Migration of glacial centers across Gondwana during Paleozoic Era

Abstract

Continental glaciation, as recorded by sedimentary facies and by pavements scoured into underlying rocks, affected northern Africa at the end of the Proterozoic Era. This glaciation was followed in the Cambrian Period by a long, warmer interval without recorded ice sheets upon the Gondwana supercontinent. Strong glaciation ensued in Late Ordovician time in central northern Africa, and centers moved into then adjoining northern Brazil and on westward into southern Brazil, southern Africa, and Bolivia and into northern Argentina by the Early Silurian. From Middle Silurian time, world-wide and Gondwanan climate ameliorated until Late Devonian (Famennian) time, when glaciation again affected Brazil and perhaps parts of Africa. Glacial centers apparently waned after the late Famennian (latest Devonian) but waxed again in Andean regions and northern Brazil in Early and mid-Early Carboniferous times to begin the strong Late Paleozoic Ice Age. Many ice caps and ice sheets came and went across the wide reaches of Gondwana during the late Paleozoic, beginning on the west, culminating in southern Africa in the Late Carboniferous, continuing strongly in India and Australia in the Permian, and dying out in eastern Australia and in Antarctica in early Late Permian time. The path of ice-center migration closely follows published paleomagnetic wander paths. The record suggests that, among other terrestrial factors which cause ice ages, glaciation flourished when Gondwana lay in south polar regions and that glaciation disappeared when Gondwana glided, so that the pole lay in oceanic or coastal regions.