Global climate is thought to be modulated by the supply of minerals to Earth’s surface. Whereas silicate weathering removes carbon dioxide (CO₂) from the atmosphere, weathering of accessory carbonate and sulfide minerals is a geologically relevant source of CO₂. Although these weathering pathways commonly operate side by side, we lack quantitative constraints on their co-variation across erosion rate gradients. Here we use stream-water chemistry across an erosion rate gradient of three orders of magnitude in shales and sandstones of southern Taiwan, and find that sulfide and carbonate weathering rates rise with increasing erosion, while silicate weathering rates remain steady. As a result, on timescales shorter than marine sulfide compensation (approximately 10⁶–10⁷ years), weathering in rapidly eroding terrain leads to net CO₂ emission rates that are about twice as fast as CO₂ sequestration rates in slow-eroding terrain. We propose that these weathering reactions are linked and that sulfuric acid generated from sulfide oxidation boosts carbonate solubility, whereas silicate weathering kinetics remain unaffected, possibly due to efficient buffering of the pH. We expect that these patterns are broadly applicable to many Cenozoic mountain ranges that expose marine metasediments.

Uplift and erosion modulate the carbon cycle over geologic timescales by exposing minerals to chemical weathering. However, the erosion sensitivity of mineral weathering remains difficult to quantify. Solute-chemistry datasets from mountain streams in different orogens isolate the impact of erosion on silicate weathering—a carbon dioxide (CO ₂ ) sink—and coupled sulfide and carbonate weathering—a CO ₂ source. Contrasting erosion sensitivities of these reactions produce a CO ₂ -drawdown maximum at erosion rates of ~0.07 millimeters per year. Thus, landscapes with moderate uplift rates bolster Earth’s inorganic CO ₂ sink, whereas more rapid uplift decreases or even reverses CO ₂ sequestration. This concept of an “erosion optimum” for CO ₂ drawdown reconciles conflicting views on the impact of mountain building on the carbon cycle and permits estimates of geologic CO ₂ fluxes dependent upon tectonic changes.

The Pamir‐Tian Shan collision zone in the western Tarim Basin, northwest China, formed from rapid and ongoing convergence in response to the Indo‐Eurasian collision. The arid landscape preserves suites of fluvial terraces crossing structures active since the late Neogene that create fault and fold scarps recording Quaternary deformation. Using geologic and geomorphic mapping, differential GPS surveys of deformed terraces, and optically stimulated luminescence dating, we create a synthesis of the active structures that delineate the timing, rate, and migration of Quaternary deformation during ongoing convergence. New deformation rates on eight faults and folds, when combined with previous studies, highlight the spatial and temporal patterns of deformation within the Pamir‐Tian Shan convergence zone during the Quaternary. Terraces spanning ~130 to ~8 ka record deformation rates between ~0.1 and 5.6 mm/yr on individual structures. In the westernmost Tarim Basin, where the Pamir and Tian Shan are already juxtaposed, the fastest rates occur on actively deforming structures at the interface of the Pamir‐Tian Shan orogens. Farther east, as the separation between the Pamir‐Tian Shan orogens increases, the deformation has not been concentrated on a single structure, but rather has been concurrently distributed across a zone of faults and folds in the Kashi‐Atushi fold‐and‐thrust belt and along the NE Pamir margin, where shortening rates vary on individual structures during the Quaternary. Although numerous structures accommodate the shortening and the locus of deformation shifts during the Quaternary, the total shortening across the western Tarim Basin has remained steady and approximately matches the current geodetic rate of 6–9 mm/yr.

The sensitivity of fluvial systems to tectonic and climatic boundary conditions allows us to use the geomorphic and stratigraphic records as quantitative archives of past climatic and tectonic conditions. Thus, fluvial terraces that form on alluvial fans and floodplains as well as the rate of sediment export to oceanic and continental basins are commonly used to reconstruct paleoenvironments. However, we currently lack a systematic and quantitative understanding of the transient evolution of fluvial systems and their associated sediment storage and release in response to changes in base level, water input, and sediment input. Such knowledge is necessary to quantify past environmental change from terrace records or sedimentary deposits and to disentangle the multiple possible causes for terrace formation and sediment deposition. Here, we use a set of seven physical experiments to explore terrace formation and sediment export from a single, braided channel that is perturbed by changes in upstream water discharge or sediment supply, or through downstream base-level fall. Each perturbation differently affects (1) the geometry of terraces and channels, (2) the timing of terrace cutting, and (3) the transient response of sediment export from the basin. In general, an increase in water discharge leads to near-instantaneous channel incision across the entire fluvial system and consequent local terrace cutting, thus preserving the initial channel slope on terrace surfaces, and it also produces a transient increase in sediment export from the system. In contrast, a decreased upstream sediment-supply rate may result in longer lag times before terrace cutting, leading to terrace slopes that differ from the initial channel slope, and also lagged responses in sediment export. Finally, downstream base-level fall triggers the upstream propagation of a diffuse knickzone, forming terraces with upstream-decreasing ages. The slope of terraces triggered by base-level fall mimics that of the newly adjusted active channel, whereas slopes of terraces triggered by a decrease in upstream sediment discharge or an increase in upstream water discharge are steeper compared to the new equilibrium channel. By combining fill-terrace records with constraints on sediment export, we can distinguish among environmental perturbations that would otherwise remain unresolved when using just one of these records.