Summit levels, bedrock control and the etchplain concept in the basement of Suriname

Abstract

A comparison between summit levels distinguished by various authors in the basement of Suriname, photogeological landscape units, lithological information from the new geological map and LANDSAT imagery shows that many summit levels coincide with photogeological and lithological units in the lowlands that form the main part of the basement. Steps that separate summit levels of different altitude commonly are also lithological discontinuities. Such steps might originate under humid climatic conditions as jumps in the weathering front due to differential chemical weathering of contrasting rock types. The steps are exposed at the surface during periods of semi-arid conditions under savanna vegetation by stripping of the saprolite. In this etchplain model, summit levels at different heights do not differ essentially in age but only in resistance of underlying rocks to deep weathering. Only those levels that are protected by means of duricrusts against further surface lowering, or that were exhumed as domed inselbergs survived several cycles of etching and stripping.