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Pleistocene–Holocene environmental change in the Canary Archipelago as inferred from the stable isotope composition of land snail shells
Authors:Yurena Yanes  Crayton J Yapp  Miguel Ibez  María R Alonso  Julio De-la-Nuez  María L Quesada  Carolina Castillo  Antonio Delgado
Institution:a Huffington Department of Earth Sciences, Southern Methodist University, 3225 Daniel Ave., Rm 207 Heroy Hall, Dallas, TX 75275-0395, USA;b Departamento de Biología Animal, Facultad de Biología, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez s/n., 38206 La Laguna, Tenerife, Canary Islands, Spain;c Departamento de Edafología y Geología, Facultad de Biología, Universidad de La Laguna, Avda. Astrofísico Fco. Sánchez s/n., 38206 La Laguna, Tenerife, Canary Islands, Spain;d Instituto Andaluz de Ciencias de la Tierra, CSIC-University of Granada, Camino del Jueves s/n, 18100 Armilla, Granada, Spain
Abstract:The isotopic composition of land snail shells was analyzed to investigate environmental changes in the eastern Canary Islands (28–29°N) over the last ~ 50 ka. Shell δ13C values range from ?8.9‰ to 3.8‰. At various times during the glacial interval (~ 15 to ~ 50 ka), moving average shell δ13C values were 3‰ higher than today, suggesting a larger proportion of C4 plants at those periods. Shell δ18O values range from ?1.9‰ to 4.5‰, with moving average δ18O values exhibiting a noisy but long-term increase from 0.1‰ at ~ 50 ka to 1.6–1.8‰ during the LGM (~ 15–22 ka). Subsequently, the moving average δ18O values range from 0.0‰ at ~ 12 ka to 0.9‰ at present. Calculations using a published snail flux balance model for δ18O, constrained by regional temperatures and ocean δ18O values, suggest that relative humidity at the times of snail activity fluctuated but exhibited a long-term decline over the last ~ 50 ka, eventually resulting in the current semiarid conditions of the eastern Canary Islands (consistent with the aridification process in the nearby Sahara). Thus, low-latitude oceanic island land snail shells may be isotopic archives of glacial to interglacial and tropical/subtropical environmental change.
Keywords:Stable Isotopes  Land Snails  Quaternary  Eolian deposits  Paleoenvironment  Canary Islands
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