La Amarga Formation
| La Amarga Formation Stratigraphic range: Barremian - early Aptian |
|
|---|---|
| Type | Geological formation |
| Sub-units | Puesto Antigual Member Bañados de Caichigüe Member Piedra Parada Member |
| Underlies | Lohan Cura Formation |
| Overlies | Agrio Formation |
| Thickness | 160 m (520 ft) |
| Location | |
| Region | Río Negro, Mendoza & Neuquén Provinces |
| Country |
 Argentina
|
| Type section | |
| Named for | La Amarga Arroyo & China Muerta Hill |
| Named by | Musacchio, 1970 |
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 (Musacchio, 1970). The La Amarga Formation unconformably overlies the marine Agrio Formation of the Mendoza Group. It is in turn overlain by the Lohan Cura Formation, separated by another unconformity.
Era: Mesozoic
Period: Early Cretaceous
Faunal stage: Barremian through early Aptian
Absolute Age: 130 to ~120 mya
There are three members within the La Amarga Formation.
The oldest is the Puesto Antigual Member, which is approximately 28.9 meters 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 meters thick. Alternating limestones, shales, and siltstones make up this member, indicating a lacustrine (lake) environment.
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