STRUCTURAL EVOLUTION OF BODE SAADU AREA, SOUTHWESTERN NIGERIA

Abstract

The Bode Saadu area comprises metasedimentary and metaigneous rocks which have been subjected to polyphase deformation and have subsequently been intruded by post-tectonic granitic rocks of probably Pan-African (600 ± 150Ma)age. Five phases of post-sedimentary tectonic deformation have been recognized in the rocks of this area. The first phase was associated with the development of the regional foliation, S1, and tight to isoclinal minor folds. The second phase involved heterogeneous deformation which gave rise to ductile shear zones, extensional and contractional faults. Second phase structures also include minor asymmetrical folds which deform S1 and S0. The third phase produced the dominant major folding on approximately N-S axis including the major Bode Saadu antiform. The fourth phase gave rise to open folds and crenulation of the earlier structures. Late brittle structures include transcurrent faults, both dextral and sinistral, which occasionally occurred in conjugate sets under generally N-S trending, maximum conpressive stress.