Tectonic regime and the preservation of Palaeosurfaces

Abstract

Common sense, as well as the conventional scientific wisdom, suggest that the Earth's surface is constantly changing. The field evidence, in some areas is, however, at odds with this supposition, for firmly dated landscape elements of great antiquity are widely distributed. Many of these palaeoforms are of exhumed type but others are of epigene-etch origin. Fragments of old palaeoforms are preserved in active tectonic regions, but the chances of survival are reduced by the intense dissection characteristic of such areas, and especially in those areas that have been uplifted sufficiently to induce the activity of frost and ice. Such remnants are not readily recognised and are also difficult to date. But extensive palaeolandscape remnants are commonplace on cratons and old orogens. Such regions are comparatively stable, and vertical movements have dominated through much of later Phanerozoic time. Alternations of planation and weathering on the one hand, and uplift and stripping of regoliths on the other, have produced etch surfaces. Uplift has also induced stream dissection, but interfluves have been preserved. Such unequal erosion and associated reinforcement effects substantially account for the survival of palaeoforms in such cratons and orogens, though several other factors contribute to their preservation.