--> Abstract: Depositional And Sequence Stratigraphic Model Of Albian Carbonates In Benguela Basin, Angola, by V. N. Vyssotski, A. V. Belopolsky, and D. E. Rice; #90928 (1999).

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VYSSOTSKI, VLADIMIR N.1, ANDREI V. BELOPOLSKY2, and DONALD E. RICE1
1Amoco Exploration and Production, Houston, TX
2Rice University, Houston, TX

Abstract: Depositional and Sequence Stratigraphic Model of Albian Carbonates in Benguela Basin, Angola

The Benguela basin of Angola is one of the west African extentional sedimentary basins with rifting initiated in Late Neocomian and terminated in Early Aptian. A large graben system, associated with rifting and transform faults, influenced sedimentation throughout the history of the basin.

Marine Albian carbonates in Benguela were formed after the deposition of the thick Aptian salt. Seismic interpretation integrated with outcrop and well data from neighboring basins allows for defining Lower Albian highstand, Middle Albian lowstand, and the Upper Albian transgressive systems tracts. Sedimentation during the highstand and successive lowstand was controlled by the distribution of the pre-salt grabens and transform faults associated with the spreading of oceanic crust. The direction of carbonate platform progradation was to the north. Highstand deposits comprise the most extensive carbonate unit. The Albian deposits exhibit two types of seismic facies: high amplitude relatively continuous reflectors, and "dim", low amplitude reflectors. The differences could be explained by the variations in lithologic composition and diagenetic overprint. The transgressive systems tract is characterized by backstepping carbonate platform confined to the southeastern part of the basin. The direction of the depositional profile by that time changed to the northwest.

Significant deformation of the Upper Cretaceous sediments can be divided into two types: steep folding deformation that creates a "pinnacle architecture", and rafted blocks. The difference can be explained by lithological composition. Pinnacles, containing a large amount of clastic material, are folded. Rafts, predominantly lithified carbonates, are fragmented.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas