Resumen
The Tithonian-Valanginian time interval in the Mendoza Shelf (Neuquén Basin, Argentina) is well exposed in the Río Salado, Puesto Loncoche and Cuesta del Chihuido sedimentary sections. From those localities, more than fifty preserved oyster shells of the genus Aetostreon sp. were selected and sampled in order to perform the first d13C curves for this particular time interval. Mineralogical and cathodoluminiscence properties, inner micromorphology of the valves, added to major and trace element geochemistry were analyzed in order to highlight the best C-O isotopic preservation. The d13C isotope curves show values varying between 0 and -3? VPDB for the Tithonian-Berriasian basal section, and a positive excursion of ~2.4-2.7? VPDB in the Valanginian upper section. This d13C up section trend is here considered in order to reveal eminent correlations with other sections from the Neuquén Basin, as well as the Weissert Event from the Tethys area, also on the basis of their ammonite faunal zones. The palaeotemperatures obtained from d18O preserved values, added to a detailed sedimentological study suggest that observed d13C anomaly may responds to a global climatic change from warm and dry to warm and humid conditions.