Late Palaeozoic Glacial Facies and the Origin of the South Atlantic Basin

Abstract

IN an attempt to add detail to the established picture of glaciation in the southern hemisphere during the Late Palaeozoic, we have studied tillites and associated rocks in Antarctica, Africa, South America and the Falkland Islands in the past few years^1–4. As well as determining the direction of ice movement from directional properties of the rocks, we have subdivided the strata into several environmentally significant facies. These distinct lithological types are further restricted geographically in such a way that their distributions add information on palaeogeography. For example, linear sand bodies interpreted as glacial eskers are interbedded with tillite in the western Falkland Islands⁵. These deposits pass laterally into a thick, massive envelope of tillite and associated turbidites in the eastern portion of the Falklands, which suggests that terrestrial ice occupied the west while, farther east, glacial-marine accumulation took place in deeper water. Similar approximate palaeogeographic reconstructions from tillite facies can now be made for widely scattered parts of the glaciated continent of Gondwanaland.