The Bajada Colorada Formation is a geologic formation of the southern Neuquén Province in the Neuquén Basin of northern Patagonia, Argentina. The formation belongs to the Mendoza Group and is late Berriasian to early Valanginian in age. The formation is renowned for preserving fossil remains of Bajadasaurus pronuspinax, a genus of dicraeosaurid dinosaurs named after the formation.
Description The Bajada Colorada Formation, first defined by Roll in 1939, pertains to the Mendoza Group.Moyano Bohórquez, 2004 It overlies the Quintuco and Picún Leufú Formations and is overlain by the Agrio Formation. The contact with the Agrio Formation is discordant and the unconformity has been dated to 134 Ma.Leanza, 2005, p.151 The formation is laterally equivalent with the Mulichinco Formation.Howell et al., 2005, p.4 The formation comprises red and greenish-brown, fine to coarse grained conglomerates and thick-bedded sandstones with well-developed bands of light brown siltstones and reddish, pinkish grey and purple-reddish claystones.Leanza et al., 2011, p.120 The formation was deposited in a fluvial environment, and the paleoenviroment resembled a braided river system with well-preserved channels and paleosols.Gallina et al., 2014, p.2
X-ray diffraction studies of sediments belonging to the Bajada Colorada Formation have revealed the presence of smectite, chlorite, illite and kaolinite.
Fossil content The formation has provided fossils of:Bajada Colorada locality at Fossilworks.org
Dinosaurs
Ornithischians Ornithischians of the Bajada Colorada Formation Genus Species Location Stratigraphic position Material Notes Images Ankylosauria Indet. Indeterminate Isolated scutes Stegosauria Indet. Indeterminate Sacral vertebrae, dorsal ribs and osteoderms
Sauropods Sauropods of the Bajada Colorada Formation Genus Species Location Stratigraphic position Material Notes Images Bajadasaurus B. pronuspinax A nearly complete skull, both proatlases, atlantal neurapophyses, axis and the ?fifth cervical vertebra. A dicraeosaurid sauropod Leinkupal L. laticauda Cervical, dorsal caudal vertebrae remains and a braincase A diplodocine diplodocid Ninjatitan N. zapatai Partial postcranial skeleton, anterior caudal vertebra of the holotype might represent diplodocoid sauropod. A titanosaurian sauropod
Theropods Theropods of the Bajada Colorada Formation Genus Species Location Stratigraphic position Material Notes Images Abelisauridae Indet. Indeterminate Proximal half of a left tibia Abelisauroidea Indet. Indeterminate Am almost complete axis (MMCh-PV 67) and two isolated caudal centra (MMCh-PV 76 and 77) Megalosauridae Indet. Indeterminate Dental remains Theropoda Indet. Indeterminate Dental remains 3 different morphotypes are present.
See also List of dinosaur-bearing rock formations Baños del Flaco Formation, contemporaneous formation of the Mendoza Group in Chile Chon Aike Formation, contemporaneous formation of central Patagonia
References
Bibliography