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

The first radiometric age for the Neuquen 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 Neuquen Group. The  tuff, exposed at Cerro Policia hill and other close localities in the Rio 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, Neuquen Basin, Patagonia, geochronology, tetrapods.