--> Abstract: Tectonic Influence on Sedimentation for the Lower Cretaceous Pre-Salt Strata of the Congo Coastal Basin, West Africa, by C. L. Farmer; #91012 (1992).

Datapages, Inc.Print this page

ABSTRACT: Tectonic Influence on Sedimentation for the Lower Cretaceous Pre-Salt Strata of the Congo Coastal Basin, West Africa

FARMER, CATHY L., Amoco Production Company, Houston, TX

Nonmarine sediments deposited during the initial stages of rifting, Neocomian through Early Aptian, in West Africa exhibit dramatic thickness and facies variations related to underlying tilted basement fault block geometries. Extension and rifting produced basement blocks bounded by normal faults. As rifting progressed, the blocks rotated, producing basement highs and adjacent half-grabens. The upthrown blocks experienced episodic uplift and erosion while the grabens become depositional troughs that continuously received sediment. Isopach maps for the total pre-salt section and for eight lithostratigraphic intervals within the pre-salt section illustrate these basement-controlled thickness variations. The total pre-salt interval varies from 7 m on the Kaba high to more than 3000 m in he deepest part of the Tchibota trough. The clastic intervals mapped within the pre-salt section exhibit consistent thickness variations through time with depositional "thins" occurring over basement highs and with depositional "thicks" occurring in grabens. Algal carbonates are localized around basement highs with thick buildups providing an exception to the pattern. Stages of deposition within the rift progressed from alluvial valley (Vandji), to lacustrine basin (Sialivakou, Djeno, Pointe Noire, Toca, Pointe Indienne, Tchibota), to marine incursion (Chela). Localized uplift and erosion occurred in an area that experienced overall subsidence, resulting in a complex interrelationship between tectonics and sedimentation.

 

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)