Late-glacial to Holocene transition in northern Spain deduced from land-snail shelly accumulations
2012
Yanes, Yurena | Gutiérrez-Zugasti, Igor | Delgado, A. (Antonio)
Shells of the helicid Cepaea nemoralis were studied using taphonomic, isotopic and morphometric measurements to estimate late glacial–Holocene (~12.1–6.3calka BP) environmental conditions in northern Spain. Higher taphonomic alteration among Holocene shells suggests lower sedimentation rates or higher shell-destruction rates than during glacial conditions. Shells preserved the aragonitic composition despite differing degree of skeleton damage. Shell δ¹³C values were −10.3±1.1‰, −8.2±2.3‰, and −7.3±1.6‰ for modern, Holocene and late-glacial individuals, respectively. Higher δ¹³C values during the late-glacial and some Holocene periods imply higher water stress of C₃ plants and/or higher limestone contribution than today. Intrashell δ¹³C values were higher during juvenile stages suggesting higher limestone ingestion to promote shell growth. Shell δ¹⁸O values were −1.1±0.7‰, −0.9±0.8‰ and −0.1±0.7‰ for modern, Holocene and late-glacial specimens, respectively. A snail flux-balance model suggests that during ~12.1−10.9calka BP conditions were drier and became wetter at ~8.4−6.3calka BP and today. Intrashell δ¹⁸O profiles reveal that glacial individuals experienced more extreme seasonality than interglacial shells, despite possible larger hibernation periods. Shell size correlated positively with δ¹⁸O values, suggesting that growth rates and ultimate adult size of C. nemoralis may respond to climate fluctuation in northern Spain.
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