GEOMORPHOLOGICAL EVOLUTION OF THE COASTAL PLAINS IN THE HOLOCENE

Abstract The last eleven thousand years have been marked by several environmental changes in coastal regions and in Brazil, evolutionary models and sea-level variation curves indicated a general phase of marine regression, interspersed with peaks of transgression. These oscillations contributed to the evolution of extensive coastal plains. However, in the smaller coastal plains, these issues need more discussions. In the case study of the Itapicuru coastal plain, north coast of Bahia State, we aimed to complement the paleoenvironmental information to define the possible geomorphological evolution scenario during the Upper-Middle Holocene. We analyzed marine terraces and floodplain using particle size distribution, quartz grain morphological analysis, and OSL. The data indicates a slow and gradual regressive phase between 5 kyrs - 0,8 kyrs BP, responsible for the highest marine terrace’s formation. Between 0.8 ka A.P. and the Present, there was a fast and abrupt regression also observed in other places of the Bahia coast, with the formation of low terraces. We suggest that short-lived events may have been responsible for the evolution of other Brazilian coastal plains with similar characteristics. (AU)