[2] Its deposition is diachronous, beginning during the Maastrichtian in the north of its distribution, and later moving to the south, where its strata reached the Late Danian.

The marine sediments of the Jagüel and Roca Formations were deposited during a transgression from the Atlantic Ocean, beginning in the Maastrichtian and ending in the Danian.

The lithological composition of this type locality contains gray-yellowish and highly fossiliferous limestones, with greenish claystones and marls, and abundant gypsum at the top.

By contrast, the marine invasions in Argentina and Chile during the Jurassic and Early Cretaceous were caused by an inflow of seawater from the Pacific Ocean.

[8][3] The first section of the Roca Formation has abundant fossiliferous content, including bivalves, gastropods, bryozoans, echinoderms, crustaceans, ostracods, foraminifera, and calcareous nanoplankton, as well as remains of fish.