Palaeoenvironmental Evolution During the Holocene in Itapeva Lake, RS, Brazil:Palynological and Geochemical Records

Meyer K.E.B. Reichnart K. Marques T.M. Ashraf A.R. Mosbrugger V.

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Palaeoenvironmental Evolution During the Holocene in Itapeva Lake, RS, Brazil:Palynological and Geochemical Records

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Based on palynological and geochemical data (Organic Carbon-Corg and Sulphur-S) of sedimentary samples from a vibrocore, considerations about the palaeoenvironmental evolution of Itapeva Lake region during the Holocene are made. The analysed core (BOXVI) consists in its lowermost part of a fine to medium sand packet, rich in glauconitic minerals, whose upper limit is considered to be the Holocene-Pleistocene contact. Using Cluster analysis on palynomorphs combined with Corg and S data, it was possible to distinguish four zones related to the Holocene transgression-regression cycle. Variations in Corg and S data permitted the recognition of changes in palaeosalinity. Zone 1 represents the beginning of the Holocene sedimentation; palynomorphs composition reveals a marsh environment under predominating freshwater conditions. In Zone 2, the occurrence of dinoflagellate cysts and high S values, indicating brackish water, reflects Holocene sea level highstand around 5100yrs. B.P. High concentration of Cyperaceae associated with a significant increase in Corg in Zone 3 indicates a typical marsh environment influenced at least sometimes by higher saline water, reflecting a regression phase. Salvinia natans (L)All. and Cyperaceae grains are considered to be the most significant palynomorpha in Zone 4, characterising a freshwater marsh. Based on the occurrence of dinoflagellates sample 2, Operculodinium sp., related to marine to estuarine environments, a question arises regarding about the time at which Barrier Ⅳ became completely closed.

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《世界地质：英文版》 |2002年第2期|142-156|共15页
作者
Meyer K.E.B. Reichnart K. Marques T.M. Ashraf A.R. Mosbrugger V.;
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作者单位

Bolsista do CNPq Brazil-Prograrna de Pós-Graduacāo em Geociencias;

Institute de Geociencias;

UFRGS;

Agronomia;

Caixa Postal 15001;

CEP 91501-970;

Porto Alegre;

RS;

Brazil Johann Wolfgang Goethe University;

Institute of Geology and Palaentology;

Frankfurt/Main;

D-60054;

Germany Bolsista do CNPq Brazil-Prograrna de Pós-Graduacāo em Geociencias;

Institute de Geociencias;

UFRGS;

Agronomia;

Caixa Postal 15001;

CEP 91501-970;

Porto Alegre;

RS;

Brazil Institute of Geology;

University of Tuebingen;

Tuebingen;

D-72076;

Germany Institute of Geology;

University of Tuebingen;

Tuebingen;

D-72076;

Germany;

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原文格式 PDF
正文语种 chi
中图分类世界政治;
关键词
Holocene; South; Brazil; Palaeoenvironment; Palynology; Organic; Carbon; Sulphur;

机译：全新世;巴西南部;古环境;古生物学;有机碳;硫;

Palaeoenvironmental Evolution During the Holocene in Itapeva Lake, RS, Brazil:Palynological and Geochemical Records

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