Abstract
Relative sea-level curves have been delineated for several sectors of the Brazilian coast. In order to have homogeneous and consistent curves, very short segments of the coastline with the same framework are considered. To minimize systematic errors tied to the particular nature of an indicator, we use the maximum number of different indicators available from former positions of relative sea level. These sea-level curves show that, during the last 7000 years, the central Brazilian coast has been subjected to a submergence phase which lasted until 5100 14C yr BP (5600 cal yr BP), followed by a drop in sea level. This drop in sea level was not continuous but was interrupted by two high-frequency oscillations. The Salvador curve, the most detailed, can be used as a reference for the central portion of the Brazilian coastline. It is now presented with corrections for isotopic fractionation and reservoir effects as well as calibrations for astronomical ages. Additional supporting evidence for the existence of high-frequency oscillations is provided. They are of the same magnitude as is predicted for the future under greenhouse conditions. These data will help us to understand how the coastal systems will respond to these sea-level changes.
Highlights
Curvas de variações do nível relativo do mar foram construidas para diversos setores do litoral brasileiro
Angulo & Lessa (1997), using sea-level reconstructions based exclusively on 14C dating of vermetid incrustations, have published a new sea-level curve for Brazil in which they questioned the existence of these oscillations and the maximum of the Holocene transgression reported above
Relative sea-level curves constructed for the last several thousand years provide an important reference against which the evolution of the coastal zone can be investigated
Summary
To reconstruct an ancient position of relative sea-level, it is necessary to fix a past sea-level record in space and time (Martin et al, 1986a). One should not forget that there are numerous sources of error in the definition, in space and time, of past sea-level positions.each reconstruction should be plotted along with error bars for the estimated altitude and the measured age of the sea-level indicator used. One should not forget that, despite exercising the utmost care in the sampling and analysis, some dates might exhibit totally incoherent results It is necessary, in order to outline a curve of variations of relative mean sea-level, to have numerous ancient sea-level reconstructions, well distributed in time. The archaeological and isotopic records do not provide precise reconstructions of past sea levels they can provide constraints or supporting evidence for information from other sources, times of maximum and minimum expansion of coastal lagoons
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