JOURNALS

ABSTRACT

The Chad basin belongs to a series of Cretaceous and later rift basins in Central and West Africa whose origin is related to the opening of the Atlantic. Despite the lack of outcrops in the area, works on the evolution and the stratigraphy of the Bornu basin have been published by many researchers. Most of these studies were based on boreholes and exploratory oil wells data as well as correlation from the adjoining basins like the upper Benue trough. The stratigraphic succession in the Bornu basin commenced in the Albian with deposition of the Bima Sandstones resting unconformably on the Precambrian basement. It is a sparsely fossiliferous, poorly sorted, medium to coarse-grained feldspathic sandstone known regionally, as the “Continental Intercalaire”. The sample was collected from ditch-cutting from Kasade-1 well. GC-MS analysis was undertaken of a waxy, paraffinic, low-sulphur source rock from Bornu Basin, apparently deriving mainly from bacterially reworked terrestrial organic matter deposited in a lacustrine environment. In addition to the regular C27-C35 hopanes, a number of pentacyclic triterpanes was identified in the range C29-C32. These components appeared to be members of at least two homologous series, one of which has been previously postulated to be 18? (H)-neohopanes. A further, previously unreported, series is characterized by a relatively intense molecular ion response during GC-MS analysis. A bacterial origin is suggested for these pentacyclic triterpane series, the presence of which may reflect a particular set of sedimentological conditions.