Earth, wind and fire: Interactions between Quaternary environmental dynamics and human occupation on the southern coast of Brazil

Abstract

The southern coast of Brazil has been settled in different episodes between ca. 7.5 and 0.5 ka before the present by hunter-fisher-gatherers, shell mound builders of the pre-colonial Sambaqui cultural tradition. The factors that influenced human migrations in these episodes are diverse. They include cultural changes due to the coming of other groups, chronic food shortages, sea level changes, and lagoon silting. This paper combines geological, geomorphological, meteorological, and archaeological data to show how interactions between environmental dynamics and human settlement played a central role in modeling coastal sedimentary and rocky landscapes on the southern coast of Brazil during the middle Pleistocene to late Holocene. On Costão do Ilhote, a north-south oriented granitic promontory in Laguna County, Santa Catarina State, erosional features such as facets, keels, grooves, flutes, pits, and polished surfaces that developed on granitic boulders and pavements were recognized as ventifacts. In the same context, hundreds of fixed sharpeners/polishers from the production of polished objects by the sambaqui culture have been found crosscutting the ventifacts. Based on crosscut relationships between pre-colonial aged fixed sharpeners/polishers and ventifacts, relative sea-level changes during the Holocene, the age of distinct generation of sand dunes, and the age of shellmounds (sambaquis), four potential intervals of ventifaction are proposed: last 650 ka, last 350 ka, between ca. 115 and 5 ka BP, and between ca. 2.0 and ∼0.5 ka BP, with separated estimated abrasion rates of approximately 3.5 × 10−5 mm/yr, 7.0 × 10−5 mm/yr, 1.7 × 10−4 mm/yr, and 1.3 × 10−2 mm/yr, respectively. The ca. ∼1.5 ka of the last ventifaction interval was synchronous with a period of sambaqui culture retreat in the southern coastal plain of Santa Catarina, and also coincided with a period of abundant sand availability. This period is characterized by a drastic decline in sambaquis construction along the sand barrier and paleolagoon and a migration towards lagoonal and coastal rocky promontories, including Costão do llhote. Based on these pieces of evidence, we propose to add new components to the close interactions between environmental evolution and prehistoric human occupation on the southern coast of Santa Catarina during the Holocene: the strong winds combined with sand availability.