『Abstract
Despite being located on high, steep, actively uplifting, and
formerly glaciated slopes of the Swiss Central Alps, soils in
the upper Rhone Valley are depleted by up to 50％ in cations relative
to their parent bedrock. This depletion was determined by a mass
loss balance based on Zr as a refractory element. Both Holocene
weathering rates and physical erosion rates of these slopes are
unexpectedly low, as measured by cosmogenic 10Be-derived
denudation rates. Chemical depletion fractions, CDF, range from
0.12 to 0.48, while the average soil chemical weathering rate
is 33±15 t km-2 yr-1. Both the cosmogenic
nuclide-derived denudation rates and model calculations suggest
that these soils have reached a weathering steady-state since
deglaciation 15 ky ago. The weathering signal varies with elevation
and hillslope morphology. In addition, the chemical weathering
rates decrease with elevation indicating that temperature may
be a dominant controlling factor on weathering in these high Alpine
basins. Model calculations suggest that chemical weathering rates
are limited by reaction kinetics and not the supply rate of fresh
material. We compare hillslope and catchment-wide weathering fluxes
with modern stream cation flux, and show that high relief, bare-rock
slopes exhibit much lower chemical weathering rates despite higher
physical erosion rates. The low weathering fluxes from rocky,
rapidly eroding slopes allow for the broader implication that
mountain building, while elevating overall denudation rates, may
not cause increased chemical weathering rates on hillslopes. In
order for this sediment to be weathered, intermediate storage,
for instance in floodplains, is required.』
1. Introduction
1.1. Geomorphic setting
2. Sampling and methodology
3. Results
3.1. CDF
3.2. Elemental mass losses
3.3. Total denudation rates
3.4. Weathering rates
3.5. Topographic correlations
3.6. Geomorphic correlations
4. Discussion
4.1. Is weathering in steady state?
4.2. Geomorphic controls
4.3. The limits of weathering
4.4. Temperature controls
4.5. Temporal and spatial variability
4.6. Implications for orogen-scale weathering
5. Conclusions
Acknowledgments
References