Page 4 - Colonese_Zanchetta_&C_2015

fall within the range of isotope values of modern specimens from the western
Mediterranean (Figure 2A). Δδ adjusts values for site-specific environmental
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condition (e.g. elevation, δ O of rainfall, temperature) and species-specific

Figure 1. Study area showing the location of the archaeological sites (Table 1)

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feeding behaviour (i.e. δ C). Late Pleistocene δ O and δ C are similar to
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higher than modern counterparts (up to 4‰ and 2‰ for δ C and δ O
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respectively), whilst Holocene δ O and δ C values are variably lower (up to
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6‰ in both δ O and δ C). Δδ O and Δδ C values are positively moderately
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correlated (r = 0.63; R = 0.40; Figure 2B), implying a major mechanism that is
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driving changes in both δ O and δ C values over time. Variations between dry
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and wet conditions would explain the δ O and δ C values between the Late
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Pleistocene and Holocene. Higher δ O and δ C values in the Late Pleistocene
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generally reflect a negative water balance, which in turn increases the δ O
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values of rainfall (Bard et al. 2002) and the δ C of vegetation (e.g. Khon 2010).
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However other factors are likely to be involved as δ O changes in the source of
precipitation.

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Figure 2. A) Shell δ O and δ C distribution in Late Pleistocene, early to late Holocene
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and modern snails. B) Corrected shell δ O and δ C values between archaeological and
modern counterparts for each site. Δδ value of 0‰ means no difference between
archaeological and modern shells.

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