Norberto Malumian


The present paper deals with the biostratigraphy of the subsurface of Buenos Aires Province by means of foraminifera; some additional data on ostracoda 2nd ca1careous nannoplankton are also given. In the, Salado basin the "Entrerriense" occurs and is considered not older than Upper Miocene and bears Globorotalia pacbyderma Ehrenberg forma sinistrorsa as the dominant planktoi. ic form and Protelphidium tubereulatum (d'Orb.), Cibieides bertheloti (d'Orb.) and Cibictdes pseudoungerianus Cushman. Ecologically the microfauna indicates warmer waters than the present waters in the neighbouring sea. The conection between the South Atlantic ocean and Antillean sea in the Upper Miocene Unes supposed by several authors is considered inconsistent upon micropaleontological data. In the Colorado basin the presence of Upper Cretaceous is verified by means of ca1careous nannoplankton: Arkhangelskiella eymbiformis Vekshina, Mieula staurophora (Gardet ), Elffeiitbus turriseiffeli (Deflandre ). And the Danian age of the greater part of the Pedro Luto Formation is also verified by the planktonic association of Globoeonusa daubjerguensis (Bronimann). Sub botina triloeulinoides (Plummer ), Turborotalia pseudobulloides (Plummer) and occurrcnce of Cruciplaeolithus tenuis (Stradner ). Ir the Barranca Final Formation, there 15 a paleontological hiatus: upon it, the "Entrerr.iense" is recognized as somewhat older than in the Salado basin. It contains Cassigerinella cbipolensis (Cushman and Ponton) and Globigerina woodi woodi Jenkins with a great percentage of ostracods related with the "Entrerriense" of the Salado basin. Below the hiatus is found Gicbigcrina ouacbitensis ciperoensis Bolli associated with the maximum frecuency of Globigerina wood woodi jenkins; below this, Globorotalia opima opima makes its first cccurrence. The age of the s part is considered Oligocene following the recommendanons of the "Comité du Néogene".

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