Stéphan Dubernet

In this article, we propose an approach to reconstruct the timing of human activity at Points Cave, an Upper Paleolithic rock art site located in the middle of the Ardèche River Gorge (Rhône valley, France), based on the dating and characterisation of a stalagmite containing soot. Points Cave (‘Grotte aux Points’ in French), also called the ‘little sister of Chauvet Cave’, is famous for its parietal art including a series of dots made of palm prints. A large number of stalagmites formed in the cave during the last 500 ka. However, quarrying of the cave floors during historic times led to the partial destruction of the sedimentary deposits, and many of the stalagmites were found lying on the floor. In particular, one of them (STM‐18‐04) showed the presence of at least four dark layers in cross‐section, which appeared as possible remnants of fire‐related activities in the cave. Despite being present at the same site, no other specific link between STM‐18‐04 and the rock art has been documented. This stalagmite, however, allows us to identify phases of human presence, located at the cave entrance. To do so, we performed a series of analyses to determine its period of growth and the nature of the dark layers that it contains. Scanning electron microscopy and Raman microspectroscopy confirmed that the dark layers include soot, and uranium‐series dating indicated that the fire events occurred, respectively, around 14,200–14,100 and 12,500 years ago, in agreement with the radiocarbon ages of charcoal specimens recovered from the excavation areas nearby. We thus highlighted phases of human activity at the site during the Upper Magdalenian and/or beginning of the Epipaleolithic. By comparing our results with the regional paleoclimatic record, the soot layers trapped in the stalagmite appear to be synchronous with two cold periods, likely the Older Dryas and the Younger Dryas.

Les fouilles archéologiques menées dans le quartier Mériadeck et ses abords témoignent de l’occupation des sols dans une zone suburbaine et humide de la capitale de cité Burdigala. À partir du i^er s. apr. J.-C., des ateliers liés notamment au travail des peaux, du cuir et de la tabletterie y sont établis. Des indices forts indiquent en outre la présence de cornetiers. Au sein de ce quartier, le site de la rue Jean-Fleuret à Bordeaux (Gironde) met en lumière les techniques de travail des peaux et la production d’objets en cuir et révèle en partie l’organisation d’un tel atelier au Haut-Empire. Dans un premier état, entre 50 et 110-120 apr. J.-C., des artisans travaillent les peaux des caprinés à l’alun et/ou à l’huile d’olive, utilisent du macro-outillage lithique et des fiches métalliques en fer sans tête et collaborent avec d’autres artisans qui produisent des objets à partir de cuirs tannés de caprinés adultes et très probablement de peaux traitées à l’alun. Puis, entre 110-120 et 130-140 apr. J.-C., la spécialité de l’atelier change et les bovinés adultes sont préférés aux caprinés pour le travail des peaux. Il s’agit de la première attestation, durant l’Antiquité, d’emploi de l’alun pour le « passage en blanc » de peaux de bovinés, procédé de hongroyage que l’on pensait apparu à l’époque moderne. L’utilisation d’alun s’amplifie sur le site durant cette période, tandis que l’huile de Bétique n’est plus sollicitée. Au sein du même atelier, tabletier et cornetier s’associent aux artisans des peaux traitant les bovinés. Des objets en peau continuent à être assemblés, sans que l’on puisse déterminer si des cuirs tannés de bovinés sont exploités par les artisans de l’atelier. L’activité identifiée rue Jean-Fleuret cesse aux environs de 150-160 apr. J.-C., période à partir de laquelle l’espace semble mis en culture, peut-être jusqu’à la fin du ii^e s. Un site voisin localisé à 100 m à l’est du premier, l’îlot Fly, semble prendre le relais en termes d’activité artisanale, comme l’indiquent les batteries de cuves en bois réparties dans deux espaces desservis par un débarcadère en bois. Au iii^e s., les installations y sont à leur tour abandonnées. Un dépotoir établi sur les berges du cours d’eau reflète une activité proche pratiquée par des cornetiers. L’association d’amphores de Lipari et d’amphores à huile africaines suggèrent que les artisans traitant les peaux devaient maintenir leur activité à proximité.

