--> Abstract: High-Resolution Sequence Stratigraphy, Reservoir Geometry and Facies Associations of Cretaceous and Tertiary Turbidites from Rift and Passive Margin Brazilian Basins, by C. H. L. Bruhn and R. G. Walker; #90987 (1993).

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BRUHN, CARLOS H. L., Petrobras, Rio de Janeiro, Brazil; and ROGER G. WALKER, McMaster University, Department of Geology, Hamilton, Ontario, Canada

ABSTRACT: High-Resolution Sequence Stratigraphy, Reservoir Geometry and Facies Associations of Cretaceous and Tertiary Turbidites from Rift and Passive Margin Brazilian Basins

Over 120 turbidite oil fields occur in rift (lacustrine) and passive margin

(marine) Brazilian basins, ranging in age from Neocomian to Miocene. Four of these oil fields represent three different types of turbidite systems: Lagoa Parda (Eocene, Espirito Santo basin), Carapeba and Pargo (Coniacian to Maastrichtian, Campos basin), and Fazenda Balsamo (Neocomian, Reconcavo basin).

Lagoa Parda field reservoirs consist of channel-levee complexes, filling part of a 4-km-wide, 15-km-long submarine canyon. Each channel-levee complex was built by the amalgamation of (a) deeply-incised, 0.2-0.8 km wide channels, filled with massive conglomerates, and generally structureless very coarse- to fine-grained sandstones; and (b) asymmetrical levees displaying mudstones and thin-bedded "CCC" turbidites.

Carapeba and Pargo reservoirs contain structureless conglomerates and very coarse- to medium-grained graded sandstone beds. Individual turbidites are as thick as 12 m, and can be traced for up to 20 km. They make a thick (up to 280 m), non-channelized sandy succession, occupying fault-controlled, 1.5-12 km wide troughs. Both Lagoa Parda and Carapeba/Pargo turbidite systems were deposited during minor third- or fourth-order drops in sea level that punctuated an overall transgressive setting.

Fazenda Balsamo reservoirs include massive and parallel-laminated, medium-grained sandstones, deposited in narrow grabens, within a deep lacustrine basin. Tectonism played an important role in providing sites for preferential accumulation of turbidites, but climatic variations seem to have influenced the development of the cyclic, 20-100 m thick, deepening (muddier)-upward parasequences, in which the reservoirs are located.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.