Registros do Holoceno Médio e Tardio no Nordeste do Brasil: análise de um perfil sedimentar em um lago no Baixo Jaguaribe (CE) a partir de indicadores biogeoquímicos

Abstract

CE1308 is a record of paleoenvironmental changes in the Baixo Jaguaribe region that may have occurred due to the paleoclimatic forcings in the Northeast of Brazil during the Middle and Late Holocene. Radiocarbon dating recorded two distinct periods, the oldest between 6,100 and 5,637 years ago, between 263 cm and 90 cm, and the most recent between 3,575 and 2,925 years ago, between 88 cm and 12 cm. The analysis of the biogeochemical indicators (organic matter, isotope ratios δ13C, δ15N, trace metals and clay minerals), indicated that the period in the Middle Holocene had estuarine characteristics, with a sub-oxide environment and high organic matter supply of vascular plants and clay minerals from the drainage basin through river transport. The Late Holocene period had lacustrine characteristics, with an oxide environment, primary algal production and a composition of clays originated in coastal plains and carried by wind processes. The analysis suggests a morphodynamic change in the Jaguaribe River, which could extend to the Lower Jaguaribe region during the Middle Holocene due to the higher rainfall, followed by the formation of a lacustrine environment with a certain degree of salinity during the driest period of the Late Holocene.