The influence of lithospheric rheology and surface processes on the preservation of escarpments at rifted margins

The formation of rift flank topography along rifted margins is related to the flexural uplift of the footwall on the rift border fault during lithospheric stretching. The preservation of rift flank topography in mature margins can be explained as a feedback mechanism between differential denudation of the margin and regional isostatic response of the lithosphere. However, the contribution of the lithospheric rifting on the escarpment amplitude in both young and mature margins is not easily quantified. In the present work, we used a 2D thermo-mechanical numerical model to simulate lithospheric extension to evaluate the sensitivity of escarpment amplitude and its preservation under different rheological conditions over timescales larger than 100 Myr, comparable with the age of mature rifted margins. We found that the evolution of escarpment uplift and its preservation for tens of millions of years are sensitive to the degree of coupling between the crust and mantle and the regional isostatic response of the lithosphere to surface processes. The flexural uplift as a response to lithospheric stretching are limited to the first 100‐150 km from the rift flank. Without the influence of surface processes, the amplitude of the escarpment monotonically decreases through time due to the lateral flow of the lower crust and thermal cooling of the margin. In the scenarios with surface processes, topographic signature inherited from the rift phase in the post-rift escarpment elevation is possible only in margins where the erosive escarpment retreat is smaller than ∼100 km. In scenarios where the escarpment retreat exceeds this distance, the escarpment elevation is mainly preserved by the combination of the inherited topography (existent before the onset of lithospheric rifting) and flexural rebound of the lithosphere due to the erosion along the margin.