Tectonic evolution of high plateaus

cited By 33The striking contrast in tectonic style between highlands like Tibet with its active grabens, and low altitude flanks, like the thrusting structures in the foothills of the Himalayas, shows that a disorder of the tectonic stresses correlates with the topography. The same is true for gravity, in particular for the geoid, as clearly observed in the case of the Altiplano. These observations can be explained physically by means of simple relationships between the dipolar mass distribution of the high topography and its compensating root. This analysis leads to a proposed scenario for plateau evolution in three stages: 1. (1) build-up with thrusting and folding, 2. (2) neutral state or strike-slip deformation, and finally 3. (3) relaxation with normal faulting. The Basin and Range represents a mature illustration of phase (3). Its Bouguer anomaly suggests the existence of an undulation of the lithosphere-astenosphere boundary with a 200 km wavelength. Physical models of lithospheric boudinage are shown for one to compare with the observed topographic and gravimetric signatures. © 1987