Angostura Formation, Ecuador

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

Description
The coarse sandstones and beds of conglomerates, about 150 m 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.

Fossil content
The formation has provided bivalve and gastropod fossils.