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Erosion and tectonic uplift are widely thought to be coupled through feedbacks involving orographic precipitation, relief development, and crustal weakening. In many orogenic systems, it can be difficult to distinguish whether true feedbacks exist, or whether observed features are a consequence of tectonic forcing. To help elucidate these interactions, we examine Gongga Shan, a 7556 m peak on the eastern margin of the Tibetan Plateau where cosmogenic 10 Be basin-wide erosion rates reach >5 mm/yr, defining a region of localized rapid erosion associated with a restraining bend in the left-lateral Xianshuihe Fault. Erosion rates are consistent with topography, thermochronometry, and geodetic data, suggesting a stable pattern of uplift and exhumation over at least the past 2–3 My. Transpression along the Xianshuihe Fault, orographically enhanced precipitation, thermally weakened crust, and substantial local relief all developed independently in the Gongga region and existed there prior to the uplift of Gongga Shan. However, only where all of these conditions are present do the observed topographic and erosional extremes exist, and their relative timing indicates that these conditions are not a consequence of rapid uplift. We conclude that their collocation at 3–4 Ma set into motion a series of feedbacks between erosion and uplift that has resulted in the exceptionally high topography and rapid erosion rates observed today. [ABSTRACT FROM AUTHOR]

The ratio of the meteoric cosmogenic nuclide 10 Be, precipitated from the atmosphere, to the stable nuclide 9 Be, released by silicate weathering, was measured in suspended sediment of the Ganga River basin to determine denudation rates, degrees of weathering, and sediment storage in the floodplain. The 10 Be precipitated and the 9 Be released are carried to ca. 90% by amorphous and to 10% by crystalline Fe-hydroxides, as revealed by chemical extractions, whereas the dissolved Be transport is negligible due to the river pH of 8. Resulting 10 Be/ 9 Be ratios increase from 0.75 × 10 − 9 for the northern and Himalaya-draining rivers to 1.7 × 10 − 9 in the downstream basin. The increase in 10 Be/ 9 Be ratios results from two compounding effects: with 1) average denudation rates decrease from 0.5 mm yr −1 in the Himalayas to 0.17 mm yr −1 for the Ganga main stem in the lowlands, 2) the southern tributaries draining the low-relief craton contribute sediment with a ratio of 2.0 × 10 − 9 , corresponding to a denudation rate of 0.03 mm yr −1 . We find that at the spatial scale of the entire basin, the atmospheric delivery flux of 10 Be equals its sedimentary export flux. Hence fluxes can be considered to be at steady state and radioactive decay of 10 Be during sediment storage is not discernible. The lack of a resolvable increase in 10 Be concentration during sediment transfer along the floodplain stretch furthermore suggests that the sediment transfer time is indeed short. We also cannot resolve any additional release of silicate-bound 9 Be there, testifying to the lower degree of weathering there. When multiplied with the basin area the 10 Be/ 9 Be-derived denudation rate of 0.14 mm yr −1 corresponds to a sediment flux of 350 Mt yr −1 which is in good agreement with gauging-derived sediment fluxes (ca. 400 Mt yr −1 ). Because they integrate over the entire basin, denudation rates from 10 Be/ 9 Be are lower than floodplain-corrected denudation rates from in situ cosmogenic 10 Be that reflect the rates of the sediment-producing mountain areas. [ABSTRACT FROM AUTHOR]

