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nostic features are absent due to intense bioturbation
by metazoans (see the Ordovician example in
Sect. 21.7.3 ). In arid climate similar to the southern
part of the Persian Gulf (Fig. 21.2a ), however, due to
high salinity and evaporite formation, burrowers and
browsers are practically absent in the upper intertidal
deposits, whereas, the lower intertidal facies are
intensely bioturbated. These deposits, except for their
lower fossil diversity and lighter color due to more oxi-
dizing condition, are similar to the adjacent subtidal
deposits (Shinn 1983a ) .
The low energy and isolated intertidal pond facies
is thin bedded and laterally discontinuous. In a humid
condition, it is characterized by thin beds of biotur-
bated lime mudstone to wackestone containing
restricted-bioclast. In an arid climate, the pond facies
may consist of planar stromatolite (Fig. 21.16a ) and/or
evaporitic dolomudstone, depending on geographical
location and salinity. Intertidal channel point bar
deposits are characterized by erosive based fi ning-
upward gravel- and sand-size sediment (may be lami-
nated and/or herringbone cross-bedded) skeletal
intraclast/peloid grainstone to packstone facies. They
are laterally discontinuous and normally are capped by
intertidal deposits (Fig. 21.16b, c ).
Fig. 21.8 High energy beach and platform margin tidal channel
facies: ( a ) Photomicrograph of a bioclastic ooid intraclast grain-
stone under polarized light; Mississippian upper Salem
Limestone (lower St. Louis Limestone equivalent), southwest-
ern Illinois. ( b ) A fi ning-upward ramp margin tidal channel
deposit ( lower arrow at the basal erosional contact) within a pre-
dominantly ooid grainstone sequence. Note that facies of this
channel deposit include fl at-bedded and laminated gravel- to
sand-sized ooid intraclast grainstone overlain by herringbone
cross-bedded grainstone, which in turn grades to laminated ooid
grainstone. The channel deposit is overlain, with a sharp contact
( upper arrow ), by rocks of a transgressive open marine mud-
stone facies; Mississippian Ste. Genevieve Limestone, Alton
Bluff section, Madison County, southwest Illinois
21.5.3 Supratidal Belt
Sediment of the supratidal environment is transported
from the subtidal carbonate factory during spring and
storm tides. Because most of the sediment is carried by
storms that transport large quantities of sediment, car-
bonate facies of the supratidal belt are intraclastic and
commonly are characterized by thick laminae and thin
to very thin beds (Figs. 21.17a, b, d and 21.18c ).
Periodic exposure of muddy tidal fl at deposits particu-
larly in the upper intertidal and supratidal settings
results in desiccation and the formation of mud cracks
and mud polygons (Figs. 21.3a, b , 21.9d , 21.12a , and
21.17 ). These cracks are strikingly different than dia-
stasis cracks (Cowan and James 1992 ) that result from
differential mechanical behavior of stiff muddy sediment,
under stress, in any subtidal environment. Desiccation
cracks may show a variety of sizes depending on expo-
sure time, layer thickness, and the presence or absence of
microbial mats (Shinn 1986 ). Mud cracks in carbonates
may develop a variety of cross-sectional shapes ranging
from classical ā€œvā€ to wide and parallel-walled or deep
These sediments, similar to a beach facies (Inden
and Moore 1983 ), commonly are characterized by
fenestral grainstone facies (e.g. Y. Lasemi 1995 )
(Figs. 21.14 and 21.15c ). Prolonged exposure in arid
to semiarid climate leads to partial dissolution of car-
bonate grains by meteoric water, pore enlargement,
and formation of iron oxide stained coated grains
(Fig. 21.14c ).
In protected modern and ancient Phanerozoic
Humid intertidal deposits, lamination and other diag-
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