Implication of klippen and a new sedimentary unit at Gibi Mountain, Liberia, West Africa, in the problem of the Pan-African–Liberian age province boundary

Pan-African tectonic evolution and glacial events registered in Neoproterozoic to Cambrian cratonic and foreland basins of West Africa

“…As well as in the Bassaride belt, lower metamorphic units and upper sedimentary units can be distinguished in the Rokelide orogen that forms a poorly exposed elongated NNW-SSE trending belt along the coastline of West Africa, south of the Bové Basin, in southern Guinea, Sierra Leone and Liberia (Allen, 1968(Allen, , 1969Thorman, 1976;Culver and Williams, 1979;Villeneuve, 1984; (Fig. 8).…”

“…The external nappes of the Mauritanide belt were thrust over the Devonian rocks of the Taoudéni Basin in Mauritania, whereas in Guinea the Cambro-Ordovician to Devonian rocks of the Bové Basin rest upon rocks of both the Bassaride and Rokelide belts (Sougy, 1962;Bassot, 1966;Villeneuve, 1984). In Sierra Leone and Liberia, the internal nappes of the Rokelide belt were thrust over the Vendian to Cambrian rocks of the Rokel River Group (Culver and Williams, 1979;Thorman, 1976).…”

“…• The Pan-African II tectonic event in the Rokelide belt (Rokelide orogen; Allen, 1969;Thorman, 1976;Culver and Williams, 1979; at 550-560 Ma. • The Hercynian tectonic event responsible for the internal nappes emplacement in the Mauritanide belt (Hercynian orogen; Sougy, 1962) at 320-270 Ma.…”

The nature and location of the suture zone in the Rokelide orogen, Sierra Leone: Geochemical evidence

“…However, at Gibi Mountain, the Gibi Mountain Formation is lithologically similar to lower units of the Rokel River Group and is overlain by klippen of Precambrian quarzite (Thorman, 1976;Magee and Culver, 1986;Culver et al, 1991). The Pan-African age Todi Shear zone in Liberia separates amphibolites and granulites of the Kasila Group from the Liberian granite-greenstone terrane of the Leo Massif (Thorman, 1976;Tysdal, 1978). Hedge et al (1975) identified a norite body and a diorite dike in the Pan-African age province (Kasila Group) of Liberia (Culver et al, 1991).…”

“…Sedimentary units of Gibi Mountain are considered to be an extension of the Rokel River Group located 225 km to the northwest (Thorman, 1976;Magee and Culver, 1986). Thorman (1976) envisioned the Kasila gneisses as reworked parts of the West African Craton. Burke and Lytwyn (1993), however, suggested that Gibi Mountain is a remnant thrust sheet (klippe) in an area where the suture is cryptic (Burke and Dewey, 1972;Burke and Dewey, 1973).…”