First fission-track age for the dinosaur-bearing Neuquén Group (Upper Cretaceous), Neuquén Basin, Argentina.

Resumen

The first radiometric age for the Neuquén Group, based on fission-track analysis made on an  ash-flow tuff at the base of the Huincul Formation, is reported in this paper. The radiometric age offers a  more precise chronological dating for the time of deposition of the first stages of the Neuquén Group. The  tuff, exposed at Cerro Policía hill and other close localities in the Río Negro Province (NW Patagonia),  has yielded a radiometric age of 88 ± 3.9 My. This value suggest that the Huincul Formation was  deposited between an age range from 84.1 to 91.9 My, that is from the base of the Turonian to the top of  the Santonian.  Key words: Upper Cretaceous, Neuquén Basin, Patagonia, geochronology, tetrapods.