Travelin’ stones: The oolitic chert blades from Zambujal Chalcolithic enclosure (Torres Vedras, Portugal)

The Oolitic chert is an important raw material for large blade production in Betic Cordillera (Spain) during 4th-3rd mill. BCE. These blades are part of a long-distance trade network of artefacts found in Chalcolithic settlements of southwestern Iberia. In Zambujal, the westernmost site with oolitic chert blades, with the source-area distance more than 500km, these utensils are included in the “import package” with remarkable implications for social change and innovation (Lillios 2020). Sourcing oolitic chert blades contributes to understanding mobility in the Chalcolithic of the Iberian Peninsula as part of a complex trade and exploitation network. In the current study, all the oolitic chert blades recovered in Zambujal are analysed which are recovered from the ancient excavations between 1964 and 1973 by H. Schubart and E. Sangmeister to the recent investigations by M. Kunst (1994-2012). After first using a techno-typological classification, the raw material characterization focused on the petrographic compositional and textural features (macro-, in hand specimen, meso-, with hand lens, and microscopic, with binocular lens and petrographic microscope). Polished thin-sections were analysed also by Raman Microspectroscopy in order to determine the main crystalline phases present. It was possible to correlate with high probability the archaeological raw material with oolitic chert from the Milanos Formation (Upper Kimmeridgian-Tithonian in Middle Subbetic, Granada) and also from the Malaver Formation (Miocene in Campo de Gibraltar Complex, Malaga), with conglomerates from Lower-Middle Jurassic oolithic chert. The identification of signs of usage, fracturing and reuse are frequently observed in the oolitic chert blades of Zambujal, as in other Portuguese sites. The association of an intensive use of the oolitic chert blades with its scarcity in the archaeological record highlight the importance of blades for domestic activities, as “prestige” functional goods (Teather 2008: 84). In this sense, the oolitic chert blades are material records of an intense mobility of humans and objects in the Chalcolithic. The presence of an expressive set of oolitic chert blades in Zambujal is related to their important role played within the network of transregional relations.