O significado das datações ao 14C na reconstrução de paleoníveis marinhos e na evolução das barreiras quaternárias do litoral paranaense

The 14 C datations are one of the main tools to reconstruct paleo-sea levels and to understand the Quaternary barriers evolution. This paper discusses the significance of 33 14 C dated samples on paleo-sea level reconstruction and in the interpretation of Upper Pleistocene and Holocene barrier evolution in the State of Parana . We have concluded that: (a) it is unlikely that humic and fulvic acids are influencing the dating of wood samples from sediments impregnated with organic matter; (b) in situ reef remains, composed mainly of vermetid tubes of Petaloconchus (Macrophragma) varians , are the most precise and reliable paleo-sea level indicators found in the coast of Parana, showing a margin of error around ±1,0 m; (c) the height of the top of the shell banks, composed mainly of Anomalocardia brasiliana and containing abundant shells in live position, indicates a paleo-sea level equal or higher than the mean sea level during the organisms’ lifetime; (d) the interpretation of paleo-sea level through composed indicators provide only maximum ages because the dated-sample could be older than the sedimentary structure used to determine paleo-sea level; (e) the marine paleo-sea level indicators suggest that, during the Late Pleistocene, the sea reached > 4.0 m above present sea level; (f) dating of vermetid tubes indicates that the maximum Holocene sea level on the Parana coast occurred between 5370 and 4630 years B.P.; (g) the Holocene high maximum was about 3.5-3.6 ± 1.0 m; (h) after the maximum, the sea level gradually dropped, but the possibility of the occurrence of decimeter oscillations is not rejected; (i) the paleo-sea level inferred from mollusk banks, mainly composed of Anomalocardia brasiliana, and composed indicators, such as sedimentary structures associated with transported shells and wood fragments, agree with paleo-sea levels inferred from vermetid tubes on the Parana coast.