Stratigraphy and Depositional Settings of Cretaceous Organic-Rich Sequences in the Brazilian Marginal Basins

MELLO, M. R., E. A. M. KOUTSOUKOS, and E. V. SANTOS NETO, Petrobras, Rio de Janeiro, Brazil

A comprehensive geochemical and paleontological survey of the stratigraphic framework and depositional setting of the organic-rich and most prolific petroleum source rocks sequences in the Brazilian marginal basins has been undertaken.

The geochemical analysis of the rocks included organic carbon determinations, Rock-Eval pyrolysis, carbon and hydrogen isotope measurements, porphyrin analysis, and biological markers investigations, using chromatography-mass spectrometry/mass spectrometry (GC-MS/MS) of the saturate and aromatic fractions. The paleontological study involved the assessment of the distribution and diversity patterns of microfossils (foraminifers, radiolarians, diatoms and ostracods), calcareous nannofossils, and palynomorphs in dating and paleoenvironmental assignments.

The results demonstrate the importance of the integration of geochemical and paleontological data for both characterization and lateral and vertical correlations of organic-rich sequences. Furthermore, such an approach is a powerful tool in ascertaining types of depositional environment and age constraints within different petroleum stratigraphic frameworks.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)