Cosmogenic nuclide methods for measuring long-term rates of physical erosion and chemical weathering

<p>Understanding how active mountain landscapes contribute to carbon dioxide cycling and influences on long-term climate stability requires measurement of weathering fluxes from these landscapes. The few measured chemical weathering rates in the Southern Alps are an order of magnitude greater than in the rest of the world. Rapid tectonic uplift coupled with extreme orographic precipitation is driving exceptionally fast chemical and physical denudation. These rates suggest that weathering in landscapes such as the Southern Alps could play a significant role in carbon dioxide cycling. However, the relative importance of climate and tectonics driving these fast rates remains poorly understood. To address this gap, in situ ¹⁰Be derived catchment-averaged denudation rates were measured in the Ōhau catchment, Canterbury, New Zealand. Denudation rates in the Dobson Valley within the Ōhau catchment, varied from 474 – 7,570 m Myr⁻¹, aside from one sub-catchment in the upper Dobson Valley that had a denudation rate of 12,142 m Myr⁻¹. The Dobson and Hopkins Rivers had denudation rates of 1,660 and 4,400 m Myr⁻¹ respectively, in these catchments. Dobson Valley denudation rates show a moderate correlation with mean annual precipitation (R²=0.459). This correlation supports a similar trend identified at local and regional scales, and at high rates of precipitation this may be an important driver of erosion and weathering. Sampling of four grain sizes (0.125 to > 8 mm) at one site in the Dobson Valley resulted in variability in ¹⁰Be concentrations up to a factor of 2.5, which may be a result of each grain size recording different erosional processes. These observations demonstrate the importance of assessing potential variability and the need to sample consistent grain sizes across catchments. Chemical depletion fractions measured within soil pits in the upper Dobson Valley indicate chemical weathering contributes 30% of total denudation, and that physical erosion is driving rapid total denudation. Chemical weathering appears to surpass any proposed weathering speed limit and suggests total weathering may not be limited by weathering kinetics. This research adds to the paucity of research in New Zealand, and for the first time presents ¹⁰Be derived denudation rates from the eastern Southern Alps, with estimates of the long-term weathering flux. High weathering fluxes in the Southern Alps uphold the hypothesis that mountain landscapes play an important role in carbon dioxide cycling and long-term climate stability.</p>

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Addressing solar modulation and long-term uncertainties in scaling secondary cosmic rays for in situ cosmogenic nuclide applications

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2005.07.001 ◽

2005 ◽

Vol 239 (1-2) ◽

pp. 140-161 ◽

Cited By ~ 229

Author(s):

Nathaniel A. Lifton ◽

John W. Bieber ◽

John M. Clem ◽

Marc L. Duldig ◽

Paul Evenson ◽

...

Keyword(s):

Cosmic Rays ◽

Solar Modulation ◽

Cosmogenic Nuclide

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Assessment of chemical weathering and physical erosion along a hillslope, southwest China

CATENA ◽

10.1016/j.catena.2019.104133 ◽

2019 ◽

Vol 182 ◽

pp. 104133 ◽

Cited By ~ 3

Author(s):

Changshun Song ◽

Hongbing Ji ◽

Howard Omar Beckford ◽

Cheng Chang ◽

Shijie Wang

Keyword(s):

Chemical Weathering ◽

Southwest China ◽

Physical Erosion

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Modeling long-term stability of the Ferrar Glacier, East Antarctica: Implications for interpreting cosmogenic nuclide inheritance

Journal of Geophysical Research Atmospheres ◽

10.1029/2006jf000599 ◽

2007 ◽

Vol 112 (F3) ◽

Cited By ~ 16

Author(s):

Jesse V. Johnson ◽

Jane W. Staiger

Keyword(s):

East Antarctica ◽

Term Stability ◽

Long Term Stability ◽

Cosmogenic Nuclide

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Late Quaternary climatic control on erosion and weathering in the eastern Tibetan Plateau and the Mekong Basin

Quaternary Research ◽

10.1016/j.yqres.2005.02.005 ◽

2005 ◽

Vol 63 (3) ◽

pp. 316-328 ◽

Cited By ~ 71

Author(s):

Zhifei Liu ◽

Christophe Colin ◽

Alain Trentesaux ◽

Giuseppe Siani ◽

Norbert Frank ◽

...

Keyword(s):

Grain Size ◽

Tibetan Plateau ◽

Chemical Weathering ◽

River Sediments ◽

River Estuary ◽

Mekong River ◽

Sediment Discharge ◽

Eastern Tibetan Plateau ◽

Mekong Basin ◽

Physical Erosion

High-resolution siliciclastic grain size and bulk mineralogy combined with clay mineralogy, rubidium, strontium, and neodymium isotopes of Core MD01-2393 collected off the Mekong River estuary in the southwestern South China Sea reveals a monsoon-controlled chemical weathering and physical erosion history during the last 190,000 yr in the eastern Tibetan Plateau and the Mekong Basin. The ranges of isotopic composition are limited throughout sedimentary records:87Sr/86Sr = 0.7206–0.7240 andεNd(0) = −11.1 to −12.1. These values match well to those of Mekong River sediments and they are considered to reflect this source region. Smectites/(illite + chlorite) and smectites/kaolinite ratios are used as indices of chemical weathering rates, whereas the bulk kaolinite/quartz ratio is used as an index of physical erosion rates in the eastern Tibetan Plateau and the Mekong Basin. Furthermore, the 2.5–6.5 μm/15–55 μm siliciclastic grain size population ratio represents the intensity of sediment discharge of the Mekong River and in turn, the East Asian summer monsoon intensity. Strengthened chemical weathering corresponds to increased sediment discharge and weakened physical erosion during interglacial periods. In contrast, weakened chemical weathering associated with reduced sediment discharge and intensified physical erosion during glacial periods. Such strong glacial–interglacial correlations between chemical weathering/erosion and sediment discharge imply the monsoon-controlled weathering and erosion.

