Oxygen stable isotope analysis of water vole (Arvicola) incisor tooth enamel: a proxy record of terrestrial climate from MIS 9 Britain

The oxygen stable isotopic composition of rainfall (δ18Ometeoric) is primarily related to air temperature. Phosphates in mammalian tooth enamel archive the oxygen isotope composition of local waters and rainfall (δ18Ophosphate) and acts as a proxy record of climatic change. In the water vole Arvicola (Rodentia), tooth growth, population dynamics, and taphonomy make upper incisors from fossil assemblages a high- resolution (approximately month long), summer-season record of climate. Using published δ18Ophosphate and meteorological data, strong and significant summer-specific models relating δ18Ophosphate with δ18Ometeoric and temperature were observed. These relationships, and a complimentary carbonate-based proxy, allowed the creation of two palaeothermometers. These were used to reconstruct climate from a warm-temperate, mid-Pleistocene interglacial sequence at Cudmore Grove, Essex, England. Summer surface water compositions were more enriched than present (-5.4‰vsmow). Mean summer palaeotemperatures were found to be warmer than present (meteorological thermometer, +22°C; carbonate thermometer, +21°C) but also warmer than other proxies indicate. Tooth phosphate based reconstructions broadly agree with other palaeoproxies but they are likely to over-estimate mean summer temperatures for a number of reasons, including: late-summer bias in climate sampling by voles; the local hydrological cycle of maritime western Europe; evaporative enrichment of surface waters; and ecological disparity between modern and fossil Arvicola.

[Submitted as an integral part of the Masters of Science Degree in Quaternary Science, Royal Holloway, University of London, in 2005]