At the Southern Limit: The Arenal Central Site and the Guaraní Occupation of the Paraná Delta (Argentina)

This study analyzes the archaeological record of the Arenal Central site, a Guaraní residential base located on Martín García Island, within the Río de la Plata estuary—marking the southernmost extent of this population originating from the tropical forests of South America. The results significantly advance our understanding of these Amazonian forager-horticulturalists in the region, allowing us to explore a range of strategies and material culture expressions developed in an environment suboptimal for canoe-based populations. The study also presents a new set of chronological data, substantially increasing the number of radiocarbon dates available for these groups in the area. Findings indicate that Arenal Central was occupied around 1400 CE, during the final phase of the Guaraní expansion across the La Plata Basin. From this location, a vast catchment area was incorporated, including the lower Uruguay River, the Paraná Delta islands, and the adjacent Uruguayan steppe. The extensive use of territory appears to have been a strategic response to the island’s limited carrying capacity and the scarcity of key resources required to sustain the Guaraní ecological niche. While the recovered assemblage preserves the core features of Guaraní material culture, a marked decline is observed in the complexity of pictorial expressions—particularly in painted ceramics. This simplification may reflect reduced intra-ethnic interaction, likely due to the low density of Guaraní populations in the surrounding area, as well as the challenges imposed by a constrained insular setting. We also compare subsistence strategies and ceramic assemblages from other sites that have been excavated and analyzed following comparable standards. Finally, the results are contextualized within the broader process of Guaraní occupation of the Paraná Delta and the Río de la Plata estuary.