Portezuelo formation

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

Together with the younger Plottier Formation , this formation forms the Río Neuquén subgroup, a rock unit of the Neuquén group . Previously, this subgroup was considered a formation itself, with the Portezuelo Formation being referred to as Portezuelo Member . The Portezuelo Formation is the fourth oldest formation in the Neuquén Group. It lies concordantly on the Lisandro Formation , which belongs to the Río Limay subgroup. The plotting formation lies above the Portezuelo formation.

The Portezuelo Formation varies in thickness between 95 and 130 meters. It consists mainly of sandstones and siltstones and was probably deposited fluviatil , i.e. by rivers. Furthermore, are occasionally cemented mudstone -Ablagerungen and numerous paleosols .

Fossil fauna

The formation's rich vertebrate fauna includes numerous finds of turtles (including Portezueloemys and Prochelidella ) and rare crocodiles . Dinosaurs include the titanosaurs Malarguesaurus and Futalognkosaurus , the ornithopod Macrogryphosaurus , the dromaeosaurids Neuquenraptor and Unenlagia , the carnosaur Megaraptor , the Alvarezsaurid Patagonykus and various other theropods and a bird, possibly a representative of the hen birds . In 2006 the bones of a pterosaur (Pterosauria) were described (probably an Azhdarchidae ), the first pterosaur find from the Upper Cretaceous of the Neuquén group.

The most important fossil site of the formation, and one of the most important in all of South America, was discovered in 2000 by a team from the Universidad Nacional del Comahue on the north coast of the Los Barreales reservoir . At this site, now known as the Futalognko site, a new paleontological center was built, the first of its kind in South America, which is entirely dedicated to paleontological field work.

Individual evidence

  1. ↑ R. Wichmann: Los Estratos con Dinosaurios y su techo en el este del Territorio del Neuquén [The dinosaur-bearing strata and the upper limit in the eastern Neuquen area] . In: Dirección General de Geología, Minería e Hidrogeología Publicación . No. 32 , 1929, pp. 1-9 .
  2. ↑ Maria Lidia Sánchez, Susana Heredia, Jorge O. Calvo: Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén), Departamento Confluencia, Neuquén [Sedimentary palaeoenvironments in the Upper Cretaceous Plottier Formation, Neuquén group), Confluencia . In: Revista de la Asociación Geológica Argentina . tape 61 , no. 1 , 2006, p. 3–18 ( PDF ( memento of July 25, 2011 in the Internet Archive )).
  3. ^ HA Leanza, S. Apesteguia, FE Novas, MS de la Fuente: Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages . In: Cretaceous Research . tape 25 , no. 1 , 2004, p. 61-87 , doi : 10.1016 / j.cretres.2003.10.005 .
  4. ↑ Alexander Kellner, Jorge Calvo, Juliana Sayão, Juan Porfiri: Pterosaur bones from the Portezuelo Formation (Cretaceous), Neuquén Group, Patagonia, Argentinia . In: Arquivos do Museu Nacional, Rio de Janeiro . tape 64 , no. 4 , 2006, ISSN  0365-4508 , p. 369-375 .
  5. ↑ Jorge Calvo, Juan Porfiri, Bernardo González Riga, Alexander Kellner: Anatomy of Futalognkosaurus dukei Calvo, Porfiri, González Riga & Kellner, 2007 (Dinosauria, Titanosauridae) from the Neuquén Group (Late Cretaceous), Patagonia, Argentinia . In: Arquivos do Museu Nacional, Rio de Janeiro . tape 65 , no. 4 , 2007, ISSN  0365-4508 , p. 511-526 .
  6. ^ JO Calvo, JD Porfiri, AW Kellner: On a new maniraptoran dinosaur (Theropoda) from the Upper Cretaceous of Neuquén, Patagonia, Argentina . In: Arq. Mus. Nacional. Rio de Janeiro . tape 62 , 2004, p. 549-566 .