Evolução Quaternária da Baixada de Jacarepaguá a partir de perfis GPR

Abstract

The present work focuses on the Baixada de Jacarepaguá s quaternary evolution using the GPR (Ground Penetrating Radar) method on the area, which is located at the state of Rio de Janeiro. The numerous studies about Baixada de Jacarepaguá based on sea level variation curves in different sectors of the Brazilian coast (MARTIN et al. 1985) as well as radiocarbon dating contributed to the elaboration of an evolutionary model on the Pleistocene and Holocene. This model shows transgressive episodes in 7000-5100 years BP, 3600 years BP and 2700-2500 years BP and regressive episodes at 5100-3900 years BP, 3600-2700 years BP e after 2500 years BP. These relative sea level variation episodes caused, as consequence, the Baixada de Jacarepaguá s constant evolution, from a state of barrier-island with one internal and afterwards, one external barrier that resulted from the plain inundation by the transgressive maritime episodes, to a state of coastal plain emerged in regressive episodes, with progressive barrier and erosive associated process. This evolutionary model does not include processed data obtained with the GPR method that allows a reflector s profile generation based on electric discontinuities on the surface, using high frequency electromagnetic impulses. The profiles raised and processed for this work allowed a confirmation of this evolutionary model, proving a succession of migrations of a beach profile and sedimentary geometry associated in answer to numerous local eustatic variations.