Specialising in the analysis of prehistoric cultural material. I apply methods from materials science to a range of archaeological artefacts to understand interactions between past populations and their environment. To study theses interactions I mainly focus on rock art pigments and hafting residues found on lithic tools.
Namibia is one of the southern African countries hosting the richest rock art heritage, with thou... more Namibia is one of the southern African countries hosting the richest rock art heritage, with thousands of rock paintings. Although numerous studies investigated their distribution, style and possible meaning, few is known about the materials used to perform these paintings. Our in situ study aimed at identifying the diversity of pigments and alterations of some rock paintings in the northwestern part of the Erongo (Namibia). It relies on extensive pXRF analyses of thirty-five figures from eight rock art sites of the area. Despite common limits of in situ pXRF analyses, the extensive number of figures analysed and the original data treatment that we performed pioneered the first scientific analyses of the pigments from rock painting sites in the Erongo Mountains. Furthermore, the study also confirmed the presence of iron oxide pigments on a portion of wall exposed during the excavations carried out at the archaeological site of Leopard Cave and of possibly datable alterations over several paintings, paving the way to future chronological analyses of past tradition of rock paintings in Central Namibia.
Cave Art is a fragile testimony of past human societies and the development of modern behaviours.... more Cave Art is a fragile testimony of past human societies and the development of modern behaviours. In limestone caves, moonmilk commonly endanger the artworks. It is a calcite deposit known to present a large variability of chemical composition and morphological structures, hosting numerous microbial communities. The possibility to characterize this deposit on the field would help to get a better understanding of the cave behaviour and set up proper conservation measures. The present study analyses the variability of a moonmilk strip of metric size in the Leye Cave. This cave located in the Vézère Valley (Dordogne, France) is not ornate, and has been selected to become a laboratory cave in which in-situ observations and micro-sampling can be carried out, before performing them into cavities hosting parietal artworks. SEM observations of twenty-four samples allowed investigating, for the first time, the variability of the moonmilk deposit over a same wall of few meters dimension. Our observations highlight low variability of moonmilk at the microscopic scale regarding the chemical composition and the morphological structures despite significant macroscopic diversity, thus providing insights to optimize the sampling strategy of moonmilk in ornate caves.
The detection and analysis of metabolically active microorganisms are useful to determine those d... more The detection and analysis of metabolically active microorganisms are useful to determine those directly involved in the biodeterioration of cultural heritage (CH). Fluorescence in situ hybridization with oligonucleotide probes targeted at rRNA (RNA-FISH) has demonstrated to be a powerful tool for signaling them. However, more efforts are required for the technique to become a vital tool for the analysis of CH's microbiological communities. Simultaneous analysis of microorganisms belonging to different kingdoms, by RNA-FISH in-suspension approach, could represent an important progress: it could open the door for the future use of the technique to analyze the microbial communities by flow cytometry, which has shown to be a potent tool in environmental microbiology. Thus, in this work, various already implemented in-suspension RNA-FISH protocols for ex situ analysis of yeast and bacteria were investigated and adapted for allowing the simultaneous detection of these types of microorganisms. A deep investigation of the factors that can affect the results was carried out, focusing particular attention on the selection of the fluorochromes used for labelling the probe set. The resultant protocol, involving the use of EUK516--6-FAM/EUB338--Cy3 probes combination, was validated using artificial consortia and gave positive preliminary results when applied in samples from a real case study: the Paleolithic archaeological site of Escoural Cave (Alentejo, Portugal). This approach represents the first dual-staining RNA-FISH in-suspension protocol developed and applied for the simultaneous investigation of CH biodeteriogenic agents belonging to different kingdoms.
The direct dating of rock paintings is not always possible due to the lack of organic carbon comp... more The direct dating of rock paintings is not always possible due to the lack of organic carbon compounds in pigments, or because sampling from a heritage site is often restricted. To overcome these limitations, dating laboratories have to develop new approaches. In this study, we consider sampling calcium oxalate crusts covering the painted artworks as a way to indirectly date the rock art. This stratigraphic approach includes isolating and extracting pure oxalate from the crusts. The approach was tested on natural bulk accretions collected in the open-air sites of Erongo Mountains in Namibia. The accretions were separated into two phases (pure oxalate and the remaining residues) with a special pretreatment. This process removes carbonates through acidification (HCl 6N) and dissolves the oxalate into the supernatant, leaving the minerals and windblown organic compounds in the residue. The efficiency of the separation was checked on the two phases by FTIR analyses and by 14 C dating and showed that pure oxalate powders were indeed obtained. AMS radiocarbon results of various accretions on the same art panels provided ages from modern periods to 2410 ± 35 BP. From these first results, more targeted sampling campaigns can be considered to provide a terminus ante quem for the rock art.
