Geoscience Reference
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∼
400 m that undergo pavement formation during both
interglacial and glacial phases. In Utah, Marchetti and
Cerling (2005) observed pavements present on a fluvial
terrace at 1780-1710 m, but not on a nearby terrace at
an elevation of
will be necessary to clarify the impact of past variations
in climate and altitudinal changes in vegetation growth on
pavement formation.
Animals modify pavements or contribute to their for-
mation by laterally displacing stones at the surface and
by burrowing in the subsurface. Haff and Werner (1996)
cleared small patches of stones and documented pave-
ment recovery by repeat photography. The cross-surface
movement of stones by animals is one means by which
topographic highs are lowered and depressions filled, con-
tributing to the nearly flat surface characteristic of mature
pavements.
2050 m. Other studies in the western
United States, however, suggest that pavement formation
is not simply 'reset' during glaciations, as pavements on
volcanic cones of different ages (75-80 ka age Lathrop
Wells cone and
∼
1 Ma Red Cone) at altitudes of 800-
900 m show clear differences according to their age, im-
plying that the surface properties were not strongly dis-
turbed or obliterated by vegetation growth. Further work
∼
well developed pavement
minimal leaching; high chloride and nitrate levels
A
plant mound
deeper leaching; low nitrate levels; burrowing by animals
B
C
plant scar
D
enhanced runoff from pavement
E
vegetated rills
vegetated channel
deep iniltration and leaching
F
D
C
E
A
B
F
Figure 9.11
A schematic diagram of ecohydrologic conditions in a Mojave Desert pavement. On well-developed pavements (A)
rainfall infiltrates to shallow depths and leaching is minimal, causing the accumulation of high concentrations of chloride and
nitrate. Vegetation is largely absent from these smooth surfaces owing to the saline nature of the soil and its low infiltration
capacity. Some vegetation may be found near the margins of pavement (B). The shrubs trap aeolian fines and burrowing animals
displace nonvarnished or carbonate-coated clasts upward, causing the mounds to be lighter in colour than the surrounding
pavement. Macropore channels from shrub roots and burrows promote deeper leaching depths than found beneath the pavement.
Plant scars (C) on barren pavements are widespread in the American southwest, indicating that vegetation and animal life was
once more widespread. The low infiltration capacity of the pavement enhances runoff, channelling water through rill systems
(E) to vegetated ephemeral washes (F) that dissect the pavements. Deep infiltration into the channels leaches salts, providing a
