Tale of three cratons: tectonostratigraphic anatomy of the Damara orogen in northwestern Namibia and the assembly of Gondwana

The Neoproterozoic Damara orogen in Namibia records the Gondwanan assembly of the Congo-Kalahari-Rio de la Plata cratons. Sedimentological and stratigraphic analyses of the Otavi (mostly carbonate) and Mulden (siliciclastic molasse) Groups exposed along the southwestern margin of the Congo craton indicate that foreland-basin orogenesis began during middle Otavi (ca. 600-750 Ma); this time frame is earlier than that for the Nama foreland (ca. 550 Ma) on the Kalahari craton. Evidence for this interpretation includes (1) an intra-Otavi angular unconformity; (2) concomitant development of increasing accommodation space, basin segmentation, and backstepping depositional systems composed mostly of deep-basin and slope hemipelagic and sediment gravity-flow deposits; and (3) a near reversal in paleocurrents (initially northward off the Congo craton, then switching to southeastward from a west-northwestern orogen). Thus, Congo-Rio de la Plata suturing predated Congo-Kalahari suturing during the assembly of Gondwana.