Quantifying passive margin denudation and landscape development using a combined fission-track thermochronology and cosmogenic isotope analysis approach

A new approach to empirically constraining numerical models of denudation and landscape development across passive continental margins is presented involving a combination of apatite fission-track thermochronology and cosmogenic isotope analysis. This integrated strategy is applied to the Namibian sector of the south-west African margin where the conventional landscape evolution model of inland retreat of an escarpment initiated at the coast at break-up implies a mean rate of retreat of similar to 1 km Ma(-1). The thermochronological and cosmogenic isotope data are incompatible with a simple escarpment retreat model since they show that denudation rates oceanward of the present escarpment position have been low (< 20 m Ma(-1)) since the end of the Eocene, and the estimated rate of escarpment retreat has been only similar to 10 m Ma(-1). This low rate of retreat is, however, consistent with numerical landscape evolution models where the escarpment is pinned at an inland drainage divide. (C) 2000 Elsevier Science B.V. All rights reserved.