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Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Geosciences

Year Degree Awarded

2016

Month Degree Awarded

May

First Advisor

Robert Mark Leckie

Subject Categories

Geology | Oceanography | Paleontology

Abstract

Benthic foraminiferal biofacies were delimited for the Maastichtian to upper Eocene of five Brazilian marginal basins (Sergipe-Alagoas, Mucuri, Campos, Santos and Pelotas) and two DSDP Sites 356 and 20C of the western South Altantic. Five biofacies, denoted with letters A to E, were defined using Q-mode cluster analysis and correspondence analysis for all of the 11 sites.

The benthic foraminiferal biofacies were used to establish a paleobathymetric and paleoenvironmental model for the Brazilian marginal basins. The model tracks the evolution of the margin as it built seaward and transitioned from abyssal (2000-3000 m) to bathyal (m) and neritic (m) depositional environments during the Maastrichtian – late Eocene. It is a powerful predictive tool for reconstructing depositional systems in deep-water and for correlation in tectonically disturbed and complex hydrocarbon basins.

The Maastrichtian – Paleocene interval was dominated by Biofacies E, which consists almost exclusively of agglutinated benthics and is also known as a flysch-type assemblage, and secondarily by Biofacies D consisting of a mix of agglutinated and calcareous benthic taxa. Sea level fluctuations may have contributed in downslope transport, as well as a shallow calcite compensation depth (CCD) along the continental margin resulting in dissolution of planktic and calcareous benthic taxa, and the alternation between biofacies E and D. An abrupt change in biofacies across the Paleocene/Eocene boundary is observed in all the Brazilian marginal basins, with the exception of the Campos Basin. The Eocene interval is characterized by calcareous-dominated biofacies A, B and C in the Sergipe-Alagoas, Mucuri, Santos and Pelotas basins due to progradation of the margin and shoaling of the slope above the CCD, allowing for better preservation of carbonate. Biofacies D and E continued to dominate the Campos Basin during the Eocene due to its continued deep-water setting and distal location relative to major centers of deposition. Major progradation of the Campos Basin segment of the margin occurred during the Oligocene and Miocene.

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