La Amarga Formation
La Amarga Formation Stratigraphic range: Barremian-Early Aptian ~ | |
---|---|
Type | Geological formation |
Unit of | |
Sub-units | Puesto Antigual, Bañados de Caichigüe & Piedra Parada Members |
Underlies | Lohan Cura Formation |
Overlies | Agrio Formation |
Thickness | 160 m (520 ft) |
Lithology | |
Primary | Sandstone |
Other | Mudstone |
Location | |
Coordinates | 39°36′S 70°12′W / 39.6°S 70.2°WCoordinates: 39°36′S 70°12′W / 39.6°S 70.2°W |
Approximate paleocoordinates | 39°36′S 35°12′W / 39.6°S 35.2°W |
Region | Río Negro, Mendoza & Neuquén Provinces |
Country | Argentina |
Extent | Neuquén Basin |
Type section | |
Named for | La Amarga Arroyo |
Named by | Musacchio |
Year defined | 1970 |
La Amarga Formation (Argentina) |
The La Amarga Formation is a geologic formation with outcrops in the Argentine provinces of Río Negro, Neuquén, and Mendoza. It is the oldest Cretaceous terrestrial formation in the Neuquén Basin.
The type locality is La Amarga Arroyo and China Muerta Hill.[1] The La Amarga Formation unconformably overlies the marine Agrio Formation of the . It is in turn overlain by the Lohan Cura Formation, separated by another unconformity.
Composition[]
There are three members within the La Amarga Formation.
- The oldest is the Puesto Antigual Member, which is approximately 28.9 metres (95 ft) thick and consists mainly of sandstone deposited in the channels of a braided river system. Paleosols, or soil deposits, are well-developed.
- The Bañados de Caichigüe Member is the next highest, approximately 20.9 metres (69 ft) thick. Alternating limestones, shales, and siltstones make up this member, indicating a lacustrine (lake) environment.
- Youngest and thickest is the Piedra Parada Member, approximately 109.4 metres (359 ft) thick in some sections. This member consists of alternating sandstones and siltstones from an ancient alluvial plain, with some swamp and paleosol deposits.
Fossil content[]
Most of the tetrapod fossils found in the La Amarga come from the Puesto Antigual Member, including:
- a crocodilian (Amargasuchus)
- a dicraeosaurid sauropod (Amargasaurus)[2]
- a diplodocoid sauropod (Zapalasaurus)
- a titanosaurian sauropod
- an abelisauroid theropod (Ligabueino)
- a stegosaur (Amargastegos)
- a mammal (Vincelestes)
Dinosaurs[]
Dinosaurs of the La Amarga Formation | |||||
---|---|---|---|---|---|
Genus | Species | Province | Member | Notes | Images |
Amargasaurus[2] | A. cazaui[2] | Neuquén[2] | Puesto Antigual | "Braincase and associated postcranial skeleton."[3] | |
Amargastegos | A. brevicollus | Neuquén | Puesto Antigual | Considered dubious by Galton & Carpenter (2016), material referred to Stegosauria indet.[4] | |
Amargatitanis | A. macni | Neuquén | Puesto Antigual | "Two caudal vertebrae, an incomplete right ischium, a right femur, an incomplete right tibia, an incomplete right fibula, a right astragalus, and an incomplete right metatarsal I." | |
Ligabueino[2] | L. andesi[2] | Neuquén[2] | Puesto Antigual | "A cervical neural arch, a mid to posterior dorsal neural arch, a posterior dorsal centrum, the left femur, left ilium, articulated pubic shafts, and two pedal phalanges."[5] | |
Stegosauria indet.[6] | Indeterminate | Neuquén | Puesto Antigual | "Supraorbital, cervical and caudal vertebrae, dermal armor".[4][6] | |
Zapalasaurus | Z. bonapartei | Neuquén | Piedra Parada |
Other tetrapods[]
Other tetrapods of the La Amarga Formation | |||||
---|---|---|---|---|---|
Genus | Species | Province | Member | Notes | Images |
Amargasuchus | A. minor | Neuquén | Puesto Antigual | A trematochampsid crocodylomorph, found in association with the holotype of Amargasaurus | |
Pterosauria indet.[7] | Indeterminate | Neuquén | An isolated femur | ||
Vincelestes | V. neuquenianus | Neuquén | Puesto Antigual | A cladotherian mammal |
Color key
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Notes Uncertain or tentative taxa are in small text; |
See also[]
- List of dinosaur-bearing rock formations
References[]
Bibliography[]
- Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 279. 185–208. , and . 2016. The plated dinosaur Stegosaurus longispinus Gilmore, 1914 (Dinosauria: Ornithischia; Upper Jurassic, western USA), type species of Alcovasaurus n. gen..
- Alcheringa: An Australasian Journal of Palaeontology 37. 1–14. doi:10.1080/03115518.2012.702531 ; ; , and . 2012. A plated dinosaur (Ornithischia, Stegosauria) from the Early Cretaceous of Argentina, South America: an evaluation.
- Smithsonian Contributions to Paleobiology 95. 1–53. ; , and . 2011. New Materials of Masiakasaurus knopfleri Sampson, Carrano, and Forster, 2001, and Implications for the Morphology of the Noasauridae (Theropoda: Ceratosauria).
- The Dinosauria, 2nd edition, 1–880. Berkeley: University of California Press. Accessed 2019-02-21. ISBN 0-520-24209-2 ; , and . 2004.
- Ameghiniana 24. 109–113. . 1987. Presencia de Pterosauria (Reptilia) en la Formación La Amarga (Hauteriviano-Barremiano), Neuquén, Argentina.
- Ameghiniana 7. 301–318. . 1970. Ostrácodos de la superfamilias Cytheraceae y Darwinulaceae de la Formación La Amarga (Cretácico inferior), provincia del Neuquén, Argentina.
Further reading[]
- The sauropod diversity of the La Amarga Formation (Barremian), Neuquén (Argentina). Gondwana Research 12. 533–546. Accessed 2016-02-16. . 2007.
- Cretaceous terrestrial beds from the Neuquén Basin (Argentina) and their tetrapod assemblages. Cretaceous Research 25. 61–87. Accessed 2019-02-16. ; ; , and . 2004.
Categories:
- La Amarga Formation
- Geologic formations of Argentina
- Lower Cretaceous Series of South America
- Cretaceous Argentina
- Sandstone formations
- Mudstone formations
- Alluvial deposits
- Fluvial deposits
- Lacustrine deposits
- Paleontology in Argentina