Tarjados Formation

Tarjados Formation
Stratigraphic range: Early-Mid Triassic ~252–236 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Sandstones in Talampaya National Park
Type	Geological formation
Unit of	Paganzo Group
Underlies	Chañares Formation
Overlies	Talampaya Formation
Thickness	Up to 250 m (820 ft)
Lithology
Primary	Sandstone
Other	Conglomerate
Location
Coordinates	Tarjados Formation (Argentina)

The Tarjados Formation is an Early to Middle Triassic geologic formation in the Ischigualasto-Villa Unión Basin of La Rioja Province in northwestern Argentina. The red to whitish sandstones and conglomerates of the formation were deposited in an arid fluvial environment. The formation overlies the Talampaya Formation and is overlain by the Chañares Formation of the Agua de la Peña Group.^{[citation needed]}

The formation has provided fossils of an archosaur and a kannemeyeriid dicynodont, both not yet placed in a dedicated genus. The formation crops out in the Talampaya National Park, which was designated a UNESCO World Heritage Site in 2000.^[1]

Description

The formation was first defined by Romer and Jensen in 1966,^[2] based on a type section exposed in the Sierra de Los Tarjados.^[3] The Tarjados Formation, as the underlying Talampaya Formation, belongs to the Paganzo Group.^[4]

The formation is exposed in the Talampaya National Park of La Rioja Province. The Tarjados Formation is overlain by the Chañares Formation, separated by a regional unconformity.^[5]

The formation, reaching a maximum thickness of 250 metres (820 ft),^[6]^[7] comprises red to greenish grey sandstones,^[8] deposited in an eolian and playa-lacustrine to fluvial environment.^[9] The sediments were deposited under arid,^[10] or semi-arid conditions.^[9]

The formation has provided fossils of an archosaur and a kannemeyeriid dicynodont, both not yet placed in a dedicated genus.^[11]^[12]

References

^ Talampaya National Park at Fossilworks.org
^ Caselli, 1998, p.22
^ Balabusic et al., 2001, p.14
^ Tarjados Formation at Fossilworks.org
^ Balabusic et al., 2001, p.26
^ Aceituno Cieri et al., 2015, p.60
^ Monetta et al., 2000, p.648
^ Monetta et al., 2000, p.644
^ ^a ^b Ezcurra et al., 2015, p.476
^ Balabusic et al., 2001, p.28
^ Ezcurra et al., 2015, p.478
^ Ezcurra et al., 2015, p.479

Bibliography

Aceituno Cieri, P.; Zeballos, M.E.; Rocca, R.J.; Martino, R.D.; Carignano, C.; Guereschi, A.; Giambastiani, M. (2015), "Condicionantes geológicos en el cruce de la sierra de Valle Fértil. San Juan - Geological constraints at the crossing of sierra Valle Fertil. San Juan", Revista de Geología Aplicada a la Ingeniería y al Ambiente, 35: 57–69
Balabusic, Ana M. (2001), Plan de Manejo del Parque Nacional Talampaya (PDF), Administración de Parques Nacionales, pp. 1–68, retrieved 2019-03-28
Caselli, Alberto Tomás (1998), Estratigrafía y sedimentología de las formaciones Patquía (Pérmico) y Talampaya (Triásico Inferior), en las Sierras Pampeanas Noroccidentales y Precordillera Central (Provincias de La Rioja y San Juan) (PhD thesis) (PDF), Universidad de Buenos Aires, pp. 1–437, retrieved 2019-03-28
Ezcurra, Martín D.; Martinelli, Agustín G.; Fiorelli, Lucas E.; Da Rosa, Attila A.S.; Desojo, Julia B. (2015), "Archosauromorph remains from the Tarjados Formation (Early-Middle Triassic, NW Argentina)", Ameghiniana, 52 (5): 475–486, doi:10.5710/AMGH.12.05.2015.2907, hdl:11336/12108, retrieved 2019-03-28
Monetta, A.; Baraldo, J.; Cardinali, A.; Weidmann, R.; Lanzilotti, M. (2000), Distribución y características del magmatismo intratriasico de Ischigualasto, San Juan, Argentina (PDF), IX Congreso Geológico Chileno, pp. 644–648, archived from the original (PDF) on 2019-03-28, retrieved 2019-03-28