Les géomatériaux meuliers : de l’identification des sources géologiques à la définition de catégories de gisements

National audienceLa recherche méthodique de provenance des géomatériaux meuliers franchit toute une série d’étapes successives. Avant toute chose, la pierre doit faire l’objet d’une détermination pétrographique et/ou géochimique. Puis, sera réalisée une recherche documentaire qui s’appuiera notamment sur les cartes géologiques régionales et leur notice explicative. Ensuite, seront réalisées des prospections géologiques ciblées, qui conduiront à valider la ressource meulière potentielle sur le terrain. L’étape finale de localisation des gisements meuliers correspond dans l’idéal à l’identification de lieux d’extraction ou de taille des meules par comparaison des meules retrouvées en site d’utilisation avec des reliques de fabrication ou des prélèvements géologiques issus des gisements.À partir d’une série d’exemples, nous montrons qu’il est possible de distinguer trois catégories de gisements : 1. Gisement quasi unique, ouvert sur une ressource géologique limitée dite rare, comme la rhyolite de La Salle des Vosges ou le grès de Fosses en Val d’Oise. 2. Gisement dominant sur ressource étendue, comme celui de Macquenoise dans les grès grossiers de la base du Dévonien des Ardennes. 3. Province meulière à gisements multiples, comme ceux du Berry ou de la Bourgogne, ouverts sur les grès de base du Mésozoïque, au nord du Massif central

The Macquenoise sandstone : a suitable Lochkovian raw material for ancient millstones : quarries, properties, manufacture and distribution (Belgium-France)

International audienceSince a few years a French-Belgian team of archeologists and geologists work on the characterization of ancient quern stones and millstones (mainly from the Antique period) linked with the identification of their stratigraphical and geographical provenances.This fruitful collaboration aims at reconstructing the ancient commercial roads and economic organization of territories during that period.In addition to the better-known volcanic rocks from the Eifel area, our study revealed the frequent occurrence of particular Devonian conglomerates and sandstones from the Ardenne area, as raw materials for the manufacturing of querns and millstones. The latter sandstones as well as the related antique millstone quarries, form an important and until now undervalued geological and cultural heritage in Belgium.Near the Ardenne border between France and Belgium, the earliest Devonian (Lochkovian) sediments deposited on the Caledonian substrate are conglomerates, which are interpreted as continental alluvial fans. The first marine sediments are littoral sandstones/quartzites or shales/slates. A sandstone formation, formally defined as the “Arkose d’Haybes” is closely linked to the former Lochkovian conglomerates (called also the “Poudingue de Fépin”). The outcrops of this particular formation around the reference localities of Haybes, Fépin and Hargnies (Ardennes, France), show a partly recrystallized, well-sorted grey to greenish sandstone (turbidite facies) with wine-red coloured joints. Another important area displaying old quarries in the same formation is located between Hirson (Aisne, France) and Macquenoise (Hainaut, Belgium): here, a more homogenous grey coarse sandstone facies occurs, with a better consistency and small amounts of dark green tourmaline crystals.These detrital formations were locally quarried, not only for building stones but also for the production of querns and millstones. The huge Proto-historical and Roman millstone quarries in Lochkovian conglomerates and sandstones from Macquenoise are known since the 19th century. Even if the lack of recent archeological excavations do not allow yet to precise the exact age of their quarrying, the dating of the various products derived from these quarries allow to consider the duration of the active extraction and how far the millstones from Macquenoise area were transported into the northern Gallo-Roman provinces

Ernolsheim-lès-Saverne – Stampfloecher, Rosskopf, Polenberg

Provenance et diffusion des matières premières lithiques dans le massif vosgien L’étude des outils macrolithiques, mis au jour sur les sites dont la fourchette chronologique est comprise entre le Néolithique et le début de l’Antiquité, révèle la diversité des roches acquises et illustre la richesse des contacts entre les populations. La multiplication des points d’acquisition montre la capacité de l’Homme à s’affranchir des distances afin de mettre en place des circuits d’approvisionnement te..

Évolution typologique et technique des meules du Néolithique au Moyen Âge

Les deux principaux axes du programme fixé pour cette année 2016 ont été atteints. Il s’agissait dans un premier temps de finaliser le travail en région Centre-Val de Loire et dans un second temps de retravailler et de fusionner les bases de données « rotative » et « va-et-vient » développées par le PCR ces dernières années. L’année 2016 a permis de poursuivre l’inventaire et la contextualisation des outils de mouture (dont l’attribution chronologique est assurée) étudiés dans la région Centr..

Évolution typologique et technique des meules du Néolithique à l’époque médiévale

Le dernier rapport rendu en décembre 2018 constitue le rapport final du PCR triennal « Évolution typologique et technique des meules du Néolithique à l’époque médiévale » réalisé en région Centre-Val de Loire. En effet, le programme du PCR arrive à son terme pour cette région. Ce PCR s’est déroulé de 2015 à 2017, avec une année probatoire préliminaire en 2014 et une année complémentaire en 2018. L’année probatoire de 2014 avait été largement dominée par la préparation du colloque de Reims et ..

