New Zealand Journal of Geology and Geophysics abstracts
Soil chronosequences in subalpine superhumid Cropp Basin,
western Southern Alps, New Zealand
P. J. TONKIN
Soil and Physical Sciences Group
Division of Soil, Plant and Ecological Sciences
P.O. Box 84
Lincoln University
Canterbury, New Zealand
email: tonkinp@lincoln.ac.nz
L. R. BASHER
Landcare Research
P.O. Box 69, Lincoln
Canterbury, New Zealand
email: basherl@landcare.cri.nz
Abstract Soil chronosequences are described from Cropp River,
western Southern Alps, New Zealand. In this area of high rainfall and bedrock
of quartzofeldspathic schist, soils are developed in alluvium on gentle slopes
and colluvium on steeper slopes, and form under indigenous grassland or
scrubland, respectively. Soil ages ranging from 70 to c. 10 000 yr
were determined from dendrochronology, radiocarbon dating, and stratigraphic
relationships.
Soil morphological and chemical changes with time reveal a similar soil
development sequence on both gentle and steep slopes. Soil development is rapid
and progressively forms Fluvial or Orthic Raw Soils (<200 yr), Fluvial or
Orthic Recent Soils, Acid Brown Soils and Orthic Podzols (500-1500 yr), and
Perch-gley Podzols (7000-10 000 yr). Strong leaching is indicated by rapid
acidification of surface horizons in Recent Soils. Morphological and chemical
evidence shows that older soils (>1000 yr) are podzolised and gleyed.
Eluvial/illuvial coefficients calculated from total element analyses, using Zr
as an internal standard, indicate large relative losses of all elements from A
and E horizons, with the greatest losses in the older soils. The formation of
low-permeability silt loam E horizons, as a result of strong weathering of
alluvium and colluvium, causes the development of perch-gley conditions in
soils on very steep slopes and in relatively young soils that do not have iron
pans. As a result of the very high rainfall, soil development is more rapid
than described from anywhere else in Westland.
Keywords soil sequences; soil genesis; podzolisation;
gleying; high rainfall; soil stratigraphy; Perch-gley Podzols
New Zealand Journal of Geology & Geophysics, 2001, Vol. 44: 37-45
0028-8306/01/4401-0037 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (850K); (scanned from paper original: notes about this process)
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