We analyze the source-to-sink variations of in situ 10 Be, 26 Al and 21 Ne concentrations in modern sediment of the Po river catchment, from Alpine, Apennine, floodplain, and delta samples, in order to investigate how the cosmogenic record of orogenic erosion is transmitted across a fast-subsiding foreland basin. The in situ 10 Be concentrations in the analyzed samples range from ∼ 0.8 × 10 4 at / g QTZ to ∼ 6.5 × 10 4 at / g QTZ . The 10 Be-derived denudation rates range from 0.1 to 1.5 mm/yr in the Alpine source areas and from 0.3 to 0.5 mm/yr in the Apenninic source areas. The highest 10 Be-derived denudation rates are found in the western Central Alps (1.5 mm/yr). From these data, we constrain a sediment flux leaving the Alpine and the Apenninic source areas (>27 Mt/yr and ca. 5 Mt/yr, respectively) that is notably higher than the estimates of sediment export provided by gauging (∼10 Mt/yr at the Po delta). We observe a high variability in 10 Be concentrations and 10 Be-derived denudation rates in the source areas. In the Po Plain, little variability is observed, and at the same time, the area-weighed 10 Be concentration of ( 2.29 ± 1.57 ) × 10 4 at / g QTZ (±1 SD of the dataset) from both the Alps and the Apennines is poorly modified (by tributary input) in sediment of the Po Plain ( ( 2.68 ± 0.78 , ± 1 SD ) × 10 4 at / g QTZ ). The buffering effect of the Po floodplain largely removes scatter in 10 Be signals. We test for several potential perturbations of the cosmogenic nuclide record during source to sink transfer in the Po basin. We find that sediment trapping in deep glacial lakes or behind dams does not significantly change the 10 Be-mountain record. For example, similar 10 Be concentrations are measured upstream and downstream of the postglacial Lake Maggiore, suggesting that denudation rates prior to lake formation were similar to today's. On the scale of the entire basin, the 10 Be concentration of basins with major dams is similar to those without major dams. A potential modification of the 10 Be-mountain record during sediment storage in the subsiding Po Plain can be excluded as measured 26 Al/ 10 Be ratios do not show the addition of deeply buried material. A barely resolvable excess 21 Ne signal in the Po plain indicates recycling of previously eroded sediment rather than accumulation of cosmogenic nuclides during surficial floodplain transport. Our results demonstrate that the cosmogenic record of mountain erosion is effectively transmitted from the source areas to the sediment sink, even across a strongly subsiding foreland basin. We show that this record is poorly influenced by a range of potential geological and anthropogenic sources of bias, and is largely independent from upstream sediment interception and sediment storage in the floodplain. [ABSTRACT FROM AUTHOR]

Meteoric cosmogenic 10Be is a powerful tracer to quantify dates and rates of Earth surface processes over timescales of 103-105 yrs. A prerequisite for its applications is knowledge of the flux at which 10Be, produced in the atmosphere, is delivered to the Earth surface. Four entirely independent approaches are available to quantify this flux: 1) General Circulation Models (GCM) combined with 10Be production functions and aerosol dynamics; 2) 10Be in precipitation collections; 3) 10Be inventories in dated soil profiles; 4) riverine 10Be exported in solid and dissolved forms. We compiled and reprocessed published globally distributed 10Be flux data from each of these methods and compared them with each other after normalization to a common atmospheric production rate. Based on precipitation records, we propose a simple framework to discriminate between two delivery effects on 10Be fluxes. In the additive effect water vapor and 10Be are continuously accumulating during long-distance transport, leading to an increase in 10Be flux with precipitation rate. In the dilution effect, the 10Be flux is delivered from proximal vapor sources, limited by the rate of 10Be introduction from the stratosphere and independent of precipitation rate. Both effects are mostly present in combination, and the relative weight of either effect depends on vapor condensation rate and on the ratio of vapor condensation area to precipitation area. A comparison between precipitation-derived fluxes and GCM-derived fluxes shows that half of the precipitation estimates are >2 times greater than GCM-derived fluxes. By comparison, soil- and GCM-derived fluxes agree within a factor of 2 for more than half (∼57%) of the dataset, and the remaining soil estimates (∼43%) are much lower than GCM-derived fluxes. 71% of 10Be flux estimates from riverine export using 10Be (meteoric)/9Be ratios also agree with GCM-derived fluxes within a factor of 2. We explain the precipitation-derived fluxes that commonly exceed all other estimates by short-term stochasticity in precipitation events that might introduce a measurement time-interval bias towards higher fluxes. This bias is not present over longer-term (103-105 yrs) flux estimates like those from soil profiles. Soil-derived fluxes might still present an underestimation when retention of 10Be in soil is incomplete. We recommend producing more 10Be depositional flux data from soil inventories with full Be retention, as these generate in our view the most relevant estimates for applications of meteoric 10Be on millennial-scale Earth surface processes. • Earth surface studies using meteoric 10Be requires a known 10Be depositional flux. • We compiled meteoric 10Be fluxes from GCM, precipitation, soil profiles, and rivers. • Rainfall-derived meteoric 10Be flux may be subject to measurement interval bias. • Millennial-scale fluxes from soil profiles are recommended for Earth surface study. [ABSTRACT FROM AUTHOR]

