Rr. Blank et al., DURIPANS OF SOUTHWESTERN IDAHO - POLYGENESIS DURING THE QUATERNARY DEDUCED THROUGH MICROMORPHOLOGY, Soil Science Society of America journal, 62(3), 1998, pp. 701-709
There is uncertainty regarding the pedogenesis of duripans on the Owyh
ee Plateau of southwestern Idaho. Micromorphology was used to deduce t
he role of polygenesis in their formation. Data suggest that during th
e Pleistocene, duripans were cyclically subaerially exposed, then reco
vered by eolian dust. Two lines of evidence indicate past duripan expo
sure. First, sinuous laminar fabrics with lenticular voids, which occu
r within most duripan plates, are similar to the fabrics produced in a
rid regions by the action of lichens and cyanobacteria at the soil sur
face. Second, a laterally extensive air-fall tephra layer in the middl
e of a duripan plate was deposited at one sampling location, indicatin
g the duripan or protoduripan was exposed at the ground surface. A sug
gested model to explain the data is as follows: (i) during cold stages
of the Quaternary, periglacial processes, possibly assisted by eolian
deflation, caused the truncation of loose soil material overlying the
duripan; (ii) cryptogamic: organisms then colonized the exposed durip
an surface and produced distinctive fabrics; (iii) in response to the
increased production and delivery of eolian dust during interglacials,
the duripan was recovered. Pedogenesis during interglacial times resu
lted in precipitation of CaCO3, thereby thickening the upward-developi
ng duripan and preserving micromorphological signatures of subaerial e
xposure. At higher elevations in this region, large-scale removal of u
nconsolidated soil may have occurred during full glacial stages of the
middle and earlier Pleistocene. Maximal development of duripans may r
equire polygenesis.