Pedological characterization of Brazilian archaeo-anthroposols: sambaquis from the lakes region (RJ) and indian dark earths from the low Negro/Solimões river region (AM) / Caracterização pedológica de arqueo-antropossolos no Brasil: sambaquis da Região dos Lagos (RJ) e terras pretas de índio na região do baixo rio Negro/Solimões (AM)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

This work surveyed some anthropogenic soils, the so-called Archaeo-Anthroposols. Those soils show advanced degree of pedogenesis, displaying tokens of their anthropic origin such as chemical and mineralogical characters and soil micromorphology. Some pottery shards are also constantly found in places where pottery making peoples dwelt, as well as shells and human skeletons, whose weathering increases soil pH, and other resistant material, such as stone made instruments and partially charred debris. These archaeologic soils were formed as a result of pre-historic human activity, and they shelter poorly studied cultural remains, so pedologic studies may help reconstruct the environment in which those cultures flourished and the soils began to form. The most widely studied Archaeo-Anthroposols in Brazil are found in the Amazon region, locally known as Indian Dark Earths (IDE), where they may occupy relatively large areas, up to several hectares wide, with thick altered soil mantles and higher chemical fertility than the surrounding non-anthropogenic soils. In coastal regions or in past hinterland riverine-marine systems human ancient human activity originated vast and generally high anthropic shell mounds, known as Sambaquis, which underwent intense pedogenesis and are chemically very rich, mainly in P, Ca, and Mg. The aim of this work was to increase the pedologic knowledge on Archaeo-Anthroposols by studying the anthropic and pedogenetic processes which originated some soil types by relating them to the environment supporting capacity, and comparing and classifying the soils through their physical, chemical and microchemical characterization. The maintenance for a long time span of high nutrient contents was observed in the IDE, which contrasts with the surrounding soils, whose nutrient levels are normally very low. This higher nutrient status in IDE soils is due to the presence of incompletely weathered nutrient sources such as biogenic apatite providing Ca and P; abundant pottery debris providing K and Na; copper, Mn, and Zn are held because of the formation of stable complexes with soil organic matter, which abounds in anthropic soil horizons. In floodplains IDEs, the concentrations of some chemical elements in non-anthropic soil horizons are equivalent to those in anthropic soil horizons, contrary to what is observed in upland IDEs, even without evidence of significant pedobioturbation and eluviation in the floodplains, which is an evidence of anthropic input of earth material from floodplains in the formation of upland IDEs. The main P and Ca sources in the Sambaqui Archaeo-Anthroposols are bone tissues, mollusk shelves and fish bones besides other more labile sources, no longer present in the soil, such as less dense and resistant (non-osseous) mollusk, fish and terrestrial animals tissues. This material is probably the cause of an initial increase in Ca and P levels, which inhibits the dissolution of more stable forms of bone apatite. In older horizons (more ancient human settlements), soil plasma is composed mainly by newly-formed calcium phosphate extremely fine fabric.

ASSUNTO(S)

ambiente environment ciencia do solo pre-history pré-história pedogênese pedogenesis

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