Late-glacial to Holocene transition in northern Spain deduced from land-snail shelly accumulations

Shells of the helicid Cepaea nemoralis were studied using taphonomic, isotopic and morphometric measurements to estimate late glacial-Holocene (similar to 12.1-6.3 cal ka 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 delta C-13 values were -10.3 +/- 1.1 parts per thousand, -8.2 23 parts per thousand, and -7.3 +/- 1.6 parts per thousand for modern, Holocene and late-glacial individuals, respectively. Higher delta C-13 values during the late-glacial and some Holocene periods imply higher water stress of C-3 plants and/or higher limestone contribution than today. Intrashell delta C-13 values were higher during juvenile stages suggesting higher limestone ingestion to promote shell growth. Shell delta O-18 values were -1.1 +/- 0.7 parts per thousand, -0.9 +/- 0.8 parts per thousand and -0.1 +/- 0.7 parts per thousand for modern, Holocene and late-glacial specimens, respectively. A snail flux-balance model suggests that during similar to 12.1 - 10.9 cal ka BP conditions were drier and became wetter at similar to 8.4 - 63 cal ka BP and today. Intrashell delta O-18 profiles reveal that glacial individuals experienced more extreme seasonality than interglacial shells, despite possible larger hibernation periods. Shell size correlated positively with delta O-18 values, suggesting that growth rates and ultimate adult size of C. nemoralis may respond to climate fluctuation in northern Spain. (c) 2012 University of Washington. Published by Elsevier Inc. All rights reserved.