Springer Science+Business Media, LLC, part of Springer Nature, 2020
The use of ochre has been documented in many Middle Stone Age sites of Southern Africa. However, ... more The use of ochre has been documented in many Middle Stone Age sites of Southern Africa. However, the literature on the exploitation of ochre within the archaeological contexts of Later Stone Age (LSA) rock art sites is scarce. Despite the discovery of several painted shelters within the Erongo Mountains (Namibia), no archaeological study of ochre assemblages has been conducted in the region. Here, we present the archaeological ochre assemblage recovered from a LSA sequence at the rock art shelter of Leopard Cave (Erongo, Namibia), spanning ca. 5,700 to 2,100 cal. BP. The use-wear traces present on some ochre fragments and the stone tools bearing red residues are indicative of different stages of ochre processing at the site. The presence of other artifacts, such as ostrich eggshell and bone beads with red residues, and the existence of rock paintings in the cave are pointers to the importance of ochre for understanding the sociocultural behaviors of the LSA populations in central Namibia.
Apesar de comumente aceite a atribuição de uma cronologia paleolítica aos vestígios de pintura de... more Apesar de comumente aceite a atribuição de uma cronologia paleolítica aos vestígios de pintura descobertos há meio século na Gruta do Escoural, o seu estudo arqueológico nunca fora além de considerações estilístico‑‑formais, dificultadas pela ausência de contextos arqueológicos seguros. No âmbito de uma abordagem mais alargada de observações e registos analíticos recorrendo a novas tecnologias disponíveis, foi pela primeira vez possível proceder a um conjunto de análises físico‑químicas aos pigmentos pré‑históricos usados no Escoural, cujos resultados agora se apresentam e discutem.
Namibia is one of the southern African countries hosting the richest rock art heritage, with thou... more Namibia is one of the southern African countries hosting the richest rock art heritage, with thousands of rock paintings. Although numerous studies investigated their distribution, style and possible meaning, few is known about the materials used to perform these paintings. Our in situ study aimed at identifying the diversity of pigments and alterations of some rock paintings in the northwestern part of the Erongo (Namibia). It relies on extensive pXRF analyses of thirty-five figures from eight rock art sites of the area. Despite common limits of in situ pXRF analyses, the extensive number of figures analysed and the original data treatment that we performed pioneered the first scientific analyses of the pigments from rock painting sites in the Erongo Mountains. Furthermore, the study also confirmed the presence of iron oxide pigments on a portion of wall exposed during the excavations carried out at the archaeological site of Leopard Cave and of possibly datable alterations over several paintings, paving the way to future chronological analyses of past tradition of rock paintings in Central Namibia.
Cave Art is a fragile testimony of past human societies and the development of modern behaviours.... more Cave Art is a fragile testimony of past human societies and the development of modern behaviours. In limestone caves, moonmilk commonly endanger the artworks. It is a calcite deposit known to present a large variability of chemical composition and morphological structures, hosting numerous microbial communities. The possibility to characterize this deposit on the field would help to get a better understanding of the cave behaviour and set up proper conservation measures. The present study analyses the variability of a moonmilk strip of metric size in the Leye Cave. This cave located in the Vézère Valley (Dordogne, France) is not ornate, and has been selected to become a laboratory cave in which in-situ observations and micro-sampling can be carried out, before performing them into cavities hosting parietal artworks. SEM observations of twenty-four samples allowed investigating, for the first time, the variability of the moonmilk deposit over a same wall of few meters dimension. Our observations highlight low variability of moonmilk at the microscopic scale regarding the chemical composition and the morphological structures despite significant macroscopic diversity, thus providing insights to optimize the sampling strategy of moonmilk in ornate caves.
