UPLIFT HISTORY OF THE TRANSANTARCTIC MOUNTAINS, VICTORIA LAND, ANTARCTICA.

Apatite fission-track ages from basement granite samples from the Wright and Victoria dry valley systems, southern Victoria Land, show the now widely known increase with sample elevation. Ages observed so far all post-date emplacement of the Ferrar dolerites at about 170 Myr, ranging between about 154 plus or minus 7 Myr and 44 plus or minus 4 Myr. The apatite age gradient indicates a steady, very slow uplift over the period between about 150 and 50 Myr at about 15 m/Myr, or possibly just a slow downward relaxation of the isotherms in the area, with little erosion. By comparing the relative offsets of the apatite age gradients at different localities it is possible to establish the relative uplift across the mountain range. The onset of relatively rapid uplift at about 50 Myr represents the onset of the major block faulting episode known as the Victoria Orogeny. The timing of this event has important implications for the establishment of widespread glacial conditions in Antarctica.