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.

Archaeological sites within physically “active” soils, such as Vertisols, are considered suspect by archaeologists because of concern for possible disturbance of stratigraphic context. Pedology, micromorphology, and geochemistry are tools useful for assessing soil mixing. Clay-rich floodplain soils (Typic Haplusterts) were examined at the Debra L. Friedkin archaeological site along Buttermilk Creek in southwestern Bell County, Texas, USA. The soil contains abundant lithic (mainly chert) artifacts and was assessed for disturbance by vertic soil processes affecting the stratigraphic integrity of the archaeological materials. Vertic features are only weakly to moderately expressed (slickensides and coarse angular blocky peds) in the field, and they are correspondingly weakly expressed in thin section, consisting mainly of stress cutans around detrital grains, microslickensides, and cross-striated birefringence fabric. Although there is evidence for clay shrink–swell, there has not been significant upward vertical displacement of older materials and no mixing of cultural horizons. Vertical fractures with dark infilling in gilgai microhighs are deep and narrow, and largely preclude downward movement of even small artifacts. Microdebitage is abundant in all levels within the soil profile above culturally sterile layers dated as >15,500 cal. yr B.P. Based on previously published OSL ages and magnetic susceptibility, sedimentation at the site was nearly continuous except for increases during the Younger and Older Dryas, possibly triggered by climate change, and subsequent pedogenesis resulted in uniform element leaching and concentration depth profiles. Vertisols can preserve “undisturbed” Paleoindian archaeological sites and therefore should not be excluded from archaeological surveys and excavations.

Although archaeologists have generally assumed that the ancient landscape in the Teotihuacan Valley was somewhat similar to the present day, recent research has documented large-scale modification of the soil by accelerated human-induced erosion–sedimentation processes from the pre-Hispanic and Colonial periods up until the present. Consequently, the Formative and Classic period soil (approximately 400 B.C.–A.D. 650) is buried in most of the Teotihuacan Valley. Recent soil survey and archaeological excavation have shown that the modern soil horizon differs remarkably from the Teotihuacan soil horizon. In this paper, we present a pedogenic interpretation of the Teotihuacan paleosol referred to as the Black San Pablo Paleosol (BSPP), which contributes to the reconstruction of regional paleoenvironment and human-induced processes. The BSPP has been identified in both natural landscapes and under Classic period Teotihuacan buildings, as well as inside the fill of the Moon Pyramid. Maize pollen and phytoliths testify to the soils use for agriculture, whereas diatoms and phytoliths indicate irrigation practices. These results are supported by soil micromorphology. The evaluation of agronomic properties of the BSPP indicates qualities suitable for agriculture; however, water infiltration is low, indicating possible problems with seasonal water saturation.

Paleosol sequences along the lowest terraces of the Usumacinta River in southern Mexico were used to reconstruct Holocene environmental changes and examine human–environmental interactions. Study sections were correlated through paleosol morphology, radiocarbon dating, and artifact seriation of Formative, Classic, and Postclassic ceramics. The oldest paleosols have gleyic features. Although they contain hard carbonate concretions dating to 5450–5380 cal. yr B.P., these Gleysols formed in the Late Pleistocene to Early Holocene. Carbonates were deposited later. The uppermost paleosols lack gleyic features, the oldest of which contains vertic features, dating to 2000–2700 cal. yr B.P., and contains abundant Formative period ceramics. The upper two paleosols are morphologically less developed and are strongly affected by human activities; radiocarbon ages and ceramic assemblages indicate that they belong to the Maya Classic and Postclassic periods. Stable carbon isotope values from the decalcified organic matter vary among paleosols of different ages and sites. δ¹³C values are highest (−16 to −20‰) in the Formative period paleosol. Although it is possible that maize cultivation could contribute to the isotopic signatures, we believe that the δ¹³C values indicate the dominance of drought-resistant C4 and CAM vegetation due to their association with vertic soils. The Classic period paleosol has a slightly lower isotopic value (−20 to −22‰), while the Postclassic paleosol shows the lowest values (−22 to −23‰), suggesting reforestation of the floodplain. These results indicate that the Early Holocene paleosols formed in a humid climate similar to that of today, which transitions toward dryer conditions around 5500 cal. yr B.P. In the Late Holocene (approximately 3000 B.P.) an increase in seasonality occurs. This condition favored the formation of Vertisols, suitable for agriculture.

The visual and chemical similarity between some chert types and individual outcrops within the same geologic formation often hinders accurate provenance determination. Fourier Transform Infrared reflectance micro-spectroscopy (FTIR-RM) is a nondestructive method demonstrating potential application in chert sourcing. Prior to analysis of archaeological assemblages, the accuracy of the technique and analytical methodology must be tested. The current pilot study examines a geologic sample database of two visually similar chert types (Dover and Fort Payne) in order to determine the technique's ability to differentiate both inter- and intra-outcrop variation. The analysis of these results gives us an improved understanding of the strengths and weaknesses of the FTIR-RM chert provenance technique and associated statistical methodology.

This paper discusses a microsampling technique using a low-technology, diver-assisted percussion coring device that was developed for minimally invasive testing of underwater archaeological sites in turbulent environments, specifically in West Africa. The simple and cost-effective technique is useful across a range of scales including shipwreck sites and larger regions, providing insights into the micro- and macro aspects of submerged sites, including site formation processes. A brief case study of its use on a historical shipwreck site is presented that highlights its efficacy as a data-collection technique used independently or in tandem with more traditional investigative methods such as excavation.