Open-Coast Tidal Flats - Principles of Tidal Sedimentology - page 211

employed to interpret the chenier development in the
Mississippi Delta (Byrne et al. 1959 ) and the Colorado
Delta in the Northern Gulf of California (Meckel 1975 ).
Sediment starvation for a coast can also result from a
reduction in fluvial input from the drainage basin instead
of the delta channel switching. The chenier ridges on

the coastal plains of North Australia were presumably
formed during low mud influx accompanying the
long-term dry periods in the drainage basins, while
mudflat deposition occurred during the wetter periods
(Rhodes 1982 ; Lees 1992 ).
The formation of cheniers could have resulted from
not only the reduced sediment availability but also the
increased energy of marine processes. There are two
series of well-developed chenier bundles on the Surinam
coastal plain, denoting that the coastal development
was interrupted at least twice by longer intervals of
erosion during the Coronie Formation (<6,000 year BP).
These two hiatuses among the three sedimentation phases
of Wanica, Moleson, and Comowine coincided with a
slight drop in sea level (Fig. 9.14 ) and a systematic
increase of more northerly wind frequencies. The che-
nier formation is therefore simply considered to link
with the more northerly wind frequencies and a fall in
sea level (Eisma et al. 1991 ; Augustinus 2004 ).

9.5 Sedimentary Structures

and Bedding

Bedforms and sedimentary structures are highly related
to sediment size and hydrodynamics (Boguchwal and
Southard 1990 ). Open-coast tidal flats vary greatly in
major grain-size composition from fine silt to sand
(Table 9.3 ). Wave energy can be dissipated higher or
less when propagating over the muddy or sandy flats
due to presence of fluid mud or not, and the wave is also
greatly modulated by tidal fluctuations. The difference

Fig. 9.23 Changes in position and length of the mudbanks
( heavy lines ) along the Surinam coast between 1947 and 1981
(After Eisma et al. 1991 )

Table 9.2 Total amounts of mud yearly eroded (−) or deposited (+) along the Surinam coast over different periods
(After Eisma et al. 1991 )

Total amount
(×10 8 tons)

Amount per year
(×10 6 tons year -1 )

Net amount over the entire
coast (×10 6 tons year -1 ) Period Section

1947-1957 I −15.90 −1.59

II +9.85 +0.99 −0.82

III −2.09 −0.21

1957-1966 I −14.19 −1.58

II +0.45 +0.05 −1.00

III +4.71 +0.52

1966-1970 I +6.55 +1.64

II +1.28 +0.32 +2.18

III +0.89 +0.22

1970-1981 I +30.85 +2.81

II +44.57 +4.05 +7.61

III +8.29 +0.75