Jean Benkhelil,2 Michel Guiraud,3 and Joël Paccolat2


Regional tectonics and detailed examination of cores recovered during Leg 159 of the Ocean Drilling Program show that four types of deformation occurred during early extension, marginal uplift and shearing of the Côte d’Ivoire-Ghana Marginal Ridge (CIGMR): (1) extensional deformation related to the opening up of pull-apart basins; (2) synsedimentary deformation related to slope instability and mass sliding of water-laden sediments; (3) deformation as a result of normal and reverse synlithification microfaulting combined with microfolding associated with well-defined, isolated, parallel-to-bedding décollement zones induced by gravity tectonics; (4) vertical shears, cleavage, and associated microfolding generated by transpressive tectonics. This paper concentrates on décollement structures (type 3 deformation). These deformations were produced by a simple shear mechanism along bedding planes that was induced by the progressive uplift of the CIGMR in the Albian during the breakup of the margin.

1Mascle, J., Lohmann, G.P., and Moullade, M. (Eds.), 1998. Proc. ODP, Sci. Results, 159: College Station, TX (Ocean Drilling Program).
2URA-CNRS n°715, Sédimentologie et Géochimie Marines, Université de Perpignan, 66860 Perpignan, France. jb@univ-perp.fr
3UMR n°5561 Paléontologie Analytique et Géologie Sédimentaire, Centre des Sciences de la Terre, Université de Bourgogne, 6 Bd Gabriel, 21000 Dijon, France.