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Fig. 11.15 ( a ) Shallow seismic records of cut-and-fi ll deposits
of a tidal channel preserved offshore, a region of lateral accre-
tion is clearly visible to the north of a channel, determined to be
a main channel close to the tidal inlet; ( b ) Schematic evolution
of channel with the inferred change in tidal prism responsible for
the growth, lateral accretion and eventual infi lling (Adapted
from Rieu et al. 2005 )
contain high proportions of heterolithics (intercalated
sand and mud). Tidal bundl es associated with differ-
ences in fl ow are formed as a result of periodic varia-
tions in tidal energy. Sandier deposits relate to
higher-energy periods such as spring tides and mud-
dier to lower-energy neap tides.
Close to the marine or fl uvial sediment sources the
channel deposits will consist of coarser sediment with
a lower mud content, and heterolithic deposits will
take the form of fl aser bedding. Moving away from
high-energy environments and sediment sources,
towards the mid regions of an estuary or the back of a
lagoon system, deposits become increasingly muddy
(wavy or lenticular bedding). In the lowest energy
reaches of an intertidal system, channel deposits are
entirely muddy making it diffi cult to distinguish
between deposits from lateral movement and channel-
fi lls that result from abandonment (Barwis and Hayes
1979 ). However, in a predominantly muddy system
Pearson and Gingras ( 2006 ) were able to discern rhyth-
mic silt-mud and sandy-mud couplets within tidal
pointbars, interpreted as neap-spring bundles.
Inclined Heterolithic Stratifi cation (IHS) is commonly
associated with tidal pointbars, representing lateral
accretion. These dipping, interbedded mud, silt, and
slightly sandy beds are formed as sediment accumu-
lates across a sloping face (either through suspended
or bedload deposition) and would be expected in mean-
dering tidal channels (Dalrymple et al. 1992 ; Santos
and Rossetti 2006 ; Pearson and Gingras 2006 ;
Dalrymple and Choi 2007 ). These deposits can lie
between 1° and 30° (angle of repose for sands) and,
may exhibit cross-stratifi cation if bedforms were pres-
ent during formation. In contrast to fl uvial settings,
stratifi cation in tidal pointbars is inclined towards the
thalweg of the channel (Barwis 1978 ; Pearson and
Gingras 2006 ), as opposed to dipping predominantly
downstream. IHS is indicative of the high frequency
variability in hydrodynamics, which occur in tidal sys-
tems. In pointbars in the Bay of Fundy, Pearson and
Gingras ( 2006 ) observe laterally continuous IHS over
a horizontal distance of 26 m.
In sandy environments, the migration of 2D- and
3D-bedforms in tidal settings typically results in cross-
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