Open-Coast Tidal Flats - Principles of Tidal Sedimentology - page 217

Fig. 9.27 Genesis interpretation of a small succession consist-
ing of sand-dominated layers ( SDLs ) and mud-dominated layers
( MDLs ) using elevation-monitoring data at the Nanhui Mudbank,
the Changjiang Delta. The net sediment increments ( a - d ) in the

right column were deposited at the time intervals ( A - D ) in the
bottom column. Maggie, Neil, Olga, and Paul are names for four
typhoons having exerted great impact on the study area in 1999
(After Fan et al. 2002, 2004b )

Fig. 9.28 Sketch drawing of the superposition of the winter
large-wave coarse deposits and the summer weak-wave fine
deposits. The coarse-bedding package characteristic of hum-
mocky cross-stratification ( HCS ) was formed during the wan-
ing stage of bigger storm. The fine-bedding package was

composed of one or two smaller upward-fining successions,
each succession presumably being formed during the waning
stage of smaller storm and during the immediate post-storm
period in summer (After Yang et al. 2005 )

9.6 Preservation Potential

potential have been extensively discussed by a series
of field observations in the Changjiang Delta (Li et al.
2000 ; Fan 2001 ; Fan et al. 2001, 2002, 2004b ; Fan and
Li 2002 ). The method is simply based on the compari-
son study of number and thickness of couplets using
the tile observation. A group of tiles were fixed closely
on the tidal-flat surface and regularly visited by diffe-
rent time intervals spanning from a semidiurnal tide to
a month or longer (Fig. 9.29 ). Two couplets were
sometimes observed to accumulate on the semidiurnal
tile, denoting both flooding and ebbing flows potential

Preservation potential of the deposits is general very
low on the open-coast tidal flats due to frequent refor-
mation by waves, especially storms. It has be recently
studied by the preservation potential of individual cou-
plets, ratios of gross and net sedimentation rates, and
numerical modeling (Li et al. 2000 ; Fan 2001 ; Fan and
Li 2002 ; Gao 2009 ).
Sand-mud couplets are basic sedimentary units of
tidal-flat deposits, and their formation and preservation