Vertebrate trace fossils and environments of the Yacoraite Formation (Maastrichtian-Danian). New records from the Valle del Tonco tracksite, northwestern Argentina

• Autores: Cónsole Gonella, Carlos Alfredo; de Valais, Silvina; Zelaya, Alfredo; Gorustovich, Sergio
• Año de publicación: 2015
• Idioma: inglés
• Tipo de recurso: documento de conferencia
• Materia: Ciencias Exactas y Naturales; Vertebrate Trace Fossils; Yacoraite Formation; New Records From the Valle del Tonco Tracksite; Ciencias Exactas y Naturales
• Institución: Universidad Nacional de Río Negro

Fil: Cónsole Gonella, Carlos Alfredo. CONICET-Instituto Superior de Correlación Geológica (INSUGEO); Argentina.
Fil: de Valais, Silvina. Universidad Nacional de Rio Negro. Instituto de Investigaciones en Paleobiologia y Geologia. Río Negro, Argentina.
Fil: Zelaya, Alfredo. CNEA-Gerencia de Exploración de Materias Primas; Argentina.
Fil: Gorustovich, Sergio. CNEA-Gerencia de Exploración de Materias Primas; Argentina.
The Valle del Tonco tracksite is known since the 60´s by unpublished works by the Comisión Nacional de Energía Atómica; and after published works by R. N. Alonso in the 80´s. The track-bearing levels came from the Yacoraite Formation (Maastrichtian-Danian), which is part of the fill at the initial transgressive postrift stage of the Salta Group (Campanian?- Oligocene). The Yacoraite Formation is composed of interbedding clastic and carbonate strata, representing lacustrine-fluvial systems with fluctuating groundwater table and progradational-aggradational shoreline architecture. At the study area, three members are recognized, from base to top: Caliza Amblayo, Complejo Don Otto and Arenisca Pedro Nicolás. Two ichnosites were previously known therein: Quebrada de la Escalera and Quebrada del Tapón, and five ichnotaxa have been originally defined from these ichnosites. Hadrosaurichnus australis, related to theropods (initially to hadrosaurids), came from Quebrada de la Escalera; and four ichnogenera from Quebrada del Tapón: Salfitichnus mentoor, related to theropods; Taponichnus donottoi and Telosichnus saltensis, assigned to ornithopods (with doubts), and Yacoraitichnus avis, related to birds. The new ichnological records are from the Quebrada del Tapón, and from three new sites: (1) Quebrada del Tapón. I- Large ornithopod track, mesaxonic, tridactyl, subsymmetrical, with one pad impression in each digit and in the heel, from the same surface where the other ichnotaxa have been formally named. II- Several large, nearly homopodial, pentadactyl tracks composing quadrupedal trackways, probably produced by ornitischian dinosaurs. III- Several avian footprint-bearing surfaces; the tracks are small, tridactyl, poorly preserved, and isolated. IVSpecimens of cf. Yacoraitichnus avis, associated with Palaeophycus isp. and Planolites isp. V- Two surfaces with asymmetrical, trydactyl hand imprints, and a tridactyl foot imprint with elongated digital impressions, assigned to pterosaurs, associated with Taenidium isp. (2) Quebrada Sunchales Sur (25°37´24.5´´S; 65°54´51´´W), top of the Caliza Amblayo Member: I- Small, nearly homopodial, symmetrical, and tetradactyl manus-pes impressions, produced by a quadrupedal trackmaker, probably a hopping or galloping mammal. II- Two associated large ornithopod tracks, with thick digit imprints. III- Poorly preserved small tridactyl avian tracks, associated with Taenidium isp. IV- Isolated, medium sized, tridactyl theropodian track. V- Several tracks probably produced by ornitischian dinosaurs, similar to those from the Quebrada del Tapón. (3) Quebrada de El Candado (25º 34´54.96´´S; 65º 54´36.12´´W), in the middle of the Caliza Amblayo Member: I- Quadrupedal, moderately wide-gauge trackway, with heteropodial manus-pes sets, assigned to sauropods. II- Surface with tens of tracks, probably produced by ornitischian dinosaurs. (4) Quebrada Estrecho del Río El Tonco (25º 34´31.08´´S; 65º 56´49.02´´W), top of the Caliza Amblayo Member: I- A trackway with three symmetrical tridactyl footprints lacking morphological details, related to an indeterminate bipedal dinosaur. Vertebrate-invertebrate trace fossils are ascribed to the Scoyenia Ichnofacies s.l.