Auto-exposure and underprinting in the exhumation of Neoproterozoic (subNama) inselbergs in southeastern Namibia

Abstract

Though most of the gneissic inselbergs exhumed from beneath a cover of essentially undisturbed Early Cambrian Nama sedimentary strata have been re-exposed by river erosion, a few stand in isolation in enclosed depressions remote from surface streams. They are attributed to auto-exposure whereby circulating groundwaters are concentrated on the relatively impermeable buried residuals, causing weathering, shrinkage and compaction in the overlying sediments. This resulted in surface subsidence and eventual exposure of the inselbergs.