The unit now known as Sierra Barrosa Formation was included in the original definition by Herrero Ducloux (1938, 1939) as "Portezuelo Superior", as part of the "Portezuelo Beds" he described.

[1] The type locality of the formation is located at the southern edge of the eponymous Sierra Barrosa, to the east of Cerro Challacó.

The formation at its type section reaches a thickness of 62 metres (203 ft).

The formation comprises fine-to-medium grained sandstones intercalated by thin levels of mudstones.

Based on the stratigraphic relations with the overlying and underlying units, the age has been estimated to be middle to late Coniacian.