Eocene bathyal and abyssal benthic foraminifera from a South Atlantic transect at 20–30° S

摘要: Abstract Eocene age (Zone P6b-P17) benthic foraminiferal faunas from 207 samples of Atlantic Ocean DSDP Sites 19, 20, 357, 363, 522 and 523 were analyzed along a transect located at approximately 30°S spanning the depth range upper lower bathyal to abyssal. There is distinct “abyssal/bathyal” faunal boundary in which was above Site 363 Zone P6b, dropping below that for remaining early middle Eocene, it rose again depths (estimated between 1500–1800 m) beginning late Eocene. Abyssal are highly dominated by spiral forms. An abyssal association (1) with codominant Nuttalides truempyi Quadrimorphina , together Abyssamina Clinapertina prevailed (Hole 20C) At (Site 19 523) persisted A N. dominant (> 25% total fauna) (2) appeared first occurred P12 interchanging In P15 an increased abundance Nuttallides umbonifer high Globocassidulina subglobosa replaced association. This replacement observed sites (all except 357) most pronounced change Bathyal contain uvigerinids, bolivinids, Lenticulina percentages buliminids characterized absence species.