Extended Abstract: Major Subsurface Stratigraphic Units of the Southern Senegal Basin, Northwest Africa (original) (raw)
Related papers
Journal of Hydrology, 1990
The superficial aquifers of the Senegal sedimentary basin, like many other coastal and internal basins in Africa, have piezometric anomalies characterized by a large cone of depression, the bottom of which can even be below sea level, but without any significant artificial withdrawal in the area. Such depressions are often referred to as 'hollow aquifers'. Several possible explanations for the cause of these anomalies have been given, such as excess loss by evapotranspiration in areas of negligible recharge or climatic and sea level variations on the Atlantic coast of Africa, following the last glaciation. The main objective of this work was to investigate the possibility that the Ferlo piezometric depression of the Senegal sedimentary basin might have been caused by the latter phenomenon. The instrument used for this investigation is a multilayered digital model of the entire hydrogeological system, integrating the superficial phreatic aquifer and the underlying Oligo-Miocene and Maestrichtian aquifers. Our simulations start from 18 000 BP, thus they cover the period from the maximum aridity and lowest sea level of the Ogolian to the present. We were able to reconstruct the hydrodynamic behaviour of the aquifers, in particular the present piezometry of the entire three-layer system, which is compatible with that observed today, including the depressed shape of the central zone of Ferlo. The simulations also enabled us to (a) evaluate the present evapotranspiration flux in the depressed zone of Ferlo, and compare it with other estimates of evaporation from deep phreatic aquifers; and (b) estimate the exploitable resources in the entire Maestrichtian aquifer, which is the most important aquifer of the area. As a result of this explanation of the piezometric depression of Ferlo, we have briefly reviewed the various cases of depressed aquifers of the internal basins of the sub-Saharan Africa. It may be concluded that not all the piezometric anomalies observed in Africa can be explained by the same factors.
Stratigraphic Lexicon: The Sedimentary Formations of The Republic of Niger, Africa
ColNes Publishing OÜ, 2022
The current knowledge of the stratigraphy of Niger benefited greatly from the mining, hydrocarbon, hydrogeological, and paleontological sciences. Exploration by early explorers and studies of the aquifers initially sparked our understanding of the surface and shallow formations. Then, the discoveries in 1957 of important Uranium reserves and soon after in 1964 of the enormous Lower Cretaceous vertebrate site of Gadoufaoua stressed the need to undertake detailed stratigraphical investigations in the western Iullemmeden Basin. The geologist Hughes Faure then published his important, and still relevant, 1966 thesis on the surface geology of Eastern Niger. From that time onward, the Oil & Gas companies started paying attention to the most prospective areas in the Eastern Niger Basin. During the last decade, these same hydrocarbon companies finally allowed some geologists to share their knowledge of the sub-surface in relevant publications. It is from all these studies that the present Lexicon draws its content. It provides the historical background of all described geological units in Niger and summarizes each unit's lithological and paleontological knowledge in an easy-to-search format.
2018
On behalf of the Local Organizing Committee of “27th Colloquium of African Geology/17th Conference of the Geological Society of Africa – CAG27”, we would like to welcome you to this important meeting regarding “Africa: The key player for a better and sustainable world” that we feel privileged to host. This Conference, sponsored by the Universidade de Aveiro and the GeoBioTec Research Centre, under the auspices of the Geological Society of Africa (GSAf), is an opportunity to continue the scientific exchanges between researchers from all over the world in the field of Geosciences, and to demonstrate the high scientific research standards that are being carried out over the world. The participants in the conference will have the opportunity to share their expertise in a range of scientific fields, such as geology, geological resources, environmental risks, environment and human health, sustainable development, education, and tourism in Africa. (...)publishe
Miocene igneous activity in the Northern Subbasin, offshore Senegal, NW Africa
Marine and Petroleum Geology, 2008
More than 70 enigmatic discordant seismic anomalies of limited lateral extent, associated with eye-shaped structures and folds, have been imaged on 2D seismic data from the offshore Northern Subbasin of the Senegal Basin, NW Africa. In this paper we define their distribution, characterise their morphology and compare them to similar features imaged by seismic data along the NE Atlantic Margin that have been demonstrated to be igneous sills, hydrothermal vents and intrusion-related forced folds. We propose that the Cretaceous and Paleogene strata in the northernmost part of the offshore Northern Subbasin were heavily intruded by igneous sills during the Miocene. The proposed timing of intrusion is coincident with that previously suggested for the development of the Cayar Seamount located 100 km NNW of Dakar and onshore volcanism in the Cap-Vert area near Dakar and in the Cape-Verde Islands. This stage of Miocene igneous activity is interpreted to be closely associated with the coeval collision between Africa and Europe. The interpreted igneous sills give rise to an unexpected ''soft'' seismic response. The preferred explanation for the ''soft'' appearance of the sills is that the majority of sills are thin (o90 m) and hence their seismic appearance is affected by interference between the acoustic response from the top and base of the sills. The identification of shallow-level igneous intrusives in the offshore Northern Subbasin has important implications for hydrocarbon exploration in the Senegal Basin and possibly more broadly for hydrocarbon exploration in Atlantic basins offshore NW Africa. r (D.M. Hansen). D.M. Hansen et al. / Marine and Petroleum Geology 25 (2008) 1-15
