This text introduces the publication of the symposium "Archaeological carbonates, the memory of water" which was held at the MSH "Mondes" in Nanterre, France. This meeting gathered nine papers around the notion of "archaeological carbonates" studied in various contexts (caves, aqueducts, baths) and in a wide geographical area. Identified since Antiquity as reveal some historical texts of ancient authors (Vitruvius, Pliny the Elder, Strabo), carbonate deposits are relatively common in hydraulic structures associated with calcium saturated waters. Following the pioneering study of the carbonates of the ancient aqueduct of Nîmes in the 1990’s, different works combining different paleo-environmental and geoarchaeological approaches have recently completed the panel of studies of these archaeological carbonates. This special publication of the journal Archéologie, Sociétés et Environnement highlights the great interest of studying these carbonate deposits preserved in an archaeological context, true sedimentary archives of human activities and water managements by past human societies.
Archaeological evidence testifies to the importance of the thermal town of Cuntis (Spain) in Roman times, an aspect that also appears to be reflected in literary sources and in its own toponym. The importance of the beneficial and cultual use of these thermal waters in Roman times is evidenced by the presence of collection wells located in the center of the village of Santa María de Cuntis, in the Burga or ‘Fuego de Dios’. It is the main collection system for the hot springs that supply the current spa, but also because it is a site steeped in an important historical tradition. In 1908, during the cleaning of this well, some objects were discovered and distributed among the neighbors, but by chance some of them were deposited in the Provincial Archaeological Museum of Ourense where they were recently identified. Among them, a key, a knife and some coins that have been altered by the action of mineral-medicinal waters from this source. In this work, we present this discovery, as well as we propose a first approach to the archaeometric study of these concretions, with the interest of evaluating how the different types of water affect the conservation and modification of the archaeological objects preserved in these thermal environments.
Archaeological investigations conducted on an ancient aqueduct supplying the antique town of Poitiers, western France, in the municipality of Vouneuil-sous-Biard (86), has uncovered a 20 cm thick calcitic crust on walls of a buried channel. Two types of facies alternate in this crust. In the lower crust laminae are mostly comparable to speleothems that would be derived from relatively pure karstic waters. The mid and upper parts of the crust are influenced by microbial communities and probably derived from capture of surface streams rich in organic matter. The δ18O and δ13C values of these two facies, formed in a dark drain with little seasonal temperature variation, are intermediate between those expected for pure speleothems and tufa deposits. Alternance of very thin dark and light laminae exist, especially at the base of the crust. This may represent annual growths, but isotopic and petrographic existing data do not prove this hypothesis which would need further geochemical investigations.
The archaeological excavations carried out on the aqueduct that supplied the Gallo-Roman city of Cahors (Divona) have discovered sections partially filled with carbonate deposits. These deposits present a laminated facies and variations in thickness along the way of the aqueduct. The recent study of a sequence of deposits 28 cm thick presented here demonstrates the ancient maintenance of the hydraulic structure by identifying anthropic traces of cleaning, sometimes followed by re-capping with hydraulic mortar, in the sedimentary sequences.
The recent archaeological study of two Roman aqueducts located in northern Gaul at Villenoy near Meaux (Seine-et-Marne) and Reims (Marne) was accompanied by a macroscopic and microscopic analysis of the carbonate concretions located on the sidewalls of the water channel. The sequencing of these concretions, although not very thick, allows us to retrace parts of the history of the aqueducts. For the aqueduct of Villenoy, the petrographic study confirms the chronological succession of two major phases and two types of operating modes. In the case of the aqueduct of Reims, it forces us to question the very short time recorded in the preserved concretions.
The aim of this study is to reconstruct the climatic variations of the region of Nîmes and Arles in Roman times by exploiting the light stable isotope content (O, C) of five carbonate deposits from the aqueducts supplying these two cities, active between the 1st and 5th centuries AD. Optical microscopy observations suggest a seasonal laminae structure, consistent with sub-annual-scale δ18O measurements. Laminae counts provide estimates of aqueduct operating times consistent with archaeological data. From the measurement of lamina thickness, an age model is developed that allows the variations in oxygen and carbon isotope ratios to be placed in time. Despite the presence of gaps that make the correlation of the samples and the absolute chronology of the deposits uncertain, a pattern of climatic variations is sketched from the 1st to the 3rd century AD.
This article aims to draw the attention of geoarchaeologists who work on the carbonate deposits (sinter) of aqueducts to the importance of the legal regulation, which framed the use of aqueducts. The approach followed is historiographic. It is based on the study of the aqueduct of Nîmes, an urban aqueduct as well as the study of the south branch of the aqueduct of Arles. This one was assigned to private use, supplying of the mills of Barbegal. The residents along the line of a public aqueduct were allowed to use the water for a fee. They had the legal obligation to maintain the conduit and its surroundings. The regulations applicable to the Barbegal aqueduct were governed by private law. The characteristics and the importance of the concretions of the Nîmes aqueduct depend as much on a natural evolution as on interventions on the canal for water intakes and for its maintenance. In the case of the Barbegal aqueduct, the observation of the concretions and their analyses show (1) that the mills did not function throughout the year, (2) that the building was originally covered only by a roof that was subsequently removed or destroyed, (3) the aqueduct served as a water reserve during its period of use.
Traces of soot reflecting past human activities are sometimes observed on the ceilings and walls of caves and rock shelters, sometimes also inside speleothems. These deposits, which result from anthropogenic fires, are proving to be a particularly suitable material for very high-resolution micro-chronological studies. Microscopic analysis of carbonate crusts from walls of various ages (Middle and Upper Palaeolithic) shows that they preserve traces of multiple occupations that can be linked to the archaeological units identified during the excavation. The generally high MNOs (Minimum Number of Occupations), which correspond to each archaeological unit, attest to the cumulative nature of the latter. Each level records a different number of occupations from one unit to another and presents particular rhythmicity. The research potential for soot deposits are diverse and suggest the possibility of studying the mobility of past human groups with previously unrivalled temporal resolution. Concerns about the concept of “archaeological floor” and “palimpsest” as applied to spatial studies in caves and under shelters/under rock is also developed.