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Open Access Dissertation
Doctor of Philosophy (PhD)
Year Degree Awarded
Month Degree Awarded
Robert Mark Leckie
Geology | Oceanography | Paleontology
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.
de Mello, Renata Moura, "A Paleobathymetric Model and Evolution of the Brazilian Marginal Basins during the Late Maastrichtian to Eocene based on Benthic Foraminiferal Biofacies" (2016). Doctoral Dissertations. 622.