• Geological and cosmogenic data from Corsica reveal two-stage river capture events. • Clast lithologies demonstrate a progressive reduction of the Paleo-Ostriconi basin. • River capture led to the formation of a large Pliocene-Quaternary submarine fan. • Focused erosion can affect sites of former river capture after millions of years. • Corsica is still adapting to the disequilibrium caused by uplift of Alpine Corsica. Quantitative analysis of fluvial topography and sediment yield changes are often independently used to detect major river capture events and episodes of drainage reorganization. Here we use a unique set of geological and in situ 10Be cosmogenic data from Corsica, Western Mediterranean, to provide evidence of major river capture events affecting the former Paleo-Ostriconi river catchment during the Pliocene, and to illustrate how the landscape of Corsica is still reacting to the disequilibrium caused by the late Miocene uplift of Alpine Corsica. We found that ∼1280 km2 of basin area originally draining towards the Ligurian Sea were abruptly connected to the Tyrrhenian Sea by the capturing Tavignano and Golo rivers, which led to the formation of a large Pliocene-Quaternary submarine fan offshore the Tyrrhenian coast. The increased sediment yield towards the Tyrrhenian margin after river capture in the Pliocene was three times greater than the average sediment yield in the same source-to-sink system during the Holocene (410±100 t·km−2· a −1 vs ∼131±8 t·km−2· a −1) and greater magnitude than any subsequent peaks in sediment yield during late Pleistocene glaciations. 10Be-derived denudation rates reveal that focused erosion still affects retreating knickpoints near the sites of former river capture in central Corsica, suggesting persistence of landscape disequilibrium for several millions of years. Our results demonstrate the potentially large impact of river capture on the stratigraphic record and highlight the importance of full consideration of landscape response times to onshore disturbances for any reliable interpretation of the offshore sedimentary archive. [Display omitted] [ABSTRACT FROM AUTHOR]

The uplift of the Shillong Plateau, in northeast India between the Bengal floodplain and the Himalaya Mountains, has had a significant impact on regional precipitation patterns, strain partitioning, and the path of the Brahmaputra River. Today, the plateau receives the highest measured yearly rainfall in the world and is tectonically active, having hosted one of the strongest intra-plate earthquakes ever recorded. Despite the unique tectonic and climatic setting of this prominent landscape feature, its exhumation and surface uplift history are poorly constrained. We collected 14 detrital river sand and 3 bedrock samples from the southern margin of the Shillong Plateau to measure erosion rates using the terrestrial cosmogenic nuclide 10 Be. The calculated bedrock erosion rates range from 2.0 to 5.6 m My −1 , whereas catchment average erosion rates from detrital river sands range from 48 to 214 m My −1 . These rates are surprisingly low in the context of steep, tectonically active slopes and extreme rainfall. Moreover, the highest among these rates, which occur on the low-relief plateau surface, appear to have been affected by anthropogenic land-use change. To determine the onset of surface uplift, we coupled the catchment averaged erosion rates with topographic analyses of the plateau's southern margin. We interpolated an inclined, pre-incision surface from minimally eroded remnants along the valley interfluves and calculated the eroded volume of the valleys carved beneath the surface. The missing volume was then divided by the volume flux derived from the erosion rates to obtain the onset of uplift. The results of this calculation, ranging from 3.0 to 5.0 Ma for individual valleys, are in agreement with several lines of stratigraphic evidence from the Brahmaputra and Bengal basin that constrain the onset of topographic uplift, specifically the onset of flexural loading and the transgression from deltaic to marine deposition. Ultimately, our data corroborate the hypothesis that surface uplift was decoupled from the onset of rapid exhumation, which occurred several millions of years earlier. [ABSTRACT FROM AUTHOR]

