Résumé
Land snails build their shells with carbon extracted principally from their diet and are a good record of the vegetation and climate variations through time. We have analyzed the carbon isotopic composition of shells of Vertigo modesta sampled in the Eustis Upper Pleistocene loess series, Nebraska, which deposited between 18,000 and 12,000 years. A trend towards aridity of the environment is observed from the base to the top of the sequence. Rhythmic and rapid oscillations, of about 1,000 years, of carbon isotopic composition indicate more humid periods. These results are compared to other independent proxies from the same or nearby loess sequences. The validation of the land snails shells as new record of paleoclimatic variations in loess sequences is thus demonstrated.