Maria Cristina de Souza

RESERVOIR EFFECT OF THE SOUTHERN AND SOUTHEASTERN BRAZILIAN COAST

A regional marine reservoir correction ( Δ R) of 33 24 14C yr for southern Brazil was obtained from 6 marine shell samples collected in the states of Santa Catarina and Paran. This work also presents a Δ R estimation of 8 17 14C yr for the southern and southeastern Brazilian coast from the states of Rio de Janeiro to Santa Catarina, obtained by including 7 ages published in previous works. The high variability of R in modern and Holocene samples from the Brazilian coast is also discussed.

A TENTATIVE DETERMINATION OF UPWELLING INFLUENCE ON THE PALEO- SURFICIAL MARINE WATER RESERVOIR EFFECT IN SOUTHEASTERN BRAZIL

Previous work has suggested that seasonal and interannual upwelling of deep, cold, radiocarbon-depleted waters from the South Atlantic has caused variations in the reservoir effect (R) through time along the southern coast of Bra- zil. This work aims to examine the possible upwelling influence on the paleoreservoir age of Brazilian surficial coastal waters based on paired terrestrial/marine samples obtained from archaeological remains. On the Brazilian coast, there are hundreds of shell middens built up by an ancient culture that lived between 6500 to 1500 yr ago, but there are few shell middens located on open-coast sites with a known upwelling influence. Three archaeological sites located in a large headland in Arraial do Cabo and Ilha de Cabo Frio on the southeastern coast of Brazil, with open-ocean conditions and a well-known strong and large upwelling of the Malvinas/Falkland current, were chosen for this study. The 14C age differences between carbonized seed and marine samples varied from 281 ± 44 to 1083 ± 51 14C yr. There are also significant age differences between car- bonized seed samples (977 14C yr) and marine samples (200 and 228 14C yr) from the same archaeological layer that cannot be explained by a reservoir effect or an old-wood effect for charcoal. Therefore, the present data from the southeastern Bra- zilian coast are inconclusive for identifying an upwelling effect on R. To do so, it would be necessary to more precisely define the present-pre-bomb R in upwelling regions, and to analyze paired marine/terrestrial samples that are contemporaneous beyond doubt.

The State of Paraná Beaches

Parana beaches are composed primarily of mature polycyclic fine quartz sand and are characterized by wave-dominated beaches along the open coast and tidal-modified beaches inside the estuaries. At the estuary mouths large ebb-tidal-deltas influence beach sand transport and budget and cause shifts in the shoreline of hundreds of meters during periods of a few (<10) years. In contrast, the open ocean coast, away from the influence of ebb-tidal deltas, has remained stable (<10 m shift) over the last 5–6 decades. Erosion problems on the Parana coast are related to natural coastline shift induced by ebb-tidal delta dynamics as well as human destruction of foredune ridges and constructions over the beach and the beach dynamic fringe. At present time, several erosion problems remain without correct environmental and long- term solutions.

Holocene paleo-sea level changes along the coast of Rio de Janeiro, southern Brazil: Comment on Castro et al. (2014).

The present work discusses and reinterprets paleo-sea level indicators used to build Holocene sea-level curve for the coast of Rio de Janeiro at former works. We conclude that: (a) the paleo-sea levels inferred by vermetid remains show that sea-level has fallen over the past 4400 years, at least; (b) the paleo-sea level inferred by the beachrock facies and dated shells of Jaconé shows that sea-level was near the present elevation between 8198 and 5786 years before present; and (c) several shells from other beachrocks were deposited probably thousands of years after the specimens died and consequently do not allow precise reconstructions of paleo-sea levels. These conclusions differ from the conclusions of the original paper.

Reply to Castro et al. 2018 on “Holocene paleo-sea level changes along the coast of Rio de Janeiro, southern Brazil”.

Discussions are useful to the advance of science, and we appreciate the opportunity to discuss the paper by Castro et al. (2014) for the second time. Here we maintain the interpretations presented in our discussion paper (Angulo et al. 2016). In the discussion paper we emphasized that the vertical position of a paleo-sea level indicator is not the position of the paleo-sea level. We pointed out that: (1) to reconstruct paleo-sea levels it is crucial to determine the vertical distance between the indicators to their present homologous one; (2) margin of errors can only be established if considering the indicators intrinsic characteristics and (3) the interpretation of a sea level 3.0 to 4.5 m below the present one at 11.9 to-11.1 ka BP is in strong contradiction with worldwide established data and would require a detailed discussion. We consider that Castro et al. (2018) do not properly address or answer the comments we made in the discussion paper. More work and discussions are necessary to elucidate several questions that still remain about the sea level behavior in the Holocene.