Geste Formation

Geste Formation
Stratigraphic range:
Priabonian (Divisaderan)
~42–36 Ma
TypeGeological formation
Unit ofPastos Grandes Group
Sub-unitsUpper, Middle, Lower Members
UnderliesPozuelos Formation
OverliesVarious Paleozoic basement formations
Thicknessup to 1,500 m (4,900 ft)
Lithology
PrimarySandstone, conglomerate
OtherShale
Location
Coordinates26°06′S 67°24′W / 26.1°S 67.4°W / -26.1; -67.4
Approximate paleocoordinates28°06′S 59°24′W / 28.1°S 59.4°W / -28.1; -59.4
RegionCatamarca & Salta Provinces
CountryArgentina
ExtentPuna Plateau
Type section
Named byTurner
Year defined1960
Geste Formation is located in Argentina
Geste Formation
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.