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In-Depth Information
and comprise thin sand bodies separated by extensive pla-
nar erosion surfaces attributed to deflation to a former wa-
ter table (Loope, 1985, 1988) (Figure 16.12). Rhizoliths
are abundant within the sandstone beds directly beneath
these deflation surfaces, suggesting a close proximity to
the water table (Loope, 1984). Sedimentary evidence also
suggests that topographic lows in former draa surfaces
contained ponds of water (Langford
et al.
, 2008). The
presence of replaced gypsum sand crystals in a number
of horizons provides further supporting evidence that the
water table was sufficiently close to the surface to allow
evaporite formation (Loope, 1988). The Jurassic Entrada
Sandstone, studied along a detailed 2.7 km traverse in
northeast Utah by Crabaugh and Kocurek (1993), is also
interpreted as having formed in a wet aeolian system.
The sandstone architecture exhibits subaqueous ripple de-
posits, contorted strata, breccias, collapse features, wavy
bedding, foundered sets, loaded set bases, corrugated sur-
faces, polygonal fractures, ball-and-pillow structures and
trains of small dunes 'frozen' in place, all indicating a
near-surface water table with occasional shallow flooding
of interdune areas.
m
500
400
Quartzose Aeolian
Sandstone
Fluvial Arkose
Marine Carbonates
Mudstone -
mainly nonmarine
Bedding planes with
abundant roots and
burrows
Gypsum sand
crystal “ghosts”
300
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200
100
UTAH
0
Figure 16.12
A stratigraphic section of Upper Pennsylvanian
(Carboniferous) and Lower Permian rocks exposed in Canyon-
