Navegando por Assunto "Geologia arqueológica"

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Fertilidade, caracterização química, mineralogia e morfologia de cerâmicas e solos de terra preta arqueológica do Sambaqui Jacarequara (Barcarena-Pa)
(Universidade Federal do Pará, 2015-07-08) REIS, André Heron Carvalho dos; SILVEIRA, Maura Imazio da; http://lattes.cnpq.br/1937795556101203; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
Archaeological Black earth (ABE) are soil stains easily found in archaeological sites. Their dark color and fertility contrasts with adjacent soils, which are usually poor in nutrients. Their formation is related to disposal of organic matter coming from old indian villages, besides the presence of “lítico” artifacts, coal and various ceramic fragments of different styles and traditions. However, researches aimed to evaluate the morfology of the ceramic set, its chemical and mineralogical characteristics and also the assessment of the sambaquis’ fertility still rare. These researches may contribute to a great advance in the knowlegde of ABE and its fertility. In addition, they may elucidate some aspects about the living style of the groups involved. This paper aims to advance in this problematic when analising the ceramic fragments (decorated or not decorated) and the archeo- stratigrafic soil layers (defined by cultural and natural features) from the Sambaqui Jacarequara ABE, in Barcarena, Pará. The samples were submitted to chemical and mineralogical analisis by ICP-MS, ICP-OES, DRX, MEV/EDS, optical microscopy, the assessmente of soil fertility and morfological analises (stylistic and technical aspects) of the sambaqui ceramic set. Regarding to the soils, the obtained data demosntrate and high fertility (V >87 e SB >10), light and strongly basic pH (6,02-8,25), a high concentration of P is avaiable (46,5-818,1 mg/dm3), and the amount of the bases composed predominantly by por Ca e Mg, reflecting the chemical composition of the carbonatic material added. These values are highighted in the layers 2, 3B and 3A with major availability P and Ca, while these values are reduced considerably in the base (Layer 6). The soils are predominantly composed by SiO2, Al2O3, CaO, Fe2O3, K2O e MgO (85, 37 %), which refletcs the mineralogy composed by quartz, calcite, argonite, kaolinite. The concentration of P2O5 is considered low (0, 46 %) when compared with the other ABE in the Amazon, possibly presented in amorphous phase. When confrotating with the crustal avarage is visible the slightly high values of SiO2, CaO, TiO2, P2O5 e MnO. In turn, the ceramics shows basic pH (7, 04-8, 00), high values of sum and base saturation (SB >29, 42; V >94, 7) demosntrating their high fertility level. The P avaiable indicates lower values in the ceramics than in the soil (12-389, 9 mg/dm3 ) displaying the FCs contribution to the soil fertility. Their chemical composition is composed by SiO2, Al2O3, CaO, Fe2O3, K2O, TiO2 P2O5 (75, 33 %). 1 0 Mineralogicaly, the ceramics do not differ from the soil, indicating a local origin to the raw material sources. These ones are composed by quartz phases, musccovite, calcite, argonite, anatase, besides the amorphous phase of metakaolinite, which suggests a burning superior to 550ºC. Crystalline stages related to phosphorus were not found. When confronting chemical data with the ceramics morphology, it is possible to notice that fragments with higher volumetric capacity, fined-grained and lower concentrations of grounded shells in the Clay have a higher concentration of P (> 0,70 %), indicating a possible relation between the materials used during the ceramics fabrication, their use and chemical signature. Morphologically, the results qualified the ceramics in the Regional traditional Mina. However, some variations in the decorative patterns were found between the stratigrafic levels: profile’s basis, one occupation composed by ceramics of introverted forms, fined grained, red engobes e major diversity in the antiplastic use, while from layer 3 there is some ceramics characterized by shells with higher fined-grained, plates with plastic decorations (incised, hand-carved) and fragments much more with the absence od engobe. Therefore, it is concluded that the FCs are fundamental to the maintainance of the fertility of the ABE and also the dissimilarities among chemistry, mineralogy, texture and technology of the ceramics of each layer. It also defines three phases of occupation to the sambaqui: the first phase indicates they would have occupied a promontory of the beach next to the river with the use of aquatics resources in temporary villages; the second one demonstrates a permanent use of the area and intense fishing activity with disposal of organic matter in the soils resulting in the ABE; while the last one demonstrates a post sambaqui occupation with fewer dependence of aquatic resources.
