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Revista geológica de Chile

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BALLENT, Sara; CONCHEYRO, Andrea  and  SAGASTI, Guillermina. Bioestratigrafía y paleoambiente de la Formación Agrio (Cretácico Inferior), en la Provincia de Mendoza, Cuenca Neuquina, Argentina. Rev. geol. Chile [online]. 2006, vol.33, n.1, pp.47-79. ISSN 0716-0208.

Biostratigraphy and palaeoenvironment of the Agrio Formation (Lower Cretaceous), Mendoza Province, Neuquén Basin, Argentina. A bioestratigraphical and palaeoenvironmental study of the Agrio Formation, at the Cuesta del Chihuido section, southern Mendoza Province (35º45'S/69º34'W), Argentina, is presented. Thirty seven species of nannofossils, thirty four of foraminifers and six of ostracods have been recognized. Nannofossils association corresponding to Zones CC4A y CC4B indicates an Upper Valanginian-Upper Hauterivian age. At the base of the section, the presence of the benthonic foraminifer Epistomina loncochensis Ballent and radiolaria suggests eutrophic conditions of surface waters and oxygen depressed sea-bottom conditions. In the middle part of the section, diversity of lagenid foraminifers and nannofossils indicates a shelf and nearshore environment with clear and well-oxygenated waters. Abundant polymorphinids, spirillinids and involitinids towards the top of the section corroborate a general regressive tendency. Mudstones and silty-sandstone intercalations containing allochthonous adherent foraminifers and adult carapaces of cytheroid ostracods represent distal storm deposits

Keywords : Lower Cretaceous; Agrio Formation; Biostratigraphy; Palaeoenvironment; Calcareous microfossils; Argentina.

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