MINIMAL PLIOCENE-PLEISTOCENE UPLIFT OF THE DRY VALLEYS SECTOR OF THE TRANSANTARCTIC MOUNTAINS - A KEY PARAMETER IN ICE-SHEET RECONSTRUCTIONS

We propose that there has been little or no Pliocene-Pleistocene uplif t of the dry valleys sector of the Transantarctic Mountains, on the ba sis of isotopic dating and mapping of in situ cinder-cone deposits on the walls of Taylor Valley. Twenty-seven Ar-40/Ar-39 incremental heati ng analyses on whole-rock samples from subaerially erupted olivine bas anite volcanic outcrops of known elevations define 14 eruptions rangin g in age from 3.89 to 1.50 Ma. Because Taylor Valley opens directly on to the Ross Sea, these results show that any surface uplift during the past 2.57 m.y. was < 300 m. Our conclusion of minimal uplift contradi cts previous models of dramatic uplift (up to 3000 m since 3 Ma) and a ssociated hypotheses that uplift caused climatic cooling and growth of a polar East Antarctic ice sheet.