The geometry of the Archean, Paleo- and Neoproterozoic tectonics in the Southwest Cameroon

Abstract

The foliations, lineations, fold axes trajectories and shear zones kinematics vary from the Archean Ntem and Paleoproterozoic Nyong complexes to Neoproterozoic Oubanguide complex. The S 1, S 2 and S 3 typified foliations are folded in F 2, F 3 and F 4 cartographic folds equivalent to thrust slices while the L 1, L 2 and L 3 lineations are oriented SSE-NNW, west-east and sub-north-south in the above complexes, respectively. Both, the foliations and lineations confirm the transport top-to-the east of the Nyong nappe onto the Congo craton during the Eburnean orogeny under amphibolitic conditions and as the transport top-to-the SSE of the Yaounde nappe onto the Ntem and Nyong complexes during the Pan-African event under granulitic to green schist conditions. The paleostress of fault and shear zones display crustal thinning and horizontal extension oriented east-west, NW-SE and sub-north-south in the Ntem, Nyong and Oubanguide complexes. All these tectonic features, completed by north-south and east-west cross sections, demonstrate litho-chrono-stratigraphical, structural and angular discordances between the three complexes.