Major strike-slip fault systems on Earth, like the North Anatolian Fault (NAF), play an important role in accommodating plate motion, but surprisingly little is known about how such structures evolve through space and time. Along the central sector of the NAF in the Central Pontides, transpression and crustal thickening along the northward restraining bend of the fault are thought to have generated rock-uplift rates of 0.2–0.3 km/Myr since at least 400 ka based on Quaternary marine and river terraces, while data from low-temperature thermochronology suggest that an enhanced exhumation phase occurred within the last 11 Myr. However, the precise onset of this faster uplift phase, which likely reflects deformation associated with the development of the central sector of the NAF, is poorly constrained. Here we define the spatiotemporal pattern of rock-uplift rates within the Central Pontides over the last ∼10 Myr by performing linear inversions of 19 river profiles that drain the northern margin of the Central Pontides, from the Sinop Range to the Black Sea. We use 21 new 10Be-derived basin-average denudation rates to calibrate an erodibility parameter, which we use to convert our χ -transformed river profiles into rock-uplift histories. Our results document an increase in rock-uplift rates after 10 Ma, with peak rates of ∼0.15–0.25 km/Myr occurring between 4 and 2 Ma. Moreover, the spatiotemporal pattern of uplift suggests that faster rock uplift started in the eastern part of the Sinop Range and migrated westward over a period of ca. 2 to 2.5 Myr, which we relate to the westward propagation of the NAF through this sector at a rate of 74 ± 13 km/Myr. In the context of previously published constraints on the westward propagation of the NAF starting in eastern Turkey at ∼12 Ma, our results suggest differences in fault-propagation rates that coincide with differences in the orientation of the NAF relative to plate-convergence velocity vectors. Fault segments with higher obliquity appear to have propagated at rates up to 2-fold slower than those oriented more parallel to the plate-convergence vector. • Rock-uplift history of Central Pontides from river linear inversions. • The uplift event after 10 Ma dates the arrival of the North Anatolian Fault (NAF). • The uplift migration provides the propagation rate of the NAF central segment. • New insights about the propagation history of all the NAF segments. • Linkage between NAF propagation rates and plate convergence directions. [ABSTRACT FROM AUTHOR]

Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Toro Basin in the southern Central Andes exhibits at least five generations of fluvial terraces that have been sculpted into several-hundred-meter-thick Quaternary valley-fill conglomerates. New surface-exposure dating using nine cosmogenic 10 Be depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 ± 7 and 487 ± 34 ka. Depositional ages of the conglomerates, determined by four 26 Al/ 10 Be burial samples and U–Pb zircon ages of three intercalated volcanic ash beds, range from 18 ± 141 to 936 ± 170 ka, indicating that there were multiple cut-and-fill episodes. Although the initial onset of aggradation at ∼1 Ma and the overall net incision since ca. 500 ka can be linked to tectonic processes at the narrow basin outlet, the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent Bolivian Altiplano, whereas deposition occurred mainly during more arid phases on the Altiplano and global interglacial periods. We suggest that enhanced runoff during global cold phases – due to increased regional precipitation rates, reduced evapotranspiration, or both – resulted in an increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. Compared with two nearby basins that record precessional (21-kyr) and long-eccentricity (400-kyr) forcing within sedimentary and geomorphic archives, the recorded cyclicity scales with the square of the drainage basin length. [ABSTRACT FROM AUTHOR]

