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Pre-delta deposits
Tide-dominated delta
Abandoned channels
Wave-dominated delta
Wave-generated beach ridges
Upper delta plain
20 Km
10
°
105
°
Gulf of
Thailand
8
°
45
ʹ
104
°
45
ʹ
9
°
15
ʹ
106
°
South China Sea
Fig. 5.
Tide-dominated to wave-dominated autogenic process change, Mekong Delta example. Note the sharp boundary
between the tide-influenced and wave-influenced parts of the delta. The transition occurred at about 3 ka (Ta
et al
., 2005).
bifurcate the channels similar to fluvial-dominated
deltas (Olariu & Bhattacharya, 2006; Edmonds &
Slingerland, 2007). Between the two areas with
stronger discharge (fluvial influenced) there is an
area that is entirely tide dominated (about 30% of
the delta) receiving minimum fluvial input (Allen,
1979; Storms
et al
., 2005). The fluvial-influenced
and tide-dominated areas are coeval and vary lat-
erally along strike because of the location of the
delta distributaries. However, it is possible that
the (middle) tide-dominated area received direct
input of fluvial sediments in the past, as is sug-
gested by the relatively even width of the delta
plain and also of the shallow (5 m deep) delta plat-
form (Fig. 6). A similar fluvial discharge switch
Fluvial-dominated to tide-dominated process
change: modern example
The Mahakam Delta prograded 60 km into the
Makassar Strait (Fig. 6) during the last 5 ka (Storms
et al
., 2005). The tidal range is mesotidal with a
maximum spring tidal range of 3 m (Storms
et al
.,
2005). The Mahakam Delta has a semi-circular
distribution of delta plain facies (Allen
et al
., 1979)
suggesting a relatively smooth shoreline prograda-
tion without distinct delta lobes, as is typical for
tide-dominated deltas. Nowadays the delta has
northern and southern distributaries that have
a fluvial-influenced to tide-dominated character
(Fig. 6) with sediments forming mouth bars that
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