Análise palinológica do Testemunho Bom Jesus, planície costeira interna do município de Soure, Ilha do Marajó/PA.

Abstract

The Marajó Island located at Pará State presents a coastal plain composed by several coastal ecosystems as mangroves, sandy flats, forests tidal flooded and grasses seasonal flooded. This work goal to study modifies of the vegetation this place as the result of climatic, ecologic and environmental changes on course of the Superior Holocene. The high resolution pollen analysis was applied according conventional method for Quaternary Palynology on 6 superficial mud samples and others 16 mud sediment samples obtained of the top portion TBJ core (1,25 m depth) with 4,20 m total depth, obtained from Bom Jesus Farm, Soure County by applications of the vibracore method. The results revealed modifications on the composition and relative abundance of pollen types, along of the sedimentary sequence, dated at 2730 ± 40 years B. P. Three palaeocozones was defined for relative abundance pollen diagrams, concentration pollen diagrams and presence/absence pollen diagrams. The results of the pollen analysis on superficial samples show that there is an actual replace of the mangrove by migration of the grasses seasonal flooded, under erosion conditions, which originate beach ridges deposits near to the ocean. The mangrove ecosystem was dominant ali sedimentary sequence of the TBJ core and was represented mainly for Rhizophora pollen type, which reaches 88% of the maximum relative abundance. However, hydrological variation was repeated and seems have cased locally a reduction of the mangrove forest and the increase of the pollen elements of the others coastal ecosystems mentioned. Ecological index as species richness, diversity (Shannon's index) and Equability was applied on pollen data for evaluation of the impacts these environmental changes. Thus, the present study contributed for the knowledge on vegetation history of the Amazonian Coastal Plain during Upper Holocene.