The presence of biochar with high carbon accumulation capacity and nutrient adsorption is causally associated with archeological soils. Although this type of soil organic matter has been known for a long time, the knowledge of its structure and environmental behavior is still limited. This work used Raman spectroscopy to obtain structural information and identify alterations in biochar particles. To this end, we studied biochar particles found in an archaeological site with a temporal window lasting 12451 to 11080 yr cal BP. The molecular, structural and sp2/sp3 characteristics of the charcoal particles were determined at the time of burning and associated with the temperature, time and characteristics of the burnt material. We propose that the process of oxidation of the biochar occurs during the first 2000 years after its genesis. The oxidation process is a reflection of decreases in the number of defects related to sp2 bonds on amorphous carbons and increases in the number of defects associated with ionic impurities, which clearly indicate the interaction between biochar particles and the soil matrix. The data confirm the hypothesis that the persistence of biochar in the environment is due to its graphite structure and suggest that over a 12000 year timeframe, biochar particles undergo several changes that occur in the disordered phase and are rapidly oxidized.

No abstract

Os vestígios líticos do sítio GO-JA-03, Serranópolis, estado de Goiás, apresentam uma produção de grandes lascas alongadas, mais e menos espessas, retiradas com percussão de pedra macia ou percussão orgânica tangencial, com procedimentos técnicos muito específicos nas proximidades do talão, as quais servirão de suporte para instrumentos unifaciais de secção plano-convexa. O método de análise compreendeu o conceito de Cadeia Operatória, que considera os instrumentos desde o seu abandono, passando por todas as fases de produção. Os resultados obtidos demonstram uma indústria bem estruturada com um alto nível de savoir-faire.

O objetivo deste artigo é apresentar alguns acidentes de lascamento encontrados em coleções líticas do Brasil Central. Os mesmos estão ligados à qualidade das matérias-primas, à ausência de destreza na realização das técnicas de lascamento, à presença de aprendizes entre os lascadores mais competentes. A fabricação de instrumentos relaciona-se a imagens mentais de ordem cultural e se faz pela sucessão de gestos rápidos, não controláveis visualmente.Eles devem, portanto, ser programados, o que demanda uma longa aprendizagem antes que os mesmos sejam assimilados e realizados de forma inconsciente. O estudo é baseando em análises de coleções a partir de conceitos e autores da Escola Francesa. A partir dos resultados obtidos, propomos uma reflexão sobre o lugar do lascamento e das indústrias líticas nessas sociedades.

The “Santana do Riacho” shelter is one of the oldest human occupation sites in Brazil. Dated to the Late Pleistocene, this shelter contains over 40 buried individuals. The shelter is located on the edge of the Espinhaço Range in Mesoproterozoic quartzites. This study aims to investigate the relationship between human activities and in situ soil formation. To this end, chemical, physical, X‐ray fluorescence, X‐ray diffraction using synchrotron light, micromorphology, and scanning electron microscope with energy‐dispersive X‐ray spectroscopy analyses were performed. In situ anthropogenic practices, such as fires and burials, have had the greatest influence on the geochemical parameters. Pedological processes were clearly detected, including (1) the formation of secondary carbonates; (2) the formation of secondary phosphates; (3) the formation of magnetic Fe nodules, and (4) degradation of magnetite into maghemite. The mobility of P, Ca, and C resulted in the enrichment of these elements in layers stratigraphically considered “sterile.” The amounts of available P, K, Ca, total organic carbon, and the pH values can be considered indicators of human occupation. This study provides information on the pedological processes in rockshelters and represents one of the few pedological and geochemical studies on deposits in a tropical rockshelter in quartzite bedrock.