HR: 1330h
AN: OS23A-02    [Abstracts]
TI: Granulometric composition of bottom sediments in the Southwest Atlantic shelf region under influence of the Plata River and the Patos Lagoon
AU: Rodrigues, A P
EM: paim@io.usp.br
AF: Instituto Oceanográfico da Universidade de São Paulo, Pça. do Oceanográfico 191, São Paulo, SP 05508-120 Brazil
AU: Mukherjee, S
EM: swapnamukherjee1@rediffmail.com
AF: Geological Survey of India, 65L/1, Bose Pukur Road, Kolkata, 700042 India
AU: * Campos, E J
EM: edmo@io.usp.br
AF: Instituto Oceanográfico da Universidade de São Paulo, Pça. do Oceanográfico 191, São Paulo, SP 05508-120 Brazil
AU: de Carvalho, F M
EM: flavio@ig.usp.br
AF: Instituto de Goecicências da Universidade de São Paulo, Rua do Lago, São Paulo, SP 05508-900 Brazil
AB: Grain-size analysis was carried out with bottom sediments collected in the region of the southeastern South American continental shelf under influence of the La Plata River and the Patos-Mirim lagoon system outflows. The samples were collected with Box-Core during cruises the of Project LAPLATA, in the Austral winter of 2003 and summer of 2004. In both cases the study area extended from approximately 40°S to 28°S. In the analysis, we preliminarily separated the finest sediment fraction by laundering the samples with water and dried them in a greenhouse. Following, we submitted the samples to a X-ray diffraction analysis. The resulting data set was then processed by a computer program to calculate the relative composition of each considered mineral. A table with the percentages in mass of the components, as well as values of crystallization of illita and smectita, was made with the results. In the samples collected more to the South, we verified the predominance of largest-grain minerals. Amongst lesser minerals we found the illita the predominant, especially in the samples more to the north. The sediment brought by the La Plata River predominates in the region near the river mouth, decaying northward. More to the north, an increase in the amount of larger-grain sediments is verified and could be related to the influence of the Brazil Current.
UR: http://www.labmon.io.usp.br
DE: 3022 Marine sediments--processes and transport
SC: Ocean Sciences [OS]
MN: 2005 Joint Assembly