Marine reservoir effect on the Southeastern coast of Brazil: results from the Tarioba shellmound paired samples

On the Southeastern coast of Brazil the presence of many archaeological shellmounds offers a great potential for studying the radiocarbon marine reservoir effect (MRE). However, very few such studies are available for this region. These archaeological settlements, mostly dating from 5 to 2 kyr cal BP, include both terrestrial and marine remains in good stratigraphic context and secure association, enabling the comparison of different carbon reservoirs. In a previous study the chronology of the Sambaqui da Tarioba, located in Rio de Janeiro state, Brazil, was established based on marine mollusc shells and charcoal samples from hearths, from several layers in two excavated sectors. We now compare the different materials with the aim of studying the MRE in this region. Calibration was performed with Oxford software OxCal v4.2.3 using the marine curve Marine13 with an undetermined offset to account for local corrections for shell samples, and the atmospheric curve SHCal13 for charcoal samples. The distribution of results considering a phase model indicates a ΔR value of −127 ± 67 ¹⁴C yr in the 1 sigma range and the multi-paired approach leads to a mean value of −110 ± 94 ¹⁴C yr. - Highlights: • We estimate Marine Reservoir Effect on the coast of Rio de Janeiro State. • We study the Tarioba shellmound. • Marine shells and Charcoal from hearths are used as paired samples. • We calculate ΔR from a phase model in the OxCal software. • We compare the results with the multipair approach