The geological history of the sedimentary basin of southern Mozambique, and some aspects of the origin of the Mozambique channel

Abstract

With the breakup of Gondwanaland a northwards-transgressing sea reached southern Mozambique in mid-Cretaceous times. The deeply weathered Karoo volcanics of southern Mozambique are overlain by glauconitic silty sandstones of Barremian to Cenomanian age, with marginal disconformities in the lowest and uppermost Albian. After a late Cenomanian to Turonian hiatus, with local deposition of continental sediments, the marine facies reappeared with silty sandstones. In the south these sandstones are of Coniacian age, becoming younger to the north, where only the Campanian or Maestrichtian are represented. A minor unconformity is present within the Upper Maestrichtian—Lower Paleocene sequence. Shallow-water sediments indicate a further regression in late Eocene times. Oligocene sediments appear only in the deeper parts of the basin. A last transgression occurred in the Early Miocene. Single local ingressions might have followeduntil the Pliocene. Since the Pliocene, a general epeirogenic uplift of the South African subcontinent, combined with the tectonic activity of the East African Rift, led to a period of erosion. The Quaternary is characterized by a thick cover of eolian sands. The geological history, stratigraphy and paleogeography on both sides of the Mozambique Channel, and recent results of deep-sea drilling in the channel, suggest a more or less unchanged position of Madagascar relative to Africa since the Late Paleozoic.