Phytolith records in organic soils: Evidence of environmental changes in the southern Brazilian highlands

ABSTRACT Soils preserve numerous proxies for paleoenvironmental reconstruction, including phytoliths, which are highly resistant to weathering and can be preserved over long periods. This study investigates the environmental history and soil formation processes in the highlands of southern Brazil through the analysis of organic soils and phytolith records. Our research focuses on the Serra Geral formation, where soils are deeply influenced by environmental factors such as climate, vegetation, and human activities. Four soil profiles in the states of Santa Catarina and Rio Grande do Sul were studied. We reconstructed the paleoenvironmental conditions using a multiproxy approach that includes phytolith analysis, δ13C isotopes, and C/N ratios. The combined proxies identified three phytolith zones in each profile, forming three paleoenvironmental phases related to soil formation. These phases represent distinct environmental moments: the first phase, related to a colder and drier environment with C 3 vegetation dominance; the second phase, associated with higher temperatures, elevated humidity, fewer trees, and an expansion of C 4 grasses; and the third phase, characterized by an overall decrease in temperature and humidity variation in the study sites, with predominant grasslands and herbaceous marsh presence in specific areas. This study aligns with previous regional research, offering information on environmental changes and their impact on soil formation. Results enhance the understanding of the soils from high-altitude grasslands, contributing valuable data on paleoenvironmental changes in southern Brazil.