The Santa Susana Formation is a Paleogene period geologic formation in the Simi Hills and western Santa Susana Mountains of southern California.

[1][2][3] The formation consists largely of light-gray shale and some fine-grained shaly sandstone, with a lens of heavy conglomerates in the lower part.

[1][4] Small beds of limestone are also present.

[1][4] The Santa Susana Formation preserves fossils from the Late Paleocene to Early Eocene epochs in the Paleogene period of the Cenozoic Era.

[4][6] Fossilized fauna in the Santa Susana Formation is entirely different from that of underlying Martinez Formation, and has very little in common with that of the overlying Meganos Formation.