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Fig. 13.4 Succession of vertically stacked carbonate crossbeds
formed by simple, large to very large dunes migrating under the
influence of unidirectional or highly asymmetric tidal currents,
Bonifacio Formation, Corsica (see Brandano et al. 2009 ; André
et al. 2011 ). The exposure shown is about 25 m high. The vertical
stacking of such thick crossbeds in successions up to hundreds of
meters thick (250 m in the Bonifacio Formation) is a characteris-
tic feature of the infill of tidal seaways or straits where accom-
modation is high. The prominent crossbed boundaries correspond
to intervals deeply bioturbated by Thalassinoides
Fig. 13.5 ( Left ) Internal structures formed by compound dunes.
Slopes of foresets range from 35° (laminae) to 4° (master beds
in c ). The internal complexity depends on the relative size of the
'master' and superimposed dunes, which controls the amount of
erosion on the lee of the large dune and therefore its overall
steepness (After Dalrymple 2010b ), modified in part from Allen
1980 ). ( Right ) Outcrop sketches of compound-dune deposits in
the Precambrian Lower Sandfjord Formation, Norway (After
Levell 1980 ). Re reactivation surfaces, si silt drapes, re-fl reverse-
flow ripples, ha hanging set boundaries, co convex-up boundar-
ies, pe : pebble horizons
be generated by erosion in the troughs of superimposed
dunes as they migrate over the brink of the larger bed-
form (Dalrymple 1984, 2010b ; Reesink and Bridge
2009 ), or to episodic wave action. It is important to
note that mud drapes, which are an important signature
of tidal sedimentation in estuarine and deltaic settings
(Visser 1980 ; Nio and Yang 1991 ; Dalrymple 2010b ),
are rare in offshore tidal deposits because of the presence
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