Paleogeographic and structural evolution of northwestern Africa and its Atlantic margins since the early Mesozoic

Abstract

The geological evolution of northwestern Africa and its continental margins is investigated in the light of nine Meso-Cenozoic paleogeological maps, which integrate original minimal extent of sedimentary deposits beyond their present-day erosional limits. Mapping is based on a compilation of published original data on the stratigraphy and depositional environments of sediments, structures, magmatism, and low-temperature thermochonology, as well as on the interpretation of industrial seismic and borehole data.We show that rifting of the equatorial domain propagated eastward from the Central Atlantic between the Valanginian (ca. 140 Ma) and the Aptian (ca. 112 Ma) as an en echelon strike-slip and rift system connected to an inland rift network. This network defines a six-microplate synrift kinematic model for the African continental domain. We document persistent, long-wavelength eroding marginal upwarps that supplied clastic sediments to the offshore margin basins and a large intracratonic basin. The latter acted as a transient sediment reservoir because the products of its erosion were transferred both to the Tethys (to the north) and the Atlantic Ocean. This paired marginal upwarpintra cratonic basin source-to-sink system was perturbed by the growth of the late Paleogene Hoggar hotspot swell that fragmented the intracratonic basins into five residual depocenters. By linking the evolution of the continental margins to that of their African hinterland, this study bears important implications for the interplay of long-wavelength deformation and sediment transfers over paired shield-continental margin systems.

Cenozoic sediment budget of West Africa and the Niger delta

“…Cenozoic sedimentary series preserved onshore include Eocene carbonates found in the Senegal‐Mauritania, Iullemmeden and Togo‐Benin basins overlain by Lutetian to Rupelian (49–29 Ma) continental deposits known as the Continental Terminal (Chardon et al ., ). Sub‐Saharan West Africa is considered as tectonically stable since Late Cretaceous rifting in the Iullemmeden, Chad and Benue basins, and has mostly undergone long‐wavelength lithospheric deformation since (Ye et al ., and references therein). The Central Atlantic Ocean opened since the Late Triassic and the Equatorial Atlantic during the Late Early Cretaceous (Brownfield & Charpentier, ; Moulin et al ., ; Labails et al ., ; Ye et al ., ; Fig.…”

Post-rift stratigraphic architectures along the African margin of the Equatorial Atlantic: Part I the influence of extension obliquity

“…112 Ma) as an en-échelon strike-slip system propagating eastward as dextral strike-slip faults (future transforms) and NW-to Wtrending normal faults (e.g. Basile et al, 2005;Ye et al, 2017). This rift was connected to an inland rift network of continental scale (Heine and Brune, 2014;Ye et al, 2017).…”

“…It has evolved from an en-échelon strike-slip system of pull-apart basins to a continental break-up leading to isolated "oceanic basin" patches separated by transform faults (e.g. Mascle et al, 1988;Basile et al, 2005;Heine et al, 2013;Basile, 2015;Ye et al, 2017). These isolated basins ultimately merged to form the conjugate margins boarding the African and South American continents.…”

Eburnean deformation pattern of Burkina Faso and the tectonic significance of shear zones in the West African craton

“…Although the regional and craton-scale strain and shear zone patterns of the sWAC evolved over tens of millions of Ye et al (2017). The shear zone pattern in South America has been compiled mostly after Gibbs and Baron (1993), Delor et al (2003b) and Cordani et al (2006).…”

“…The new reconstruction (Fig. 9b) is based on a recent prerift continental fit taking into account syn-rift extensional deformation of the continental margins (Ye et al, 2017) and a structural correlation that allows aligning the longest and most rectilinear shear corridor in the Guiana shield with the B-T mega shear. This shear corridor is flanked to the SE by (or hosts) an Archean Carajas-Imataca unit (e.g., Delor et al, 2003b;Cordani et al, 2006;Fig.…”