The authors propose a petroarchaeological approach to understanding the exploitation of the environment and its resources by prehistoric groups. Petroarchaeology broadly defined includes the geological field study of formations containing lithic raw materials; the characterisation of these lithic materials and the study of their circulation. Most of the silica-rich rocks found within the Aquitainian basin were exploited during the Upper Palaeolithic. Some of these are well known, especially the Bergeracois flint from western Perigord which contains the fossil Orbitoides media. This flint is often used as a 'tracer' to study the circulation of lithic raw materials in the Upper Palaeolithic of southwest France. Recent work in the Pyrenean Piedmont has identified several other flint sources that offer similar potential as 'tracers'. This article focuses on the flint-bearing formations of the Chalosse region that contain the fossil Lepidorbitoides sp. The authors provide a brief overview of the archaeological and geoarchaeological work done in the region of La Chalosse. Four main geological areas contain flints and were targeted: the Tercis, Saint-Lon-les-Mines and Audignon anticlines, and the Bastennes-Gaujacq dome-diapir. Geological maps for the region, outcrop photos and thin section images of fossil species are provided. Archaeological research demonstrates that the Maastrichtian age silicified members of the Chalosse region were clearly used throughout the Upper Palaeolithic. A preliminary survey of archaeological sites from the Aquitainian-Pyrenean region that have produced the Chalosse Lepidorbitoides sp. type flint is presented and mapped. The Chalosse flints are shown to travel over considerable distances along the Pyrenean Piedmont and northeast to the Aquitainian basin. In order to study the technological use of the Chalosse flint, the Solutrean-Badegoulian lithic assemblage from the Abri du Cozoul de Vers in the Quercy region was analysed. The chaîne opératoire of the Chalosse flint is Pierre Chalard et al. 14 diversified, and differs from that of other non-local flints which together make up a small proportion of the lithic assemblage (10%-15%). According to the authors, more geological fieldwork is needed and the fossil markers for Chalosse flint needs to be more precisely defined; however, the Chalosse Lepidorbitoides sp. type flint already shows great promise as a 'tracer' for understanding prehistoric group mobility, territory and interaction.