Robert J. Hooper¹, Roy J. Fitzsimmons¹, Neil T. Grant¹, Bruno C. Vendeville²

(1) Conoco Inc, Houston, TX
(2) Bureau of Economic Geology, University of Texas at Austin

ABSTRACT: Linked Extensional and Contractional Structures in the Niger Delta

The south-central Niger Delta has a distinctive structural and stratigraphic zonation. Regional and counter-regional growth faults, developed in an outer-shelf and upper-slope setting, are linked, via a translational zone containing shale diapirs, to a contractional-zone defined by a fold-thrust belt developed in a toe-of-slope setting. Structural and depositional systems have migrated with the progradation of the delta. Buried under the modern upper-slope, is a paleo fold-belt. The structural system in this paleo fold-belt is complex and comprises a series of en echelon thrust-cored folds and associated ponded slope-basins, shale diapirs and extensional growth faults. Primary accommodation on the paleo delta-slope was controlled by structural movement. Analysis of the growth sections filling the ponded slope-basins therefore provide a record of how this accommodation was created and subsequently destroyed. Detailed analysis of the depositional systems within this growth-section reveals that the structural system is fully linked and developed from the complex interaction between contractional faulting and folding, extensional faulting, shale-diapirism and withdrawal and subsidence, all processes having acted simultaneously.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado