The great age of some Australian landforms: examples of, and possible explanations for, landscape longevity

Abstract

Abstract According to the major conventional models of landscape evolution there ought to be no land surfaces older than Oligocene, save some that have been exhumed. In reality, substantial areas of the Australian continent (as well as other parts of Gondwana and of Laurasia) are of Mesozoic or greater ages. Surfaces of Late Jurassic or Early Cretaceous ages are especially widespread. Many are of exhumed origin, but several notable features are of epigene-etch type. Their age ranges have been determined stratigraphically. In some instances (e.g. Gawler Ranges, Hamersley Surface, Eastern Uplands), the stratigraphic evidence is incontrovertible. Elsewhere the position and elevation of massifs, such as Arnhem Land, relative to Cretaceous shorelines demonstrate their essential antiquity. The survival of such very old palaeosurfaces is attributed to several factors, but particularly to unequal erosion, reinforcement mechanisms and the prevalence of vertical (epeirogenic or isostatic), rather than orogenic, earth movements.