Pleistocene seasonal temperature variations recorded in the δ18O of Bison priscus teeth

Oxygen isotope analysis of phosphate in tooth enamel of mammals (delta O-18(p)) constitutes a valuable method to reconstruct past air temperatures in continental environments. The method is based on interdependent relationships between the delta O-18 of apatite phosphate, body fluids, environmental waters and air temperatures. Continuous tooth growth and absence of enamel remodelling in bovid teeth ensures a reliable record of the intra-annual variability of air temperature through an incremental delta O-18 analysis from apex to cervix. This method has been applied to Bison priscus dental remains of the late Middle Pleistocene from the fossiliferous layer of a cave at Coudoulous I in South-Western France (Layer 4). The stacked oxygen isotope signal obtained by combining 9 bison teeth shows sinusoidal variations (15.0 parts per thousand to 19.1 parts per thousand V-SMOW) of seasonal origin over 2.5 yr. The corresponding computed MAT of 9 +/- 3 degrees C is about 4 degrees C lower than at present. Seasons appear more contrasted in Coudoulous I during Layer 4 deposition with summers as warm as present ones (19 +/- 3 degrees C) and significantly colder winters about 0 +/- 3 degrees C compared to 6 +/- 1 degrees C at present. (C) 2009 Elsevier B.V. All rights reserved.