Aeolian sand dispersals and modern erosion processes...

ISLA F; TOMAZELLI

Thalassas

Universidade de Vigo

Año: 1999 vol. 15 p. 45 - 52

0212-5919

The Holocen sea-level fluctuation left coastal lagoons and barrier environments along the shore- lines of northem Argentina and southern Brazil. Recent dunes are very young (usually less the 1000 years BP). These barriers are less than 4 km width. They have grown from north to south in Argentina, but it is not as clear wether a longshore drift was dominant during the Holocene along the Rio Grande do Sul coast. In Argentina, Upper Pleistocene aeolian depo- sits on the mainland denote the action of wester- lies, but modern barrier dunes have an alongshore component. In Mar Chiquita Barier (MCB, Buenos Aires), these coastal dunes are transverse to the winds coming from the SSW. On the other hand, Patos Barrier (PB, Rio Grande do Sul) was constructed by multiple barriers of Pleistocene and Holocen age. Dominant winds are today from the NE. The succession of transverse dunes in that direction indicates a pro- gressive sand scarcity landwards. In MCB, dune succession is parabolic - trans- verse - barchanoid - compound (startype) towards the north. In PB, the succession is transverse - bar- chanoid- barchans towards the south. In both cases, sand availabitlity is higher towards the head- lands of the barriers, north and shorewards.