The University of Arizona

From an Estuary to a Freshwater Lake: A Paleo-Estuary Evolution in the Context of Holocene Sea-Level Fluctuations, Southeastern Brazil

Antonio Alvaro Buso Junior, Luiz Carlos Ruiz Pessenda, Paulo Eduardo de Oliveira, Paulo César Fonseca Giannini, Marcelo Cancela Lisboa Cohen, Cecília Volkmer-Ribeiro, Sonia Maria Barros de Oliveira, Deborah Ines Teixeira Favaro, Dilce de Fátima Rossetti, Flávio Lima Lorente, Marcos Antonio Borotti Filho, Jolimar Antonio Schiavo, José Albertino Bendassolli, M C França, J T F Guimaraes, Geovane Souza Siqueira

Abstract


A sediment core was studied to characterize the influences of Holocene sea-level variations in the Barra Seca River valley, in the Atlantic rainforest, Linhares, Espírito Santo, southeastern Brazil. Biological proxies (pollen, spores, and sponge spicules), 14C dating, granulometry, δ13C, δ15N, C/N and major chemical elements revealed the establishment and the evolution of a paleo-estuary during the interval from ~7700–585 cal BP. During the interval ~7700–7000 cal BP, the study site was occupied by a bay-head delta, the inner portion of the paleo-estuary, presenting the most dense mangrove coverage of the entire record. In the interval ~7000–3200 cal BP, the site was occupied by the central basin, possibly a consequence of the landward migration of the paleo-estuary. This interval presents reduced mangrove coverage, probably due to the permanent flooding of the valley. From ~3200 cal BP, the marine influence at the site decreased probably as result of the seaward migration of the coast line. From ~600 cal BP, the modern floodplain and freshwater lake were established. This interpretation is in agreement with the sea-level curves for the southeastern Brazilian coast, except for the fact that evidence of sea levels lower than the present at ~4000 and ~2500 cal BP as suggested by some authors were not found.

DOI: 10.2458/azu_js_rc.55.16210


Keywords


Estuary; sea-level rise; Holocene; mangrove

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