Resumo

SCHILLIZZI, Roberto  e  LUNA, Liliana. Paleoambientes lacustres en la sección inferior de la Formación Río Negro, (Mioceno - Plioceno), Río Negro, Argentina. Geoacta [online]. 2008, vol.33, pp.91-96. ISSN 1852-7744.

This paper describes pond paleoenvironments from a marine platform sited in La Lobería, Río Negro Province, Argentina. Ponds are good indicators of paleoenvironmental evolution because they are very sensitive to changes in climatic conditions. The methodology used for this research consisted in dry sieving, X-ray diffractometry analysis and paleontological observations. Three sections belonging to the lower section of the Río Negro formation were determined in the intertidal platform. The lower section is composed of fine-grained greenish gray sandstones deposited in an aeolian dune environment with acueos influence. The middle section consists of stratifield pinkish brown clayey to sandy fine silts with freshwater bivalve remnants and vertebrate footprints. The section is associated to restricted shallow ponds, extending to the NE. This level is overlaid by the upper section made of light bluish gray sandstones with cross to horizontal stratification, being deposited in an aeolian environment. At present the described ponds environment its affected by a strong marine erosion.

Palavras-chave : Paleoponds; Bivalve´s and Mammal foot prints; Río Negro Formation.

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