Geology Reference
In-Depth Information
Fig. 9.8
Open-coast tidal flats shifting temporally from tide-dominated or mix-energy (tide-dom.) to wave-dominated regimes for
a few days to weeks during summer/winter storms (Adapted from Davis and Hayes
1984
)
Fig. 9.9
Schematic map showing the cross-profile variations of tidal-flat morphology and sedimentology from the supratidal flats
to the subtidal zones
60 km wide on average (Figs.
9.11
and
9.13
), and the
Holocene Guiana coastal plain ranges from 10 to
100 km wide with an average of ~30 km (Figs.
9.4
and
9.14
, Rine and Ginsburg
1985
; Allison et al.
1995a
). In
some sediment-starved coasts, the supratidal flats are
narrow or even absent, bordering directly on the rocky
hills like those along the Korean coast (Alexander et al.
1991
; Yang et al.
2005
).
The transition from the vegetated to the bare flats
can be smooth or drastic with erosional cliff or chan-
nels. The mangrove land is usually surrounded by deeply
cut tidal channels or cliffs (Semeniuk
1981
; Plaziat
and Augustinus
2004
). A smooth transition generally
occurs ahead of the accretional salt marshes, while
recessional salt marshes tend to have an erosional
escarpment at the front. Swash bars can be developed
at the salt-marsh front on both accretional and reces-
sional flats, resulting from wave breaking when storm
waves ride on the high tides. On the Chongming
Eastern Flat (Changjiang Delta), an accretional and
smoothly transitional profile is favorable during weak-
wave conditions (Fig.
9.12a
), while it is replaced by
the presence of erosional escarpment, scouring ponds,
and swash sand sheets/bars consisting of coarse
