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| Author(s): |
Flavio Lima Lorente
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Piracicaba. |
| Institution: | Universidade de São Paulo (USP). Centro de Energia Nuclear na Agricultura (CENA/STB) |
| Defense date: | 2015-04-24 |
| Examining board members: |
Luiz Carlos Ruiz Pessenda;
Maria Judite Garcia;
Paulo Cesar Fonseca Giannini;
Karin Elise Bohns Meyer;
Kenitiro Suguio
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| Advisor: | Luiz Carlos Ruiz Pessenda |
| Abstract | |
An interdisciplinary study was carried out in the north coast of the state of the Espírito Santo in order to understand the environmental changes that occurred during the Holocene in the region. The results were obtained from microfossil analyses (palynofacies, phytoliths and palynology), particle size, isotope geochemistry (total organic carbon - TOC, total nitrogen - TN, total sulfur - TS, ?13C, ?15N, C/N and C/S), and radiocarbon dating. The sedimentary deposits studied were obtained from three lakes (Lake Macuco, Lake Bonita and Lake Canto Grande) and one core was sampled in the deltaic plain of Doce River (Li01). Isotopic and elemental values suggest that the sedimentary organic matter was derived from different sources, such as land plants (mostly C3 plants), and marine and/or freshwater phytoplankton. The multidisciplinary data was used to infer the formation of a lagoon-estuarine system between ~ 7,500 cal years BP and ~ 4,000 cal years BP due to increase in relative sea level. Mangrove, \"Restinga\" and Atlantic rainforest vegetation occupied the region. As a consequence of marine regression after ~4,000 years BP, the estuary and mangrove vegetation shifted seaward. The estuarine basin was gradually abandoned and closed off as a result of progradation of the Doce River delta and higher fluvial input. The evolution of Lake Macuco and Lake Bonita was directly related to the changes in relative sea level, while Lake Canto Grande formed as a result of changes in the river input and to the base level. No significant changes in vegetation were observed in the palynological data, and it is likely that the climate was predominantly warm and humid during the Holocene. Palynofacies analysis, in combination with other analyses, proved invaluable as an important tool for paleoenvironmental characterization of lacustrine deposits that evolved under the influence of marine transgression and regression events (AU) | |