Strandplain Evolution along the Southern Coast of Santa Catarina, Brazil

The central Santa Catarina coast of southern Brazil has a relatively narrow discontinuous coastal plain that is bordered by crystalline rocks. Exposed granitic plutons form numerous low-relief headlands that dominate this section of coast. The irregular coastline has been smoothed through the deposition of extensive strandplains (2-8 km wide) with sediment derived from small rivers and the continental shelf. Forcing coastal progradation was the mid-Holocene (5-6 ka BP) sea-level fall of 2-4 m. Rivers can be directly linked to the construction of some strandplains, such as Tijucas (Tijucas River) and Navegantes Plains (Itajaí River), but other strandplains, including those comprising much of the exposed coast along Santa Catarina Island can only be attributed to sandy shelf deposits. Preliminary work on the strandplain coast, including surveying, coring, and geophysical studies, demonstrates that these low-gradient plains consist of dune/beach ridges and chenier systems and have evolved through shoreface and foreshore accretion producing low-angle, ubiquitous, seaward-dipping clinoforms as seen in ground-penetrating radar transects. Data collected from Navegantes, Tijucas, and Pinheira strandplains indicate that considerable variability exists in the sedimentology, stratigraphy, and facies architecture among these plains, resulting from differences in wave exposure, the origin, volume and composition of the sediment supply, and antecedent topography of the coastal basin. Grain size correlates well with clinoform geometry and cheniers are best developed in proximity to muddy rivers. Centennial-to-millennial-scale variations in the organization and type of paleo-shorelines within these plains suggest periods of climatic change and/or the impact of major meteorological or oceanographic events.