Candeleros formation

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The Candeleros 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 early Cenomanian about 100 to 97 million years ago. Outcrops of this geological formation can be found in the provinces of Río Negro , Neuquén and Mendoza . Name-giving information and type locality of the formation is the Candeleros Hill in Neuquén.

The Candeleros Formation reaches a thickness of nearly 300 meters in some areas. It was mostly deposited fluviatil in a branched river system and consists mainly of sandstone and conglomerate . However, some isolated areas have also been deposited aeolian (by wind) or as siltstone under marshy conditions. Paleo soils are also common in some areas.

This formation is the oldest member of the Neuquén group and belongs to the Rio Limay subgroup. In the past, this sub-group itself was considered a formation, with the Candeleros formation being referred to as Candeleros Member . Today the Rio Limay subgroup is divided into three formations: The Huincul Formation and the Cerro Lisandro Formation lie above the Candeleros Formation, the oldest layer member . The sediments of the Huincul Formation show lighter, greenish, and yellowish colors, with the boundary between the Huincul and Candeleros Formations easily recognizable. The Candeleros formation is discordant on the older Lohan-Cura formation .

Fossil fauna

Reconstruction of Giganotosaurus carolinii , a dinosaur of the Candeleros formation

The formation is known for its rich vertebrate fauna. Fish, frogs, Sphenodontidae , primitive legged snakes (including Najash ), various turtles (including two species of the genus Prochelidella ), crocodiles (including Araripesuchus ), and mammals from the Cladotheria group can be found . Dinosaurs of the formation include titanosaurs such as Andesaurus and the Rebbachisauriden Limaysaurus and Nopcsaspondylus, as well as theropods such as the Dromaeosauriden Buitreraptor and the Carcharodontosauriden Giganotosaurus .

In addition to body fossils, trace fossils such as fossil footprints and eggshells of theropods, sauropods and ornithopods have also been found. Traces of pterodactyls (Pterosauria) were the Ichnogattung Pteroichnus attributed.

One of the most productive sites is La Buitrera (“place of the vultures”, from Spanish el buitre - “vultures”), which shows well-preserved three-dimensional skeletons of small terrestrial vertebrates. Skeletons of larger animals such as dinosaurs are rare in La Buitrera , although Giganotosaurus , one of the largest land-dwelling carnivores, has been discovered at other nearby sites of the Candeleros Formation .

Individual evidence

  1. ↑ R. Wichmann: Los Estratos con Dinosaurios y su techo en el este del Territorio del Neuquén [ "The dinosaur-bearing strata and Their upper limit in esters Neuquén Territory"] . In: Dirección General de Geología, Minería e Hidrogeología Publicación . No. 32 , 1929, pp. 1-9 .
  2. ↑ a b H. A. 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 .
  3. ^ A b Maria Lidia Sánchez, Susana Heredia, Jorge O. Calvo: Paleoambientes sedimentarios del Cretácico Superior de la Formación Plottier (Grupo Neuquén), Departamento Confluencia, Neuquén [Sedimentary paleoenvironments in the Upper Cretaceous Plottier Formation (Neuquencia Group), Neuquencia Group), ] . 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 )).
  4. ^ M. Lockley, JD Harris, L. Mitchell: A global overview of pterosaur ichnology: tracksite distribution in space and time . In: Zitteliana . B28, 2008, ISSN  1612-4138 , p. 187-198 .
  5. ^ Peter J. Makovicky, Sebastián Apesteguía, Federico L. Agnolín: The earliest dromaeosaurid theropod from South America . In: Nature . tape 437 , 2005, pp. 1007-1011 , doi : 10.1038 / nature03996 .