La Chilca Formation (Spanish: Formación La Chilca) is a geological formation that crops out in the Precordillera of San Juan Province, Argentina.
Rocks of the formation are mostly shale and sandstone that deposited during the Ordovician and Silurian periods.
[1] The formation contains a high diversity of graptolite fossils.
[1][2] Graptolite fossil taxa found include:[1]
This article about a specific stratigraphic formation in Argentina is a stub.