Miombo Ecoregion Vision Report - Biodiversity Foundation for Africa

Miombo Ecoregion Report, page 12
In Africa, Karoo rocks can be traced from extensive areas across South Africa to Namibia,
Botswana, Zimbabwe (particularly Matabeleland and the Zambezi Valley), Zambia and small
patches in Malawi, Tanzania and Kenya. Lower Karoo rocks, deposited during the glacial and
cool temperatures, are principally shales and sandstones with coal derived from Glossopteris
flora. The basal formation is a tillite, which commonly rests on a glaciated pavement – the Pre-
Karoo erosion surface.
Figure 3. Miombo Ecoregion – rainfall.
Upper Karoo sediments are lighter-coloured grits, sandstones, shales and mudstones that contain
Permian therapsids, Triassic dinosaurs and a variety of plant fossils. Some of the finer grained
rocks are highly erodible, and in certain localities in Hwange National Park, the floor of the
Zambezi Valley and south of Harare exhibit spectacular gully and sheet erosion. The basalts can
be seen today in Lesotho, the Limpopo Valley, Victoria Falls and smaller outliers elsewhere.
The break-up of Gondwanaland produced new coastlines along the eastern and western margins
of Africa, and Cretaceous and Cainozoic times are recorded by littoral sediments associated with
shoreline fluctuations. In the hinterland, however, the Kalahari and Congo basins have been the
loci of continental deposition. The most recent deposits are the Kalahari Sands which date from
the Miocene Epoch and which have been blown repeatedly, in various directions, until the
present day. Deposits of these sands now occur far beyond the present Kalahari region, in
scattered patches through Zimbabwe and Zambia, and locally provide the uppermost soil for the
Miombo Ecoregion. The underlying geology of the ecoregion covers a wide spectrum of rock