Impact of the Holocene sea-level changes in coastal, eastern and Central Amazonia

Pollen records from six sites are summarised and compared to provide insights in Holocene changes in the Amazon coastal and lowland regions of northern Brazil. The hydrology of Amazonian wetlands, especially those in the eastern part of the Basin, is strongly influenced by the Atlantic sea-level. Rapid sea-level rise in the early Holocene stabilized at near modern levels at ca. 7500 C-14 yr B.P. Mangroves first occur in coastal sequences of northeastern Pari State about 7500 C-14 yr B.P. The arrival of the mangroves in the pollen sequences is taken as an indication of sea-level. The retreat of mangroves after about 6700 C-14 yr B.P. reflects a lower relative sea-level. The modem mangroves developed mostly between 4000 and 3500 C-14 yr B.P. or somewhat later at the present-day coastline. First impact of early Holocene sea-level rise in the Amazon Basin is found by the change of active to passive river systems between at ca. 8300 and 8000 C-14 yr B.P. Later, local Mauritia palm swamps developed along river margins in central and eastern Amazonia. The timing and length of this period differs and is probably related to the different location and topography of the rivers. It is suggested that the Mauritia palm swamp stage is a regional phenomenon for the whole low lying Amazon Basin. First vdrzea and igapo forests (seasonally inundated forests) developed at that time as well, but the area of this seasonally inundated forests was still small. The modem large extension of virzea and igapo forest areas is relatively young in age. In eastern Amazonia, marked increase of varzea/igapo forests is documented since 3120 C-14 yr B.P., especially since 2470 C-14 yr B.P., and in central Amazonia since 4070 C-14 yr B.P. and especially since 2080 C-14 yr B.P. The development of huge seasonally inundated areas must have had an important influence on the Amazonian water and carbon cycle and the regional climate in Amazonia.