Palynostratigraphic análisis of the Río Foyel Formation (Latest Oligocene-Early Miocene), northwestern Patagonia, Argentina

BARREDA, V. D.; GARCIA, V.; QUATTROCCHIO, M.; VOLKHEIMER, W.

REVISTA ESPANOLA DE MICROPALEONTOLOGIA

Instituto Geológico Minero

Año: 2003 p. 229 - 239

0556-655X

A palynologic and palynofacies analysis of the Río Foyel Formation, from outcrops within theÑirihuau Basin (Río Negro Province, Argentina) is presented. The recovered organic matter isstrongly altered both by bacterial activity and thermally. Although the palynologic assemblages areof low diversity they are integrated by marine (dinoflagellates and microforaminiferal linings) andcontinental elements (spores, pollen grains, fungal spores, algae, woody particles and cuticles).Among the dinoflagellates Tuberculodinium vancampoae (Rossignol) Wall dominates, followed bya subordinate assemblage of protoperidinioids. The spore-pollen assemblage is dominated by fernsbelonging to the Lophosoriaceae, Dicksoniaceae and Cyatheaceae. Less frequent are the gymnospermpollen representing the Podocarpaceae and Araucariaceae. Angiosperms are subrepresentedconsisting mainly of Fagaceae. The palynologic spectre shows strong affinities with other palynoflorasidentified in the Late Oligocene and Early Miocene of the San Jorge Gulf Basin andMazarredo Subbasin, especially the dinoflagellates. Continental elements are comparable withthose recognized in the Ñirihuau Formation, through the megafloristic record (Early Miocene of theÑirihuau Basin). The presence of forms of recognized stratigraphic value, such as T. vancampoaeand additional forms observed, indicate a latest Oligocene to Early Miocene age for the studiedsequence. A restricted marine littoral environment with salinities lower than normal marine andwarm-temperate water, rich in nutrients, is indicated. The basin may have been surrounded by atemperate forest, populated by pockets of warm-temperate relict assemblages.