Aeolian Transgressive Dunefield Barriers of Northern and Southern Brazil

An overview of the Holocene transgressive dunefield barrier systems of northernmost and southernmost Brazil will be presented. The surficial landforms of these barriers are predominantly aeolian in origin and comprise some of the largest aeolian transgressive dunefield barrier types in the world. They extend from the equator to the border with Uruguay.

In Pará and Maranhão States, astride the equator, the tides are macrotidal, and a system of highly irregular, digitate capes, islands and bays dominated by mangrove and funnel-shaped marcotidal estuaries and channel systems are typical. Sandy beaches, spits, foredunes, beach ridge plains (and cheniers or foredune plains?), and some active transgressive dunefields mostly forming prograded barriers occur along this coast. Many of the islands display pseudo-anvil or ‘trilobite' shapes with the beach and dune systems forming a convex form wrapped around the larger seaward margin of the islands.

The largest dunefield in Brazil, and one of the largest in the world, occurs at Lençois Maranhenses National Park (Ceara State). At its widest, the active portion is 31km wide (measured in the dune migration direction), and the total dunefield including the vegetated portion is approximately 120+km wide. This prograded barrier extends 76 km alongshore and is dominated by transverse, barchanoidal transverse and barchan dunes.

In the three northernmost States there is only one complex foredune plain-transgressive dunefield barrier system.

To the south, the States of Santa Catarina and Rio Grande do Sul display very micro-tidal beaches and are also dominated by transgressive dunefield barriers. These range from extensive (5 -8km wide), prograded barriers comprising multiple overlapping dunefield phases, to retrogradational barriers comprising a single, active phase.

The principle characteristics of these aeolian-domianted barrier systems will be compared, and the driving forces (climate, sediment supply and Holocene sea level change) will be examined.