[1] The formation has provided fossils of ammonites, gastropods, bivalves, brachiopods, serpulids, equinoderms, ostracoids, radiolarians, lobsters and Crabs.

[7] The Riachuelo Formation is a 500 metres (1,600 ft)[8] thick mix of Aptian and Albian sediments formed by high-energy shelf carbonate deposits (oncolitic-oolitic-peloidal-bioclastic packstones and grainstones), interbedded with lagoonal mudstones and siltstones, and fan-delta like siliciclastic rocks.

[10] It also has outcrops in the cities of Riachuelo, Santa Rosa de Lima, Divina Pastora, Laranjeiras, Rosário do Catete, Maruim, General Maynard and Carmópolis.

Then, in 1959, Bender made a new interpretation, separating the upper part of the Riachuelo Formation from the lower one, naming it Maruim.

Feijó, in 1994, classified the formation as a siliciclastic-carbonatic platform complex and divided it into the members: Angico, Taquari and Maruim, which is the classification currently used.