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Abstract: Opal phytolith, geochemical and sedimentological data from two cores taken in Peña Lagoon, a small water body on the Atlantic shore of Uruguay, are presented in this paper. The choice of this specific sampling location aimed to obtain high resolution records to infer late Holocene environmental and climatic changes in southeastern Uruguay, in order to improve previous models for early and middle Holocene. The combined record of two cores extends to 2500 14C BP, with a sedimentation rate ranging between 0.6 and 2 mm y−1. A multiproxy approach allowed the identification of changes in dynamics, particularly organic matter and sediment input variability from the watershed. With this information, differences in the amount and extent of environmental signals were evaluated and a comprehensive climate change model was generated, especially for the last 1500 years. Three main climatic events were distinguished. The oldest, which lasted until 700 AD, was characterized by temperate and humid conditions. The second extended until 1200 AD and warmer and wetter conditions were inferred, but also a colder and drier pulse was observed in between. This second event was assigned to the Warm Medieval Period (WMP). During the third event, assigned to the Little Ice Age (LIA), which extended until the present, a high variability in climate was observed, but also three dry/cold phases reaching their maxima by 1300, 1600 and 1900 AD were inferred. [Copyright &y& Elsevier]

Abstract: The strong correspondence between the spatial arrangement of archaeological sites and wetland environments is one of the main axes of the Merín Lagoon basin archaeology. Without implying a deterministic simplification from the epistemological point of view, the cultural and environmental history of the region hold evidence suggesting a more complex scenario, where cultural responses to climate change were not so mechanical or direct as previously argued. The relationship between paleoclimate and prehistoric mound builders development between 7.0 and 0.6ka 14C BP was studied in SE Uruguay. Paleoclimatic data were inferred from the phytolith record of three lagoon sediment cores. Four paleoclimatic periods were identified according to temperature/humidity changes. The first period, dated at 7.0–4.5ka 14C BP, was characterized by a warm/humid climate. Between 4.5 and 3.5ka 14C BP, the onset of a cool/dry climate was inferred. A hiatus between 3.5 and 2.6ka 14C BP was identified. In the third period, 2.5–1.2ka 14C BP, similar climate conditions to those of the present were inferred. Finally, the period 1.2 and 0.6ka 14C BP, was characterized by warmer and wetter conditions than those of the present. According to these data, it was determined that mounds were first observed during the transition from warm/humid to cool/dry conditions, but the complexity of the mounds increased after the full establishment of cool/dry conditions. With the inception of warm/humid conditions, an increased number of mounds was observed in the plains located close to the Merín Lagoon littoral. The mounds showed lower density and height than those recorded for the cool/dry period. This behavioral modification in mound construction was explained because of the paleoenvironmental change. [Copyright &y& Elsevier]

Abstract: This paper reviews the relationship between prehistoric mounds (5000 years BP to 17th century) with main landscape features, particularly wetlands, in the east of Uruguay. Former archeological researchers did recognize this relationship, but it was interpreted by extrapolating current environments to 5000 years of cultural behavior. In an effort to better understand how environmental dynamics were linked to the cultural record, a set of proxy records (diatoms, opal phytoliths, gastropods, shells) were introduced to take into account local environmental evolution data according to global and regional environmental evolution models. The main environmental events during the mid and late Holocene show a high correspondence with mound builders’ spatial arrangements. [Copyright &y& Elsevier]