Improved methodology for identification of Göktepe white marble and the understanding of its use: A comparison with Carrara marble

The provenance of marbles used for ancient statuary and architecture is of utmost importance for archaeologists, art historians and archaeometrists. The aim of this paper is to provide a comprehensive characterisation of the white marble exploited in antiquity in Göktepe (Muğla Province, Turkey) to increase the reliability for identifying this marble in ancient artefacts. A campaign of interdisciplinary archaeological and geological fieldwork undertaken by the Marmora Asiatica project is based on a multi-method approach and on a representative set of samples used for the archaeometric analyses. Petrographic investigation showed that the Göktepe marble is more variable with regard to fabrics and grain size than previously suggested, whereas it is generally non-luminescent and dolomite-free. Stable C and O isotope and elemental analyses confirmed the results reported so far. We also report, for the first time for Göktepe white marble, the results of Sr isotope measurements, which in combination with elemental ratios, e.g. Sr/Mg and Mn/Sr, and δ18O values, greatly improve the discrimination among Göktepe, Carrara and other fine-grained white marbles. Applicability of these proxies was tested on artefacts from Hadrian's Villa, for which Carrara and Goktepe provenance had been proposed. The paper also reports new archaeological findings and results of estimates of stone extracted from the quarries, which allowed for a recontextualization of the significance of quarries at Göktepe. High-resolution topographic measurements, performed for the first time with the use of a 3-D laser scanner, combined with geological field study, allowed for precise calculation of the volume of the white variety extracted in antiquity. Estimates of 17000 m3 is almost a half less than previously suggested. Moreover, a careful study of the existing literature showed that in some instances assignment of white marble artefacts to the Göktepe quarries may not be accurate. Verification of provenance for those problematic artefacts and a more reliable identification of Göktepe marbles in the future can be achieved by application of the set of analyses proposed in this work, which has a higher discrimination potential.