Recuperação de palinomorfos e dados isotópicos (δ13C e δ15N) em sedimentos turfosos e seu significado paleoambiental para a região de Campo Mourão/PR (Palynomorphs and Isotopic Data (δ13c and δ15n) recovery from peaty sediment and its ...)
DOI:
https://doi.org/10.5935/1984-2295.20160080Keywords:
Palinologia, Quaternário, Holoceno, Cerrado.Abstract
O município de Campo Mourão está situado em zona de transição entre a Floresta Ombrófila Mista e Floresta Estacional Semidecidual com enclaves de Cerrado. O professor Reinhard Maack (1892-1969) foi o primeiro a admitir a hipótese de que o Cerrado seria um relicto de climas mais secos no Quaternário. Visando entender a origem dessa vegetação na região, estudou-se os palinomorfos presentes em um testemunho sedimentar (110cm) obtido na planície aluvial do rio Água dos Papagaios. Associou-se à quantificação dos palinomorfos dados isotópicos (δ13C e δ15N), além de datações (14C) nas profundidades de 75 cm (7.280 anos cal. A.P.) e 45 cm (3.248 anos cal. A.P.). O sedimento não apresentou boa preservação polínica (menos de 400 grãos na maioria dos intervalos avaliados), entretanto a ocorrência de esporos de pteridófitas, briófitas e algas alcançaram valores superiores a 50% dos palinomorfos ao longo do testemunho. Foram observados grãos de pólen de Caryocariaceae e Araucariaceae na porção basal (75-110cm), nestes intervalos os valores de δ13C evidenciam a predominância de plantas C4 (campo), tal situação sugere a existência de Cerrado na região desde o Holoceno Médio. Nos intervalos superficiais tem-se o empobrecimento isotópico, aumento de plantas C3 em relação a plantas C4. Os dados de δ15N sugerem que a planície sempre possuiu alguma umidade, fato reforçado pela presença constante de Pseudoschizaea ao longo do perfil. As interpretações estabelecidas nesta pesquisa corroboram os dados paleoambientais estabelecidos pela recuperação e quantificação de fitólitos com o mesmo testemunho, mostrando fases mais secas que a atual durante o Holoceno.
A B S T R A C T
The municipality of Campo Mourao is located in the transition zone between the Araucaria Forest and Forest Semideciduous with Cerrado enclaves. The professor Reinhard Maack (1892-1969) was the first to hypothesize that the Cerrado would be a relict of the driest climates in the Quaternary. With the objective to understand the origin of this vegetation in the region, we have studied the palinomorphs present in a sedimentary record (110cm) obtained in the floodplain of the Água dos Papagaios river. Associated to the quantification of palinomorphs isotopic (δ13C and δ15N), and datings (14C) in the depths of 75cm (7,280 years cal. BP.) and 45 cm (3,248 years cal. BP.). The sediment did not show good preservation pollen (less than 400 grains in most intervals evaluated), however, the occurrence of spores of pteridophyte, bryophytes and algae reached values higher than 50% of palynomorphs along the testimony. Caryocariaceae and Araucariaceae pollen grains were observed in the basal portion (75-110cm), these intervals δ13C values show the predominance of C4 plants (field), this situation suggests the existence of Cerrado in the region since the Middle Holocene. In intervals surface has isotope impoverishment, increased C3 plants in relation to C4 plants. The δ15N data suggest that the plain has always some moisture, actually enhanced by the constant presence of Pseudoschizaea water along the profile. Interpretations established in this study corroborate the paleoenvironmental data set for recovery and quantification fitolítica with the same testimony, showing drier stages that the current during the Holocene.
Keywords: Palynology; Quaternary; Holocene; Cerrado
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Copyright (c) 2016 Daianne Patrícia Pulcinelli Tavares Ladchuk, Mauro Parolin, Soraia Girardi Bauermann
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