The temporal evolution of erosion over million-year timescales is key to understand the development of mountain ranges and adjacent fold-and-thrust belts. While models of orogenic wedge dynamics predict an instantaneous response of erosion to pulses of rock uplift, stream-power based models predict that catchment-wide erosion maxima significantly lag behind a pulse of rock uplift. Here, we explore the relationships between rock uplift, erosion, and sediment deposition in the Argentine Precordillera fold-and-thrust belt at 30°S. Using a combination of 10 Be-derived paleo-erosion rates, constraints on re-exposure using 26 Al/ 10 Be ratios, geomorphic observations and detrital zircon provenance, we demonstrate that the attainment of maximum upland erosion rates lags the maximum rate of deformation over million-year timescales. The magnitudes and causes of the erosional delays shed new light on the catchment erosional response to tectonic deformation and rock uplift in orogenic wedges. [ABSTRACT FROM AUTHOR]

Deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Kangra Basin (northwest Sub-Himalaya, India), upper Pleistocene to Holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on timescales of 10 3 to 10 5 yr. To evaluate the potential influence of climate change on these fluctuations, we compare the timing of aggradation and incision phases recorded within remnant alluvial fans and terraces with climate archives. New surface-exposure dating of six terrace levels with in-situ cosmogenic 10 Be indicates the onset of incision phases. Two terrace surfaces from the highest level (T1) sculpted into the oldest preserved alluvial fan (AF1) date back to 53.4 ± 3.2 ka and 43.0 ± 2.7 ka (1 σ ). T2 surfaces sculpted into the remnants of AF1 have exposure ages of 18.6 ± 1.2 ka and 15.3 ± 0.9 ka , while terraces sculpted into the upper Pleistocene–Holocene fan (AF2) provide ages of 9.3 ± 0.4 ka (T3), 7.1 ± 0.4 ka (T4), 5.2 ± 0.4 ka (T5) and 3.6 ± 0.2 ka (T6). Together with previously published OSL ages yielding the timing of aggradation, we find a correlation between variations in sediment transport with oxygen-isotope records from regions affected by the Indian Summer Monsoon. During periods of increased monsoon intensity and post-Last Glacial Maximum glacial retreat, aggradation occurred in the Kangra Basin, likely due to high sediment flux, whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision. [ABSTRACT FROM AUTHOR]

Drainage-divide migration, controlled by rock-uplift and rainfall patterns, may play a major role in the geomorphic evolution of mountain ranges. However, divide-migration rates over geologic timescales have only been estimated by theoretical studies and remain empirically poorly constrained. Geomorphological evidence suggests that the Sierra de Aconquija, on the eastern side of the southern Central Andes, northwest Argentina, is undergoing active westward drainage-divide migration. The mountain range has been subjected to steep rock trajectories and pronounced orographic rainfall for the last several million years, presenting an ideal setting for using low-temperature thermochronometric data to explore its topographic evolution. We perform three-dimensional thermal-kinematic modeling of previously published thermochronometric data spanning the windward and leeward sides of the range to explore the most likely structural and topographic evolution of the range. We find that the data can be explained by scenarios involving drainage-divide migration alone, or by scenarios that also involve changes in the structures that have accommodated deformation through time. By combining new 10Be-derived catchment-average denudation rates with geomorphic constraints on probable fault activity, we conclude that the evolution of the range was likely dominated by west-vergent faulting on a high-angle reverse fault underlying the range, together with westward drainage-divide migration at a rate of several km per million years. Our findings place new constraints on the magnitudes and rates of drainage-divide migration in real landscapes, quantify the effects of orographic rainfall and erosion on the topographic evolution of a mountain range, and highlight the importance of considering drainage-divide migration when interpreting thermochronometer age patterns. • Orographic rainfall has likely persisted for millions of years at S. de Aconquija. • Thermochronology constrains drainage-divide migration rates over millions of years. • 10Be-derived catchment average denudation rates support active divide migration. • West-vergent thrusting combined with westward drainage-divide migration. • Thermochronologic data interpretation should consider lateral topographic shifts. [ABSTRACT FROM AUTHOR]

