Seca Formation
Stratigraphic range: Late Eocene ( Divisaderan- Tinguirirican) ~37–34  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Unit of	Ancón Group
Underlies	Punta Ancón Formation
Overlies	Socorro Formation
Lithology
Primary	Shale
Location
Coordinates	2°18′S 80°48′W / 2.3°S 80.8°W / -2.3; -80.8
Approximate paleocoordinates	4°48′S 73°48′W / 4.8°S 73.8°W / -4.8; -73.8
Region	Santa Elena Province
Country	Ecuador
Extent	Progreso Basin
Seca Formation, Ecuador (Ecuador)

The Seca Formation is a Late Eocene ( Divisaderan to Tinguirirican in the SALMA classification) geologic formation of the Progreso Basin in southwestern Ecuador. The shales of the formation have provided fossils of the marine snake Pterosphenus sheppardi. ^[1]

The Seca Formation, part of the Ancón Group, conformably overlies the Socorro Formation and is overlain by the Punta Ancón Formation. The Seca Formation comprises grey to greenish shales deposited in a marine platform with submarine fans environment. ^[2] The formation is a reservoir rock, ^[3] and potential source rock, ^[4] in the oil-rich Progreso Basin.

• List of fossiliferous stratigraphic units in Ecuador

• Lorenzo, Erica (2018), "Correlación geoquímica entre crudos y rocas del sistema petrolero de la península de Santa Elena y el golfo de Guayaquil" (PDF), Boletín de Geología, 40: 31–42, doi: 10.18273/revbol.v40n1-2018002, retrieved 2018-09-11

• R. Hoffstetter. 1958. Un serpent marin du genre Pterosphenus (Pt. Sheppardi nov. sp.) dans L’Éocène supérieur de L’Équateur (Amérique de Sud). Bulletin de la Société Géologique de France 6:45-50