Geo-Temas 10, 2008 (ISSN: 1567-5172.) Environmental impact provoked by Roman mining activities (2000 years BP) on the coastal area of the Southern Bay of Biscay Impacto ambiental en la zona costera del sur del Golfo de Bizkaia provocado por actividades mineras romanas (2000 años BP) N. Cuevas Zuazo, A. Cearreta Bilbao and E. Leorri Soriano Micropaleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/EHU, Apartado 644, 48080 Bilbao, Spain. Tel.: +34 946 012 637; Fax: +34 946 013 500. alejandro.cearreta@ehu.es Abstract: Combined geochemical and micropalaeontological studies have been proved suitable to understand the environmental evolution derived from historical mining activities. This approach has been successful to show the environmental impact of the mining and urban activities around the Roman harbour of Oiasso (Irun, Bidasoa estuary) as reflected by the extremely high lead concentrations and reduction of foraminiferal abundances. Key words: Heavy metals, foraminifera, Oiasso harbour, environmental evolution. Resumen: Con el fin de entender la evolución ambiental provocada por las actividades mineras históricas es posible combinar estudios geoquímicos y micropaleontológicos. Esta aproximación ha demostrado ser muy útil para la reconstrucción del impacto ambiental provocado por las actividades urbanas y mineras en los alrededores del antiguo puerto romano de Oiasso (Irun, estuario del Bidasoa) mostrando una concentración extremadamente alta de plomo y una reducción en la abundancia de foraminíferos. Palabras clave: Metales pesados, foraminíferos, puerto de Oiasso, evolución ambiental. INTRODUCTION Mining and metal foundries represented the main interest of the Romans on the southern Bay of Biscay. These activities were mostly concentrated on the abundant iron deposits (Triano, Cabárceno,…). However few of these were dedicated to the exploitation of precious metals (silver) from the lead ores. Geochemical signatures of such historical activities are difficult to find in coastal sediments for the case of Fe exploitation as sediments are naturally highly enriched in this metal, whereas they are possible to distinguish for Pb as its concentrations are very low in the regional geochemical background. Such activities were carried out intensively during the 1st and 2nd centuries causing, in some cases, severe Pb pollution episodes (Alfonso et al., 2001). In the Bidasoa estuary, located on the border between Spain and France (Figure 1), Romans founded a civitas called Oiasso and constructed a harbour of regional importance between the years 70-120 that it was abandoned towards the end of the 2nd century (Figure 2; Urteaga, 2005). This work studies the impact of these activities on the estuarine system using a combined geochemical and micropalaeontological approach in order to evaluate the pollution levels produced by the Roman activities and their ecological impact on the coastal environment. FIGURE 1. Geographical location of Oiasso (Irun) (see number 1 in the map).