Phytoliths as indicators of pedogenesis and paleoenvironmental changes in the Brazilian cerrado

摘要

This paper presents the preliminary results of phytolith analyses of a peat located in the cerrado of the Uberaba municipality,State of Minas Gerais,Brazil.The phytolith soil sequence is discussed by comparison with phytolith assemblages extracted from dominant plants (Cyperaceae and Poaceae).Increasing mean age of phytolith assemblages with depth is assumed.Poaceae Cuneiform bulliform cell,Parallelepiped bulliform cell and Elongate smooth long cell types dominate up to 80 cm,rapidly drop to 42% at 80 cm and regularly decrease from 42% to 2% upwards.Cyperaceae Rondel concave type shows the inverse trend,being dominant in the upper part of the profile.This pattern can be assigned to increasing selective dissolution of the Cyperaceae phytolith type with depth,or/and to a decrease of water stress suffered by the grasses,leading to a decrease of bulliform cell silicification.Soil processes and paleo-environmental changes hypotheses are discussed.