Estúdio palinológico de las formaciones Lõpez de Bertodano y sobral, Isla Vicecomodoro Marambio, Antártida

Alicia M Baldoni, Viviana Barreda

Resumo


The present paper deals with the palynomorph content in the López de Bertodano and Sobral Formations, cropping out on Vicecomodoro Marambio (Seymour) Island, Antarctica. In the López de Bertodano Fm., marine phytoplankton is dominant, but Nothofagidites spp (mainly "brassi" type), podocarpaceous species (Podocarpidites, Microcachrydites, Phyllocladidites and Dacrydiumites), some proteaceous pollen and pteridophyte spores (Perotrilites, Lycopodiumsporites, Laevigatosporites, Baculatisporites and Azolla sp.) are also present. The dominant palynomorphs in the lower part of the Sobral Formation are dinoflagellates, accompanied by a poor assemblage composed of Nothofagidites sp., proteaceous pollen and pteridophyte spores. The continental association is more frequent in the middle part of the sequences; in this same levei the best development of the podocarpaceous group is registered. Recycled palynomorphs of Permian? age are present in both formations. The palynological content of the López de Bertodano and Sobral Formations was compared with those of the Cerro Dorotea (Maastrichtian-Paleocene), Bororó (Paleocene), Salamanca (Paleocene), Rio Chico (Paleocene) and Rio Turbio (Eocene) Formations from Argentina and with those of the Rio Blanco (Maastrichtian), Cheuquemó (Eocene) and Loreto (Eocene-Oligocene) Formations from Chile, and it was concluded that the López de Bertodano Formation has practically no exclusive elements in common with the units under consideration, while the Sobral Formation presents the greatest number of resemblances with the Rio Turbio Formation. Finally, the different groups represented in the units were treated statistically. A clear marine advance, indicated by an increase of paleomicroplankton, was evident at the base of the Sobral Formation. As far as continental representatives are concerned, spores have quite an even distribution in ali the sequence, even though there is a slight predominance in the López de Bertodano Formation and at the base of the Sobral Formation; gymnosperms show, on the contrary, a greater development in the middle and upper sections of the latter. Angiosperms, for their part, have three peaks of maximum abundance ali within the Sobral Formation

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DOI: http://dx.doi.org/10.11606/issn.2316-8986.v17i0p89-96

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