Calcium Carbonate Sedimentation on Continental Shelf off Southern Brazil, with Special Reference to Benthic Foraminifera

Abstract Changes in the oceanographic and sedimentologic regime off southern Brazil are reflected in the carbonate enrichment and foraminiferal assemblages of the shelf sediments. North of Cabo Frio, carbonate-rich sands and gravels are characterized by Halimeda, bryozoans, and coralline algae; tropical Foraminifera include various species of miliolids and peneroplids, as well as the encrusting Homotrema rubrum. Subtropical deposits of carbonate-rich sediments between Cabo Frio and Sao Paulo are primarily restricted to the outer shelf, and are dominated by coralline algae and increased amounts of agglutinated Foraminifera. Temperate-water carbonate deposits off southernmost Brazil contain mainly barnacles and mollusks, and fewer agglutinated Foraminifera. Carbonate sediments generally are not important in the middle-shelf muds and inner-shelf sands. Benthonic Foraminifera in nearshore waters (particularly in temperate areas) are characterized by paucity of both species and individuals.