THE MACAU FORMATION IN THE SUBMERSED PORTION OF THE POTIGUAR BASIN

Abstract

ln the submerse portion of the Potiguar Basin, the Macau Formation is composed of olivine basalt lava flows and diabase associated to volcanoclastic rocks. Petrographic and petrological criteria reveal three distinct facies within this formation: lava, breccia, and hyaloclastite. Associations of similar facies have been linked to basic lava extrusions in shallow subaqueous environments. The igneo·basic and volcanoclastic rock of this formation are associated with intervals of sedimentarv rock. The presence of sedimentary rock intervals in volcanic complexes indicates periods of quiescence between consecutive lava flows. As far as hydrocarbon reservoirs, data collected indicate that onlv the hydroclastic volcanoclastic rocks displav significant moldic type porosity values. Radiometric dating using the potassium-argon method (KlAr} assigns these rocks to the Tertiary,