Angostura Formation
Stratigraphic range: Late Miocene (Mayoan-Montehermosan) ~11.6–5.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Santiago Group
Underlies	Onzole Formation
Overlies	Viche Formation
Thickness	150 m (490 ft)
Lithology
Primary	Sandstone
Other	Conglomerate
Location
Coordinates	1°00′N 79°36′W / 1.0°N 79.6°W / 1.0; -79.6
Approximate paleocoordinates	0°36′N 78°00′W / 0.6°N 78.0°W / 0.6; -78.0
Region	Esmeraldas Province
Country	Ecuador
Extent	Borbón Basin
Angostura Formation, Ecuador (Ecuador)

The Angostura Formation is a Late Miocene (Mayoan to Montehermosan in the SALMA classification) geologic formation of the Borbón Basin in northwestern Ecuador.^[1]

The coarse sandstones and beds of conglomerates, about 150 metres (490 ft) in thickness. The formation is resistant to erosion and is largely barren, but at a few places there are lenses or interbeds filled with finely preserved fossils. The formation overlies the Viche Formation, and is overlain by the lower Onzole Formation. The Angostura Formation is time-equivalent with the fossiliferous Gatún Formation of Panama.^[1]

The formation has provided bivalve and gastropod fossils.^[1]

• List of fossiliferous stratigraphic units in Ecuador

• Beu, A.G (2010), "Neogene Tonnoidean Gastropods of Tropical and South America; contributions to the Dominican Republic and Panama Paleontology Projects and Uplift of the Central American Isthmus", Bulletins of American Paleontology, 377–378: 1–550, retrieved 2019-02-09
• P. Jung. 1989. Revision of the Strombina-group (Gastropoda; Columbellidae), fossil and living. Schweierische Paläontologische Abhandlungen 111:1-298
• A. A. Olsson. 1964. Neogene Mollusks From Northwestern Ecuador
• E. H. Vokes and H. E. Vokes. 2000. Catalogue of Tulane University fossil localities.