Detailed fieldwork in parts of the Benin (Dahomey) Basin SW, Nigeria has allowed the recognition of sedimentary successions deposited in different continental depositional environments interpreted as fluvial sedimenta...Detailed fieldwork in parts of the Benin (Dahomey) Basin SW, Nigeria has allowed the recognition of sedimentary successions deposited in different continental depositional environments interpreted as fluvial sedimentation characterised by abandoned channels and subaerial exposure features. The lithofacies recognised are: conglomerates, debris flow deposits, very coarse grained sandstone, ferruginous cross bedded sandstone, siltstone, shale/clay and massive sand. The lithofacies were interpreted in terms of sequence stratigraphic elements with the recognition of sequence boundaries characterised by distinct facies dislocations and subaerial exposures. Four depositional sequences (DS I to DS IV) were identified. Depositional sequences (DS I) exhibited a complete regressive–transgressive cycle comprising LST, TST and HST, while DS II to DS IV were incomplete comprising of sediments interpreted as LST deposits. On the basis of the depositional facies and sequence stratigraphic elements, the sediments in the area of study are interpreted as predominantly of Ilaro Formation while fewer exposures are sediments of the Coastal Plain Sands/ Benin Formation. This observation suggests a re-interpretation of the Tertiary sedimentary successions, which hitherto recognised all the sediments in the area of study as Coastal Plain Sands.展开更多
Ditch cutting samples from Kasade-1 well were processed for microfauna, nannofossil and palynomorphs to throw more light on biostratigraphic events in the northern portion of the Bornu Basin, Nigeria. The lower sectio...Ditch cutting samples from Kasade-1 well were processed for microfauna, nannofossil and palynomorphs to throw more light on biostratigraphic events in the northern portion of the Bornu Basin, Nigeria. The lower section of the well within interval 990 - 1565 m yielded fairly abundant foraminifera species, while the upper section was barren. Palynomorph distribution follows the same pattern as observed for foraminifera except that few fresh-water algal species, Botryococcus braunii, were recovered from the upper section. The samples are devoid of nannofossil but contain few ostracod species, echinoid remains and fish tooth. Recognition of two planktonic foraminifera zones, Globotruncanella havanensis and Globotruncana aegyptiaca, enabled the delineation of the Campano-Maastrichtian and Maastrichtian boundary. The Cretaceous Tertiary boundary was inferred based on the top occurrence of palynomorph Dinogymnium euclaense. An abrupt truncation in the distribution of foraminifera species at a depth of about 990 m suggests unconformity, a widely reported event that followed the Santonian squeeze in the entire mega-Chad Basin.展开更多
文摘Detailed fieldwork in parts of the Benin (Dahomey) Basin SW, Nigeria has allowed the recognition of sedimentary successions deposited in different continental depositional environments interpreted as fluvial sedimentation characterised by abandoned channels and subaerial exposure features. The lithofacies recognised are: conglomerates, debris flow deposits, very coarse grained sandstone, ferruginous cross bedded sandstone, siltstone, shale/clay and massive sand. The lithofacies were interpreted in terms of sequence stratigraphic elements with the recognition of sequence boundaries characterised by distinct facies dislocations and subaerial exposures. Four depositional sequences (DS I to DS IV) were identified. Depositional sequences (DS I) exhibited a complete regressive–transgressive cycle comprising LST, TST and HST, while DS II to DS IV were incomplete comprising of sediments interpreted as LST deposits. On the basis of the depositional facies and sequence stratigraphic elements, the sediments in the area of study are interpreted as predominantly of Ilaro Formation while fewer exposures are sediments of the Coastal Plain Sands/ Benin Formation. This observation suggests a re-interpretation of the Tertiary sedimentary successions, which hitherto recognised all the sediments in the area of study as Coastal Plain Sands.
文摘Ditch cutting samples from Kasade-1 well were processed for microfauna, nannofossil and palynomorphs to throw more light on biostratigraphic events in the northern portion of the Bornu Basin, Nigeria. The lower section of the well within interval 990 - 1565 m yielded fairly abundant foraminifera species, while the upper section was barren. Palynomorph distribution follows the same pattern as observed for foraminifera except that few fresh-water algal species, Botryococcus braunii, were recovered from the upper section. The samples are devoid of nannofossil but contain few ostracod species, echinoid remains and fish tooth. Recognition of two planktonic foraminifera zones, Globotruncanella havanensis and Globotruncana aegyptiaca, enabled the delineation of the Campano-Maastrichtian and Maastrichtian boundary. The Cretaceous Tertiary boundary was inferred based on the top occurrence of palynomorph Dinogymnium euclaense. An abrupt truncation in the distribution of foraminifera species at a depth of about 990 m suggests unconformity, a widely reported event that followed the Santonian squeeze in the entire mega-Chad Basin.
