FORAMINIFERAL ASSEMBLAGES AND THE EARLY OPEN MARINE RECORD (UPPER APTIAN-ALBIAN) OF NORTHEASTERN BRAZIL

During the Aptian occurred the first marine incursions into the northern coastal basins of the South Atlantic when the São Paulo Plateau-Walvis Ridge complex was bypassed and saline waters flooded the central rift-graben system from the south. A mixed carbonate-siliciclastic platform/ramp system developed in a shallow epicontinental sea from late Aptian to mid-Albian. The paleoceanographic conditions also suggest an arid, dominantly dry climate, salinity-stratified water-masses with episodic dysoxic-anoxic bottom conditions, and intermittent S-N Atlantic surface-water connection, through the Gulf of Guinea and/or across the Brazilian Northeast buldge. By mid- to late Albian oceanographic circulation improved with more oxidizing conditions, and interchange of epi- to mesopelagic water masses with low-latitude northern regions. The microfossil record yield abundant and diversified benthic foraminiferal assemblages characteristic of paralic to neritic and upper bathyal biotopes. The rich and diversified planktonic foraminifera, recovered throughout the succession, are characteristic of water masses with well-oxygenated epipelagic layers, and provide a detailed biostratigraphic subdivision. The paleogeographic and stratigraphic occurrence of the planktonic foraminifera further suggests that their distribution was primarily controlled by a complex set of environmental variables (depth-related in part), such as rate of clastic influx upon the shelf and slope, dissolved oxygen concentrations, and calcium carbonate availability.