Paleogeography and tectono-stratigraphy of carboniferous-Permian and Triassic "Karoo-like" sequences of the congo basin
Abstract
The Congo Basin is a large Phanerozoic sedimentary basin with up to 3–6 km of Carboniferous to Triassic sequences, comparable to those of the Karoo Basins of southern Gondwana. Here, we present a substantially revised stratigraphy for the Congo Basin, based on new field observations, seismic and borehole data, together with paleontology and new geochronology. In the center of the basin, the deepest boreholes intercept 3 to 4 km thick successions of conglomerates and red sandstones that overlie carbonate rocks, which correlate to deformed upper Neoproterozoic (Pan African) platform sequences extending beyond the Congo Basin into the Pan African orogenic zones (e.g. the West Congolian Group). The overlying sequences are dated biostratigraphically to be Carboniferous-Permian (the Lukuga Group) and Triassic (the Haute Lueki Group) in age. A regional erosion surface separates these two groups, possibly related to late Paleozoic intracontinental deformation associated with the Mauritanian-Variscan and Cape-de la Ventana orogens flanking the northwestern and southern margins of Gondwana, respectively. This change in basin paleogeography is consistent with detrital zircons dated from these sequences that suggest the ca. 1.4 Ga Kibaran Belt along the eastern margin of the Congo Basin stopped acting as a major source during the early Mesozoic.