Developing a Coherent Stratigraphic Scheme of the Albertine Graben-East, Africa
Journal of Earth Science and Engineering, 2016
The Albertine Graben is one of the most petroliferous onshore rifts in Africa. It forms the northernmost termination of the western arm of the East African Rift System. Its surface exposures were first studied by Wayland [1] and Pickford et al. [2] among others. Pickford et al. [2] especially developed the basic stratigraphic framework of the graben which was later modified by the government geoscientists and international oil companies using subsurface data. However, the stratigraphic units were not fully and formally described, and have been used informally in different and often confusing ways. The current study therefore aims to solve this challenge by establishing a coherent stratigraphic scheme for the entire graben through an integral study of surface and subsurface data. The study involves precise description of the type and reference sections for various formations both in exposure and wells; and has therefore led to the development of lithostratigraphic columns of different basins in the graben. The approach reveals that the Semliki area, south of Lake Albert, has the most complete sedimentary succession in the graben, spanning the period from middle Miocene (ca 15 Ma) to Recent. It also reveals that platform deposits, which form a small fraction of the thickness of the basinal succession, represent a highly condensed sequence which only saw deposition at times of Lake highstand.
Precambrian Research, 1989
ViUeneuve, M., 1989. The geology of the Madina-Kouta basin (Guinea-Senegal) and its significance for the geodynamic evolution of the western part of the West African Craton during the Upper Proterozoic period. Precambrian Res., 44: 305-322. The Madina-Kouta basin is a southward extension of the upper Proterozoic Taoudeni basin. This sedimentary basin formed in a SW-NE tectonic fault zone in the Leo shield at ~ 1000-800 Ma. The deposits indicate a quiet and slightly subsiding area. An important uncofformity allows us to distinguish two lithostratigraphic groups: the Sdgou Group below and the Madina-Kouta Group above. Sedimentation in this area ended with the Late Proterozoic glaciation 650-620 Ma. The correlations with the Taoudeni basin show a close relationship between the foreland area and the Mauritanides/ Bassarides fold belt during the Pan-African I cycle (800-650 Ma). In particular we suppose that the lower part of the Taoudeni basin deposits which correlate with the Madina-Kouta Group (group of Souroukouto) is on the passive margin of the Pan-African I rift, and the post-Madina-Kouta deposits in the Taouc]~ni basin (Group of Bakoye) correspond to the molassic stage of the Pan-African I fold belt (rift closure stage).
The structural evolution of the Dialé-Daléma basin, Kédougou-Kéniéba Inlier, eastern Senegal
Journal of African Earth Sciences, 2017
The Dial e-Dal ema group is located in the eastern part of the K edougou-Kenieba Inlier (KKI) and is essentially composed of Paleoproterozoic rock formations. Lithostructural studies in this area, hassuggested, often controversial, deformational regimes and geodynamic evolution models. In this study, we suggest the existence of an initial tangential D 1 deformation and transpressional D 2 deformational phases. D 1 is characterized by an initial metamorphic schistosity denoted as S 1 and by F 1 folds with the main shortening stress direction generally oriented in NW-SE direction. D 2 in the study area is divided into two stages. The first stage designated as D 2a is coaxial and compressive in nature. It is characterized by a N-S to NNE-SSW trending metamorphic schistosity termed S 2a. The D 2a phase evolves gradually to a transcurrent phase connoted as D 2b and characterized by a NNE-SSW S 2b metamorphic schistosity which is axial planar to the F 2b folds with subvertical fold axes. During the D 2 phase, the main shortening stress direction rotates gradually in a clockwise motion from an E-W to a NW-SE direction within a continuum of deformation. The third deformation phase D 3 in the Dial e-Dal ema basin, is also divided into two stages, thus D 3a and D 3b. D 3a is transcurrent and transtensive in nature and is characterized by NE-SW sinistral shear corridors with local extensional jogs. During this deformation stage, the maximum shortening stress (s 1) direction acts in a N-S direction and rotate to a NE-SW direction, thereby creating a N-S transcurrent dextral shear corridors. D 3b component of the D 3 deformation is compressive in nature with a weak sinistral shear component. The D 4 corresponds to a N-S extensional phase which is characterized by E-W directed normal faults. D 4 in the study area denotes the final stage of the evolution of the Eburnean orogeny in the KKI.