Separating ecological assemblages using stable isotope signals: Late paleocene to early eocene planktic foraminifera, DSDP Site 577

Analysis of late Paleocene to early Eocene planktic foraminifera from DSDP Site 577 indicates the presence of two and possibly three isotopically and morphologically distinct assemblages. The surface dwelling assemblage includes species with pustulate-muricate wall texture (e.g., species of the genera Morozovella, Acarinina, Igorina, and Muricoglobigerina). This assemblage is characterized by light δ¹⁸O values and large interspecific δ¹³C variation. It accounts for 82% of the population. The subsurface dwelling assemblage includes species with cancellate-pitted and smoothed-granulate wall textures (e.g., species of the genera Subbotina, "Turborotalia," Planarotalites, Pseudohastigerina, and Chiloguembelina). This assemblage is characterized by heavier δ¹⁸O values and small interspecific δ¹³C variation. It accounts for 14% of the population. The questionable deep dwelling assemblage includes some species with pitted wall texture (e.g., species of the genus "Planorotalites"). This assemblage is characterized by the heaviest δ¹⁸O values and accounts for only 4% of the population.