Santa Juana Formation a Late Triassic (Carnian stage) sedimentary rock formation near Santa Juana in the lower course of the Biobío River in south-central Chile.

[2] The sediments that consolidate into the rocks of the formation deposited in alluvial, fluvial, lacustrine and playa lake environment.

Overall, the formation is rich in plant fossils.

[2] The formation was deposited over the rocks of the Coastal Batholith of central Chile in a sedimentary basin that formed along the Gastre Fault.

It has been posited that the basin developed as a rift during the early break-up of Gondwana in the Triassic.