Models of landscape evolution and the survival of Palaeoforms

Abstract

One of the factors mitigating against the recognition and acceptance of very old palaeosurfaces was, and in some measure remains, the tacit acceptance of some of the better known models of landscape evolution. Thus both the steady state and peneplanation models imply virtual contemporaneity of surface, and though scarp retreat allows for a greater age, the maximum is determined by the duration of a cycle, probably of the order of 33 Ma; much younger than many firmly dated epigene surfaces. Basically landform and landscape persistence involves the stability, or only slow rate of change, of surfaces (divides) of bounding scarps, or both. Such slow rates of change are induced by such factors as resistant bedrock: hence the preservation of many palaeoforms on quartzites, etc. In addition, several mechanisms, such as uplift, through drainage, and consequent local 'aridity'; incision and unequal activity; and reinforcement or positive feedback mechanisms, enhance the persistence of surfaces.