Bracco, R., del Puerto, L., Inda, H., Panario, D., Castineira, C. and Garcia-Rodriguez, F. 2011. The relationship between emergence of mound builders in SE Uruguay and climate change inferred from opal phytolith records. Quaternary International 245: 62-73.
Focusing on coastal lagoons within the Merin Lagoon Basin, which is located between 31-34°S and 52-54°W in the easternmost part of the South American plains, and working with phytoliths found within various sediment cores which they used to create a temperature index indicative of relative warmth, Bracco et al. discovered a period of time straddling the division of the last two millennia (AD 750-1350) that they identified as having "warmer and wetter conditions than those of the present."