The Talacasto Formation is exposed in the
Precordillera Basin of
Argentina, with outcrops most widespread in
San Juan Province, though an isolated exposure also exists at Sierra de las Minitas in
La Rioja Province. Along with the
Punta Negra Formation, it makes up the
Gualilán Group, which represent
Devonian-aged deposits in the Argentine Precordillera. The thickness of the Talacasto Formation varies across its extent; at the
type locality of Quebrada de Talacasto in the south it is thick, while at the Loma de los Piojos section near the
Jáchal River in the north it exceeds in thickness. ==Fossil content==