Short   Communication:   Increasing   vertical   attenuation   length   of   
cosmogenic  nuclide  production  on  steep  slopes  negates  topographic shielding corrections for catchment erosion rates

DiBiase, Roman A.

doi:10.5194/esurf-2018-48

Cited by 10 publications

(11 citation statements)

References 28 publications

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“…We estimated catchment average bedrock lowering rates from the measurements of 10 Be and 26 Al using the CRONUS‐Earth online calculators (Balco et al., 2008). In our calculations, we used catchment average elevations that were estimated using the LiDAR DEM and neglected topographic shielding (DiBiase, 2018). We used bedrock bulk densities of 2.65 g cm −3 and a nuclide‐dependent scaling framework (Lifton et al., 2014).…”

Section: Methodsmentioning

confidence: 99%

The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys

et al. 2021

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Bedrock weathering regulates nutrient mobilization, water storage, and soil production.Relative to the mobile soil layer, little is known about the relationship between topography and bedrock weathering. Here, we identify a common pattern of weathering and water storage across a sequence of three ridges and valleys in the sedimentary Great Valley Sequence in Northern California that share a tectonic and climate history. Deep drilling, downhole logging, and characterization of chemistry and porosity reveal two weathering fronts. The shallower front is ∼7 m deep at the ridge of all three hillslopes, and marks the extent of pervasive fracturing and oxidation of pyrite and organic carbon. A deeper weathering front marks the extent of open fractures and discoloration. This front is 11 m deep under two ridges of similar ridge-valley spacing, but 17.5 m deep under a ridge with nearly twice the ridge-valley spacing. Hence, at ridge tops, the fraction of the hillslope relief that is weathered scales with hillslope length. In all three hillslopes, below this second weathering front, closed fractures and unweathered bedrock extend about one-half the hilltop elevation above the adjacent channels. Neutron probe surveys reveal that seasonally dynamic moisture is stored to approximately the same depth as the shallow weathering front. Under the channels that bound our study hillslopes, the two weathering fronts coincide and occur within centimeters of the ground surface. Our findings provide evidence for feedbacks between erosion and weathering in mountainous landscapes that result in systematic subsurface structuring and water routing. Plain Language SummaryThe patterns of bedrock weathering concealed beneath the surface have important implications for the water cycle. In many upland landscapes, sequences of ridges and valleys result from river incision into bedrock, which organizes the landscape into hillslopes separated by channels. While surface topography of these landscapes is easily visible, the structure of weathered bedrock beneath the surface and its relationship to overlying topography are unknown. In this study, we observed systematic patterns of weathering and water storage under three hillslopes that make up a repeating ridge-valley sequence formed in sedimentary bedrock. Across the study area, weathering is thickest under ridges and thins downslope toward adjacent valleys, where fresh bedrock lies almost directly below channels. Interestingly, the depth of extensive weathering and seasonal water storage at the ridges was comparable across all three hillslopes, while open fractures and discoloration persist to a deeper depth under the longer hillslope. These observations provide a basis for scaling point measurements of weathering to the landscape scale, which is a much-needed tool for models of earth surface processes.

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Section: Methodsmentioning

confidence: 99%

The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys

et al. 2021

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“…The ice cover and associated shielding have probably varied significantly since 6 Ma, with an apparent impact remaining in the range of our uncertainties. We included neither topographic shielding 66 nor paleomagnetic variation corrections.…”

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confidence: 99%

Steady erosion rates in the Himalayas through late Cenozoic climatic changes

et al. 2020

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“…However, this optional correction must be used with caution. Indeed, DiBiase () suggests that the topographic shielding correction is inappropriate in many settings. According to this author, the correction is only needed for steep catchments with non‐uniform distribution of quartz and/or erosion rate.…”

Section: Discussion and Implementation In Basingamentioning

confidence: 99%

Basinga: A cell‐by‐cell GIS toolbox for computing basin average scaling factors, cosmogenic production rates and denudation rates

Charreau

Blard

Zumaque

et al. 2019

Earth Surf Processes Landf

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The calculation of denudation rates from the measured cosmogenic nuclide concentrations in river sediments requires assumptions and approximations. Several different approaches and numerical tools are available in the literature. A widely used analytical approach represents the muogenic production with one or two exponentials, assumes the attenuation length of muons to be constant and also neglects temporal variations in the Earth's magnetic field. The denudation rates are then calculated directly and analytically from the measured concentrations. A second numerical and iterative approach was more recently proposed and considers a more rigorous muogenic production law based on pre‐calculated variable attenuation length of muons and accounts for temporal changes of the magnetic field. It also assumes a specific distribution of denudation rates throughout the basin and uses an iterative approach to calculate the basin average denudation rates. We tested the two approaches across several natural basins and found that both approaches provide similar denudation results. Hence, assuming exponential muogenic production and constant attenuation length of muons in the rock has little impact on the derived denudation rates. Therefore, unless a priori known distributions of denudation rates are to be tested, there does not appear to be any particular gain from using the second iterative method which is computationally less effective. Based on these findings, we developed and describe here Basinga, a new ArcGIS® and QGIS toolbox which computes the basin average scaling factors, cosmogenic production rates and denudation rates for several tens of drainage basins together. Basinga follows either the Lal/Stone or the Lifton/Sato/Dunai scaling schemes and includes several optional tools for correcting for topographic shielding, ice cover and lithology. We have also developed an original method for correcting the cosmogenic production rates for past variations in the Earth's magnetic field. © 2019 John Wiley & Sons, Ltd.

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Short Communication: Increasing vertical attenuation length of cosmogenic nuclide production on steep slopes negates topographic shielding corrections for catchment erosion rates

Cited by 10 publications

References 28 publications

The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys

The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys

Steady erosion rates in the Himalayas through late Cenozoic climatic changes

Basinga: A cell‐by‐cell GIS toolbox for computing basin average scaling factors, cosmogenic production rates and denudation rates

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