2 - Global glacial chronologies and causes of glaciation

Abstract

This chapter provides a brief review of glacial stratigraphic records with some consideration of causal factors and mechanisms responsible for driving climatic changes and the spectrum of glacial advances and retreats. Glaciations represent significant perturbations in the Earth's climatic regime. The evidence of such glaciations is commonly preserved and relatively easy to be recognized in geological records. Geological records are strongly at odds with such an interpretation becaue the oldest rocks on Earth contain clear evidence of the presence of liquid water. The earliest evidence of glaciation is recorded by terrestrial and marine diamictites and proglacial deposits. The oldest substantiated evidence of widespread glaciation is found in the rocks of Paleoproterozoic age reported from North America, Finland, South Africa, Australia, and India. The Neoproterozoic records reveal the greatest proliferation of ice sheets the world has known. Many of these glacial centers developed at low paleolatitudes. Widespread evidence of rifting and some paleomagnetic data support the concept of the existence of a supercontinent or supercontinents during this period. The chapter focuses on the global terrestrial and marine records of the present ice age. These records delineate glacial and interglacial intervals of 10,000 to 100,000 years, stadial and interstadial events within the glaciations that span 1,000 to 10,000 years, and major fluctuations of mountain glaciers in postglacial and historic times involving decades to centuries to millennia.