Geochemical and Magnetic Provenancing of Roman Granite Columns from Andalucía and Extremadura, Spain

One hundred and fifty two granite columns were examined in eight towns and archaeological sites in Andalucía and Extremadura, Spain, in order to determine the geological provenance of the columns. Three non-destructive methods of characterization were used: mineralogical features, magnetic susceptibility, and concentrations of radioelements (K, U, Th) determined by portable gamma ray spectrometry. Columns were compared with potential sources within Spain and in the Mediterranean area using analogous data previously published and also new data obtained for this work. The majority of the columns are made of Spanish granites, some of which were probably quarried near Mérida. Different chemical types of Spanish granites were used in the northern part of the area studied (Extremadura) and in the southern part (Andalucía). Twenty five columns are not of Spanish granites, but were imported from other sources, namely the Troad and Kozak Dağ areas of western Turkey, the Italian islands of Elba and/or Giglio, and Sardinia (confirming a column previously identified in the literature). The imported columns are found in Itálica, Hispalis (Seville) and Astigi (Écija), and were probably carried along the River Guadalquivir and its tributaries.