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Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes

Earth Surface Dynamics ◽

10.5194/esurf-4-675-2016 ◽

2016 ◽

Vol 4 (3) ◽

pp. 675-684 ◽

Cited By ~ 4

Author(s):

Maarten Lupker ◽

Christian France-Lanord ◽

Bruno Lartiges

Keyword(s):

Cation Exchange ◽

Chemical Weathering ◽

Sediment Load ◽

Relative Proportion ◽

River System ◽

Exchange Capacity ◽

Sediment Flux ◽

Continental Scale ◽

The Impact

Abstract. Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga–Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga–Brahmaputra is estimated ca. 6.5 meq 100 g−1. The cationic charge of sediments in the river is dominated by bivalent ions Ca2+ (76 %) and Mg2+ (16 %) followed by monovalent K+ (6 %) and Na+ (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca2+ for marine Na+ yields a maximal additional Ca2+ flux of 28  ×  109 mol yr−1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga–Brahmaputra is responsible for an additional Ca2+ flux of 23  ×  109 mol yr−1, while ca. 27  ×  109 mol yr−1 of Na+, 8  ×  109 mol yr−1 of Mg2+ and 4  ×  109 mol yr−1 of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na+ flux, 8 % of the dissolved K+ flux and 4 % of the Mg2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment–seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and its main effect is the sequestration of a significant fraction of the riverine Na flux to the oceans. The limited exchange fluxes of the Ganga–Brahmaputra relate to the lower than average CEC of its sediment load that do not counterbalance the high sediment flux to the oceans. This can be attributed to the nature of Himalayan river sediment such as low proportion of clays and organic matter.

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Chemical weathering of silicate rocks in Aldan Shield and Baikal Uplift: insights from long-term seasonal measurements of solute fluxes in rivers

Chemical Geology ◽

10.1016/j.chemgeo.2004.10.003 ◽

2005 ◽

Vol 214 (3-4) ◽

pp. 223-248 ◽

Cited By ~ 42

Author(s):

E.A. Zakharova ◽

O.S. Pokrovsky ◽

B. Dupré ◽

M.B. Zaslavskaya

Keyword(s):

Chemical Weathering ◽

Aldan Shield ◽

Solute Fluxes ◽

Silicate Rocks

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A photogrammetry-based approach for soil bulk density measurements with an emphasis on applications to cosmogenic nuclide analysis

Earth Surface Dynamics ◽

10.5194/esurf-8-995-2020 ◽

2020 ◽

Vol 8 (4) ◽

pp. 995-1020

Author(s):

Joel Mohren ◽

Steven A. Binnie ◽

Gregor M. Rink ◽

Katharina Knödgen ◽

Carlos Miranda ◽

...

Keyword(s):

Bulk Density ◽

Soil Formation ◽

Soil Condition ◽

Soil Bulk Density ◽

Small Scale ◽

Soil Density ◽

Cosmogenic Nuclide ◽

Sampling Campaign ◽

Accuracy And Precision

Abstract. The quantification of soil bulk density (ρB) is a cumbersome and time-consuming task when traditional soil density sampling techniques are applied. However, it can be important for terrestrial cosmogenic nuclide (TCN) production rate scaling when deriving ages or surface process rates from buried samples, in particular when short-lived TCNs such as in situ 14C are applied. Here, we show that soil density determinations can be made using structure-from-motion multi-view stereo (SfM-MVS) photogrammetry-based volume reconstructions of sampling pits. Accuracy and precision tests as found in the literature and as conducted in this study clearly indicate that photographs taken from both a consumer-grade digital single-lens mirrorless (DSLM) and a smartphone camera are of sufficient quality to produce accurate and precise modelling results, i.e. to regularly reproduce the “true” volume and/or density by >95 %. This finding holds also if a freeware-based computing workflow is applied. The technique has been used to measure ρB along three small-scale (<1 km) N–S transects located in the semi-arid to arid Altos de Talinay, northern central Chile (∼30.5∘ S, ∼71.7∘ W), during a TCN sampling campaign. Here, long-term differences in microclimatic conditions between south-facing and north-facing slopes (SFSs and NFSs, respectively) explain a sharp contrast in vegetation cover, slope gradient and general soil condition patterns. These contrasts are also reflected by the soil density data, generally coinciding with lower densities on SFSs. The largest differences between NFSs and SFSs are evident in the lower portion of the respective slopes, close to the thalwegs. In general, field-state soil bulk densities were found to vary by about 0.6 g cm−3 over a few tens of metres along the same slope. As such, the dataset that was mainly generated to derive more accurate TCN-based process rates and ages can be used to characterise the present-day condition of soils in the study area, which in turn can give insight into the long-term soil formation and prevailing environmental conditions. This implies that the method tested in this study may also being applied in other fields of research and work, such as soil science, agriculture or the construction sector.

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