THE STRUCTURE AND ORIGIN OF MOUNTAINS: PRE-PLANATION AND POST-PLANATION GRAVITY STRUCTURES

Abstract

Mountains are not made directly by folding, but result from uplift of plains (planation surfaces) to form plateaus, which are subsequently eroded into rugged mountains. Most folding of rocks occurs before planation and plateau uplift, but folding and faulting can also occur during and after pla­teau uplift. In all instances the folding may be caused by gravitatio­nal sliding or spreading rather than the "squeeze box" type of com­pression favoured in conventional hypotheses of mountain building. It is important to distinguish between the tectonic structures created before planation, and those that occurred after planation and uplift. Evidence for the two types is presented, and criteria for distinguishing the two different types are proposed.