Chachao Formation
Chachao Formation Stratigraphic range: Valanginian ~ | |
---|---|
Type | Geological formation |
Unit of | |
Underlies | Agrio Formation |
Overlies | Vaca Muerta |
Lithology | |
Primary | Limestone |
Other | Mudstone |
Location | |
Coordinates | 35°00′S 69°42′W / 35.0°S 69.7°WCoordinates: 35°00′S 69°42′W / 35.0°S 69.7°W |
Approximate paleocoordinates | 33°48′S 33°00′W / 33.8°S 33.0°W |
Region | Mendoza Province |
Country | Argentina |
Extent | Neuquén Basin |
Chachao Formation (Argentina) |
The Chachao Formation is a geological formation in the Mendoza Province in northern Patagonian Argentina. It is Valanginian in age and is predominantly marine, being deposited at a time of marine transgression in the Neuquén Basin, and predominantly consists of carbonate rocks.
The formation belongs to the , sediments deposited on the Mendoza Shelf. The formation overlies the Vaca Muerta and is overlain by the Agrio Formation.
Description[]
A typical feature of the Chachao Formation is the dominance of oysters, many of them quite large e.g. , and others small, e.g. . Different kinds of semi-infaunal soft bottom dwellers and swimming bivalves were recognized. Additional forms are represented by gastropods, ammonites (), and ichnofossils such as Thalassinoides sp. Serpulids are represented by the colonial Sarcinella sp., and the solitary form The highly diverse fauna of the analyzed succession, made up with numerous stenohaline elements such as echinoderm, bryozoa, ammonite as well as serpulids and typical marine pelecypods indicate a fully marine environment.[1]
Fossil content[]
The formation has provided the following fossils:[2]
- Decapods
- Ammonites
- Polychaeta
- Bivalves
- Exogyra caudoni
- Cucullaea sp.
- Exogyra (Aetostreon)
- Eriphyla sp.
- Pinna sp.
- Pecten sp.
- Trigonia sp.
- Ichnofossils
References[]
- ^ a b Chachao Coquina - Taphofacies 3 at Fossilworks.org
- ^ Chachao Formation at Fossilworks.org
Bibliography[]
- First record of the Valanginian positive carbon isotope anomaly in the Mendoza shelf, Neuquén Basin, Argentina: palaeoclimatic implications. Andean Geology 45. 111–129. Accessed 2019-02-22. ; ; ; ; , and . 2018.
- Carbonates and Evaporites 16. 168-180. , and . 2001. Shell Bed Stacking Patterns in the Chachao Formation (Early Valanginian) in Malargüe Area, Mendoza Province, Neuquen Basin, Argintina.
- Scripta Geologica 3. 15-29. , and . 1999. The Berriasian genus Groebericeras in Argentina and the problem of its age.
- , and . 1992. Early Cretaceous serpulid limestones: Chachao Formation, Neuquen basin, Argentina. 27. 175-178.
- Palaeontology 32. 499-552. . 1989. The Cretaceous decapod Crustacea of Argentina and the Antarctic Peninsula.
- Geologic formations of Argentina
- Lower Cretaceous Series of South America
- Cretaceous Argentina
- Valanginian Stage
- Limestone formations
- Mudstone formations
- Open marine deposits
- Shallow marine deposits
- Neuquén Basin
- Fossiliferous stratigraphic units of South America
- Paleontology in Argentina
- Geology of Mendoza Province