PERFORACION GIL 1, PROVINCIA DE BUENOS AIRES (FORAMINIFEROS, EDAD, PALEOAMBIENTE)

Abstract

Benthonic and planktonic foraminifers were studied in 42 samples from drillhole "Gil 1", province of Buenos Aires, district of Dorrego). With exception of the lowermost 50 m, foraminiferal tests are badly preserved and rare. Several samples are completely barren. The entire sequence can be subdivided, on the basis of foraminifera, into five (biostratigraphic) units. The uppermost unit, Unit A (98.50-168.60 m), consists of near.shore Quaternary deposits. Water temperatures were approximately the same as those now occuring in this area. Unit B 190.80- 304.40 m) is probably Miocene in age. The very poor fossil record does not allow a more definite age determination. This unit was also deposited on the inner shelf. Unit C (304.40- 325.20 m) presumably contains Lower Miocene deposits. The thanatocoenoses found in this interval are rather poor and badly preserved. Unit D (325.20-350.45 m) is almost barren with only five specimens of non-indicative benthonic foraminifers presento The lowermost unit, Unit E (350.25-401.90 m), is the most interesting. It contains moderately well preserved and in some samples quite abundant specimens of planktonic and benthonic species indicative of the Late Oligocene age. The assemblage found here suggests an outer shelf environment (depth about 100-150 m). Brazilian warm water faunal influences are apparent. Cold or cold-temperate elements are not present. Similarities between faunas of the area studied and those of the Caribbean nnd New Zealand areas are evident. Most of the significant taxa are illustrated by scannlng electron micrographs.