INTERACTION OF TECTONIC UPLIFT AND EXOGENOUS DESTRUCTION OF A SLOPE COMPOSED OF NON UNIFORM SUBSTRATES

Abstract

Landform morphology created by combined action of endogenous deformations and exogenous (denudation) processes depends on whether these forces performed concurrently or in succession in this study, different formation scenarios for a tectonic arch composed of heterogenous substrates are analyzed based on kinematic modeling techniques.

Following the start of the uplift, a lengthwise zone of softer rocks is being transformed into a gorge with a narrow outlet either in case of tectonic tilt and vertical (block) elevation. V-shaped cross-section is being preserved in the outlet as long as the elevation above base level increases. This scenario is valid for many young alpine regions such as Kopet Dag, Himalaya, etc. After the uplift has been finished, gorges start to widen and become trough-like in cross section, and a progressively widening step starts to form at the base of the arch slope (a pediment). In a block that contains a hard vertical dyke, a gently sloping crest is formed following the uplift start. After the uplift cessation, the crest preserves its form retreating together with the whole arch slope.

Slow elevation of an arch containing a hard horizontal layer results in transformation of the upper part of the arch into a small spherical remnant. At the side of the hard layer, a steep cliff forms that passes below into a conical pedestal produced by denudation in softer rocks. In case if the arch contains a softer horizontal layer the surface of the raising block evolves rather to conical than to spherical form.