LATE WEICHSELIAN TO HOLOCENE EVOLUTION OF THE MAPUTO BAY, MOZAMBIQUE

During the Quaternary the volume of the world’s oceans fluctuated, with sea level falls as the water has been incorporated into polar and high latitude ice sheets, and sea level rise as these have subsequently melted. Sea-level lowstands were therefore related to the Pleistocene glaciations, while high-stands correlate with interglacials. In general the climate variations in Africa shows a simple relation: Cold or cool climates are associated with dry episodes and warm climates are associated with wet episodes. This applies to the major Milankovich driven glacials and interglacials, as well as to short-lived intervals related to sun spot activities. The reconstruction of palaeo-shorelines in the Maputo Bay, and the climate around the Maputo Bay is based on bathymetric maps. At about 18,000 yr BP (-130 meters sea level) the Maputo Bay was located in an inland position. As the sea level rose to about 20 m below present around 9000 - 10000 years BP, a barrier island complex developed in the northern coast, which is well defined by 20 m contour palaeoshoreline. The Maputo Bay is only formed around 8000 – 9000 years BP (when the sea level was 10 to 12 m below the present, and it was a long lasting still stand sea level. A huge island was protecting the bay from the sea. Tidal inlet and its associated ebb delta were separating the island from the peninsula in the south and were connecting the lagoon into the sea. The complete picture of Maputo Bay patterns with its modern sedimentary environments including Inhaca Island may have evolved when the sea level has stood close to its present level around 7000 – 5000 years BP, after which the Maputo Bay became more or less stable. Coral reefs may have also developed during this period. Submarine modifications of the topography during and after the sea-level rise make it difficult to make safe interpretations of the coastal palaeomorphology. However, we believe that many of the present major submarine bottom forms, which are seen on the maps today, are related to coastal processes during the sea-level rise, and were preserved when they were flooded during the Holocene transgression.