FORAMINIFEROS BENTONICOS DE LA LOCALIDAD TIPO DE LA FORMACION LA DESPEDIDA (EOCENO, ISLA GRANDE DE TIERRA DEL FUEGO). PARTE II, NODOSARlACEA, BULIMINACEA, ELPHIDIIDAE Y ROTALIDOS TUBERCULAOOS

Abstract

Foraminifera of the Superfamilies Nodosariacea and Buliminacea, and the Family Elphidiidae and tuberculate rotaliids from the La Despedida Formation (type locality, Middle Eocene, Tierra del Fuego Island) are illustrated. Forty seven species of nodosariaceous foraminifera are recognized. The lower member bears thirty species, some of them represented by large specimens which are the biggest smaller foraminifera described in Argentina. The upper member bears eighteen species, showing an abrupt decrease in the number of species, individuals and size in the history of the nodosariaceous of the Austral Basin. Sixteen species ofbuliminacea are recognized, among them Uvigerina spinicostata andBulimina sp. seem to be restricted to the lower member, and U. havanensis Cushman and Bermúdez and Kolesnikovella severini (Cañón and Emst) to the upper member of the La Despedida Fm. The latter is a widespread species, and a good local marker in the Austral Basin. Six species of the Family Elphidiidae are recognized including Elphidium deferrariisi n. sp. Besides, Neorotalia? sp.; Buccella sp., and an indeterminate form of tuberculate rotaliid are illustrated. Elphidium saginatum Finlay and Cribrorotalia cf. C. tainuia (Dorreen) characterize, respect ively by their abundance and distribution, the lower and upper members of the Formation. The di stribution of the genera Cribrorotalia and Elphidium shows throughout the middle Eocene up to Recent mutual exclusion in shallow environments.