Palinologia holocênica do testemunho Bom Jesus, margem leste da ilha do Marajó, Pará, Amazônia

Abstract

RESUMOA porção superior (1,25m) do testemunho de sondagem Bom Jesus (TBJ), coletado no limite campo-mangue da Fazenda Bom Jesus, município de Soure, ilha do Marajó, Pará, Brasil, foi estudada através de análise palinológica de alta resolução objetivando a determinação da composição, abundância e diversidade de tipos polínicos bioindicadores de modificações na paleovegetação durante o Holoceno. 16 amostras sedimentares de 2cm 3 foram tratadas de acordo com metodologia padrão em palinologia. Os programas Tilia e Tilia Graph foram utilizados para a construção dos diagramas palinológicos de abundância e concentração. A base do testemunho foi datada por 14 C em 2730 ± 40 anos A.P. Foram definidas três zonas palinológicas. A presença de pólen de Rhizophora com abundância máxima de 88% apontou dominância de mangue ao longo de todo o testemunho sedimentar. Variações recorrentes na hidrodinâmica da baía do Marajó, caracterizadas por pulsos erosivos de curto período, parecem ter provocado redução na dominância de mangue. O incremento na abundância de tipos polínicos bioindicadores de campo inundável associados a elementos de restinga e floresta, evidenciam a migração do campo inundável sobre o manguezal. Os dados indicam correlação com outros registros polínicos holocênicos de transgressão marinha para a costa norte amazônica no Holoceno Superior. PALAVRAS-CHAVE: palinologia, manguezal; planície costeira, Holoceno, Amazônia. Palynological study of Holocene sediments of Bom Jesus core, east margin of the Marajó Island, Pará, Amazonia ABSTRACTThe upper portion (1.25 m) of the sediment core Bom Jesus (TBJ), was collected in the field-mangrove limit of Bom Jesus Farm, municipality of Soure, island of Marajó, Pará, Brazil, was studied through pollen analysis high resolution aimed at determining the composition, abundance and diversity of the pollen types bioindicators of changes in the palaeobotany. 16 samples of sedimentary 2cm 3 were treated according to standard methodology. Tilia and Tilia Graph software were used for to construct abundance and concentration palinological diagrams. The core base was dated by 14 C in 2730 ± 40 years AP. Three palynological zones were identified. The mangrove ecosystem was dominant all sedimentary sequence of the TBJ core and was represented mainly for Rhizophora pollen type, which reaches 88% of the maximum relative abundance. Variations applicant hydrodynamics in the Marajó bay, characterized by short pulses of erosive period, seem to have caused reduction in the dominance of mangroves. The increase in the abundance of types growth bioindicators of field associated with elements of swamp forest and restinga, indicate the migration of the field on the mangrove swamp. The data show correlation with other palynological records of Holocene marine transgression to the north coast in the Upper Amazon Holocene.

Late Holocene Palynological Record and Landscape Change From the Piraquê-Açu and Piraquê-Mirim Estuarine System, Espírito Santo, Brazil

“…It was well preserved in estuaries and bay regions, and has also been observed by other authors (Behling et al, 2004;Barth et al, 2006;Rodrigues and Senna, 2011) in sediment cores collected in the North, Northeast and Southeast regions of Brazil.…”

“…These studies play an important role in understanding the dynamics of the vegetation along the Holocene to the coastal regions that are under the influence of both rivers and sea (Miranda et al, 2002). In Brazil, there are few studies of palynological approach-developed estuaries, the most concentrated being in the North (Behling et al, 2004;Cohen et al, 2005;Vedel et al, 2006;Rodrigues and Senna, 2011). Some studies have focused on the Northeastern (Behling and Costa, 1997), Southeastern (Belem, 1985;Amaral et al, 2006;Barth et al, 2006) and Southern regions (Medeanic, 2006).…”