Paleoindian sites in eastern South America are generally found inside rock-shelters. Recently, we designed a program to find open-air Paleoindian sites in the Lagoa Santa region of Brazil. Here, we present data gathered at Sumidouro site, a multicomponent site with a Paleoindian horizon, detected on a shoreline slope of Sumidouro Lake, Minas Gerais State. We present a model for late Pleistocene/Holocene slope evolution that suggests at least three different episodes of instability (erosion/sedimentation) followed by periods of stability (pedogenesis). Higher soil accretion rates during the Mid-Holocene are probably not linked to a stable dry climate, but to greater climatic instability. We also found that the position of both archaeological materials and charcoal can be explained by burial of ancient surfaces and are not the result of downslope movement. The role of bioturbation in the vertical displacement of such materials is much less important than previously acknowledged.