Unravelling the oxygen isotope signal (δ18O) of rodent teeth from northeastern Iberia, and implications for past climate reconstructions

Small mammals, especially rodents, constitute valuable proxies for continental Quaternary environments at a regional and local scale. Recent studies have demonstrated the relation between the stable oxygen isotope composition of the biogenic phosphate from rodent teeth (delta O-18(p)), and the oxygen isotope composition of meteoric waters (delta O-18(mw)), which is related to air temperatures at mid and high latitudes. This work explores the delta O-18(p) of rodent tooth enamel (from Murinae and Arvicolinae subfamilies) to investigate the palaeoenvironmental conditions in northeastern Iberia during Marine Isotope Stage 3 (MIS 3; ca. 60-30 ka). Fourteen new delta O-18(p) analyses from modern samples in conjunction with forty-six delta O-18(p) analyses previously published are used to decipher the isotope record of present-day rodent teeth in this region. Two main factors should be considered in Iberian palaeoenvironmental reconstructions: the singular nature of Iberian delta O-18(mw) records and the potential seasonality bias of small-mammal accumulation. Methodological proposals are made with a view to ensuring the correct interpretation of the delta O-18(p) of small mammals in reconstructing past air temperatures. This methodology is applied to the MIS 3 sequence of the Cova dels Xaragalls site (Vimbodi-Poblet, Tarragona, Spain), where fifty-one delta(18)Oanalyses were performed on wood mouse (Apodemus sylvaticus) lower incisors. A spring-early summer accumulation of small mammals is suggested for the layers at Cova dels Xaragalls. In agreement with previous environmental studies of the site, variations in the delta O-18(p) values suggest slight fluctuations in the climatic conditions throughout the sequence, which are consistent with the stadial-interstadial alternations that characterized MIS 3. Complementary palaeoenvironmental methods determine cooler conditions than nowadays, but within a globally stable climatic period. (C) 2019 Elsevier Ltd. All rights reserved.