Portezuelo-Formation

The Portezuelo Formation is a sequence of continental sedimentary rocks of the Upper Cretaceous of Argentina, which is known for its very diverse fossil fauna. These rocks were deposited in the late Turonian and early Coniacian in front of about 91 to 88 million years. Outcrops of this geological formation can be found in the provinces of Río Negro, Neuquén and Mendoza. Type locality of the formation is the Sierra del Portezuelo in the province of Neuquén.

Together with the recent Plottier lineup makes this formation the Río Neuquén - subgroup, a rock unit of the Neuquén Group. Earlier this subgroup was even considered as formation, the Portezuelo lineup was designated as Portezuelo members. The Portezuelo lineup is the fourth oldest formation of the Neuquén Group. It lies conformably on the Lisandro Formation, which belongs to the Río Limay - subgroup. About the Portezuelo lineup is the Plottier lineup.

The Portezuelo formation varies in thickness 95-130 meters. It consists mainly of sandstones and siltstones, and was probably fluvial, ie, deposited by rivers. Furthermore, are occasionally cemented mudstone deposits and numerous paleosols.

Fossil Fauna

To the rich vertebrate fauna of the formation include numerous finds of turtles (including Portezueloemys and Prochelidella ) and rare crocodiles. Dinosaurs include the Titanosaurier Malarguesaurus and Futalognkosaurus a, the ornithopod Macrogryphosaurus that Dromaeosauriden Neuquenraptor and Unenlagia, the Carnosaurier Mega Raptor, the Alvarezsauriden Patagonykus and various other theropod and a bird, possibly a representative of Galliformes. 2006, the bones of a pterosaur ( Pterosauria ) have been described ( probably a Azhdarchidae ), the first pterosaur - Fund from the Upper Cretaceous of the Neuquén Group.

The important fossil, reference of the formation, and one of the most important in South America, was discovered in 2000 by a team from the Universidad Nacional del Comahue on the north coast of Los Barreales Reservoir. At this locality, which is now famous as Futalognko locality, a new paleontological center was built, the first of its kind in South America, the wholly devoted to the paleontological field work.