Bar Oryan, Boris Gailleton, Jean-Arthur Olive, Luca Malatesta, Romain Jolivet

Earth surface processes encode the combined forcing of tectonics and climate in topography. Separating their contributions is essential for using landscapes as quantitative records of crustal deformation. Here, we develop a method for inverting spatially-variable fields of long-term rock uplift and rock erodibility from fluvially-incised landscapes, while accounting for climatic variability. Our approach operates in the χ reference frame and uses B-spline interpolating functions to represent spatial heterogeneities in key geomorphological parameters. Upon inverting 170 synthetically-generated landscapes, we demonstrate that our method accurately recovers the spatial variability of key geomorphic agents, even when applied to settings that deviate from the ideal model of equilibrated detachment-limited channels, which underpins the χ-space framework. We subsequently apply our inversion to five natural landscapes shaped by normal faults (half-grabens), and to a 200-km wide region of the Himalayas. We show that our inversion can resolve the effect of climate and lithology while extracting uplift fields that are consistent with patterns expected from upper crustal flexure and previous estimates derived from geomorphological markers. The success of our method in recovering uplift patterns, isolated from the effects of climate and erodibility, highlights its applicability to settings where long-term uplift trends are unknown, paving the path to deciphering time-averaged tectonic fingerprints recorded in landscapes over tens of thousands of years.