Since the 19th century, it has been proposed that the wide geographic distribution of the Guaraní indigenous populations in large areas of South America was the result of prehistoric movements of large numbers of people through the main rivers of the La Plata Basin and the Brazilian coastline. However, no detailed spatial and temporal analysis has been carried out with the dated Guaraní archaeological sites of the different zones of Brazil, Argentina, and Uruguay. This is one of the reasons why some of the main ideas about this past population expansion still lack empirical validation. This paper presents a study on the geographic and temporal distribution of the Guaraní archaeological sites in the La Plata Basin and the Atlantic coast of southern Brazil. The overall purpose is to contribute to understanding the Guaraní expansion using the analysis of two basic archaeological variables: space and time. Based on available numerical dates ( 14 C and thermoluminescence) and the application of GIS software, potential dispersion routes are discussed. To date, more than 1100 archaeological sites assigned to the Guaraní, along with almost 250 numerical dates were analyzed. With this data, it was possible to elaborate a Dispersion Routes Model and a Temporal Visualization Model, which enabled identification of the sequence of population dispersal, with two main expansion pulses, throughout nearly two millennia of Guaraní movements across the South American Lowlands.

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In this paper, we present the results of the geoarchaeological studies carried out in two archaeological localities of the Upper Delta of the Paraná River (Argentina). The main objective of these studies is to depict the pre-Hispanic strategies involved in the colonization and settlement of southern South America wetlands. Paraná Delta is one of the most conspicuous areas of these lowlands and comprises a large wetland macrosystem. Its current geomorphological configuration was established after the last transgressive mid-Holocene event c. 6000 14 C yr BP. In this environment, a high ecological heterogeneity, with diverse and abundant tropical and temperate biota, was developed. These features were important factors to the human colonization and utilization of these wetlands. However, this environment has the highest hydrometeorological susceptibility of La Plata basin. This susceptibility had an impact on settlement systems and resource exploitation strategies established in the area since at least 2000 14 C yr BP. These strategies involved at least two settlement types: semi-permanent residential camps and transitory camps oriented to exploit particular resources. The semi-permanent settlements were located in anthropogenic elevated mounds, locally known as 'cerritos', and were not subjected to seasonal inundations. Conversely, the transitory camps are found in levees exposed to recurrent flooding.