T. E. Miskelly, Jr1, W. E. Galloway1, and T. Ziegler2
1University of Texas, Austin, TX
2Petroleum Geo-Services, Inc., London, England
ABSTRACT: Depositional Systems of a Complex Transform Margin: Deep Ivorian Basin, Blocks 104 and 105, Ivory Coast
A 3D seismic data set was used to analyze the depositional systems during an active extensional basin adjacent to a transform margin. The data set consists of 1800 km2 3D seismic covering blocks 104 and 105 offshore the Ivory Coast. The complex structure in the area of interest is an extension of the wrench faulting along the Saint Paul Fracture Zone to the southeast and is analogous to the rotated fault blocks found on the eastern side of the Ivory Coast Basin from the Romanche Fracture Zone. Previous studies and DSDP cores near the area of interest show the slope and base-of-slope settings to be primarily siliciclastic. Three tectono-sedimentary regimes were identified and related to the extensional tectonics: 1) pre-rift lacustrine, 2) active rift margin, and 3) post-rift passive margin. The post-rift deposits are concentrated within a narrow graben between the tilted rift blocks. The sediment is transported by gravity into the baseof- slope environment bypassing the slope setting. Chaotic, convergent, and drape seismic facies differentiate between sedimentary facies. Slumps, debris flows, turbidites, toe thrusts, and erosional surfaces were some of the features imaged in the seismic survey. Depositional facies, such as debris aprons, slides, submarine fans, drapes, and erosional features, such as canyons and bypass disconformities, were identified and mapped out using seismic facies analysis.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado