A Mutual Temperature Range method for Quaternary palaeoclimatic analysis using European nonmarine Ostracoda

A new Mutual Temperature Range method for estimating past air temperatures is presented, based on European Quaternary nonmarine Ostracoda and using the Nonmarine Ostracod Distribution in Europe (NODE) database and a modern climate dataset in conjunction with DIVA-GIS software. The value of nonmarine ostracods in Quaternary palaeoclimate reconstruction has long been recognised, mainly in terms of the use of indicator species and, more recently, analyses of the trace element and stable isotope chemistry of their calcareous valves. The new Mutual Ostracod Temperature Range (MOTR) method uses a nonanalogue approach based on the presence/absence of species in a fossil assemblage; preliminary testing has yielded good matches with both modern temperatures (using living assemblages not already in NODE) and palaeotemperatures inferred by the Coleopteran Mutual Climate Range method, but further testing and refinement are needed. Assumptions about the climatic tolerances of living and fossil ostracod species, as well as complicating factors (such as the relationship between water temperature and air temperature, habitat preferences and taxonomic errors) require careful examination; nevertheless, the MOTR method shows considerable promise and is a valuable addition to the Quaternary palaeoclimatologist's toolbox.