It has been proposed that at short timescales of 102–105 yr, climatic variability can explain variations in sediment flux, but in orogens with pronounced climatic gradients rate changes caused by the oscillating efficiency in rainfall, runoff, and/or sediment transport and deposition are still not well-constrained. To explore landscape responses under variable climatic forcing, we evaluate time windows of prevailing sediment aggradation and related paleo-erosion rates from the southern flanks of the Dhauladhar Range in the western Himalaya. We compare past and present 10Be-derived erosion rates of well-dated Late Pleistocene fluvial landforms and modern river sediments and reconstruct the sediment aggradation and incision history based on new luminescence data. Our results document significant variations in erosion rates ranging from 0.1 to 3.4 mm/yr over the Late Pleistocene. We find that, during times of weak monsoon intensity, the moderately steep areas (hillslope angles of 27 ± 13°) erode at lower rates of 0.1–0.4 mm/yr compared to steeper (>40°) crestal regions of the Dhauladhar Range that erode at 0.8−1.3 mm/yr. In contrast, during several millennia of stronger monsoon intensity, both the moderately steep and high slope areas record higher erosion rates (>1-3.4 mm/yr). Lithological clast-count analysis shows that this increase of erosion is focused in the moderately steep areas, where Lesser Himalayan rocks are exposed. Our data thus highlight the highly non-linear response of climatic forcing on landscape evolution and suggest complex depositional processes and sedimentary signals in downstream areas. • Paleo-erosion rates in the Himalaya are modulated by climate forcing. • Erosion rates are higher during episodes of strong monsoon. • Topographic response to climate change is non-linear. • Rapid erosion during short-lived strong monsoon phases result in valley aggradation. [ABSTRACT FROM AUTHOR]

Terrestrial cosmogenic nuclide concentrations in fluvial deposits allow estimation of paleo-erosion rates and reconstruction of the response of landscapes to climatic perturbations. In partly ice-covered landscapes, however, incorporation of subglacially-derived sediments that were shielded by ice from cosmic can lead to erroneous erosion rate calculations. Here, we combine in situ -produced 10Be-derived erosion rates, based on sand and pebbles from a fluvial fill terrace and the modern riverbed in the upper Yamuna catchment, with numerical ice flow modelling to quantify this bias. New luminescence and surface exposure ages suggest that aggradation of the exposed deposits occurred between 29.9 ± 2.5 ka and 14.8 ± 2.8 ka. During most of the deposition, glaciers probably covered ∼19% of the catchment. 10Be concentrations of terrace sand samples differ from those of pebble samples. We obtained the lowest erosion rates from quartzite pebbles, which stem from low elevations, and the highest erosion rates from crystalline pebbles, which stem from high elevations in the Yamuna catchment. We explain these different erosion rates by differences in the steepness of the source areas, an effect that prevails throughout the entire aggradation period despite significant former ice-cover. Sand samples, which are thought to be derived from all elevation parts of the catchment, however show lower 10Be concentrations during the aggradation compared to present-day. We argue that this difference is due to a substantial subglacial origin of the sand during the aggradation period, and not necessarily related to enhanced erosion. We conclude that aggradation of the valley fill in the Yamuna catchment is most likely due to reduced discharge, and only marginally related to higher erosion rates during the late Pleistocene. • Paleo-erosion rates from a ∼135-m high river terrace in the Yamuna catchment. • New luminescence and surface exposure ages from the river terrace. • Aggradation occurred during marine isotope stage 2, when discharge was reduced. • Lower 10Be] in terrace sand compared to river sand can be explained by ice cover. [ABSTRACT FROM AUTHOR]