Paleoclimactic and structural environment at the end of the Cretaceous along the western flank of the Congo Basin, with application of underground microdiamonds around Brazzaville
In Brazzaville (R.P. Congo), the study of outcrops and well sections permitted an investigation of the sedimentary evolution of the Continental Palcoenvironments during the Cretaceous and Tertiary, along a vertical thickness of 70 m (so-called Stanley Pool Formations). The base of the deposits is made of reworked red Precambrian sandstone of Inkisi which is associated with an argillaceous phase with dominant montmorillonite. The late-Cretaceous involved arenewal of erosion which was manifested by the deposition of coarse sands of alluvial-flats where general metamorphic minerals are associated with relatively important evidence of microdiamonds. Climatic changes indicate a more ferralitic pedogenesis of the drainage basins as evident by an increase in kaolin content. Towards the top of the section and the beginning of the Tertiary, kaolin tends to dominate the clay mineral fraction. The metakimberlites of Gabon and the diamond cc0acentrations of Bouenzien at the flank of the granitic massif of Challlu are considered as probable origins of the microdiamonds.