『Abstract
The major element mobility within soil profiles of brown to gleyic
Andosols that developed under diverse climatic conditions in Iceland
is assessed. The volcanic soils were selected from areas with
good monitoring of annual temperature and precipitation and the
degree of weathering and elemental behavior is compared. Icelandic
soils are subject to high fluxes of aeolian dust, and at times,
to tephra ejecta from volcanic eruptions. The source of dust input
is assessed for each profile based on comparison of the chemical
signatures found in the less weathered upper horizons with those
of volcanic systems supplying material to source areas. Results
show that TiO2, Al2O3 and Fe2O3(T)
and MnO are the least mobile species and generally found enriched
within more mature horizons. The mobile base cations MgO, CaO
and Na2O are depleted in these horizons as
a result of chemical weathering during pedogenesis. Soils developed
in colder climatic conditions with mean annual temperature (MAT)〜-1℃
give values for the Chemical Index of Weathering (CIW) of 37-45
that reflect only weak chemical weathering. Soils developed in
milder climates (MAT = 2-4℃) are more strongly affected by weathering
(CIW = 50-77). The parent material has CIW values of 〜37. Temperature
is demonstrated as the dominant variable exerting control on the
extent of weathering, with only minor mobilization following the
incipient near-surface weathering stage. A robust linear relationship
is found between CIW and model MAT (MAT = 0.21CIW -8.93, R2
= 0.81). This climofunction can deliver proxy climate estimations
from volcanic soils and paleosols of basaltic origin in cool to
subarctic conditions (-2 to +6℃).
Keywords: Andosols; Major elements; Chemical weathering; Climofunction』
1. Introduction
2. Geology and climate of Iceland
2.1. Geological setting
2.2. Climate
2.3. Soils
3. Methods
3.1. Soil profile sampling
3.2. Analytical methods
3.3. Mobility calculations
3.4. Chronology of pedons
4. Results
4.1. Morphology and physical properties
4.2. Major element geochemistry
5. Discussion
5.1. Sources of dust input
5.2. Element mobilization
5.3. Weathering processes
5.4. Extent of weathering
5.5. Climate control on weathering extent
5.6. Development of a paleoclimate proxy
6. Conclusions
Acknowledgments
Appendix A. Supplementary data
References