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Evidence from landscape evolution may provide critical constraints for past geodynamic processes, but has been limited by the large uncertainties of topographic reconstructions. Here we present continuous 30-million-year rock uplift histories for three catchments in the Calabrian forearc of southern Italy, using a data-driven inversion of tectonic geomorphology measurements. We find that rock uplift rates were high (>1 mm yr−1) from about 30 to 25 million years ago (Ma) and progressively declined to <0.4 mm yr−1 by ~15 Ma, then remained low before abruptly increasing around 1.5–1.0 Ma. These uplift rates do not match the forearc’s subduction velocity record, implying that uplift was not dominated by crustal thickening due to subduction-driven sediment influx. Through comparisons with slab descent reconstructions, we instead argue that the forearc uplift history primarily reflects the progressive establishment and abrupt destruction of an upper-mantle convection cell with strong negative buoyancy. We suggest that the convection cell vigour increased as the slab-induced mantle flow field began to interact with the 660-km mantle transition zone, causing uplift rates to decline from 25 to 15 Ma. Then, once the slab encountered the transition zone, the fully established convection cell subdued uplift rates, before being disrupted by slab fragmentation in the Quaternary, driving rapid forearc uplift. 

Abstract. Carbonate rocks are highly reactive and can have higher ratios of chemical weathering to total denudation relative to most other rock types. Their chemical reactivity affects the first-order morphology of carbonate-dominated landscapes and their climate sensitivity to weathering.However, there have been few efforts to quantify the partitioning ofdenudation into mechanical erosion and chemical weathering in carbonatelandscapes such that their sensitivity to changing climatic and tectonicconditions remains elusive. Here, we compile bedrock and catchment-averagedcosmogenic calcite–36Cl denudation rates and compare them to weathering rates derived from stream water chemistry from the same regions. Local bedrock denudation and weathering rates are comparable, ∼20–40 mm ka−1, whereas catchment-averaged denudation rates are ∼2.7 times higher. The discrepancy between bedrock and catchment-averaged denudation is 5 times lower compared to silicate-rich rocks, illustrating that elevated weathering rates make denudation more spatially uniform in carbonate-dominated landscapes. Catchment-averaged denudation rates correlate well with topographic relief and hillslope gradients, and moderate correlations with runoff can be explained by concurrent increases in weathering rates. Comparing denudation rates with weathering rates shows that mechanical erosion processes contribute ∼50 % of denudation in southern France and ∼70 % in Greece and Israel. Our results indicate that the partitioning between largely slope-independent chemical weathering and slope-dependent mechanical erosion varies based on climate and tectonics and impacts the landscape morphology. This leads us to propose a conceptual model whereby in humid, slowly uplifting regions, carbonates are associated with low-lying, flat topography because slope-independent chemical weathering dominates denudation. In contrast, in arid climates with rapid rock uplift rates, carbonate rocks form steep mountains that facilitate rapid, slope-dependent mechanical erosion required to compensate for inefficient chemical weathering and runoff loss to groundwater systems. This result suggests that carbonates represent an end member for interactions between climate, tectonics, and lithology. 

Bedrock river width is an essential geometric parameter relevant to understanding flood hazards and gauging station rating curves, and is critical to stream power incision models and many other landscape evolution models. Obtaining bedrock river width measurements, however, typically requires extensive field campaigns that take place in rugged and steep topography where river access is often physically challenging. Although prior work has turned to measuring channel width from satellite imagery, these data present a snapshot in time, are typically limited to rivers ≥ 10–30 m wide due to the image resolution, and are physically restricted to areas devoid of vegetation. For these reasons, we are generally data limited, and the factors impacting bedrock channel width remain poorly understood. Due to these limitations, researchers often turn to assumptions of width‐scaling relationships with drainage area or discharge to estimate bedrock channel width. Here we present a new method of obtaining bedrock channel width at a desired river discharge through the incorporation of a high‐resolution bare‐earth digital elevation model (DEM) using MATLAB Topotoolbox and the HEC‐RAS river analysis system. We validate this method by comparing modeled results to US Geological Survey (USGS) field measurements at existing gauging stations, as well as field channel measurements. We show that this method can capture general characteristics of discharge rating curves and predict field‐measured channel widths within uncertainty. As high‐resolution DEMs become more available across the United States through the USGS three‐dimensional elevation program (3DEP), the future utility of this method is notable. Through developing and validating a streamlined, open‐source, and freely available workflow of channel width extraction, we hope this method can be applied to future research to improve the quantity of channel width measurements and improve our understanding of bedrock channels.

 

Abstract Classically held mechanisms for removing mountain topography (e.g., erosion and gravitational collapse) require 10-100 Myr or more to completely remove tectonically generated relief. Here, we propose that mountain ranges can be completely and rapidly (<2 Myr) removed by a migrating hotspot. In western North America, multiple mountain ranges, including the Teton Range, terminate at the boundary with the relatively low relief track of the Yellowstone hotspot. This abrupt transition leads to a previously untested hypothesis that preexisting mountainous topography along the track has been erased. We integrate thermochronologic data collected from the footwall of the Teton fault with flexural-kinematic modeling and length-displacement scaling to show that the paleo-Teton fault and associated Teton Range was much longer (min. original length 190-210 km) than the present topographic expression of the range front (~65 km) and extended across the modern-day Yellowstone hotspot track. These analyses also indicate that the majority of fault displacement (min. 11.4-12.6 km) and the associated footwall mountain range growth had accumulated prior to Yellowstone encroachment at ~2 Ma, leading us to interpret that eastward migration of the Yellowstone hotspot relative to stable North America led to removal of the paleo-Teton mountain topography via posteruptive collapse of the range following multiple supercaldera (VEI 8) eruptions from 2.0 Ma to 600 ka and/or an isostatic collapse response, similar to ranges north of the Snake River plain. While this extremely rapid removal of mountain ranges and adjoining basins is probably relatively infrequent in the geologic record, it has important implications for continental physiography and topography over very short time spans. 

Rock strength is a fundamental property of earth materials that influences the morphology of landscapes and modulates feedbacks between surface processes, tectonics, and climate. However, rock strength remains challenging to quantify over the broad spatial scales necessary for geomorphic investigations. Consequently, the factors that control rock strength in the near‐surface environment (i.e., the critical zone) remain poorly understood. Here we quantify near‐surface rock strength on a regional scale by exploiting two hillslope‐stability models, which explicitly relate the balance of forces within a hillslope to Mohr‐Coulomb strength parameters. We first use the Culmann finite‐slope stability model to back‐calculate static rock strength with high‐density measurements of ridge‐to‐channel hillslope height and gradient. Second, we invert the Newmark infinite‐slope stability model for strength using an earthquake peak ground acceleration model and coseismic landslide inventory. We apply these two model approaches to a recently inverted sedimentary basin in the eastern Topatopa Mountains of southern California, USA, where a tectonic gradient has exposed stratigraphic units with variable burial histories. Results show similar trends in strength with respect to stratigraphic position and have comparable strength estimates to the lowest values of published direct‐shear test data. Cohesion estimates are low, with Culmann results ranging from 3 to 60 kPa and Newmark results from 6 to 30 kPa, while friction angle estimates range from 24° to 44° from the Culmann model. We find that maximum burial depth exerts the strongest control on the strength of these young sedimentary rocks, likely through diagenetic changes in porosity, cementation, and ultimately, lithification.