The sediments of the Casma Group reflect deposition in two distinct environments of the West Peruvian Basin.

Some sediments were deposited near the Casma Volcanic Arc in an intra-cratonic sedimentary basin that was occasionally connected to the ocean.

Other sediments were deposited in what was once a continental platform bounded by reefs and with anoxic pockets.

[2] The folding of the Casma Group sediments is the result of the Cretaceous Mochica Phase of the Andean orogeny.

[2] The Casma Group include the following lithologies: gypsum, limestone, marl, tuff, lava flows, sandstone and conglomerate.