polity. We consider whether these individuals with isotopic values consistent with "nonlocal" geographic origins could represent first-generation migrants, marriage exchange partners, or occupationally mobile herders, traders or other travelers. By combining isotopic life history studies with mortuary treatment data, we use a person-centered migration history approach to state integration and expansion. Isotopic analyses of paleomobility at the Rio Muerto site complex contribute to the role of diversity in ancient states by demonstrating the range of geographic origins rather than simply colonists from the Lake Titicaca Basin.

Asunto(s)