Pediments as Etch Forms: Implications for Landscape Evolution

Pediments are convergent forms. Of the recognized types, the covered is of epigene derivation and is characteristic of certain sectors of fold mountains. The more widely distributed mantled forms (shield lands, dissected plateaus, and fold mountains) are of etch origin. The associated rock pediments are two-stage features resulting from the stripping of the regolith from the mantled forms. They remain in physical continuity with the scarp or outcrop, whereas platforms, also of two-stage origin, stand in isolation. Etching also accounts for those several streamless mantled pediments that presently lack any substantial backing upland and, hence, source of seepage. The interpretation of pediments as etch and, hence, azonal forms directs attention to the role played by subsurface weathering and pediments in landscape evolution.