Glacial events of the past and their geological significance

Abstract

Traces of glaciations are unevenly distributed in the stratigraphic column and exhibit rhythmicity of several ranks. This rhythmicity makes it possible to establish the corresponding hierarchy of climatic events (in descending order): glacio- and thermo-eras, glacial and interglacial periods and epochs, as well as smaller events which appear, to be compared to the most important climatic fluctuation during the Pleistocene. The direct factors causing initiation and termination of glaciations were climatic fluctuations. The palaeolatitudinal position of the continents controlled a degree of asymmetry and, perhaps, a certain diachronism of glaciations in different hemispheres. During the glacial periods in high and middle latitudes of the Earth the glacial and cold—temperate climates either were predominant, or alternated. The thermo-eras and at least some interglacial periods were characterized by warm—temperate and warm climates at high and middle latitudes. Glaciations have been numerous and important geological events; they affected all outer spheres of the Earth from asthenosphere to atmosphere. They apparently stimulated the biological evolution too. The study of ancient glaciations is important from both the scientific and economical points of view.