Planktonic foraminifera in the sediment of a western boundary upwelling system off Cabo Frio, Brazil

The distribution of planktonic foraminifera in box-core tops under the influence of a western boundary upwelling system along the southeastern Brazilian continental margin was examined to evaluate the similarity percentage (SIMPER) and to create a biofacies model for paleoenvironmental applications. Species associated with warm and oligotrophic water were distributed in the Rio de Janeiro sector of the Campos Basin, while productive water species were most abundant in the Rio de Janeiro sector of the Santos Basin, and cold-water species were most abundant in the Cabo Frio Upwelling System (CFUS). Four major biofacies are associated with the oceanographic setting of the CFUS: one from the Campos Basin (A — Brazil Current front), one from the Santos Basin (B — mixture of coastal and oceanic waters), and two associated with the Cabo Frio High in the northern biofacies (C) and southern biofacies (D). The distribution of biofacies C and D was associated with temperature differences. Biofacies C represents a mixture of upwelling and tropical waters, while biofacies D represents a mixture of cold, nutrient-rich and Santos Basin waters. These biofacies were also defined in core CF10-01B, in which six main paleoceanographic phases were characterized during the last 9 cal kyr, predominantly showing alternating dominance between biofacies C and D. From 9.0 to 5.0 cal kyr before the present (BP), the system was dominated by biofacies C. Between 4.0 and 3.5 cal kyr BP, biofacies D was dominant. Between 3.5 and 2.5 cal kyr BP, a strong influence of coastal waters and weakened upwelling activity were indicated by the dominance of biofacies B + C + D. The last 2.5 cal kyr was dominated by biofacies D. The SST in this core was reconstructed using the Modern Analog Technique (MAT), which revealed 0.35 °C of variability, indicating no SST changes during the Holocene. The weak sensitivity of the MAT was due to the interplay among different oceanographic features.