Cerro Azul Formation

Cerro Azul Formation
Stratigraphic range: Tortonian (Huayquerian)
~10–5.7 Ma
Fossil burrow fills in the Cerro Azul Formation
TypeGeological formation
Underliesalluvium
OverliesArroyo Chasicó Formation or
Crystalline basement
Thickness54 m (177 ft) (outcrop)
180 m (590 ft) (subsurface)
Lithology
PrimarySiltstone, sandstone
OtherConglomerate
Location
Coordinates35°42′S 64°42′W / 35.7°S 64.7°W / -35.7; -64.7
Approximate paleocoordinates35°54′S 62°42′W / 35.9°S 62.7°W / -35.9; -62.7
RegionBuenos Aires & La Pampa Provinces
CountryArgentina
ExtentColorado Basin
Type section
Named forCerro Azul, Epecuén Lake
Named byLinares et al.
Year defined1980

Outcrop map of the Cerro Azul Formation

The Cerro Azul Formation (Spanish: Formación Cerro Azul), also described as Epecuén Formation, is a geological formation of Late Miocene (Tortonian, or Huayquerian in the SALMA classification) age in the Colorado Basin of the Buenos Aires and La Pampa Provinces in northeastern Argentina.[1][2]

The fluvial and aeolian siltstones, sandstones and tuffs of the formation contain many mammals, such as Thylacosmilus and Macrauchenia, reptiles, amphibians and fossils of terror birds as well as Argentavis, the largest flying bird ever discovered.