Ancient Quarries on the Estremoz Anticline (Ossa Morena Zone, Portugal): Exploitation, Use and Dispersion of Estremoz Marbles during Roman times

The use of crystalline marbles from Estremoz Anticline, Alentejo (Southern Portugal), and their historical exploitation are documented since the Roman period. While most of the ancient quarries in the area were originally discovered due to the intense mining activity of the 20th century, the remains that still preserved in situ are very scarce, as this recent exploitation has often erased the existing evidence. However, in several of the cases here documented, recent quarrying operations have contrastingly provided and helped preserve these traces of earlier extractive activity. The analysis of aerial photographs, confirmed by a field visit to the area, identifies almost five hundred marble quarrying and exploration sites in the Estremoz Anticline, most of which were opened in the 70s and 90s of the 20th century, while official records show that in the late 80s there were 187 quarries operating simultaneously around the villages of Estremoz, Vila Viçosa and Borba.Today, for various reasons (including the globalisation of the economic market, the ageing of the population, recurring economic crises, the recent tightening of safety regulations, etc.), only around 40 quarries are still active, some of which are over 150 metres deep. Nevertheless, the analysis and conservation of the archaeological evidence of exploration remains a significant challenge. This paper presents a summary and characterisation of the identified ancient quarries and remains in terms of their location, geological setting and marble type, but also of the ancient exploitation methods observed. It also explains the current challenges for the conservation of the relevant geodiversity found and some resulting geoconservation measures, defined according to the site, which could be implemented on a larger scale to conserve and display the unique architectural and cultural heritage of these sites. This study assumes a particular relevance so that both landowners and industry continue to support and preserve this historical and cultural, tangible and intangible heritage of undeniable and differentiating value for this raw material.