The discontinuous glacio-eustatic fall in tertiary sea level

Abstract

In eastern Antarctica at latitude 86° S and 3,000 m elevation, a solifluxion layer and overlying drifts from temperature glaciers are older than the East Antarctic Ice Sheet, which built up after the glacier tongues had reached low ground. The glacial-eustatic drop in sea level eventually amounted to about 60 m by the time this ice sheet had an equilibrium profile. Land ice also covered the western Antarctic archipelago, but no more could accumulate in Antarctica until further cooling allowed “cold” shelf ice to spread, thicken, and come to ground in the former strait between eastern Antarctica and the western Antarctic archipelago. The West Antarctic Ice Sheet then built up, causing an additional drop in sea level of about 5 m. Intensely glaciated landscapes in the Horlick Mountains, now partially buried by this ice sheet, indicate a long interval of glacial erosion in eastern Antarctica before the West Antarctic Ice Sheet existed. The Greenland Ice Sheet, with less critical temperature requirements, may have formed either during this interval, causing a further drop in sea level of about 6 m, or contemporaneously with the West Antarctic Ice Sheet, resulting in a total fall at that time of about 11 m. The crucial spread of Antarctic shelf ice preceded the formation of the first North American and European ice sheets, for until then temperatures were higher than they are today. It probably marks the Pliocene-Pleistocene transition, if this is defined as the point when falling temperatures first reached today's level.