A sedimentary sequence of Permian age provides both the source and reservoirs for the major portion of the hydrocarbons discovered in the Cooper Basin. This sequence is composed of shales, siltstones, coals and sandstones, and in 1967 was named the Gidgealpa Formation after the discovery well on the Gidgealpa Field. With information from further drilling the formation was divided into members. This division was recognized as a temporary measure because the members were, in fact, mappable units and because a disconformity was recognized within the section. Results of recent drilling activity have shown that the members themselves could be subdivided and that these subdivisions were also mappable units.This paper follows on from one published recently by Kapel, where he raised the members of the Gidgealpa Formation to formation status and the original formation to a group. The Upper, Middle and Lower members of the Gidgealpa Formation were renamed the Toolachee, Moomba and Patchawarra formations. It is the purpose of the current paper to raise the three parts of the Moomba Formation to formation status because of their mappable nature, and to define the formations of the Gidgealpa Group according to the Australian Code of Stratigraphic Nomenclature.The Gidgealpa Group includes Permian strata from the top of the Merrimelia Formation, where present, upward to the top of the Toolachee Formation. Knowledge of the included palynological stages gained through study of cores and cuttings from recently increased drilling activity in the basin indicates that some of the newly defined units may be diachronous.