Multi-proxy analysis of a Holocene records from a high-altitude tropical peatland in the Serra do Espinhaço Meridional, Brazil

Abstract

Peatland ecosystems are valuable archives of paleoenvironmental changes, as they preserve organic and inorganic records that enable the reconstruction of the paleoenvironment. A Holocene record of the Araçuaí River peatland in the Serra do Espinhaço Meridional, in the state of Minas Gerais, Brazil, was studied using isotopic composition, environmental geochemistry, and phytolith analysis. As a result, it was possible to determine and quantify the main constituent elements of the peatland and the chronology of paleoenvironmental changes. Five phases of paleoenvironmental changes were inferred: Phase I – 8.9 to 6.6 cal kyr BP - cold local environment (high phytolith index), which was very wet (higher tree cover density and high occurrence of C3 plants) and with watershed instability (higher incidence of erosion and sedimentation); Phase II – 6.6 to 3.9 kyr - very cold local environment, with reduced moisture in relation to the previous phase (decrease of the temperature and mixture of C3 and C4 plants), and increased stability in the watershed, with episodes of erosion at the end of the phase; Phase III – 3.9 to 2.1 cal kyr BP – warmer, drier local environment in relation to the previous phase (increase in the temperature and decrease of tree cover density) and instability in the watershed, with an episode of temperature decrease and moisture increase (respective increase in the climatic phytolith index and in δ15N) in the middle of the phase; Phase IV – 2.1 to 0.25 kyr - colder climate, increased humidity in the local environment in relation to the previous phase (increase in Ic% and D/P and a decrease in the palm cover density phytolith index), and greater stability in the watershed; Phase V – 0.25 kyr to present - increase in temperature, decrease in humidity (decrease in Ic% and expansion of C4 plants), and increased instability in the watershed, possibly influenced by human activity. The results evidence that the Araçuaí River peatland records demonstrate Holocene climate variations, capable of providing information about the paleoenvironment.