Characterisation, sourcing, and processing of Upper Palaeolithic ochre in the Lessini Mountains (NE Italy)

Goethite and hematite based geomaterials commonly referred as “ochre” were employed in a variety of utilitarian ways by early humans. They used these geomaterials as abrasives and skin protection, in food preservation and pharmacological applications, and for hide tanning and hafting. In addition, these materials were used in symbolic and funerary practices. However, the most well-known use of ochre in Prehistory is as a pigment for the creation of painted scenes in caves. The Western sector of the Lessini Mountains in NE Italy is an ideal location for studying ochre sourcing and processing due to the presence of the important archaeological sites Fumane cave and Tagliente rockshelter. The goethite and hematite based geological raw materials in the Lessini Mountains are found as infilling sediments of palaeokarst caves (Ponte di Veja, Cà de la Pela, Via Tirapelle and Colombare mines), karst fractures, and caves (Sant’Andrea, San Bortolo); they are found associated with basalts (San Giovanni Ilarione and Salgari), or in the form of limited outcrops (Cà del Paver, Manune). In order to approach the study of these materials, a specific analytical program was designed, taking into account the particularities of the geological and archaeological contexts. Microscopic (stereomicroscope, Polarizing Light Microscopy PLM, and Scanning Electron Microscopy coupled with Energy Dispersive X-Ray Spectrometer SEM/EDXS) and Diffractometric (X-Ray Powder Diffraction XRPD) techniques were used in a preliminary investigation of the collected raw materials and archaeological ochre; analysed materials were then grouped on the basis of characteristic mineral assemblages, as well as typical textural and microstructural features; and following these analyses, representative samples were selected in order to study the geochemistry of major and trace elements (Inductively Coupled Plasma Mass Spectrometry ICP-MS). Finally, the heat treatment of some samples of goethite-based ochre was investigated and confirmed using Transmission Electron Microscopy (TEM) whilst the presence of organic compounds in possible artificial mixture was checked with micro-Infrared Spectroscopy (-FTIR). Two potential principal districts were identified for the procurement of Fe-based resources: Ponte di Veja where both quartz-rich and calcite-rich goethite with detrital quartz occur associated with San Vigilio Oolite (Early-Middle Jurassic) and Rosso Ammonitico Veronese (Middle-Late Jurassic) and the sites associated with Mesozoic Dolomitised Limestones (San Bortolo and Sant’Andrea). These sites are in an aerial distance that varies between 7-20 kilometres indicating local procurement. Thermal induced transformation of goethite into hematite was initially supported by the results of the XRPD analyses due to the presence of selective broadening of some reflections and later proven on selected samples through TEM analysis based on the presence of characteristic pores formed during the process of goethite dehydration. According to the scientific and archaeological evidence, ochre was transported to the sites, fragmented, powdered and then used as painting material at Fumane cave. Both yellow and red ochre was mixed with bone fragments for the preparation of a paste whose composition is comparable with that evidenced at Blombos cave in South Africa where a tool-kit containing these ingredients was found. Due to the lack of wear marks on the archaeological ochre from Tagliente rockshelter, it is very difficult to understand the use of ochre in this site. A change in the procurement strategy was identified as quartz-rich materials were exploited during the oldest occupation phases of the site whilst dolomite-based and calcite-based raw materials were selected during the late phases of occupation. No strategy was identified for Fumane cave where dolomite-based raw materials where selected during the different phases of the occupation of the site.