The Department of Maine-et-Loire, located on the eastern margins of the Armorican Massif and the western margins of the Paris Basin, offers a remarkable field of investigation for lithic specialists studying the acquisition territories and diffusion routes of siliceous raw materials exploited by prehistoric populations. However, before any geo- or petroarchaeological studies, an inventory of all potentially available and exploitable resources, as exhaustive as possible, is necessary. The landscape of this department, at the crossroads of the Paris Basin and the Armorican Massif, has a complex geological history. The reconstruction of this geological history and its understanding is the subject of a historiographical chapter here, presenting the major scientific figures who have contributed to the development of this knowledge (chapter 1). This presentation leads to a detailed presentation of the geology of Anjou (chapter 2). Chapter 3 outlines the methodology adopted from field sampling to database construction, including the necessary terminological reflection, the method used for analysis, and the presentation of archaeological collections. Chapter 4 presents all the knappable materials of Maine-et-Loire, serving as an introduction to understanding the online database Petra and the catalogue compiled as a result of this work. Nearly a hundred samples of rocks, with extremely varied clastic qualities ranging from Carboniferous cinérites to Cenozoic silcretes, and including a multitude of Jurassic and Cretaceous flints, have been collected, described, photographed, mapped, and assembled into a lithothèque. This is intended to present an evolving and improvable database that future research will contribute to refining and enriching. This phase of the work demonstrates the coexistence of a strong variability of knappable materials in the Department of Maine-et-Loire. On one hand, an outcrop may yield a diversity of facies or sub-facies. On the other hand, the macroscopic characteristics of each sub-facies can vary greatly from one sample to another. Through several lithic assemblages, ranging from the Paleolithic to the Bronze Age, we can appreciate the diversity of rocks, their circulation in a territory strongly influenced by the Loire axis, and the exploitation methods specific to certain materials (chapter 5). This brief diachronic overview of the exploitation of raw materials in Maine-et-Loire shows specificities unique to each chronological period. In the earliest periods, Neanderthal populations selected a wide variety of siliceous resources, indicating an excellent knowledge of their occupation territory. During the Late Glacial period, hunter-gatherer groups focused on local materials, derived from the ancient terraces of the Loire. The exploitation of opal-resinite, for example, seems to be a specificity of Neolithic agro-pastoral populations. In the Bronze Age, local bartonian-ludian silcretes of poor quality were exploited for opportunistic lithic production. The ultimate goal of this database, presented in a geographic information system, accessible online, for all audiences, is to become a reference for anyone interested in this subject, both for studies on the Department of Maine-et-Loire and the entire Pays de la Loire region. Furthermore, this work has highlighted the significant variability of the materials presented, which represents a considerable constraint for the identification of raw materials in archaeological assemblages. The diversity of sub-facies remains difficult to exploit to this day. It is quite noticeable in archaeological corpora. However, correlating this macroscopic classification variability with the identified geological variability remains complex. This level of detail in the work represents a perspective that must undoubtedly be coupled with a genuine petrographic analysis at the microscopic scale of the materials presented in this study. This should help better understand the paths of prehistoric populations in their environment.
Le département du Maine-et-Loire, implanté sur les marges orientales du Massif armoricain et celles occidentales du Bassin parisien, offre un formidable champ d’investigation pour tout lithicien travaillant sur les dynamiques d’acquisition et de circulation des matières premières siliceuses exploitées par les populations préhistoriques. Mais, préalablement à toutes études géo- ou pétroarchéologiques, un inventaire de l’ensemble des ressources potentiellement disponibles et exploitables, et aussi exhaustif que possible, s’impose. Ce sont ainsi plus de 200 échantillons de roches, aux qualités clastiques extrêmement variées, allant des cinérites carbonifères, aux silcrètes du Cénozoïque, en passant par une multitude de silex jurassiques, qui ont été collectés, décrits, photographiés, cartographiés et rassemblés au sein de la lithothèque de l’UMR 6566 : PETRA. Au travers de plusieurs assemblages lithiques, allant du Paléolithique à l’âge du Bronze, nous pouvons apprécier toute cette diversité de roches, leur circulation dans un territoire fortement influencé par l’axe ligérien, et les modalités d’exploitation propres à certains matériaux. Le but ultime de cette base de données, présentée dans un système d’information géographique (SIG), mise en ligne et accessible pour tout public, est qu’elle devienne une référence à toute personne s’intéressant à ce sujet, aussi bien pour les études portant sur le département du Maine-et-Loire, que sur l’ensemble des Pays de la Loire, voire en dehors de la région.
