Measuring rock-uplift rates using calibrated inverse landscape evolution modelling

• Applicant: Dr. Fergus McNab
• Subject Area: Geology ; Mineralogy, Petrology and Geochemistry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559578079

Uplift of the Earth’s crust (so-called “rock uplift”) is a key driver of its surface evolution. It builds mountain ranges that host natural hazards and exerts a first-order control over climatic systems and biodiversity. It also displaces paleo-sea-level markers, hindering reconstruction of past sea level and ice-sheet stability. Understanding the diverse causes and consequences of rock uplift requires detailed observations of its spatio-temporal evolution, but direct uplift markers are scarce or absent in many settings. A landscape that exemplifies this issue is southern Africa, where a high plateau sits over 1 km above sea level despite being underlain by old, thick lithosphere and situated far from active plate boundaries. The region’s uplift has been linked to its exceptional biodiversity and patterns of atmospheric circulation. It may also have displaced rare sea-level markers from the mid-Pliocene Warm Period, an analogue for near-future climate. A lack of direct constraints has led to controversy surrounding the timing of, and mechanisms controlling, regional uplift. Unlike sparsely distributed uplift markers such as emergent marine rocks, landscapes are ubiquitous. Understanding relationships between rock uplift and landscape form may therefore allow us to infer rock-uplift patterns across the continents. Until recently, such efforts have focused on the evolution of river profiles. In particular, inverse modeling is used to identify uplift histories that best fit observed profiles. However, in recent years, efficient landscape evolution models have been developed that also account for hillslope evolution and lateral migration of river channels. These advances lay the groundwork for inverse modelling of the full landscape, which will be the focus of this project. By analysing a combination of simulated and natural topography, I will explore how changing uplift patterns are reflected in the shape of the whole landscape. I will also explore the extent to which landscape models can be calibrated with observations of surface erosion rate derived from thermochronology and cosmogenic radionuclide analyses. These insights will inform design of a strategy for calibrated inverse landscape evolution modelling that includes a holistic treatment of surface processes and is applicable in a wide range of settings. This framework will also provide a means to test and compare the predictions of diverse landscape evolution models. Following field and laboratory work to generate new local erosion-rate measurements, I will apply these novel techniques to southern Africa. This work will provide new constraints on the region’s controversial uplift history and facilitate correction of nearby sea-level markers, refining knowledge of global sea-level change in the mid-Pliocene Warm Period, and, by analogy, the future. The techniques developed here will be released for use by the community, with potential applications in a range of geoscience disciplines.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Pieter van der Beek