Elemental signatures of an Amazonian Dark Earth as result of its formation process

Barbosa, Julierme Zimmer; Motta, Antônio Carlos Vargas; Corrêa, Rodrigo Studart; Melo, Vander de Freitas; Muniz, Aleksander Westphal; Martins, G. C.; Silva, Lucas C. R.; Teixeira, W. G.; Young, Scott D.; Broadley, Martin R.

doi:10.1016/j.geoderma.2019.114085

Cited by 18 publications

(14 citation statements)

References 51 publications

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“…Subsequent analysis of Ag, Al, As, Ba, Be, Ca, Cd, Co, Cu, Cr, Cs, Fe, K, Li, Mg, Mn, Mo, Ni, P, Pb, Rb, Se, Sr, Ti, Tl, U, V and Zn was carried out by inductively coupled plasma mass spectrometry (ICP-MS; Model iCAP-Q™, ThermoScientific, Bremen, Germany). All samples were blank-corrected using the operational digestion blanks 6 .…”

Section: Methodsmentioning

confidence: 99%

“…The exceptional fertility of ADEs, combined with a high concentration of pyrogenic carbon 3 , and frequent observations of pre-Columbian artefacts led to their ubiquitous classification as anthropic soils 4 , often referred to as Pretic Anthrosols 5 . The current paradigm of ADE formation postulates that pyrolysis of nutrient-rich biomass created hundreds of high-fertility patches (some as large as 350 hectares) 4 surrounded by the acidic dystrophic soils 6 that covers most of the Amazon basin 7 . However, neither the timing nor the magnitude of human occupation needed for ADE formation is well-defined.…”

Section: Introductionmentioning

confidence: 99%

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A new hypothesis for the origin of Amazonian Dark Earths

et al. 2021

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Amazonian Dark Earths (ADEs) are unusually fertile soils characterised by elevated concentrations of microscopic charcoal particles, which confer their distinctive colouration. Frequent occurrences of pre-Columbian artefacts at ADE sites led to their ubiquitous classification as Anthrosols (soils of anthropic origin). However, it remains unclear how indigenous peoples created areas of high fertility in one of the most nutrient-impoverished environments on Earth. Here, we report new data from a well-studied ADE site in the Brazilian Amazon, which compel us to reconsider its anthropic origin. The amounts of phosphorus and calcium—two of the least abundant macronutrients in the region—are orders of magnitude higher in ADE profiles than in the surrounding soil. The elevated levels of phosphorus and calcium, which are often interpreted as evidence of human activity at other sites, correlate spatially with trace elements that indicate exogenous mineral sources rather than in situ deposition. Stable isotope ratios of neodymium, strontium, and radiocarbon activity of microcharcoal particles also indicate exogenous inputs from alluvial deposition of carbon and mineral elements to ADE profiles, beginning several thousands of years before the earliest evidence of soil management for plant cultivation in the region. Our data suggest that indigenous peoples harnessed natural processes of landscape formation, which led to the unique properties of ADEs, but were not responsible for their genesis. If corroborated elsewhere, this hypothesis would transform our understanding of human influence in Amazonia, opening new frontiers for the sustainable use of tropical landscapes going forward.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A new hypothesis for the origin of Amazonian Dark Earths

et al. 2021

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“…However, the approach is not used to sample profiles. When stratigraphic sections are sampled this commonly happens in vertical series, assuming horizontal homogeneity within a profile (e.g., Arroyo-Kalin, 2012;Barbosa et al, 2020).…”

Section: Evaluation Of the Approachmentioning

confidence: 99%

Making the Invisible Stratigraphy Visible: A Grid-Based, Multi-Proxy Geoarchaeological Study of Umhlatuzana Rockshelter, South Africa

et al. 2021

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Umhlatuzana rockshelter is an archaeological site with an occupational record covering the Middle Stone Age, Later Stone Age, and Iron Age. The presence of both Middle and Later Stone Age assemblages makes Umhlatuzana the ideal location for the study of the MSA–LSA transition (20–40 ka) in southern Africa. This transitional period is characterized by important modifications in stone tool technology, from prepared core technology to a toolkit based on microlith production. These changes are argued to have occurred in response to changes in climate and environment leading up to the Last Glacial Maximum. The deposits bearing the transitional assemblages at Umhlatuzana rockshelter appear homogeneous with no visible stratigraphic boundaries. This study integrates geoarchaeological techniques in order to explore fine-resolution geochemical differentiations of the sediments that are macroscopically invisible, and that will provide insight into (post-)depositional processes over time. Samples were systematically retrieved from the western profile of the site following a grid-based sampling strategy and analyzed for pH, elemental composition (XRF), and Magnetic Susceptibility. Additionally, the results were integrated with preliminary micromorphological observations. Our study reveals a steady, gradual change in the geochemistry of the deposits throughout the Pleistocene, related to a combination of environmental change and occupation intensity. We suggest that the part of the sequence reported to bear Middle to Later Stone Age transitional industries is characterized by wetter environmental conditions compared to the underlying deposits. Additionally, we support results from previous studies that excluded large scale post-depositional movement of the sedimentary sequence. Our study offers a successful multi-proxy approach to systematically sample and study archaeological deposits at the macro and micro scale, integrating a variety of geoarchaeological techniques. The approach provides insight into the depositional and post-depositional history of the site, and allows for questions of stratigraphic integrity, anthropogenic input, preservation, and environmental change to be addressed.

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“…In P3, the superficial diagnostic horizon was classified as anthropic A, due to its thickness > 20 cm, presence of ceramic artifacts and bone remains, and high horizons, reaching up to 355 mg kg -1 in the Au1 horizon of P5. Moreover, in P3, P contents were higher than 100 mg kg -1 in all horizons, at a depth greater than 200 cm; these values come from the bone remains of both animal and human origin, which are also a source of calcium (Mattar et al, 2014;Barbosa et al, 2020).…”

Section: Resultsmentioning

confidence: 87%

Characterization and classification of soils from an Amazonic Biome in western Pará

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Pinheiro

Pereira

et al. 2021

Agraria

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Despite its great soil diversity, the Amazon Biome still lacks pedological studies that would also contributes to the Brazilian Soil Classification System. Based on this, this study aimed to characterize and classify the soils from an area in western Pará state. Six soil profiles were described and collected, characterized both physically and chemically, and then classified according to the Brazilian Soil Classification System. There were soils with anthropic influence with thick superficial horizons, with high levels of organic carbon, Ca 2+ , Mg 2+ and P, differing from the observed pattern concerning non-anthropized soils. A great variability of texture was also observed due to the nature of parental material. A high weathering degree was found in the Entisols located in the floodplain area, with low activity clays and low base saturation. Due to observing a superficial diagnostic anthropic horizon A in "Cambissolos Háplicos" and "Húmicos" profiles, it is suggested to create the "antrópico" (anthropic) subgroup for these soil classes in the Brazilian Soil Classification System.

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Elemental signatures of an Amazonian Dark Earth as result of its formation process

Cited by 18 publications

References 51 publications

A new hypothesis for the origin of Amazonian Dark Earths

A new hypothesis for the origin of Amazonian Dark Earths

Making the Invisible Stratigraphy Visible: A Grid-Based, Multi-Proxy Geoarchaeological Study of Umhlatuzana Rockshelter, South Africa

Characterization and classification of soils from an Amazonic Biome in western Pará

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