FIRST-CLASS AND SECOND-CLASS OROGENIC PLATEAUS

Understanding what controls the distributed deformation of diffuse deformation in the continents remains a fundamental problem in tectonics. Orogenic plateaus are representative of a type of distributed deformation in the continents and the ~ 5 km high Altiplano and Tibetan plateaus are classic examples of plateaus developed at convergent continental tectonic boundaries. These plateaus have a clear spatial and temporal association with fold and thrust belts along their margins and have experienced significant crustal thickening that largely supports their high elevations in Airy isostatic equilibrium. However, along the Alpine-Himalaya orogenic system several other secondary plateaus of lesser geographic extent and generally lower elevation (~ 1 ½-3 km) exist (i.e. the Iberian pennisula, Morroco/Algeria, and the Anatolian-Iranian plateau). These plateau areas are also associated with fold and thrust belt deformation, however tend to be supported by buoyant sub-crustal mantle rather than thickened crust. This talk explores the geologic and geophysical data available to argue whether these lower elevation ‘2nd class’ plateaus are precursors to their ‘1st class’ counterparts (i.e. Tibet and the Altiplano) or whether the represent a fundamentally different style of plateau formation.