The aim of this research work was to conduct a comparative study on the effectiveness of the application of chemical cleaning versus laser cleaning in the removal of surface congruent dissolution products from a potash-lime–silica historical stained-glass sample. EDTA was selected as the chemical cleaning agent. Laser cleaning was performed using a 238 fs pulse UV (343 nm) laser. The comparative cleaning studies were carried out on a stained-glass piece supplied by the Maison Lorin Glass Restoration Workshop from Chartres, France. Given the complex nature, irregular thickness and heterogeneity of the encrustations found on the glass, the two cleaning approaches were carefully performed step by step, while monitoring the process using an optical microscope. Raman spectroscopy and field emission scanning electron microscopy were used to characterize the changes induced on the sample surface during the cleaning process. The results demonstrate that the two cleaning approaches were able to eliminate the outer surface dark layer associated with carbon compounds, as well as the external part of the white layer generated by the crystallization of salts, formed with the dissolved elements after a reaction with the air. A comparison of the advantages and disadvantages of each method is also presented.

The origin and evolution of hominin mortuary practices are topics of intense interest and debate^1,2,3. Human burials dated to the Middle Stone Age (MSA) are exceedingly rare in Africa and unknown in East Africa^1,2,3,4,5,6. Here we describe the partial skeleton of a roughly 2.5- to 3.0-year-old child dating to 78.3 ± 4.1 thousand years ago, which was recovered in the MSA layers of Panga ya Saidi (PYS), a cave site in the tropical upland coast of Kenya^7,8. Recent excavations have revealed a pit feature containing a child in a flexed position. Geochemical, granulometric and micromorphological analyses of the burial pit content and encasing archaeological layers indicate that the pit was deliberately excavated. Taphonomical evidence, such as the strict articulation or good anatomical association of the skeletal elements and histological evidence of putrefaction, support the in-place decomposition of the fresh body. The presence of little or no displacement of the unstable joints during decomposition points to an interment in a filled space (grave earth), making the PYS finding the oldest known human burial in Africa. The morphological assessment of the partial skeleton is consistent with its assignment to Homo sapiens, although the preservation of some primitive features in the dentition supports increasing evidence for non-gradual assembly of modern traits during the emergence of our species. The PYS burial sheds light on how MSA populations interacted with the dead.

Radiocarbon (¹⁴C) dating of anthropogenic carbonates (CaCO₃) such as ash, lime plaster and lime mortar, has proven a difficult task due to the occurrence of a number of contaminants embedded within the CaCO₃ pyrogenic binder. These include ¹⁴C-free geologic components and/or secondary phases bearing an unknown amount of ¹⁴C, and thus the alteration of the original pyrogenic isotopic signature of the material results in major age offsets when carbon recovery is performed through acid hydrolysis. Here we present a characterization/quantification approach to anthropogenic carbonates that includes Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, thin section petrography, thermogravimetric analysis and scanning electron microscopy coupled with high-resolution cathodoluminescence, with which we identified the pyrogenic CaCO₃ fraction in an aerial lime plaster and two hydraulic mortars. The preserved pyrogenic component was then isolated by density separation and its purity checked again using FTIR. Carbon was recovered through thermal decomposition in vacuum. The resulting ¹⁴C age matches the expected age of the lime plaster, whereas hydraulic mortars are slightly offset due to the carbonation of calcium hydroxide lumps. This approach highlights the importance of a dedicated characterization strategy prior to dating and may be applied to aerial lime plasters to obtain accurate ages.

Lime plaster and mortar are pyrotechnological materials that have been employed in constructions since prehistoric times. They may nucleate as calcite and/or aragonite under different environmental settings. In nature, aragonite and calcite form through biogenic and geogenic processes that lead to different degrees of atomic order. The latter is a result of defects in the crystal lattice, which affect the properties of crystals, including their interaction with infrared light. Using Fourier transform infrared spectrometry (FTIR) with the KBr pellet method, it is possible to exploit these differences and assess the degree of atomic order of aragonite and calcite crystals and thus their mechanisms of formation. Here we use FTIR to characterize the degree of short-range atomic order of a pyrogenic form of aragonite recently observed in experimental and archaeological lime binders. We show that pyrogenic aragonite has a unique signature that allows its identification in archaeological sediments and lime binders of unknown origin. Based on these results, we developed a new FTIR-based method to assess the integrity and degree of preservation of aragonite and calcite when they occur together in the same material. This method allowed a better assessment of the diagenetic history of an archaeological plaster and finds application in the characterization of present-day conservation materials, such as lime plaster and mortar, where different polymorphs may nucleate and undergo recrystallization processes that can alter the mechanical properties of binders.