Mid to late Holocene evolution of transgressive dunefields from Rio Grande do Sul coast, southern Brazil

摘要

The aim of this paper is to examine the dunefield evolution of the Rio Grande do Sul (RS) coastal stretch from Torres to Mostardas, which presents progradational, aggradational and retrogradational barriers. The stratigraphy and sedimentary facies of 26 cores along 9 profiles were analyzed. The stratigraphy of the cores along the profiles agreed with the suggested barrier types. The northern area comprises prograded barriers; in Jardim do Eden and Magisterio, retrograded barriers; in Dunas Altas an aggradational barrier; and the southernmost profiles, Solidao, Sao Simao and Mostardas retrograded barriers. Three major periods of soil formation and dunefield stabilization were found: from 4820 to 3970 cal yr BP, in 2760-2460 cal yr BP and from 1570 to 710 cal yr BP. These periods coincide with periods where the literature cites an increase in moisture during the mid to late Holocene. This coincidence of soil formation and wet climate indicates that the climate might be controlling dunefield evolution on the RS coast since 5000 yr BP. The stratigraphic data of the three most representative cores were correlated, and along with the available ages from palaeosols and the facies descriptions 10 phases of aeolian activity and stabilization were recognized for the mid-littoral of RS.