2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 131-5
Presentation Time: 10:00 AM

SOUTH ATLANTIC PALEOCENE-EOCENE BENTHIC FORAMINIFERAL TAXONOMY


DE MELLO, Renata M., Geosciences, University of Massachusetts, 611 North Pleasant St - Geosciences Dept, University of Massachusetts, Amherst, MA 01003-9297, LECKIE, Mark, Dept. of Geosciences, Univ of Massachusetts, 611 North Pleasant Street, Amherst, MA 01003 and THOMAS, Ellen, Geology and Geophysics and Department of Earth and Environmental Sciences, Yale University and Wesleyan University, P O Box 208109, New Haven, CT 06520-8109

Paleocene-Eocene benthic foraminifera were studied in the western South Atlantic in samples from industry cores and well cuttings from Brazilian marginal basins (Sergipe-Alagoas, Bahia-Sul, Campos, Santos and Pelotas) and cores from DSDP Leg 39 Site 356 (São Paulo Plateau) and Leg 3 Site 20C (Rio Grande Rise) in order to recognize benthic foraminiferal biofacies and develop a paleoslope model.

Approximately 180 calcareous and 150 agglutinated taxa were recognized in the entire sample. In the Brazilian marginal basins late Paleocene agglutinated assemblages changed to assemblages dominated by calcareous taxa during the early Eocene. The agglutinated assemblage includes Gaudryina pyramidata, Gaudryina sp., Cribostomoides trinitatensis, Glomospira charoides, Recurvoides sp., Haplophragmoides sp. and especially the tubular forms (Psammosiphonella cylindrica, Rhizammina sp., Bathysiphon sp., Nothia sp.). The more diverse early Eocene assemblages are dominated by Cibicidoides sp., C. eocaenus, Anomalinoides sp., Planulina costata, Globocassidulina subglobosa, Bulimina alazanensis, Oridorsalis umbonatus, Aragonia aragonensis. In the Santos and Bahia-Sul basins there is an increase in radiolarian during the early Eocene.

At DSDP sites, the late Paleocene assemblage is composed of deep-water species, e.g. Bulimina trinitatensis, Nuttallides truempyi, Stensioeina beccariiformis, Gyroidinoides globosus, Dorothia trochoides, Gaudryina pyramidata. In the early Eocene assemblages, the diversity of calcareous taxa increased, with most expressive taxa: Cibicidoides sp., C. eocaenus, Anomalinoides sp., Planulina costata, Globocassidulina subglobosa, Bulimina alazanensis, Oridorsalis umbonatus, Aragonia aragonensis.

This initial work provides the groundwork to reconstruct environmental change, and will be combined with planktic foraminiferal fragmentation, planktic/benthic ratio and calcareous/agglutinated values to trace changes in the Paleogene lysocline/CCD of the western South Atlantic.

Session No. 131

T203. Timing, Tempo, and Mode of Evolutionary and Paleoenvironmental Changes across Boundary Events and Transitions: The Protistan Evidence (Posters)
Monday, 20 October 2014: 9:00 AM-6:30 PM
Exhibition Hall C (Vancouver Convention Centre-West)
Geological Society of America Abstracts with Programs. Vol. 46, No. 6, p.328
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