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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. [ABSTRACT FROM AUTHOR]

Abstract: The Tandilia range is a discontinuous series of hills and valleys located at the central area of the Pampean region (Argentina). The process of human settlement reached in this zone the highest population densities and reoccupation levels of Southern South America, developing under the strongly changing climatic conditions that characterized the Pleistocene–Holocene transition. This paper analyzes the geoarchaeological and paleoenvironmental record of the Pleistocene–Holocene transition (c. 9400–10,500 14C BP) recovered from cave and rockshelter sedimentary successions of the Tandilia range. The analysis of several lines of evidence (stratigraphic, geoarchaeological, archaeological, zooarchaeological, and paleobotanical), suggests that a cold arid to semi-arid climate characterized the late Pleistocene (c. 10,500 BP), and changed abruptly to warmer conditions towards the beginning of the Post-Glacial Period. As a consequence of this climatic amelioration, the populations inhabiting the Tandilia range would have been benefited by a higher availability of resources, which could explain the higher levels of site density and reoccupation found in the area during this period. [Copyright &y& Elsevier]

Abstract: The recently excavated Paso Otero 4 site is located within the Paso Otero archaeological locality (Necochea District, Pampean Region). The site is characterized by the presence of a great variety of archaeological materials and a rich and complex stratigraphic record which allows use of an interdisciplinary approach. The objective of this paper is to present the results of the geoarchaeological, palynological, phytolith, and diatom analyses in order to reconstruct the paleoenvironmental conditions for the final Late Pleistocene through Holocene. These lines of research allow inference of paleoenvironmental and palaeoclimatic conditions on both local and regional scales. At the site, the Río Salado Member (Unit 2), where the archaeological deposit is buried, underwent sudden and fluctuating changes in water availability conditions, although the setting was basically characterized by calm depositional processes within and along the margins of interconnected lagoons. Paleoclimatic reconstructions indicate the existence of abrupt climatic changes throughout the sequence. Early Holocene human occupations took place under regionally temperate-warm climates while the end of the Middle Holocene witnessed cold and arid or cold temperate climates. In general terms, paleoenvironmental conditions inferred for Paso Otero 4 are in accordance with regional reconstructions proposed for the Pampas. [Copyright &y& Elsevier]