1 - Geodynamic controls on glaciation in Earth history

Summary

Abstract

The geological record of glaciation is sporadic. It begins with poor and fragmentary evidence from Archean rocks but there is unequivocal evidence of glaciation in the Paleoproterozoic of North America, Scandinavia and possibly South Africa, western Australia and India. There follows a long Mesoproterozoic nonglacial period, between about 2.0 and 1.0 Ga with no well-constrained evidence of glaciation but there is a return to sporadic glacial conditions from about 800 Ma to the Cambrian. Neoproterozoic glaciations were very widespread and evidence is preserved on all the present day continents. Some palaeomagnetic evidence suggests that Neoproterozoic glaciation may have taken place at low paleolatitudes but new data supports earlier concerns with regard to rapid plate motions and low latitude ‘overprinting’ in the Cambrian. ‘Warm’ climate strata in many Neoproterozoic glacial successions appear to be detrital in origin.

In Phanerozoic times, glaciation is reported from Ordovician successions in Africa, possibly Brazil and Arabia; evidence of Silurian and Devonian glaciation is largely limited to South America. The most significant Phanerozoic glaciation took place in the Permo-Carboniferous, between 350 and 250 Ma, across a large area of the Gondwanan supercontinent. There is no direct geologic record of Mesozoic glaciation but small ice masses may have developed in the interiors of landmasses at high latitudes (e.g. Antarctica, Siberia). Small-scale fourth-order cycles of sea-level change recorded on several carbonate and siliclastic shelves at this time are unlikely to be of glacio-eustatic origin.

The earliest Late Tertiary glaciation is recorded from Antarctica about 36 Ma; glaciation in the northern hemisphere was initiated at about 6 Ma with large continental ice sheets developing after about 3 Ma.