No abstract

-SPONGE SPICULES AND CHANGES IN SEA LEVEL IN THE IGUAPE REGION, SOUTHEAST BRAZIL. Sponge spicules recorded in peaty sediments obtained by coring (520 cm depth) was analyzed in order to detail the paleoenvironmental changes in the lower course of the Ribeira de Iguape River (Iguape/SP -24º34'17"S/47º37'33"W) in southeast Brazil. The sediment core was dated at three horizons using radiocarbon dating as follows: (i) 6,240± 30 years BP at 430 cm; (ii) 4,500± 25 years BP at 225 cm and (iii) 2,920±25 years BP at 145 cm. Gemmoscleres of the continental sponge Oncosclera navicella (Carter) and microscleres of Corvoheteromeyenia sp. were identified, as were spicules of marine sponges, but these could not be determined to the species level. The variations in the content between of marine and continental sponge spicules indicated: (i) a phase with a predominance of freshwater flows when sea level was lower than at present prior to 6,240 years BP; (ii) a phase of marine transgression that started at least 6,240 years BP; (iii) a phase with large fluctuations in sea level between 6,240 and 4,500 years BP; and (iv) a phase with a predominance of freshwater flows between 4,500 and 2,920 years BP. The results also suggest a possible change in the direction of the channel of the Ribeira de Iguape River to the west of the study site during the Holocene.