Depositional Environment, Diagenesis and Reservoir Properties of Oncolitic Packstones, Macaé Formation (Albian-Cenomanian), Campos Basin, Offshore Rio de Janeiro, Brazil

The stratigraphy of the Campos Basin (Fig. 1 A, B) was controlled by the following sequence of tectonic stages characteristic of rifted continental margins (Ponte et al. 1980); pre-rift arching: denudation of Paleozoic cover (Permian-Jurassic); intracratonic rift valley: N-S collapse trough enlarged to rift valley system (late Jurassic — early Cretaceous) filled by Lagoa Feia fluvio-deltaic to lacustrine clastics; proto-oceanic gulf: restricted embayment (late Aptian) with deposition of Lagoa Feia evaporites; open marine continental margin: subsidence and seaward tilting, generation of carbonate platform consisting of offshore bars of oncolitic packstones separated by mudstones (Lower Macaé, Albian); further tilting, subsidence of platform, transgression of argillaceous pelagic mudstones and intercalated turbidites (Upper Macaé, Cenomanian) followed by basinal shales and turbidites (Carapebus Member, Campos Formation, Senonian-Eocene); renewed tilting of continental margin and rejuvenation of source areas with intense deltaic progradation (Ubatuba Member, Campos Formation (Oligocene — Pliocene).