Geste Formation

Geste Formation
Stratigraphic range: Priabonian (Divisaderan) ~42–36 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Pastos Grandes Group
Sub-units	Upper, Middle, Lower Members
Underlies	Pozuelos Formation
Overlies	Various Paleozoic basement formations
Thickness	up to 1,500 m (4,900 ft)
Lithology
Primary	Sandstone, conglomerate
Other	Shale
Location
Coordinates	26°06′S 67°24′W / 26.1°S 67.4°W / -26.1; -67.4
Approximate paleocoordinates	28°06′S 59°24′W / 28.1°S 59.4°W / -28.1; -59.4
Region	Catamarca & Salta Provinces
Country	Argentina
Extent	Puna Plateau
Type section
Named by	Turner
Year defined	1960
Geste Formation (Argentina)

The Geste Formation (Spanish: Formación Geste) is a fossiliferous geologic formation of the Puna Plateau in the western Salta Province and northern Catamarca Province of the Argentine Northwest, northwestern Argentina.

The formation, reaching a thickness of 1,500 metres (4,900 ft), is the oldest unit of the Pastos Grandes Group, underlying the Pozuelos Formation and unconformably overlying various Paleozoic formations. The Geste Formation comprises red sandstones and conglomerates deposited in a fluvial to alluvial environment. The formation was initially dated to the Mustersan (Middle Eocene), but subsequent research proved the formation to date to the Late Eocene (Divisaderan in the SALMA classification, ranging approximately from 42 to 36 Ma.

The Geste Formation has provided a faunal assemblage of vertebrates unique for the Argentine Northwest, with several groups of mammals, most notably the only Paleogene interatheres of northwestern Argentina, reptiles and frogs. Only partly they correspond to other fossiliferous formations in the area; the upper part of the Lumbrera Formation and the Quebrada de los Colorados Formation.