Reconstrução paleoambiental do maciço de Água Branca, semiárido de Alagoas, a partir da análise dos sedimentos de encosta

The research aimed to analyze sedimentary deposits located in the Agua Branca massif, State of Alagoas, northeast of Brazil, approaching them as evidence of changes in paleoenviromental dynamics along the Holocene. Therefore, granulometric and morphoscopic analysis of the sediments were carried out, alongside with the absolute dating of the quartz grains by the OSL method. The results showed that sediments stored in landscape relate to three depositional phases. The oldest colluvium dates from 10200 ± 880 years BP and demonstrate sedimentary characteristics of cascade. The Middle Holocene deposit is 4590 ± 325 years old, indicate that, with the decrease in humidity the deposits are associated with torrential events. Lastly, the three deposits referring to the Late Holocene cover the period between 3900 and 3100 years BP and prove the predominance of a semi-arid climate, with punctual torrential rains. Colluvium deposits presented similar sedimentological characteristics, they are composed mostly of mud flows, with the exception of just one layer of drebris flow at the Preguicoso site.