This paper is a regional overview and revision of the Neocomian basin developed in the province of Chubut and Santa Cruz. The Neocomian deposits lie, mainly, on the western subsurface sector of both Provinces. They correlate with Tres Lagunas F., Katterfeld F. and Apeleg F., or Coyhaique Group, which outcrop in Argentina and Chile.The Neocomian Cycle sensu lato, was deposited during the Berriasian up to Barremian? in a NW trending rift system. The base of the Neocomian fill lies on top of the Complejo Volcanico Sedimentario, (which correlated with Lago La Plata F.), or on early to middle Jurassic metasedimentary deposits, or on paleozoic shales and sandstones. The synrift sequence, regarded as Anticlinal Aguada Bandera Sub Cycle, is composed of matrix supported conglomerates, interbedded with volcanic ashes at the base, and covered by dark brown shales. The sag or postrift sequence, known as Cerro Guadal Sub cycle, filled up the depocenters with sandstones and shales.The paper describes the main morphotectonics features of the area and the stratigraphic architecture of the Cycle. A marine basin is defined in the NW of the area, and a relevant extended NE paleo high. From this high to SE long narrow NW trending depressions develop. The rift fill of these depressions is lacustrine in the southeast, changing to marine- deltaic to the North and West.The rift fill is covered, unconformably by the Grupo Chubut volcaniclastic and clastic sediments.The results of this study suggest the occurrence of two Petroleum Systems: Anticlinal Aguada Bandera/Cerro Guadal(!) and Anticlinal Aguada Bandera/ Grupo Chubut