The detection and analysis of metabolically active microorganisms are useful to determine those d... more The detection and analysis of metabolically active microorganisms are useful to determine those directly involved in the biodeterioration of cultural heritage (CH). Fluorescence in situ hybridization with oligonucleotide probes targeted at rRNA (RNA-FISH) has demonstrated to be a powerful tool for signaling them. However, more efforts are required for the technique to become a vital tool for the analysis of CH's microbiological communities. Simultaneous analysis of microorganisms belonging to different kingdoms, by RNA-FISH in-suspension approach, could represent an important progress: it could open the door for the future use of the technique to analyze the microbial communities by flow cytometry, which has shown to be a potent tool in environmental microbiology. Thus, in this work, various already implemented in-suspension RNA-FISH protocols for ex situ analysis of yeast and bacteria were investigated and adapted for allowing the simultaneous detection of these types of microorganisms. A deep investigation of the factors that can affect the results was carried out, focusing particular attention on the selection of the fluorochromes used for labelling the probe set. The resultant protocol, involving the use of EUK516--6-FAM/EUB338--Cy3 probes combination, was validated using artificial consortia and gave positive preliminary results when applied in samples from a real case study: the Paleolithic archaeological site of Escoural Cave (Alentejo, Portugal). This approach represents the first dual-staining RNA-FISH in-suspension protocol developed and applied for the simultaneous investigation of CH biodeteriogenic agents belonging to different kingdoms.
The direct dating of rock paintings is not always possible due to the lack of organic carbon comp... more The direct dating of rock paintings is not always possible due to the lack of organic carbon compounds in pigments, or because sampling from a heritage site is often restricted. To overcome these limitations, dating laboratories have to develop new approaches. In this study, we consider sampling calcium oxalate crusts covering the painted artworks as a way to indirectly date the rock art. This stratigraphic approach includes isolating and extracting pure oxalate from the crusts. The approach was tested on natural bulk accretions collected in the open-air sites of Erongo Mountains in Namibia. The accretions were separated into two phases (pure oxalate and the remaining residues) with a special pretreatment. This process removes carbonates through acidification (HCl 6N) and dissolves the oxalate into the supernatant, leaving the minerals and windblown organic compounds in the residue. The efficiency of the separation was checked on the two phases by FTIR analyses and by 14 C dating and showed that pure oxalate powders were indeed obtained. AMS radiocarbon results of various accretions on the same art panels provided ages from modern periods to 2410 ± 35 BP. From these first results, more targeted sampling campaigns can be considered to provide a terminus ante quem for the rock art.
Springer Science+Business Media, LLC, part of Springer Nature, 2020
The use of ochre has been documented in many Middle Stone Age sites of Southern Africa. However, ... more The use of ochre has been documented in many Middle Stone Age sites of Southern Africa. However, the literature on the exploitation of ochre within the archaeological contexts of Later Stone Age (LSA) rock art sites is scarce. Despite the discovery of several painted shelters within the Erongo Mountains (Namibia), no archaeological study of ochre assemblages has been conducted in the region. Here, we present the archaeological ochre assemblage recovered from a LSA sequence at the rock art shelter of Leopard Cave (Erongo, Namibia), spanning ca. 5,700 to 2,100 cal. BP. The use-wear traces present on some ochre fragments and the stone tools bearing red residues are indicative of different stages of ochre processing at the site. The presence of other artifacts, such as ostrich eggshell and bone beads with red residues, and the existence of rock paintings in the cave are pointers to the importance of ochre for understanding the sociocultural behaviors of the LSA populations in central Namibia.
Apesar de comumente aceite a atribuição de uma cronologia paleolítica aos vestígios de pintura de... more Apesar de comumente aceite a atribuição de uma cronologia paleolítica aos vestígios de pintura descobertos há meio século na Gruta do Escoural, o seu estudo arqueológico nunca fora além de considerações estilístico‑‑formais, dificultadas pela ausência de contextos arqueológicos seguros. No âmbito de uma abordagem mais alargada de observações e registos analíticos recorrendo a novas tecnologias disponíveis, foi pela primeira vez possível proceder a um conjunto de análises físico‑químicas aos pigmentos pré‑históricos usados no Escoural, cujos resultados agora se apresentam e discutem.
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