Bedrock features represent various economic, social, and symbolic aspects of past societies, but have historically received little study, particularly in North America. Fortunately, new techniques for analyzing spatial configurations, use-wear, and organic residues are beginning to unlock more of the interpretive potential of these features. Though preliminary in nature, the present study contributes to this trend by documenting an application of lipid analysis to bedrock features in a dry rockshelter. Results of this initial application indicate that bedrock features in dry rockshelters may provide especially favorable conditions for the preservation and interpretation of ancient organic residues. Abundant lipids, comparable to concentrations present in some pottery sherds, were extracted from a bedrock grinding surface at Gila Cliff Dwellings National Monument and analyzed using gas chromatography-mass spectrometry. Though the lipids were highly oxidized, degradation products indicative of former unsaturated fatty acids were retained. Comparisons to experimentally aged residues, and absence of a known biomarker for maize, indicate that the bulk of the lipids preserved in the milling surface probably derive from processing an oily nut or seed resource, and not from processing maize. Substantially lower amounts of lipids were recovered from a small, blackened cupule. It is hypothesized that some portion of the lipids in the blackened cupule was deposited from condensed smoke of cooking and heating fires in the caves. Potential for the preservation of organic residues in similar sheltered bedrock contexts is discussed, and a practical method for sampling bedrock features in the field is described.

Les pétroglyphes de l’Âge du Bronze (1500-500 BC) en Suède se situent essentiellement au Bohuslän. Les résultats précédents portaient généralement sur l’identification et l’interprétation des items et des scènes. D’autres éléments comme le regroupement des cupules, la position des bateaux, la pente et l’orientation des dalles ne sont généralement pas traités. Nous avons utilisé un corpus déjà existant, constitué de 300 relevés de sites d’une petite région du Bohuslän englobant trois petites villes Kville, Bottna et Svenneby. Les données sont traitées par des analyses statistiques exploratoires multidimensionnelles. Les résultats apportent tout d’abord des signatures particulières pour chaque site e.g. Bottna présente un caractère marin, Kville est riche en anthropomorphes mais pauvre en bateaux et Svenneby est particulièrement riche en bateaux avec des hommes à leur bord. Ils montrent ensuite la nécessité de distinguer différentes représentations d’un même item. Par exemple la subdivision de l’item « bateaux » en 5 types permet d’établir que Bottna est riche en deux types de bateaux caractéristiques de deux périodes de l’Âge du Bronze, Svenneby particulièrement peu dense est lui riche en bateaux d’une autre époque. De plus, le regroupement des cupules (en matrice, groupe, ligne ou cupules isolées) montre des particularités liées aux sites dont il accentue la différenciation. La notion de « certitude raisonnable » avec la probabilité d’erreur renforce la validité des conclusions. Par ailleurs, une étude numérique sur l’inclinaison des bateaux montre qu’ils sont très généralement en position horizontale et suggère qu’ils ont probablement été gravés tout près du rivage. / Swedish Bronze Age rock carvings (1500-500 BC) are primarily located in Bohuslän. Previous research generally consisted in identifying and interpreting both items and scenes. Other aspects such as cup marks clusters, boats position, slope and panels orientation have been largely ignored. This thesis relies on a pre-existing corpus of 300 panels from a small region of Bohuslän including three small towns Kville, Bottna and Svenneby. Individual items were analyzed using Principal Component Analysis. We first identify specificities for each site, e.g. marine focus in Bottna, numerous anthropomorphic figures in Kville but with few boats, low density of artifacts in Svenneby but many figures onboard boats. We then demonstrate the importance of distinguishing between different forms of given items. For example, when boats are classified into five different types, Bottna appears to be featuring two of these five types, namely the two types attributed to two periods of Bronze Age. Relying on the same classification, Svenneby that generally has a low density of artifacts, is characterized by boats attributed to another period. In addition, the analysis of different cup marks clustering (matrix, group, line or isolated) enables us to identify more precise specificities for site differentiation. We also introduce the concept of “reasonable certainty” to indicate the error risk in conclusions and strengthen the reliability of our results. Furthermore, we report a quantitative study on boat inclination demonstrating that boats were generally carved along the horizontal axis, suggesting that they were carved close to the waterside.