A high-resolution Holocene record on the Southern Brazilian shelf: Paleoenvironmental implications Michel Michaelovitch de Mahiques a, * , Ilana Klein Coaracy Wainer a , Leticia Burone a , Renata Nagai a , Silvia Helena de Mello e Sousa a , Rubens Cesar Lopes Figueira a , Ilson Carlos Almeida da Silveira a , Ma ´ rcia Caruso Bı ´cego a , Daniel Pavani Vicente Alves a , Øyvind Hammer b a Institute of Oceanography, University of Sa ˜o Paulo, Praça do Oceanogra ´fico, 19105508-120 Sa ˜o Paulo, Brazil b Natural History Museum, University of Oslo, Oslo, Norway article info Article history: Available online 1 November 2008 abstract A high-resolution, multi-proxy record has been used to determine the environmental changes during the Holocene on the southern Brazilian shelf. Present oceanographic conditions reveal wind and freshwater input as the determinants of short-term productivity changes in the study area. Magnetic susceptibility and grain-size variations, together with proxies of productivity (organic carbon, carbon accumulation rate, Ba, Sr, and Ca content, Ba/Al, Ba/Ti, and Al/Ti ratios) were analyzed and compared with proxies of redox condition (V/Ti ratio), terrigenous input (Fe/Ca and Ti/Ca ratios), as well as other Element/Ti ratios, to evaluate the paleoceanographic and paleoclimatic changes over the period. The core covers a time interval of about 7650 years, with sedimentation rates varying from 0.025 to 0.250 cm a 1 , which represent time intervals of between 8 and 80 a per sample. There is a clear change in the sedimentation rate at about 2800 B.P. All grain-size and elemental results indicate the occurrence of conspicuous changes between 5200 and 5000 cal. B.P., as well as between 3000 and 2800 cal. B.P. A comparison of the results with the palyno- logical information available from the adjacent continental areas suggests that the sedimentary changes in this last interval may be correlated with the onset of modern climatic conditions in South America, and especially, with the onset of the Plata Plume Water, a water mass that carries cold, less saline waters towards the north. However, minor changes are observed at ca. 1500 B.P. and are correlated with an increase in the atmospheric humidity. Furthermore, a time-series analysis undertaken using several proxies indicated the occurrence of Sub-Milankovitch cycles, which may be compared with those reported worldwide. Ó 2008 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction The present oceanographic conditions offer the southern Bra- zilian shelf a privileged status for the study of short-term (seasonal and decadal) changes in the wind-driven currents and freshwater discharge regimes of the Southwestern Atlantic Ocean. In this area, the wind-dependent northward displacement of cold and less saline waters originating in the Rı ´o de La Plata and the discharge of the southern Brazilian lagoons (Piola et al., 2000; Piola and Romero, 2004) control the seasonal variation in primary productivity (Ciotti et al., 1995). Sedimentological evidence of the northward displacement of this water flow can be observed both in the organic and inorganic constituents of the bottom sediments and can be traced as far north as the 24  S parallel (Mahiques et al., 1999, 2004). Also, this northward flow, which was originally attributed to the Malvinas Current, has been used to explain the occurrence of cold- water foraminiferal forms on the Southwestern Atlantic Shelf (Stevenson et al., 1998). By assuming that the Rı ´o de La Plata river mouth has undergone only very slight changes in its geographical position over the last 7500 years (Cavallotto et al., 2004; Violante and Parker, 2004) and that the relative sea-level crossed its present height approximately at this time (Mahiques and Souza, 1999), and the later oscillations in the Holocene sea-level were unable to expose significant portions of the shelf (Suguio and Martin, 1978; Angulo et al., 1999, 2006), the middle and late Holocene paleoceanographic changes on the Southwestern Atlantic shelf were mainly dependent on the wind regime and freshwater input, and that the millenial variations in the sedimentary pattern may have been resulted from the vari- ations in this wind-driven water mass. * Corresponding author. Tel.: þ55 11 30916609; fax: þ55 11 30916610. E-mail address: mahiques@usp.br (M.M. de Mahiques). Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint 1040-6182/$ – see front matter Ó 2008 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2008.09.010 Quaternary International 206 (2009) 52–61