Palynofacies and stable C and N isotopes of Holocene sediments from Lake Macuco (Linhares, Espirito Santo, southeastern Brazil): Depositional settings and palaeoenvironmental evolution

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Lorente, Flavio Lima ; Ruiz Pessenda, Luiz Carlos ; Oboh-Ikuenobe, Francisca ; Buso, Antonio Alvaro, Jr. ; Lisboa Cohen, Marcelo Cancela ; Bohns Meyer, Karin Elise ; Fonseca Giannini, Paulo Cesar ; de Oliveira, Paulo Eduardo ; Rossetti, Dilce de Fatima ; Borotti Filho, Marcos Antonio ; Franca, Marlon Carlos ; de Castro, Darcilea Ferreira ; Bendassolli, Jose Albertino ; Macario, Kita

• Tipo de documento: Artigo Científico
• Fonte: PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY; v. 415, p. 14-pg., 2014-12-01.

Resumo

Particulate organic matter in sediments constitutes a valuable proxy for paleoenvironmental reconstructions. A 192 cm lacustrine sediment core (similar to 7521 cal yr. B.P.) from the northern coast of the State of Espirito Santo, southeastern Brazil, was radiocarbon dated and then analyzed for palynofacies, stable isotopes (C and N), and grain size. The values for total organic carbon - TOC (1.91% to 20.89%), total nitrogen - TN (0.08% to 1.1%), delta C-13 (-27.10 parts per thousand to -29.01 parts per thousand), delta N-15 (1.92 parts per thousand to 5.09 parts per thousand) and C/N (12.87 to 50.11) suggest predominance of C-3 plants and changing mixtures of terrestrial and aquatic organic matter in the sediments. Palynofacies and cluster analyses were used to identify four palynofacies associations that reflect different phases in the Lake Macuco evolution. Palynofacies 1 (192 to 106 cm, similar to 7521 cal yr. B.P. to similar to 7054 cal yr. B.P.-interpolated age) is characterized mainly by amorphous organic matter (AOM), non-opaque phytoclasts (NOPs), mangrove pollen grains (Rhizophora sp. L. 1753 and Avicennia sp. L. 1753), and foraminiferal test linings. Palynofacies 2 (106 to 65 cm, similar to 7054 cal yr. B.P. interpolated age to similar to 4847 cal yr. B.P.) is dominated by NOPs and AOM, with an increase in the values of mangrove pollen grains relative to Palynofacies 1. Both palynofacies reflect marine and fluvial influences in a depositional environment related to the development of an estuarine system during the mid-Holocene transgressive stage. Palynofacies 3 (65 to 27 cm, similar to 4847 cal yr. B.P. to similar to 3800 cal yr. B.P.-interpolated age) comprises high abundances of fluvial elements (NOP and opaque phytoclasts-OP) and low values of AOM. The depositional environment is interpreted as being an estuary during the marine regression, with the displacement of the estuarine basin and mangroves towards the sea. Palynofacies 4 (27 to 0 cm, <similar to 3800 cal yr. B.P.) is characterized by the predominance of AOM and NOP, increase in the values of freshwater algae, and no evidence of marine influence. This last phase reflects the beginning of the establishment of Lake Macuco and floodplain of the Barra Seca River under conditions similar to the present-day. (C) 2013 Elsevier B.V. All rights reserved. (AU)

• Processo FAPESP: 11/00995-7 - Estudos paleoambientais interdisciplinares na costa do Espírito Santo
• Beneficiário: Luiz Carlos Ruiz Pessenda
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Temático
• Processo FAPESP: 10/52606-1 - Caracterizacao paleoambiental de depositos quaternarios da costa norte do estado do espirito santo (es-brasil): uma abordagem interdisciplinar.
• Beneficiário: Flávio Lima Lorente
• Modalidade de apoio: Bolsas no Brasil - Doutorado