Quaternary interglacial environmental stability in San Salvador Island (Bahamas): A land snail isotopic approach Yurena Yanes a, ⁎, Christopher S. Romanek b a Department of Geology, University of Cincinnati, Cincinnati, OH 45221, United States b Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506, United States abstract article info Article history: Received 6 September 2011 Received in revised form 3 September 2012 Accepted 16 September 2012 Available online 4 October 2012 Keywords: Land snails Stable isotopes Paleoenvironment Quaternary San Salvador Bahamas The 13 C/ 12 C and 18 O/ 16 O ratios of modern and fossil shells of two ecologically-distinct land snail taxa (Cerionidae and Annularidae) from San Salvador Island were analyzed to estimate the interglacial Pleistocene and Holocene paleoenvironmental conditions in the Bahamas. The average δ 13 C value of Cerion was -5.0±1.8‰ for modern (~0–0.1 ka) specimens, -4.3±0.7‰ for late Holocene (~2–4.6 ka) individuals, -3.4±1.6‰ for middle Holocene (~5–6.3 ka) shells, -4.0±1.5‰ for ~85 or ~110 ka specimens, and -3.6±0.4‰ for individuals that grew during OIS 5e (~125 ka). Annularidae specimens displayed average δ 13 C values of -6.3±2.5‰, -6.1±1.0‰, -2.4 ± 1.0‰, -4.4±1.1‰, and -5.0±2.9‰, respectively. These results suggest that snails con- sumed C 3 and C 4 plants arbitrarily through time, however, higher proportion of C 4 plants may have been con- sumed in the past compared to the present. Cerion was ~1‰ higher in average δ 13 C value than Annularidae specimens for some time-intervals, indicating greater C 4 plant consumption and/or higher ingestion of carbonate-rich sediments. The average δ 18 O value of Cerion was -0.5 ± 0.8‰ for modern individuals, -0.5 ± 0.5‰ for late Holocene specimens, -0.8±0.2‰ for middle Holocene shells, -0.4±0.6‰ for ~85 or ~110 ka specimens, and -0.3±0.6‰ for OIS 5e individuals. Annularidae individuals exhibited average δ 18 O values of -0.7±0.8‰, -0.5±0.9‰, -0.9±0.3‰, -0.3±0.6‰, and -0.9±0.9‰, respectively. These results point to similar atmospheric conditions over time-intervals when shell was deposited. The shell δ 18 O values did not sig- nificantly differ between species despite the apparent differences in lifestyle. Calculations from a snail evapora- tive steady-state flux balance model and proxy data suggest that modern individuals deposited shell at air temperatures of ~24–25 °C, ambient water δ 18 O values between -4.5‰ and -3.5‰ (SMOW), and relative hu- midity of ~87–89%. Late to middle Holocene and interglacial late Pleistocene shells appear to have precipitated under a similar environmental setting. Overall, atmospheric conditions during these Quaternary interglacial time-intervals at coastal sites of San Salvador were largely comparable to the present. This apparent environ- mental similarity is consistent with the relatively comparable snail richness and diversity observed at those same locales and time-intervals. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Land snail assemblages are increasingly used as an effective retro- spective proxy for paleoenvironmental and paleoecological condi- tions at both spatial and temporal scales. It has been repeatedly demonstrated that variations in the isotopic signature (e.g., Yapp, 1979; Balakrishnan and Yapp, 2004), taxonomic composition and taphonomic feature (e.g., Yanes et al., 2008a, 2011a; Yanes, 2012), and body size (e.g., Hearty and Schellenberg, 2008; Huntley et al., 2008; Hearty, 2010) of land snails are linked to fluctuations of abiotic and biotic factors. Land snails are an abundant and diverse fauna of ocean islands worldwide (Solem, 1984) and, thanks to their calcareous hard parts, they are frequently well-preserved in the Quaternary fossil record (e.g., Goodfriend, 1992, 1999). San Salvador Island, an isolated platform on the eastern Bahamas, located ~ 640 km southeast from Miami, Florida (Fig. 1), is a tropical (24° 00′ N, 74° 30′ W), low-altitude (> 40 m a.s.l.) and carbonate-rich island that contains an exceptional native terrestrial malacofauna which has been preserved in local Quaternary eolian sedi- ments and paleosols (e.g., Rosse, 1989; Baldini et al., 2007; Hearty and Schellenberg, 2008). The popular tropical pulmonate Cerion (Gastropoda: Cerionidae) (Fig. 2A–B) is highly abundant in the Caribbean, and it ex- hibits an extraordinary morphological diversity that is well-preserved in Quaternary rocks (e.g., Gould et al., 1975; Goodfriend and Gould, 1996; Gould, 1988; Hearty and Schellenberg, 2008; Hearty, 2010). Be- sides Cerion, many other taxa, such as those of the family Annularidae, e.g., Opisthosiphon coloni (Fig. 2C) or Colonella watlingensis (Fig. 2D), are also relatively abundant, overlap in distribution with Cerion and have been preserved in the local sedimentary record. However, they have traditionally received much less scientific attention than Cerion. Such shell material provides a superb opportunity to explore Palaeogeography, Palaeoclimatology, Palaeoecology 369 (2013) 28–40 ⁎ Corresponding author. E-mail address: yurenayanes@ugr.es (Y. Yanes). 0031-0182/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.palaeo.2012.09.019 Contents lists available at SciVerse ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo