Mid- to Late-Holocene estuarine infilling processes studied by radiocarbon dates, high resolution seismic and biofacies at Vitoria Bay, Espirito Santo, Southeastern Brazil

Anais da Academia Brasileira de Ciências

Alex C. Bastos²  Claudia G. Vilela¹  Valéria S. Quaresma²  Fabiana K. Almeida² 

[1] ,Universidade Federal do Espírito Santo Departamento de Oceanografia e Ecologia Laboratório de Oceanografia GeológicaVitória ES ,Brasil

关键词: high-resolution seismic;    Holocene estuarine evolution;    radiocarbon dating;    Vitoria Bay;    biofacies;    sísmica de alta-resolução;    evolução estuarina holocênica;    datação por radiocarbono;    Baía de Vitória;    biofácies;   

DOI  :  10.1590/S0001-37652010000300022

来源: SciELO

【 摘 要 】

Vitoria Bay is a 20 km long estuary, morphologically narrow, with a microtidal regime and, as other modern estuaries, was formed during the last post-glacial transgression. The estuarine bed morphology is characterised by a main natural channel limited by tidal flats with developed mangroves. Original radiocarbon dates were obtained for the site. Five radiocarbon ages ranging from 1,010 to 7,240 years BP were obtained from two sedimentary cores, which represent a 5 m thick stratigraphic sequence. The results indicate that, until about 4,000 cal. yrs BP, environmental conditions in Vitoria Bay were still of an open bay, with a free and wide connection with marine waters. During the last 4,000 yrs, the bay has experienced a major regression phase, by becoming more restricted in terms of seawater circulation and probably increasing tidal energy. Three main stratigraphic surfaces were recognised, which limit trangressive, trangressive/highstand and regressive facies. The present channel morphology represents a tidal scouring surface or a tidal diastem, which erodes and truncates regressive facies bedding. Foraminiferal biofacies, which change from marine to brackish and mangrove tidal-flat environments, support the seismic stratigraphic interpretation. Absence of mangrove biofacies at one of the two cores is also an indication of modern tidal ravinement.

【 授权许可】

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