Geoscience Reference
In-Depth Information
Chapter 16
Glossic Horizon
16.1
Introduction
The glossic horizon is defined as tonguing that “develops as a result of the
degradation of an argillic
horizon from which clay and free iron oxides are
removed” (Soil Survey Staff
2010
, p. 11). Glossic horizons occur in several orders
besides Alfisols, including Mollisols, Aridisols, Ultisols, and Spodosols.
The origin of glossic horizons is poorly understood. Several hypotheses have
been offered for the origin of glossic horizons, primarily in soils with a fragipan. In
northern UT aeolian material from Lake Bonneville sediments and the Snake River
plain has been added throughout the Holocene to Alfisols, leading to the develop-
ment of glossic horizons at the interface of the loess and underlying parent materials
(Jalalian and Southard
1986
; Bockheim et al.
2000
). Glossic horizons are common
in degrading fragipans of Fragiudalfs and Fragiorthods in widely varying areas such
as the lower Mississippi River valley (Lindbo et al.
2000
), Michigan (Bockheim
2003
; Weisenborn and Schaetzl
2005a
,
b
), and Great Britain (Payton
1992
,
1993a
,
b
).
Glossic horizons form in bisequal soils of the upper Great Lakes region as water is
held up at the contact of two texturally contrasting parent materials (Bockheim
2003
).
In loess-derived soils of France, hydromorphism from blockage of pores due to
lessivage leads to degradation of the upper part of the argillic horizon in Hapludalfs
(Jamagne et al.
1984
;Caillieretal.
1985
).
The glossic horizon in Cryalfs of the Rocky Mountains was attributed to an
input of eolian silt which created a lithologic discontinuity and a mid-Holocene
(5,000 yr BP to present) lowering of treeline containing the strongly podzolizing
species
Picea engelmannii
and
Abies lasiocarpa
(Bockheim
2012
). Although
glossic horizons were common in upper montane soils now containing lodgepole
pine (
Pinus contorta
), they were uncommon in lower montane soils supporting
lodgepole and ponderosa (
P. ponderosa
) pines. Therefore, the glossic horizon may
yield important clues regarding environmental change.
...
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