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First Notice of Open-Air Paleoamerican Sites at

Lagoa Santa: Some Geomorphological and

Paleoenvironmental Aspects, and Implications for

Future Research

Astolfo G. M. Araujo and James K. Feathers

Lagoa Santa, a karstic region in central Brazil, is known for the discovery of more than 250 Paleoamerican human skeletons (Neves and Hubbe 2005), allfrom sheltered contexts. Despite study since the 1830s (Neves et al. 2007), noPaleoamerican sites have been found outside caves until very recently.

A surface survey complemented by 15-m-interval probes with a motorizedauger was conducted recently along the shores of doline Lake Sumidouro,resulting in the discovery of three open-air lithic sites: Lund, Coqueirinho, and

Sumidouro. The lithics, similar to those found in the rockshelters, represent ageneralized core technology (Teltser 1991), lacking formalized tools and made

Astolfo G. M. Araujo, School for Arts, Sciences and Humanities, University of São Paulo, Brazil;

e-mail: [email protected]

James K. Feathers, Laboratory of Luminescence Dating, University of Washington, Seattle, WA

98195; e-mail: [email protected]

CRP 25, 2008 A RAUJO/FEATHERS 27



almost entirely on hyaline quartz and quartzite with some chert. The Lund sitereturned late-Holocene 14C dates, but the other two sites appear to date to thePaleoamerican period. Only Sumidouro is discussed here.

The site, found by augering, is located near the lake shore on the lower

portion of a 380-m 14-percent slope. Soils consist of a reddish micro-aggregated horizon overlying a yellowish prismatic horizon, a typical patternin Lagoa Santa (Piló 1998). Lower stratigraphic layers contain gleyed andmottled horizons subject to the water level.

At least three discrete layers of archaeological materials are present. Theupper occupation contains ceramics, lithics and burnt earth concentrated at adepth of 15–40 cm and with 14C dates of 510 ± 40 (Beta-234512) and 340 ± 40(Beta-234518) RCYBP. A middle occupation at a depth of 70–80 cm containsmainly lithics and is bracketed by 14C dates of 2210 ± 40 (Beta-234510) and

1350 ± 40 (Beta-234517) RCYBP. The lower occupation, at a depth of 160–210cm, consists only of lithics and is dated by 14C on charcoal at 8310 ± 40 RCYBP.Some anomalously recent dates obtained from lower in the stratigraphy aresuspected to result from contamination from the water table.

Tropical sites are often heavily bioturbated, although the discrete archaeo-logical levels suggest vertical movement may not be severe. However, charcoal,being less dense and having a different geometry from lithics, may not behavethe same way and may thus be more prone to movement. For this reason andbecause of the anomalous dates mentioned above, an alternative dating tech-

nique, luminescence dating, was employed on five sediment samples. Weapplied single-grain dating using optically stimulated luminescence (OSL)not only to cross-check the 14C chronology but to provide evidence of any mixing (Jacobs and Roberts 2007).

Only equivalent dose (De), the numerator of the age equation, is deter-mined on single grains, the dose rate being obtained from the bulk sample.

Variation in De values among grains can be evaluated by over dispersion, ameasure of variation beyond that accounted for by differential precision.Unmixed, single-aged samples generally have over-dispersion values of 10–20

percent, but the Sumidouro samples have values ranging from 30–60 percent (Table 1). We have ruled out microvariations in dose rate as a probable causefor such high values, and have concluded the variation represents different-aged grains, either because of insufficient sunlight exposure during colluvialdeposition or because of post-depositional mixing. Table 1 shows ages com-puted (1) by assuming random post-depositional mixing so that the centraltendency reflects the depositional age and (2) by assuming insufficient expo-sure so that the youngest grains represent the depositional age. The ages fromthe central tendency are in the correct stratigraphic order and agree with the14

C results in the lower part of the profile. The minimum ages contain onestratigraphic inversion but agree with 14C dates in the upper part. We arecurrently trying to sort out these processes, and it is possible both are involved,but the lowest lithic occupation appears to date to 9000–12,000 CALYBP.

The 14C ages suggest a strong increase in soil-accretion rates after 5000RCYBP, rising from 0.07 mm/year to 0.27 mm/year. We attribute this 400-percent increase to mid-Holocene drying, also responsible for human de-

28 A RAUJO/FEATHERS Archaeology: Latin America



population in central Brazil (Araujo et al. 2005). Reduced vegetation andheavy seasonal rains could increase erosion from slopes above the lake. Thisalso suggests that open sites along lakes will be deeply buried and not likely tobe found accidently because the artifacts are non-diagnostic. The lake shores

are a good starting point for surveys, but we do not know if all karstic lakes were active during the Pleistocene.

References Cited

Araujo, A. G. M., W. A. Neves, L. B. Piló, and J. P. V. Atui 2005 Holocene Dryness and Human

Occupation in Brazil during the “Archaic Gap.” Quaternary Research 64:298–307.

Jacobs, Z., and R. G. Roberts 2007 Advances in Optically Stimulated Luminescence Dating of

Individual Grains of Quartz from Archaeological Deposits. Evolutionary Anthropology 16:210–23.

Neves, W. A., and M. Hubbe 2005 Cranial Morphology of Early Americans from Lagoa Santa,Brazil: Implications for the Settlement of the New World. Proceedings of the National Academy of

Sciences 102:18309–14.

Neves, W. A., M. Hubbe, and L. B. Piló 2007 Early Holocene Human Skeletal Remains from

Sumidouro Cave, Lagoa Santa, Brazil: History of Discoveries, Geological and Chronological con-

text, and Comparative Cranial Morphology. Journal of Human Evolution 52:16–30.

Piló, L. B. 1998 Morfologia Cárstica e Materiais Constituintes: Dinâmica e Evolução da

Depressão Poligonal Macacos-Baú - Carste de Lagoa Santa, Minas Gerais. Unpublished Ph.D.

dissertation, University of São Paulo, Brazil.

Teltser, P. A. 1991 Generalized Core Technology and Tool Use: A Mississipian Example. Journal

of Field Archaeology 18:363–75.

Table 1. OSL dates for soil samples from the Sumidouro site.

Sample* Depth (m) Over-dispersion (%) Age, central tendency (ka) Age, minimum value (ka)

UW1388 1.96 33.7 12.5 ± 0.9 8.6 ± 0.9

UW1389 1.60 40.2 10.1 ± 0.7 4.8 ± 0.4

UW1390 1.37 39.0 9.9 ± 0.7 6.3 ± 0.6UW1391 0.70 38.2 4.3 ± 0.3 2.7 ± 0.2

UW1392 0.27 64.2 1.9 ± 0.2 0.8 ± 0.1

*All samples processed at the University of Washington

CRP 25, 2008 BUENO 29

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