First Ordovician Foraminifera in South America: a Darriwilian (Middle Ordovician) fauna from the San Juan Formation, Argentina

NESTELL, G.,; MESTRE, A.; HEREDIA, S.

MICROPALEONTOLOGY

MICROPALEONTOLOGY PRESS

Lugar: New York; Año: 2009 vol. 55 p. 329 - 344

0026-2803

The first Middle Ordovician (Darriwilian) foraminifers in Argentina are described from strata of the upper part of the San Juan Formation in Argentina and represent the first find of Ordovician foraminifers in South America. The foraminifers are found together with conodonts of the Eoplacognathus pseudoplanus /Dzikodus tablepointensis Zone that enhances the stratigraphic significance of the foraminifers. The assemblage of foraminifers described includes the agglutinated genera Lakites, Amphitremoida, Lavella, Ordovicina and Pelosina. The distribution of the genera Lakites and Lavella, previously known only from the Lower Ordovician (Tetragraptus phyllograptoides graptolite Zone), now can be extended up into the Middle Ordovician (Darriwilian). The find of representatives of the xenophyophorean genus Pelosina extends the first appearance of this genus down into the Middle Ordovician.