Diversidade e composição de paleomangues holocênicos da Costa Norte Amazônica

Abstract

Mangroves stand out as a landscape unit, associated with mudflats, typical of tropical low coasts. Mangrove plant species are specialized and zoned according to various environmental factors, which also determine their structure. Other plant species that are not exclusive to mangroves are associated with contiguous or non-mangrove environments. However, differences in local species richness originate from the particular history and biogeographical circumstances of each region, completely apart from the local contemporary environment. The present work aims to determine and evaluate the diversity of pollen grains along a Holocene sedimentary sequence, located in Lago da Aranha, municipality of Magalhães Barata, Pa. The data were generated from palynological studies on a 5, 28m core site using standard analytical techniques at 5 em intervals. Pollen types were obtained from the counting of 500 grains/ 2cm stratigraphic level. The composition of pollen types varied over time, defining three distinct palynological assemblages, indicative of environmental changes associated with sea level variations: a transgressive basal sequence, dated 6,850 ± 40 years B.P. with muddy sediments and associated mangrove; a regressive intermediate sequence, dated 4,943 ± 40 years B.P. with peat and associated igapó; a transgressive upper sequence, dated 2,350 ± 40 years B.P. with mangrove and floodplain associated with muddy sediments. The data were compared to four other mangrove palynological study sites: Santos/SP, Lake Aquiri/MA, Bragança/PA and Maná River/French Guiana.