The Volta basin in Burkina Faso: Lithologic and structural geology constraints along the leading edge of the foreland Dahomeyide fold-thrust belt

The Volta basin in Ghana, Togo and Benin has a narrow NE-striking panhandle extension into Burkina Faso where the Pan-African Dahomeyide fold-thrust belt approaches Paleoproterozoic basement rocks (ca. 2.25–2.10 Ga). We present the results of integrated stratigraphic, structural geology studies of the Volta Basin in Burkina Faso that combines interpretations of high-resolution remote sensing imagery, radiometrics and magnetics to appraise the metasedimentary sequences and stratigraphic setting. We evaluate the degree of deformation and metamorphism across the Volta basin in Burkina Faso and contextualize the tectonic domains with reference to published data for the broader Volta Basin. The results indicate that felspathic sandstones and greywackes of the Madjoari and Gobnangou massifs were deposited in the Tonian Period (ca. 1000-855 Ma) in a shallow marine environment along the Rodinia continental passive margin. Diamictites, dolomite, chert, phosphorite (576 ± 13 Ma) of the Kodjari Group and siltstone-shale sequences of the Porga Group were deposited in an offshore basin in the middle Ediacaran Period (ca. 635-538 Ma) syn-to post Ediacaran glaciation and possibly during a period of deglaciation. These metasedimentary rocks were deformed during two deformation events, D1 and D2. D1 ductile-brittle deformation was concomitant to NW-directed fold-thrust formation within the foreland Dahomeyide fold-thrust belt. The intensity of deformation decreases across the panhandle (SE to NW) from isoclinal folding and thrust formation in Atacora Structural Unit, to open style low fold forms near the Madjoari and Gobnangou massifs. In concert, metamorphic grade decreases from greenschist-amphibolite to very low grade (anchimetamorphic). D2 brittle deformation was progressive, with incremental development of joints, fracture-corridors, fracture-faults and open fold forms during east-west directed shortening. • The lithostratigraphy and character of deformation of the Volta basin in Burkina Faso has been revised. • The Volta Basin in Burkina Faso is located within the marginal foreland of the Dahomeyide fold-thrust belt. • All rocks units were deformed during D1 ductile brittle deformation and brittle D2 deformation. • Encroachment of the Pan African belt in D1 was during the late Ediacaran. • D2 is associated with gentle folding (warping), progressive formation of joints, fracture corridors and faults.