Page 3 - Colonese_Zanchetta_&C_2015

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reconstructing local hydrological balance and vegetation cover. Shell δ O has
been related to atmospheric conditions, and in particular to the oxygen isotope
ratio of precipitation, relative humidity and temperature (Balakrishnan and Yapp
2004). However, the imprinting of atmospheric conditions on the shell oxygen
isotope ratio is not straightforward and it is shown as distinctive regional
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relations (e.g. Zanchetta et al. 2005). Shell δ C is mainly a function of respired
CO 2 from the diet, which for most of the species means vegetation (e.g. Stott
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2002). Shell δ C thus reflects vegetation type (e.g. C3, C4), but also species-
specific feeding behaviour (calciophilous) and potentially the effect of
environmental conditions on the plants carbon isotope fractionation.

Here we analyse the stable carbon and oxygen isotope of shells from several
archaeological sites of the Iberian and Italian Peninsula and Sicily (Figure 1;
Table 1). Through a comprehensive compilation of previously published data
(n = 854) we explore shell isotope variations between the Late Pleistocene
(~14.5 to 10.7 ka cal BP) and the early-late Holocene (~10.7 to 2.5 ka cal BP)
and discuss their implications to understand millennia-scale changes in
hydrological conditions and vegetation dynamics. This work also aims at
stimulating research efforts to complement the land snail archive with other
environmental proxies from multiple sites (speleothems, lake cores etc.).

Table 1. Archaeological sites reported in Figure 1

Site 14 C age (ka cal BP) Reference
1 - Los Castillejos ~7.2 – 4.0 Yanes et al. 2011
2 - Marroquíes ~4.1 Yanes et al. 2013a
3 - Arena de la Virgen and Casa Corona ~8.5 – 12.2 Yanes et al. 2013b
4 - Bauma del Serrat del Pont ~2.5 – 9.0 Colonese et al. 2013
5 - Grotta di Latronico 3 ~7.8 – 8.8 Colonese et al. 2010a
6 - Grotta del Romito ~13.0 – 14.5 Colonese et al. 2007
7 - Grotta della Serratura ~7.2 – 12.1 Colonese et al. 2010b
8 - Grotta d’Oriente ~7.8 – 14.2 Colonese et al. 2011

Materials and Methods

Archaeological and modern shell values are compared at the regional scale. The
comparison also includes modern shell isotope data from Italian Peninsula and
Sicily (e.g. Zanchetta et al. 2005; Colonese et al. 2014) not associated with
archaeological sites (Figure 2A). Variations in shell isotope composition are
also analysed on a site-by-site basis by correcting archaeological values for the
modern average shell isotope data at each site (Δδ = archaeological-modern;
Figure 2B).

Results and discussion

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Early to late Holocene shells in general are depleted in O and C compared to
Late Pleistocene and modern counterparts. By contrast Late Pleistocene shells

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