Huitrera Formation

The Huitrera Formation is a geological formation in the Neuquén Basin in northern Patagonian Argentina whose strata date back to the Early Eocene of the Paleogene, or Casamayoran in the South American land mammal age classification.

The formation is together with the Reyhuau basalts part of the Pilcaniyeu Belt, a volcanic belt active in Paleocene to middle Eocene times.

Description
The Huitrera Formation was first defined by Ravazzoli and Sesana in 1977. The name has been used to identify various volcaniclastic sequences, among others in the Ñirihuau fold-and-thrust belt. The up to 1300 m thick formation comprises mudstones and sandstones deposited in a crater lake environment. Part of the formation comprises andesites, dacitic and rhyolitic ignimbrites, volcanic breccias, tuffs and trachybasalts.

The formation was initially described as Late Eocene to Early Oligocene, but was later dated to 54.24 ± 0.45 Ma, meaning the Huitrera Formation is Ypresian, or in the SALMA classification, Casamayoran in age.

Fossil content
The following macrofossils were reported from the formation:
 * Birds
 * Ueekenkcoracias
 * Amphibians
 * Llankibatrachus truebae
 * Patagopipa corsolinii
 * Insects
 * Odonata
 * Inacayalestes aikunhuapi
 * Beetles
 * Thesaurus punctatus (originally Catogenus)
 * Flora
 * Menispermites calderensis
 * Raiguenrayun cura
 * Cupressaceae indet.
 * Podocarpaceae indet.
 * Lauraceae indet.

The formation has also provided many pollen, analyzed in 2003 by Melendi et al.