A great deal is known about the late Palaeozoic glacial phase owing to intensive study since its recognition in the early part of this century. We now know that glaciations of this time were centred in polar to subpolar latitudes, that they were developed in parts of Laurasia as well as Gondwana, that their inception was regionally related to both collisional and extensional orogenic activity, that ice sheets developed in the centres of continents, and that glaciers underwent waxing and waning in response to changes in their palaeolatitudinal position. There are many other aspects of the late Palaeozoic Cool Mode about which we are relatively ignorant. What was the full duration of glacier development? What were the climates of the nonglaciated parts of the globe? Why did the glaciation cease?

Distribution and age of the glacials

Late Palaeozoic glacial deposits occur widely in Gondwana and also in displaced terranes which are now part of Asia (Fig. 5.1). These have been summarized most recently by publications in Hambrey and Harland (1981), Frakes (1979) and Crowell (1983). Africa is the continent with the most widespread deposits from this glaciation; glacial deposits are known from South Africa to the Arabian peninsula and from the east (Madagascar) to the west (Namibia). The southern exposures consist of the Dwyka Tillite, which occurs in the Karroo basin across the full length of the Cape Fold Belt and eastward into coastal Natal. An ice sheet occupied the northern part of South Africa and adjacent countries to the north (Zimbabwe, Botswana, Zambia) and radiated lobes to the south-east, and south-west (Kaokoveld Lobe).