Acesso aberto (Open Access)
Mineralogia e química de solo e fragmentos cerâmicos de sítios arqueológicos em Salobo, Carajás-PA
(Universidade Federal do Pará, 2013-07-31) SILVA, Mônia Maria Carvalho da; COSTA, Marcondes Lima da; http://lattes.cnpq.br/1639498384851302
Many archaeological sites in the Amazon are characterized by presenting Dark Earth soils type commonly called Dark Earth Archaeological (ADE), in which the main records of prehistoric human occupation are represented by the most common materials of everyday life such as ceramic fragments (CFs), lithic artifacts and charcoal. The soils are characterized by high ADE fertility conferred by high levels of nutrients such as Ca, Mg, Na, K, Mn, Zn and P, a standout compared to predominantly poor soils of the Amazon. Among the several regions rich in archaeological sites with ADE is the Carajás Mineral Province, more specifically the area of the field of copper mine Solobo, which are situated on the slopes of valleys and even on top of the mountain. In this region, field studies were conducted by researchers at the Goeldi Museum, which delimit two archaeological sites, one called Cachorro Cego containing ADE, and the Orlando site, although rich in CFs is presented devoid of ADE in its composition. Of the two sites, the Cachorro Cego was selected to evaluate the contribution of CFs on soils, especially the ADE on the chemistry of ceramic fragments, particularly regarding the content of phosphorus. For this purpose 14 samples were selected CFs collected at the two sites investigated, as well as six soil samples restricted to Cachorro Cego from soil point where the ceramics were extracted. The ceramics were collected previously cleaned, sprayed and subsequently subjected to mineralogical analysis by XRD and optical microscopy, total chemical analysis by ICP-MS and ICP-OES via alkaline fusion, optical microscopy and scanning fertility analysis. These same analytical techniques were employed in soil samples, except for light and electron microscopy. The results indicate similarities in both chemical composition and mineralogy of the two sites in the CFs investigated. CFs are composed of quartz, albite and metakaolin as major minerals, a background matrix represented by amorphous material, equivalent to metakaolin, and microcline and muscovite as accessory minerals. The analysis emphasize the high content of SiO2, Al2O3 and Na2O, and MgO, CaO and K2O in smaller proportions. The contents of Fe2O3, 5.26% in 5.8% and Cachorro Cego in Orlando showed no correspondence with oxide-hydroxides (goethite and hematite, perhaps maghemite), CFs found in other sites. The concentration of P2O5 is less than 0.5% also at the two sites, contrasting with values observed in most sites ADE. Among the trace elements analyzed, only Y, Zr, Th, Cu, Ga and U stand out with above average crustal values in the two sites studied. The rare earth elements when normalized to chondrites showed enrichment in LREE with subtle positive Ce anomalies and negative. In terms of fertility CFs of Cachorro Cego stand out by high levels of available Ca and available P corresponding to (57.02 mg / dm3 and 2.44 cmol/dm3) against Orlando (13.47 and 1.79 mg/dm3 cmol/dm3). However Orlando stands out in available K (0.77 cmol/dm3) and Mg available (cmol/dm3 1.05) vs 0.42 and 0.63 cmol/dm3 cmol/dm3 respectively. The soils vary in texture Cachorro Cego franco silty to sandy loam, consisting predominantly of quartz and kaolinite, anatase and hematite with a lesser proportion, mirroring themselves in the abundance of SiO2 and Al2O3, with lower contents of Fe2O3 and TiO2. The content of K2O, Na2O, CaO and MgO is very low. The average of the nutrients provided by the soil was 33.49 mg.Kg-1 to P to 55.88 mg.Kg Na+, 59.12 mg. Kg-1 K+, 75.9 mg.Kg-1 for Mg2+ and 835.7 mg.Kg-1 for Ca2+, confirming the signature data ADE. CFs of the two sites are both so similar in their chemical composition and mineralogy, the levels of nutrients such as Ca, Mg, K, Na content presented next except P, higher in TPA. The Cachorro Cego soils are comparable to other Amazon sites, both in mineralogy, chemistry, particle size and in fertility. Apparently CFs contributed to soil fertility TPA, like Cachorro Cego.