Human Evolution and Environmental Changes in the Late Cenozoic. Global Ice Volume during the Last Glacial and Human Migrations.

Abstract

Global ice volume during the last glacial stage was obtained using geological observations from the sites located away from the former glaciated regions. The advantage using such records is that the area has been less influenced from the readjustments of the crust due to glacial isostasy. However the effect is still not negligible in those areas and hence it is required to correct sea-level records for both glacio- and hydro-isostatic effect to extract past global ice volume information. The record shows progressive growth of global ice volume since the end of the Last Interglacial. Rapid fluctuations of the volume were also observed during the last ice age corresponding to the Heinrich events observed in the North Atlantic ocean as well as Dansgaard-Oschgar events seen in the Greenland Ice cores. The Last Glacial Maximum was ranged between 30,000 years ago to 19,000 years ago and ended by the rapid disintegration of the ice volume that corresponding to decrease of the ca. 10 m of ice-volume equivalent sea-level. Gradual sea-level rise was seen during the late glacial stage, except the time known as melt-water pulse 1a in the Barbados coral, but other catastrophic rises were not found in the records. Main phase of deglaciation was ended until ca. 7000 years ago, yet slight decrease in ice volume equivalent to the 3 m global sea-level has been occurred since then. Sea-level change namely global ice volume fluctuations had been played as major role for human migration from Africa to the other parts of the world during the last ice age. Therefore studies on coastline changes will provide an useful information for the research on spatial and temporal histories of past human life styles.