Quantifying the feedbacks between tectonic processes in the lithosphere and climatic processes in the atmosphere is an overarching goal in Earth-Systems research. Long-term cooling during the Cenozoic has been linked to the growth of mountain belts, which enhanced erosion, chemical weathering, organic-carbon burial and drawdown of atmospheric CO₂. Conversely, it has been proposed that the cooler and more variable climate of the late Cenozoic led to increased topographic relief and erosion. However, the topographic and erosional response of mountainous topography to late-Cenozoic climatic cooling culminating in Quaternary glaciations, and the potential couplings between these processes, remain poorly constrained. Advancing our understanding requires the development of tools that record erosion rates and topographic relief changes with higher spatial and temporal resolution than the current state-of-the-art, and the integration of newly obtained data into next-generation numerical models that link observed erosion-rate and relief histories to potential driving mechanisms. Within the ERC-funded COOLER project, we are building a new ⁴He/³He thermochronology lab in Potsdam, developing numerical modelling tools that incorporate the latest insights in kinetics of thermochronological systems to make sample-specific predictions, coupling these tools to glacial landscape-evolution models to enable modelling of real landscapes with real thermochronology data as constraints and, finally, studying potential couplings between glacial erosion, relief development, and tectonics in selected field areas.

Species richness of Madagascar is uneven, with the highest species richness and endemism found on the steep great escarpment of the eastern margin. The unevenness is further observed within the escarpment region in that phylogenic turnover shows both latitudinal and altitudinal variations. Madagascar has remained almost tectonically inactive since the last rifting with Seychelles-India such that the fundamental topographic framework has been in place since Cretaceous. The high diversity and endemism of Madagascar challenge the conventional notion of uplift-driven speciation, which argues that speciation is driven by the formation of diverse habitat types. To investigate the causal mechanisms of the diversity at the eastern escarpment, we constructed landscape evolution models, tracing the dynamics of habitable land surface patches throughout model simulations.

The landscape of a great escarpment is dynamic and the heterogenous retreat of the escarpment and the water divide makes the geographically isolated drainage basins expand landward at different rates. Within the escarpment region, habitat patches dynamically appear, disappear, fragment, or merge at a frequency that scales with the retreat rate. The models predict that escarpment retreat fosters habitat patch dynamics such that patches isolate, or reconnect with a frequency on the order of a million years, appropriate for allopatric speciation. We conclude that the spatially heterogeneous but temporally steady retreat of the Madagascar escarpment since rifting has sustained allopatric speciation over evolutionary timescales resulting in the observed high diversity and its spatial pattern of eastern Madagascar.

River networks function as conduits for water and sediment transport across Earth's landscapes, while the elevated boundaries separating these networks, termed drainage divides, determine the partitioning of material fluxes among adjacent basins and establish physical barriers that restrict biotic dispersal. Variations in tectonics, climate, and lithology can alter the position of these divides, influencing water balance, erosion rates, sediment flux, and the geographic connectivity and evolutionary trajectories of biota. This study focuses on the overlooked temporal evolution of 'wind-gaps' (i.e. old river valleys transformed into in-valley drainage divides by drainage capture events) as an unstudied but key capture-related landform hypothesised to be fundamental in shaping post-capture-related landscape evolution. Using numerical landscape evolution modelling, our findings challenge the prevailing perception of wind-gaps as static landforms, revealing previously unrecognised mobility, with wind-gaps serving as mobile divides that reshape entire landscapes. Moving wind-gaps can trigger cascading morphological and erosional changes beyond an initial capture event, initiating a domino effect of captures of lateral tributaries to the pre-capture river. This can repeatedly alter the connectivity of riverine ecosystems, driving complex but predictable patterns of biotic diversification and leaving abiding imprints in the sedimentary and landscape records. Wind-gap propagation offers a mechanistic framework that opens avenues for deciphering complex linkages over time between landscape evolution, sediment dynamics, and biodiversity.

The application of the triple oxygen isotope system (¹⁶O-¹⁷O-¹⁸O) provides a new tool for stable isotope paleoaltimetry. Here, we use triple oxygen isotope (Δ’¹⁷O) geochemistry to determine the past elevation of the Eocene Kettle Metamorphic Core Complex (MCC) (Washington, USA). We analyze quartz-muscovite pairs from mylonitic quartzites from the MCC-bounding shear zone. δ¹⁸O values range from 4.8 to 11.3‰ (muscovite) and 6.8 to 14.6‰ (quartz) and Δ’¹⁷O values (λ_ref = 0.528) range from -0.054 to -0.077‰ (muscovite) and -0.052 to -0.071‰ (quartz). The calculated quartz-mica oxygen isotope equilibrium temperature averages 390°C ± 90°C, which in line with observed quartz microstructures. Compared to existing muscovite hydrogen isotope data (δD = -101 to -138‰), both approaches, δD-δ¹⁸O and δ’¹⁸O-Δ’¹⁷O, indicate oxygen and hydrogen isotopic exchange between syntectonically formed minerals and a meteoric-derived fluid within the Kettle shear zone. We find that the shear zone minerals are in isotopic equilibrium with a fluid having a δ¹⁸O_water value of ~-14‰, which likely reflects high-elevation inland precipitation. Combined with a low-elevation δ¹⁸O_water estimate (-6 to -8 ‰) from the Eocene near-coastal Chumstick Basin (WA, USA), the δ¹⁸O_water estimate translates into a paleoelevation of 3-4 km for the Eocene Kettle MCC. This is consistent with δD-based elevation estimates of 4.2 km and underscores the robustness and complementary nature of the two different isotopic approaches.

Chemical weathering in Southeast Asia is increasingly recognised as being a core control over global climate, particularly the cooling of Earth during the Cenozoic. This is particularly true during the Neogene when chemical weathering fluxes from the Himalayas decreased through time, meaning that silicate weathering in that region was not the primary control over falling CO₂ levels in the atmosphere. Instead, chemical weathering of sediments eroded from the arc and ophiolite terrains in Southeast Asia may be critical. Recent study of marine sedimentary deposits offshore Eastern New Guinea now show that there is a trend towards more intense chemical weathering in that region over the last 20 million years and especially since 6 Ma. Collision between New Guinea and Australia primarily commenced around 15 Ma when erosion from uplifting arc terrains made the sources especially reactive. Since that time uplift has created a large island with increasing erosion from continental Australian sources, reducing the reactivity. We estimate that sediments eroded from New Guinea maybe approximately 2 to 3 times as effective at consuming of CO₂ as their equivalents in South Asia. Over shorter, orbital timescales there is more erosion from accreted Australian crust during interglacial times when the stronger rainfall was able to penetrate deep into the New Guinea Highlands than during glacial times when erosion was more focused on mafic rocks along the coast. Chemical weathering intensity follows global climatic cycles with generally less weathering during interglacial warm periods, likely related to faster transport driven by high fluvial discharge.