Mineralogical petrographic and geochemical characterization of marmora from the Roman quarries of Cabra (Córdoba) and Antequera (Málaga), External Sector Areas of the Betic Chain, Spain

Abstract

This paper the results of the mineralogical-petrographic and geochemical characterization of marmora from the quarry sectors of Cabra, Córdoba, and Antequera, Málaga in Spain. They are located in the western area of the Subbetic Zone within the Betic Chain and were exploited as marmora in Roman times. The archaeometric analysis of these quarries has a great importance for archaeological research since the proper characterization of geological outcrops to know the source of a significant number of architectural, epigraphic, sculptural, inscription and decoration elements used in the Roman Baetica province. As it is very difficult to determine the commercialization area or use for each rock type found in these two quarries sectors, the study methodology proposed in this paper is based on the characterization of the rocks sampled from these quarries by using also different analytical techniques, including polarized optical microscopy, X-ray diffraction and X- ray fluorescence. In the Cabra quarries three stone lithotypes have been identified: CW1, C-R1 and C-R2. The C-R1 and C-R2 lithotypes (Red Cabra varieties) show differences from a petrographic-mineralogical and chemical point of view: higher SiO2 and Al2O3 in C-R1 than in C-R2, which is related to a higher content in quartz and phyllosilicates, the C-R2, which also presents calcite-filled veins and traces of hematite. In the Antequera quarries, four stone lithotypes have been identified: A-RS, A-W2, A-R and A-BR lithotypes. The A-R lithotype (Red Antequera variety) is characterized by presence of siderite, iron oxides and pelagic ooids. The breccia (A-BR) show fragments of red micritic and oolitic limestones, a characteristic stone variety of the Penibetic. The A-RS lithotype contains siderite and hematites. Petrographic or mineralogical differences have not been found in the white varieties (CW1 and A-W2), but some geochemical differences related to higher content in P2O3 in CW1 are of particular interest.