GEOPHYSICAL INVESTIGATIONS OF THE TECTONIC BOUNDARY BETWEEN EAST AND WEST ANTARCTICA

The Transantarctic Mountains (TAM), which separate the West Antarctic rift system from the stable shield of East Antarctica, are the largest mountains developed adjacent to a rift. The cause of uplift of mounta ins bordering rifts is poorly understood. One notion based on observat ions of troughs next to many uplifted blocks is that isostatic rebound produces a coeval uplift and subsidence. The results of an over-snow seismic experiment in Antarctica do not show evidence for a trough nex t to the TAM but indicate the extension of rifted mantle lithosphere u nder the TAM. Furthermore, stretching preceded the initiation of uplif t, which suggests thermal buoyancy as the cause for uplift.