Late Quaternary vegetation history based on phytolith records in the eastern Chaco (Argentina)

Abstract

The Chaco plain is a sedimentary basin filled by alluvial fans repeatedly generated by large rivers during the late Quaternary under diverse climatic conditions. The Eastern Chaco is characterized by semi-deciduous forests intermingled with extensive palm-savannas, grasslands, and wetlands. These vegetation patterns of the Chaco have been proposed to be the result of the Pleistocene-Holocene alluvial dynamics of the plain as well as of the intensive migration of fluvial belts of the main rivers. In this paper we present silica microfossil records from a Pleistocene-Holocene sedimentary sequence from the Eastern Chaco Region. Results show that phytoliths were the most abundant elements compared to the other siliceous and non-siliceous microfossils. Differences in the microfossil associations suggest that climate changes along the Late Quaternary were given mainly by humidity changes, and that rivers migrated mostly during the Holocene. Grasslands and wetlands predominated in the described paleocommunities.