Water-repellent and biocide treatments: Assessment of the potential combinations

International audienceIt is a common practice to use several chemical products during restoration projects of monuments or sculptures. However, care must be taken when combining the products to avoid a misuse. For example, it is well-known that applying a biocide on stone before a water-repellent leads to a diminishment of the hydrophobic effect of the treatment. But the application of biocide after a water-repellent treatment has been poorly analysed, although studies have proven that the stone looses its hydrophobicity after the application of the biocide. Henceforth, this study investigates the effects of biocide application on a water-repellent film and focuses on the possibilities to restore the efficiency of the previous water-repellent treatment (after the application of the biocide). At first, the tests were performed on glass slides to understand the mechanisms, with the subsequent results revealing that the biocide product deposits on the water-repellent film. Then, the study focuses on determining methods to remove the remains of biocide on limestone samples, previously treated with a water-repellent. The water-repellent used in the study is an alkylpolysiloxane, Rhodorsil H224 from Rhodia

The macquenoise sandstone (Devonian – Lochkovian), a suitable raw material for ancient querns and millstones : quarries, properties, manufacture and distribution in France and Belgium

For some years, a French-Belgian team of archaeologists and geologists is investigating the provenance of ancient quern-stones and millstones. Their study revealed the frequent occurrence of particular coarse sandstones derived from Lower Devonian strata in the Ardenne region, known as either the “Arkose of Haybes” by geologists or the “Arkose of Macquenoise” by archaeologists. Material for Late Iron Age and Roman quern-stones and millstones was quarried from open pits located west of the border between France and Belgium, between the Belgian village of Macquenoise (Commune of Momignies, Province of Hainaut) and the French town of Hirson (Aisne Department, Hauts-de-France region). This paper describes the raw materials, presents the different types of grindstones produced through historical times and provides a detailed diffusion map of the millstones

Querns and mills during Roman times at the northern frontier of the Roman Empire (Belgium, Northern France, Southern Netherlands, Western Germany): Unraveling geological and geographical provenances, a multidisciplinary research project

This paper presents the results of a multi-disciplinary provenance study of querns and millstones during the Roman period (1st-4th century CE) in the northern part of the Roman Empire (provinces of Gallia Belgica and Germania Inferior). Comparative petrographical, mineralogical and geochemical analysis allowed an international team of archaeologists and geologists to identify the different raw materials used for the manufacturing of querns and millstones. As a result, (litho-) stratigraphic assignments as well as geological-geographical provenances are suggested or corroborated for the broad spectrum of these natural geo-materials. We give evidence for the exploitation of at least seven different rock types. They include sedimentary rocks (fine- to coarse-grained quartzitic and arkosic sandstones, conglomerates, limestones) and volcanic rocks (vesicular lavas) derived from different geological strata in the following geological-geographical settings: the volcanic Eifel area (Pleistocene lava), the Ardennes Massif (Palaeozoic sedimentary rocks) and the Paris and Northern Sea Basin (Cenozoic sedimentary rocks). Furthermore we show that a large diversity existed within different productions (different types of hand-mills and mechanical powered mills) and distribution patterns. This paper provides new data which will lead to new insights into the socio-economics of the local “Gallo-Roman” communities and into their networks within the northern Roman Empire

Infrared thermography monitoring of the NaCl crystallisation process

In this work, we describe the growth of NaCl crystals by evaporating droplets of aqueous solution while monitoring them with infrared thermography. Over the course of the evaporation experiments, variations in the recorded signal were observed and interpreted as being the result of evaporation and crystallisation. In particular, we observed sharp and transient decreases in the thermosignal during the later stages of high-concentration drop evaporation. The number of such events per experiment, referred to as “pop-cold events”, varied from 1 to over 100 and had durations from 1 to 15 s. These events are interpreted as a consequence from the top-supplied creeping (TSC) of the solution feeding the growth of efflorescence-like crystals. This phenomenon occurred when the solution was no longer macroscopically visible. In this case, efflorescence-like crystals with a spherulite shape grew around previously formed cubic crystals. Other crystal morphologies were also observed but were likely fed by mass diffusion or bottom-supplied creeping (BSC) and were not associated with “pop-cold events”; these morphologies included the cubic crystals at the centre, ring-shaped at the edge of droplets and fan-shaped crystals. After complete evaporation, an analysis of the numbers and sizes of the different types of crystals was performed using image processing. Clear differences in their sizes and distribution were observed in relation to the salt concentration. Infrared thermography permitted a level of quantification that previously was only possible using other techniques. As example, the intermittent efflorescence growth process was clearly observed and measured for the first time using infrared thermography.This work was partially funded by the BQR call from the University of Reims Champagne-Ardenne (project Transels)