*3.2. Isotopic Signature of the Studied Samples*

Isotopic values of the six samples can be generally characterized as homogeneous, despite the observed variation in their δ13C and δ18O val ues and are summarized in Table 4.

<sup>δ</sup>18O values are negative in all samples and range from <sup>−</sup>2.49 to <sup>−</sup>1.13. The majority of the samples (OM10, OM13, OM49 and OM50) display very homogeneous <sup>δ</sup>18O values (ranging from <sup>−</sup>1.89 to −1.13 ‰ V-PDB), while the rest two samples (OM11 and OM51) are isotopically lighter, with values <sup>−</sup>2.49 and <sup>−</sup>2.06 ‰ V-PDB respectively. Regarding the <sup>δ</sup>13C values, they vary slightly from 2.43 to 3.37 ‰ V-PDB.

Values of the studied samples are plotted in the marble isotopic reference diagram (Figure 17, after Gorgoni et al. 2002 [18]). In this diagram, isotopic fields of white marbles that were commonly used in antiquity have been marked, based on published isotopic data for marbles from Carrara (Italy), Penteli, Naxos, Paros, Thassos (Greece) and Afyon, Aydin, Proconnesos (Turkey). Samples from this study plot in the central part of the Proconnesos-1 marble field. Overlapping in this area is noticed with parts of other fields, which represent marbles from other localities. In particular, some samples plot along or inside the subfields for Thasos (subfields T1,2,3), Paros (subfields Pa2,3) and Carrara (field C).


V-PDB: Vienna Pee Dee Belemnite.

**Table 4.** δ18O and δ13C values (‰ V-PDB) of the studied samples.

**Figure 17.** δ18O versus δ13C plot, displaying the isotopic values of the studied samples. Fields of ancient quarrying samples are from Gorgoni et al. 2002 [18]. Pr1,2 = Proconnesos, variety 1 and 2; T1,2 = Thasos-Alyki; T3 = Thasos-Vathy; C = Afyon (Dokimeion); Pa1 = Paros-Lychnites, Pa2,3 = Paros-Chorodaki, Pa4 = Paros-Lakkoi; Pe = Penteli; N = Naxos; Aph = Aydin.
