ESR dating of a subfossil shell from Couve Island, Ubatuba, Brazil.

The occurrence of subfossil material in bottom sediments of Couve Island, Ubatuba region, São Paulo State, is confirmed. The analyzed material consists of a bivalve shell that was dated by the electron spin resonance technique. By the additive irradiation method an archaeological absorbed dose of (25 +/- 5) Gy was obtained and calibration with other dating works in the same area allows the inference of an age of (25 +/- 5) x 10(2) years. The importance of this finding and its paleoecological implications could contribute to elucidating the nature of short-term environmental changes in the Brazilian coastline during the Holocene, as well as becoming an important tool to the understanding of the distribution and biological aspects of the bivalve fauna.