The La Amarga Formation is a geologic formation with outcrops in the

Argentine Argentines (mistakenly translated Argentineans in the past; in Spanish (masculine) or (feminine)) are people identified with the country of Argentina. This connection may be residential, legal, historical or cultural. For most Argentines, s ...

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.Musacchio, 1970 The La Amarga Formation unconformably overlies the

marine Marine is an adjective meaning of or pertaining to the sea or ocean. Marine or marines may refer to: Ocean * Maritime (disambiguation) * Marine art * Marine biology * Marine debris * Marine habitats * Marine life * Marine pollution Military * ...

Agrio Formation The Agrio Formation is an Early Cretaceous geologic formation that is up to thick and is located in the southern Mendoza Province and northern-central Neuquén Province, in the Neuquén Basin of northwestern Patagonia, Argentina.Weaver, C. E. (1 ...

of the

Mendoza Group Mendoza may refer to: Places Argentina * Greater Mendoza, the name given to the large urban conurbation around the city of Mendoza * Mendoza, Argentina, the capital of the province of Mendoza * Mendoza Department, subdivision of the Mendoza Provi ...

. It is in turn overlain by the

Lohan Cura Formation The Lohan Cura Formation is a geologic formation with outcrops in the Argentine provinces of Río Negro, Neuquén, and Mendoza. It is the second oldest Cretaceous terrestrial formation in the Neuquén Basin. The Lohan Cura Formation unconformabl ...

, separated by another unconformity.

Composition

There are three members within the La Amarga Formation. # The oldest is the Puesto Antigual Member, which is approximately thick and consists mainly of sandstone deposited in the channels of a

braided river A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''. Braided streams tend to occur in rivers with high sediment l ...

system. Paleosols, or soil deposits, are well-developed. # The Bañados de Caichigüe Member is the next highest, approximately thick. Alternating limestones, shales, and siltstones make up this member, indicating a lacustrine ( lake) environment. # Youngest and thickest is the Piedra Parada Member, approximately thick in some sections. This member consists of alternating sandstones and siltstones from an ancient

alluvial plain An alluvial plain is a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions, from which alluvial soil forms. A floodplain is part of the process, being the sma ...

, with some

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

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 ''Amargasuchus'' is an extinct genus of crocodylomorph. It was a member of the Trematochampsidae, an enigmatic family of mesoeucrocodylians. Fossils have been found from the La Amarga Formation in Argentina and date back to the Barremian and Ap ...

'') * dicraeosaurid sauropods ('' Amargasaurus'', '' Amargatitanis'')Weishampel et al., 2004, "Dinosaur distribution (Early Cretaceous, South America).", pp.563-570 *a diplodocoid

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...

(''

Zapalasaurus ''Zapalasaurus'' is a genus of sauropod dinosaur described by Leonardo Salgado, Ismar de Souza Carvalho and Alberto Garrido in 2006. It was named after the city of Zapala, which is approximately away from where the holotype was discovered. The t ...

'') *a titanosaurian sauropod *an abelisauroid theropod ('' Ligabueino'') *a

stegosaur Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europe, ...

(''

Amargastegos This list of informally named dinosaurs is a listing of dinosaurs (excluding Aves; birds and their extinct relatives) that have never been given formally published scientific names. This list only includes names that were not properly published ...

'') *a

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

Composition

Fossil content

Dinosaurs

Other tetrapods

See also

References

Bibliography

Further reading