Dinâmica temporal na lagoa do Campelo, região norte do Estado do Rio de Janeiro, baseada em estudos palinológicos

Abstract

RESUMO - Este trabalho visa analisar os processos temporais que influenciaram a sedimentacao de palinomorfos em depositos da lagoa do Campelo (municipio de Campos dos Goitacazes, Estado do Rio de Janeiro). Formada no Holoceno, durante a colmatacao de uma vasta paleolaguna, a lagoa conectava-se ao rio Paraiba do Sul pelo canal da Cataia, que a alimentava de agua durante as cheias. Obras de drenagem realizadas em 1950 mudaram a configuracao geomorfologica original e geraram dois novos canais, um ligando a lagoa ao rio, outro ao mar, que, por varios motivos, acabaram transformando em negativo o balanco hidrico da lagoa. As analises das amostras refletiram uma vegetacao hidrofita bem representada em cerca de 2.790 anos A.P.( 14 ABSTRACT - TEMPORAL DYNAMICS IN LAGOA DO CAMPELO, NORTHERN REGION OF THE STATE OF RIO DE JANEIRO, BASED ON PALYNOLOGYCAL STUDIES. This study aims to analyze the temporal processes that influenced the palynomorph sedimentation in the Campelo Lake (Campos dos Goitacazes municipality, Rio de Janeiro State, Brazil). Formed during the Holocene by the isolation of a large paleolagoon, this lake was connected in the past to the Paraiba do Sul River by Cataia's channel which fed it with waters during the inundations. Drainage modifications in the Campos municipality realized in 1950 changed the geomorphological configuration of the Campelo Lake and two new channels were constructed, connecting the lake to the river and to the sea, respectively, which transformed in negative the hydrological balancing of the lake by several reasons. The palynological analysis reflected around 2,790 years B.P. ( 14 C conventional age) hydrophytic vegetation well represented, with low number of pollen types and a high Pseudoschizaea deposition characterizing the development of a wet environment with lower water level. That period corresponded to the descent of the sea level initiated in 2,800 years B.P. which carried the progradation of the outlet of the Paraiba do Sul River. With the elevation of sea level starting from 2,700 years B.P., that causes the erosion in the outlet of the river Paraiba, occurred a progressive damming of waters in the low plain. Near the period of a maximum sea level around 2.500 years B.P. (interpolated age) pollen deposition in the local was facilitated by the rise of water level in the lake. About 2,320 years B.P. ( 14 C conventional age) the Rate of Total Accumulation of palinomorphs was very high, mostly by increase of the herbaceous types and of the hydrophytes. In the location of the core the sedimentation behind 2,320 years B.P. was practically null.